diff --git a/contrib/checkstyle/readme.adoc b/contrib/checkstyle/readme.adoc
new file mode 100644
index 00000000000..24c2f7743b6
--- /dev/null
+++ b/contrib/checkstyle/readme.adoc
@@ -0,0 +1,128 @@
+= Checkstyle
+:page-aliases: Plugin_Checkstyle.adoc
+
+Performs quality checks on Java source files using https://checkstyle.org[Checkstyle] and generates reports from these checks.
+
+== CheckstyleModule
+
+To use this plugin in a Java/Scala module,
+
+1. Extend `mill.contrib.checkstyle.CheckstyleModule`.
+2. Define a https://checkstyle.org/config.html[configuration] file `checkstyle-config.xml`.
+3. Run the `checkstyle` command.
+
+=== checkstyle
+
+- flags
+[source,sh]
+----
+
+// if an exception should be raised when violations are found
+checkstyle --check
+
+// if Checkstyle output report should be written to System.out
+checkstyle --stdout
+----
+
+- sources (optional)
+[source,sh]
+----
+// incorrect paths will cause a command failure
+// checkstyle a/b
+
+// you can specify paths relative to millSourcePath
+checkstyle src/a/b
+
+// process a single file
+checkstyle src/a/B.java
+
+// process multiple sources
+checkstyle src/a/b src/c/d src/e/F.java
+
+// process with flags
+checkstyle --check --stdout src/a/b src/c/d
+
+// process all module sources
+checkstyle
+----
+
+=== Shared configuration
+
+To share `checkstyle-config.xml` across modules, adapt the following example.
+[source,scala]
+----
+import mill._
+import mill.contrib.checkstyle.CheckstyleModule
+import mill.scalalib._
+
+object foo extends Module {
+
+  object bar extends MyModule
+  object baz extends Module {
+    object fizz extends MyModule
+    object buzz extends MyModule
+  }
+
+  trait MyModule extends JavaModule with CheckstyleModule {
+
+    override def checkstyleConfig = T {
+      api.PathRef(T.workspace / "checkstyle-config.xml")
+    }
+  }
+}
+----
+
+
+=== Limitations
+
+- Version `6.3` or above is required for `plain` and `xml` formats.
+- Setting `checkstyleOptions` might cause failures with legacy versions.
+
+== CheckstyleXsltModule
+
+This plugin extends the `mill.contrib.checkstyle.CheckstyleModule` with the ability to generate reports by applying https://www.w3.org/TR/xslt/[XSL Transformations] on a Checkstyle output report.
+
+=== Auto detect XSL Transformations
+
+XSLT files are detected automatically provided a prescribed directory structure is followed.
+[source,scala]
+----
+/**
+ * checkstyle-xslt
+ *  ├─ html
+ *  │   ├─ xslt0.xml
+ *  │   └─ xslt1.xml
+ *  └─ pdf
+ *      ├─ xslt1.xml
+ *      └─ xslt2.xml
+ *
+ * html/xslt0.xml -> xslt0.html
+ * html/xslt1.xml -> xslt1.html
+ * pdf/xslt1.xml  -> xslt1.pdf
+ * pdf/xslt2.xml  -> xslt2.pdf
+ */
+----
+
+=== Specify XSL Transformations manually
+
+For a custom setup, adapt the following example.
+[source,scala]
+----
+import mill._
+import mill.api.PathRef
+import mill.contrib.checkstyle.CheckstyleXsltModule
+import mill.contrib.checkstyle.CheckstyleXsltReport
+import mill.scalalib._
+
+object foo extends JavaModule with CheckstyleXsltModule {
+
+    override def checkstyleXsltReports = T {
+      Set(
+        CheckstyleXsltReport(
+          PathRef(millSourcePath / "checkstyle-no-frames.xml"),
+          PathRef(T.dest / "checkstyle-no-frames.html"),
+        )
+      )
+  }
+}
+----
diff --git a/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleArgs.scala b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleArgs.scala
new file mode 100644
index 00000000000..b075e2ea2b1
--- /dev/null
+++ b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleArgs.scala
@@ -0,0 +1,21 @@
+package mill.contrib.checkstyle
+
+import mainargs.{Leftover, ParserForClass, main}
+
+/**
+ * Arguments for [[CheckstyleModule.checkstyle]].
+ *
+ * @param check   if an exception should be raised when violations are found
+ * @param stdout  if Checkstyle should output report to [[System.out]]
+ * @param sources (optional) files(s) or folder(s) to process
+ */
+@main(doc = "arguments for CheckstyleModule.checkstyle")
+case class CheckstyleArgs(
+    check: Boolean = false,
+    stdout: Boolean = false,
+    sources: Leftover[String]
+)
+object CheckstyleArgs {
+
+  implicit val PFC: ParserForClass[CheckstyleArgs] = ParserForClass[CheckstyleArgs]
+}
diff --git a/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleModule.scala b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleModule.scala
new file mode 100644
index 00000000000..203c67978cd
--- /dev/null
+++ b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleModule.scala
@@ -0,0 +1,106 @@
+package mill
+package contrib.checkstyle
+
+import mill.api.{Loose, PathRef}
+import mill.scalalib.{DepSyntax, JavaModule}
+import mill.util.Jvm
+
+/**
+ * Performs quality checks on Java source files using [[https://checkstyle.org/ Checkstyle]].
+ */
+trait CheckstyleModule extends JavaModule {
+
+  /**
+   * Runs [[https://checkstyle.org/cmdline.html#Command_line_usage Checkstyle]] and returns one of
+   *  - number of violations found
+   *  - program exit code
+   *
+   * @note [[sources]] are processed when no [[CheckstyleArgs.sources]] are specified.
+   */
+  def checkstyle(@mainargs.arg checkstyleArgs: CheckstyleArgs): Command[Int] = T.command {
+
+    val CheckstyleArgs(check, stdout, leftover) = checkstyleArgs
+
+    val output = checkstyleOutput().path
+    val args = checkstyleOptions() ++
+      Seq("-c", checkstyleConfig().path.toString()) ++
+      Seq("-f", checkstyleFormat()) ++
+      (if (stdout) Seq.empty else Seq("-o", output.toString())) ++
+      (if (leftover.value.nonEmpty) leftover.value else sources().map(_.path.toString()))
+
+    T.log.info("running checkstyle ...")
+    T.log.debug(s"with $args")
+
+    val exitCode = Jvm.callSubprocess(
+      mainClass = "com.puppycrawl.tools.checkstyle.Main",
+      classPath = checkstyleClasspath().map(_.path),
+      mainArgs = args,
+      workingDir = millSourcePath, // allow passing relative paths for sources like src/a/b
+      check = false
+    ).exitCode
+
+    val reported = os.exists(output)
+    if (reported) {
+      T.log.info(s"checkstyle output report at $output")
+    }
+
+    if (exitCode == 0) {
+      T.log.info("checkstyle found no violation")
+    } else if (exitCode < 0 || !(reported || stdout)) {
+      T.log.error(
+        s"checkstyle exit($exitCode); please check command arguments, plugin settings or try with another version"
+      )
+      throw new UnsupportedOperationException(s"checkstyle exit($exitCode)")
+    } else if (check) {
+      throw new RuntimeException(s"checkstyle found $exitCode violation(s)")
+    } else {
+      T.log.error(s"checkstyle found $exitCode violation(s)")
+    }
+
+    exitCode
+  }
+
+  /**
+   * Classpath for running Checkstyle.
+   */
+  def checkstyleClasspath: T[Loose.Agg[PathRef]] = T {
+    defaultResolver().resolveDeps(
+      Agg(ivy"com.puppycrawl.tools:checkstyle:${checkstyleVersion()}")
+    )
+  }
+
+  /**
+   * Checkstyle configuration file. Defaults to `checkstyle-config.xml`.
+   */
+  def checkstyleConfig: T[PathRef] = T {
+    PathRef(millSourcePath / "checkstyle-config.xml")
+  }
+
+  /**
+   * Checkstyle output format (` plain | sarif | xml `). Defaults to `plain`.
+   */
+  def checkstyleFormat: T[String] = T {
+    "plain"
+  }
+
+  /**
+   * Additional arguments for Checkstyle.
+   */
+  def checkstyleOptions: T[Seq[String]] = T {
+    Seq.empty[String]
+  }
+
+  /**
+   * Checkstyle output report.
+   */
+  def checkstyleOutput: T[PathRef] = T {
+    PathRef(T.dest / s"checkstyle-output.${checkstyleFormat()}")
+  }
+
+  /**
+   * Checkstyle version.
+   */
+  def checkstyleVersion: T[String] = T {
+    "10.18.1"
+  }
+}
diff --git a/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleXsltModule.scala b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleXsltModule.scala
new file mode 100644
index 00000000000..a9de7d2fe34
--- /dev/null
+++ b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleXsltModule.scala
@@ -0,0 +1,98 @@
+package mill
+package contrib.checkstyle
+
+import javax.xml.transform.TransformerFactory
+import javax.xml.transform.stream.{StreamResult, StreamSource}
+
+/**
+ * Extends [[CheckstyleModule]] with the ability to generate [[CheckstyleXsltReport]]s.
+ */
+trait CheckstyleXsltModule extends CheckstyleModule {
+
+  /**
+   * Runs [[CheckstyleModule.checkstyle]] and uses [[CheckstyleModule.checkstyleOutput]] to generate [[checkstyleXsltReports]].
+   */
+  override def checkstyle(@mainargs.arg checkstyleArgs: CheckstyleArgs): Command[Int] = T.command {
+    val numViolations = super.checkstyle(checkstyleArgs)()
+    val checkOutput = checkstyleOutput().path
+
+    if (os.exists(checkOutput)) {
+      checkstyleXsltReports().foreach {
+        case CheckstyleXsltReport(xslt, output) =>
+          val xsltSource = new StreamSource(xslt.path.getInputStream)
+          xsltSource.setSystemId(xslt.path.toIO) // so that relative URI references can be resolved
+
+          val checkSource =
+            new StreamSource(checkOutput.getInputStream)
+
+          val outputResult =
+            new StreamResult(os.write.outputStream(output.path, createFolders = true))
+
+          T.log.info(s"transforming checkstyle output report with $xslt")
+
+          TransformerFactory.newInstance()
+            .newTransformer(xsltSource)
+            .transform(checkSource, outputResult)
+
+          T.log.info(s"transformed output report at $output")
+      }
+    }
+
+    numViolations
+  }
+
+  /**
+   * `xml`
+   */
+  final override def checkstyleFormat: T[String] = T {
+    "xml"
+  }
+
+  /**
+   * Set of [[CheckstyleXsltReport]]s.
+   *
+   * The default implementation maps XSLT files, under `checkstyle-xslt`, as depicted below:
+   * {{{
+   *
+   * checkstyle-xslt
+   *  ├─ html
+   *  │   ├─ xslt0.xml
+   *  │   └─ xslt1.xml
+   *  └─ pdf
+   *      ├─ xslt1.xml
+   *      └─ xslt2.xml
+   *
+   * html/xslt0.xml -> xslt0.html
+   * html/xslt1.xml -> xslt1.html
+   * pdf/xslt1.xml  -> xslt1.pdf
+   * pdf/xslt2.xml  -> xslt2.pdf
+   *
+   * }}}
+   */
+  def checkstyleXsltReports: T[Set[CheckstyleXsltReport]] = T {
+    val dir = millSourcePath / "checkstyle-xslt"
+
+    if (os.exists(dir)) {
+      val dest = T.dest
+      os.list(dir)
+        .iterator
+        .filter(os.isDir)
+        .flatMap(childDir =>
+          os.list(childDir)
+            .iterator
+            .filter(os.isFile)
+            .filter(_.ext == "xml")
+            .map(xslt =>
+              CheckstyleXsltReport(
+                PathRef(xslt),
+                PathRef(dest / s"${xslt.baseName}.${childDir.last}")
+              )
+            )
+        )
+        .toSet
+    } else {
+      T.log.info(s"expected XSLT files under $dir")
+      Set.empty[CheckstyleXsltReport]
+    }
+  }
+}
diff --git a/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleXsltReport.scala b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleXsltReport.scala
new file mode 100644
index 00000000000..2235bf30b77
--- /dev/null
+++ b/contrib/checkstyle/src/mill/contrib/checkstyle/CheckstyleXsltReport.scala
@@ -0,0 +1,17 @@
+package mill.contrib.checkstyle
+
+import mill.api.PathRef
+
+/**
+ * A report obtained by transforming a Checkstyle output report.
+ *
+ * @param xslt path to an [[https://www.w3.org/TR/xslt/ XSLT]] file
+ * @param output path to the transformed output report
+ */
+case class CheckstyleXsltReport(xslt: PathRef, output: PathRef)
+object CheckstyleXsltReport {
+
+  import upickle.default._
+
+  implicit val RW: ReadWriter[CheckstyleXsltReport] = macroRW[CheckstyleXsltReport]
+}
diff --git a/contrib/checkstyle/test/resources/compatible-java/checkstyle-config.xml b/contrib/checkstyle/test/resources/compatible-java/checkstyle-config.xml
new file mode 100644
index 00000000000..f0298e17b39
--- /dev/null
+++ b/contrib/checkstyle/test/resources/compatible-java/checkstyle-config.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+
+<module name="Checker">
+
+  <module name="TreeWalker">
+
+    <module name="HideUtilityClassConstructor" />
+
+  </module>
+
+</module>
diff --git a/contrib/checkstyle/test/resources/compatible-java/src/com/etsy/sbt/TestClass.java b/contrib/checkstyle/test/resources/compatible-java/src/com/etsy/sbt/TestClass.java
new file mode 100644
index 00000000000..b76bfb5fe4a
--- /dev/null
+++ b/contrib/checkstyle/test/resources/compatible-java/src/com/etsy/sbt/TestClass.java
@@ -0,0 +1,11 @@
+package com.etsy.sbt;
+
+public class TestClass {
+
+    private TestClass() {
+    }
+
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+}
diff --git a/contrib/checkstyle/test/resources/compatible-scala/checkstyle-config.xml b/contrib/checkstyle/test/resources/compatible-scala/checkstyle-config.xml
new file mode 100644
index 00000000000..f0298e17b39
--- /dev/null
+++ b/contrib/checkstyle/test/resources/compatible-scala/checkstyle-config.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+
+<module name="Checker">
+
+  <module name="TreeWalker">
+
+    <module name="HideUtilityClassConstructor" />
+
+  </module>
+
+</module>
diff --git a/contrib/checkstyle/test/resources/compatible-scala/checkstyle-xslt/html/noframes.xml b/contrib/checkstyle/test/resources/compatible-scala/checkstyle-xslt/html/noframes.xml
new file mode 100644
index 00000000000..b9c5e7106d1
--- /dev/null
+++ b/contrib/checkstyle/test/resources/compatible-scala/checkstyle-xslt/html/noframes.xml
@@ -0,0 +1,199 @@
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
+  <xsl:output method="html" indent="yes" />
+  <xsl:decimal-format decimal-separator="." grouping-separator="," />
+
+  <!-- Checkstyle XML Style Sheet by Stephane Bailliez <sbailliez@apache.org>         -->
+  <!-- Part of the Checkstyle distribution found at http://checkstyle.sourceforge.net -->
+  <!-- Usage (generates checkstyle_report.html):                                      -->
+  <!--    <checkstyle failonviolation="false" config="${check.config}">               -->
+  <!--      <fileset dir="${src.dir}" includes="**/*.java"/>                          -->
+  <!--      <formatter type="xml" toFile="${doc.dir}/checkstyle_report.xml"/>         -->
+  <!--    </checkstyle>                                                               -->
+  <!--    <style basedir="${doc.dir}" destdir="${doc.dir}"                            -->
+  <!--            includes="checkstyle_report.xml"                                    -->
+  <!--            style="${doc.dir}/checkstyle-noframes.xsl"/>                        -->
+
+  <xsl:template match="checkstyle">
+    <html>
+      <head>
+        <style type="text/css">
+          .bannercell {
+          border: 0px;
+          padding: 0px;
+          }
+          body {
+          margin-left: 10;
+          margin-right: 10;
+          font:normal 80% arial,helvetica,sanserif;
+          background-color:#FFFFFF;
+          color:#000000;
+          }
+          .a td {
+          background: #efefef;
+          }
+          .b td {
+          background: #fff;
+          }
+          th, td {
+          text-align: left;
+          vertical-align: top;
+          }
+          th {
+          font-weight:bold;
+          background: #ccc;
+          color: black;
+          }
+          table, th, td {
+          font-size:100%;
+          border: none
+          }
+          table.log tr td, tr th {
+
+          }
+          h2 {
+          font-weight:bold;
+          font-size:140%;
+          margin-bottom: 5;
+          }
+          h3 {
+          font-size:100%;
+          font-weight:bold;
+          background: #525D76;
+          color: white;
+          text-decoration: none;
+          padding: 5px;
+          margin-right: 2px;
+          margin-left: 2px;
+          margin-bottom: 0;
+          }
+        </style>
+      </head>
+      <body>
+        <a name="top"></a>
+        <!-- jakarta logo -->
+        <table border="0" cellpadding="0" cellspacing="0" width="100%">
+          <tr>
+            <td class="bannercell" rowspan="2">
+              <!--a
+              href="http://jakarta.apache.org/">
+          <img src="http://jakarta.apache.org/images/jakarta-logo.gif" alt="http://jakarta.apache.org"
+              align="left" border="0"/>
+          </a-->
+            </td>
+            <td class="text-align:right">
+              <h2>CheckStyle Audit</h2>
+            </td>
+          </tr>
+          <tr>
+            <td class="text-align:right">Designed for use with <a
+                href='http://checkstyle.sourceforge.net/'>CheckStyle</a>.</td>
+          </tr>
+        </table>
+        <hr size="1" />
+
+        <!-- Summary part -->
+        <xsl:apply-templates select="." mode="summary" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- Package List part -->
+        <xsl:apply-templates select="." mode="filelist" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- For each package create its part -->
+        <xsl:for-each select="file">
+          <xsl:sort select="@name" />
+			  <xsl:apply-templates select="." />
+			  <p />
+			  <p />
+        </xsl:for-each>
+        <hr size="1" width="100%" align="left" />
+
+
+      </body>
+    </html>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="filelist">
+    <h3>Files</h3>
+		<table class="log" border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Name</th>
+        <th>Errors</th>
+      </tr>
+      <xsl:for-each select="file">
+        <xsl:sort select="@name" />
+				<xsl:variable name="errorCount" select="count(error)" />				
+				<tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <a href="#f-{@name}">
+              <xsl:value-of select="@name" />
+            </a>
+          </td>
+          <td>
+            <xsl:value-of select="$errorCount" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+  </xsl:template>
+
+
+  <xsl:template match="file">
+    <a name="f-{@name}"></a>
+    <h3>File <xsl:value-of select="@name" /></h3>
+    
+    <table class="log"
+      border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Error Description</th>
+        <th>Line</th>
+      </tr>
+      <xsl:for-each select="error">
+        <tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <xsl:value-of select="@message" />
+          </td>
+          <td>
+            <xsl:value-of select="@line" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+    <a
+      href="#top">Back to top</a>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="summary">
+    <h3>Summary</h3>
+		<xsl:variable name="fileCount" select="count(file)" />
+		<xsl:variable
+      name="errorCount" select="count(file/error)" />
+		<table class="log" border="0" cellpadding="5"
+      cellspacing="2" width="100%">
+      <tr>
+        <th>Files</th>
+        <th>Errors</th>
+      </tr>
+      <tr>
+        <xsl:call-template name="alternated-row" />
+        <td>
+          <xsl:value-of select="$fileCount" />
+        </td>
+        <td>
+          <xsl:value-of select="$errorCount" />
+        </td>
+      </tr>
+    </table>
+  </xsl:template>
+
+  <xsl:template name="alternated-row">
+    <xsl:attribute name="class">
+      <xsl:if test="position() mod 2 = 1">a</xsl:if>
+      <xsl:if test="position() mod 2 = 0">b</xsl:if>
+    </xsl:attribute>
+  </xsl:template>
+</xsl:stylesheet>
\ No newline at end of file
diff --git a/contrib/checkstyle/test/resources/compatible-scala/src/com/etsy/sbt/TestClass.java b/contrib/checkstyle/test/resources/compatible-scala/src/com/etsy/sbt/TestClass.java
new file mode 100644
index 00000000000..b76bfb5fe4a
--- /dev/null
+++ b/contrib/checkstyle/test/resources/compatible-scala/src/com/etsy/sbt/TestClass.java
@@ -0,0 +1,11 @@
+package com.etsy.sbt;
+
+public class TestClass {
+
+    private TestClass() {
+    }
+
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+}
diff --git a/contrib/checkstyle/test/resources/compatible-scala/src/com/etsy/sbt/TestClass.scala b/contrib/checkstyle/test/resources/compatible-scala/src/com/etsy/sbt/TestClass.scala
new file mode 100644
index 00000000000..93cecc34fd5
--- /dev/null
+++ b/contrib/checkstyle/test/resources/compatible-scala/src/com/etsy/sbt/TestClass.scala
@@ -0,0 +1,7 @@
+package com.etsy.sbt
+
+object TestClass {
+
+// Checkstyle should ignore a Scala file
+// introduce a compile error to trigger failure in case this file is processed
+//}
diff --git a/contrib/checkstyle/test/resources/non-compatible/checkstyle-config.xml b/contrib/checkstyle/test/resources/non-compatible/checkstyle-config.xml
new file mode 100644
index 00000000000..4bd20f0438c
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/checkstyle-config.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+
+<module name="Checker">
+
+  <module name="TreeWalker">
+
+    <module name="ArrayTrailingComma" />
+
+    <module name="EmptyStatement" />
+
+  </module>
+
+</module>
diff --git a/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/noframes-copy.xml b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/noframes-copy.xml
new file mode 100644
index 00000000000..b9c5e7106d1
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/noframes-copy.xml
@@ -0,0 +1,199 @@
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
+  <xsl:output method="html" indent="yes" />
+  <xsl:decimal-format decimal-separator="." grouping-separator="," />
+
+  <!-- Checkstyle XML Style Sheet by Stephane Bailliez <sbailliez@apache.org>         -->
+  <!-- Part of the Checkstyle distribution found at http://checkstyle.sourceforge.net -->
+  <!-- Usage (generates checkstyle_report.html):                                      -->
+  <!--    <checkstyle failonviolation="false" config="${check.config}">               -->
+  <!--      <fileset dir="${src.dir}" includes="**/*.java"/>                          -->
+  <!--      <formatter type="xml" toFile="${doc.dir}/checkstyle_report.xml"/>         -->
+  <!--    </checkstyle>                                                               -->
+  <!--    <style basedir="${doc.dir}" destdir="${doc.dir}"                            -->
+  <!--            includes="checkstyle_report.xml"                                    -->
+  <!--            style="${doc.dir}/checkstyle-noframes.xsl"/>                        -->
+
+  <xsl:template match="checkstyle">
+    <html>
+      <head>
+        <style type="text/css">
+          .bannercell {
+          border: 0px;
+          padding: 0px;
+          }
+          body {
+          margin-left: 10;
+          margin-right: 10;
+          font:normal 80% arial,helvetica,sanserif;
+          background-color:#FFFFFF;
+          color:#000000;
+          }
+          .a td {
+          background: #efefef;
+          }
+          .b td {
+          background: #fff;
+          }
+          th, td {
+          text-align: left;
+          vertical-align: top;
+          }
+          th {
+          font-weight:bold;
+          background: #ccc;
+          color: black;
+          }
+          table, th, td {
+          font-size:100%;
+          border: none
+          }
+          table.log tr td, tr th {
+
+          }
+          h2 {
+          font-weight:bold;
+          font-size:140%;
+          margin-bottom: 5;
+          }
+          h3 {
+          font-size:100%;
+          font-weight:bold;
+          background: #525D76;
+          color: white;
+          text-decoration: none;
+          padding: 5px;
+          margin-right: 2px;
+          margin-left: 2px;
+          margin-bottom: 0;
+          }
+        </style>
+      </head>
+      <body>
+        <a name="top"></a>
+        <!-- jakarta logo -->
+        <table border="0" cellpadding="0" cellspacing="0" width="100%">
+          <tr>
+            <td class="bannercell" rowspan="2">
+              <!--a
+              href="http://jakarta.apache.org/">
+          <img src="http://jakarta.apache.org/images/jakarta-logo.gif" alt="http://jakarta.apache.org"
+              align="left" border="0"/>
+          </a-->
+            </td>
+            <td class="text-align:right">
+              <h2>CheckStyle Audit</h2>
+            </td>
+          </tr>
+          <tr>
+            <td class="text-align:right">Designed for use with <a
+                href='http://checkstyle.sourceforge.net/'>CheckStyle</a>.</td>
+          </tr>
+        </table>
+        <hr size="1" />
+
+        <!-- Summary part -->
+        <xsl:apply-templates select="." mode="summary" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- Package List part -->
+        <xsl:apply-templates select="." mode="filelist" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- For each package create its part -->
+        <xsl:for-each select="file">
+          <xsl:sort select="@name" />
+			  <xsl:apply-templates select="." />
+			  <p />
+			  <p />
+        </xsl:for-each>
+        <hr size="1" width="100%" align="left" />
+
+
+      </body>
+    </html>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="filelist">
+    <h3>Files</h3>
+		<table class="log" border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Name</th>
+        <th>Errors</th>
+      </tr>
+      <xsl:for-each select="file">
+        <xsl:sort select="@name" />
+				<xsl:variable name="errorCount" select="count(error)" />				
+				<tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <a href="#f-{@name}">
+              <xsl:value-of select="@name" />
+            </a>
+          </td>
+          <td>
+            <xsl:value-of select="$errorCount" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+  </xsl:template>
+
+
+  <xsl:template match="file">
+    <a name="f-{@name}"></a>
+    <h3>File <xsl:value-of select="@name" /></h3>
+    
+    <table class="log"
+      border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Error Description</th>
+        <th>Line</th>
+      </tr>
+      <xsl:for-each select="error">
+        <tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <xsl:value-of select="@message" />
+          </td>
+          <td>
+            <xsl:value-of select="@line" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+    <a
+      href="#top">Back to top</a>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="summary">
+    <h3>Summary</h3>
+		<xsl:variable name="fileCount" select="count(file)" />
+		<xsl:variable
+      name="errorCount" select="count(file/error)" />
+		<table class="log" border="0" cellpadding="5"
+      cellspacing="2" width="100%">
+      <tr>
+        <th>Files</th>
+        <th>Errors</th>
+      </tr>
+      <tr>
+        <xsl:call-template name="alternated-row" />
+        <td>
+          <xsl:value-of select="$fileCount" />
+        </td>
+        <td>
+          <xsl:value-of select="$errorCount" />
+        </td>
+      </tr>
+    </table>
+  </xsl:template>
+
+  <xsl:template name="alternated-row">
+    <xsl:attribute name="class">
+      <xsl:if test="position() mod 2 = 1">a</xsl:if>
+      <xsl:if test="position() mod 2 = 0">b</xsl:if>
+    </xsl:attribute>
+  </xsl:template>
+</xsl:stylesheet>
\ No newline at end of file
diff --git a/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/noframes.xml b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/noframes.xml
new file mode 100644
index 00000000000..b9c5e7106d1
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/noframes.xml
@@ -0,0 +1,199 @@
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
+  <xsl:output method="html" indent="yes" />
+  <xsl:decimal-format decimal-separator="." grouping-separator="," />
+
+  <!-- Checkstyle XML Style Sheet by Stephane Bailliez <sbailliez@apache.org>         -->
+  <!-- Part of the Checkstyle distribution found at http://checkstyle.sourceforge.net -->
+  <!-- Usage (generates checkstyle_report.html):                                      -->
+  <!--    <checkstyle failonviolation="false" config="${check.config}">               -->
+  <!--      <fileset dir="${src.dir}" includes="**/*.java"/>                          -->
+  <!--      <formatter type="xml" toFile="${doc.dir}/checkstyle_report.xml"/>         -->
+  <!--    </checkstyle>                                                               -->
+  <!--    <style basedir="${doc.dir}" destdir="${doc.dir}"                            -->
+  <!--            includes="checkstyle_report.xml"                                    -->
+  <!--            style="${doc.dir}/checkstyle-noframes.xsl"/>                        -->
+
+  <xsl:template match="checkstyle">
+    <html>
+      <head>
+        <style type="text/css">
+          .bannercell {
+          border: 0px;
+          padding: 0px;
+          }
+          body {
+          margin-left: 10;
+          margin-right: 10;
+          font:normal 80% arial,helvetica,sanserif;
+          background-color:#FFFFFF;
+          color:#000000;
+          }
+          .a td {
+          background: #efefef;
+          }
+          .b td {
+          background: #fff;
+          }
+          th, td {
+          text-align: left;
+          vertical-align: top;
+          }
+          th {
+          font-weight:bold;
+          background: #ccc;
+          color: black;
+          }
+          table, th, td {
+          font-size:100%;
+          border: none
+          }
+          table.log tr td, tr th {
+
+          }
+          h2 {
+          font-weight:bold;
+          font-size:140%;
+          margin-bottom: 5;
+          }
+          h3 {
+          font-size:100%;
+          font-weight:bold;
+          background: #525D76;
+          color: white;
+          text-decoration: none;
+          padding: 5px;
+          margin-right: 2px;
+          margin-left: 2px;
+          margin-bottom: 0;
+          }
+        </style>
+      </head>
+      <body>
+        <a name="top"></a>
+        <!-- jakarta logo -->
+        <table border="0" cellpadding="0" cellspacing="0" width="100%">
+          <tr>
+            <td class="bannercell" rowspan="2">
+              <!--a
+              href="http://jakarta.apache.org/">
+          <img src="http://jakarta.apache.org/images/jakarta-logo.gif" alt="http://jakarta.apache.org"
+              align="left" border="0"/>
+          </a-->
+            </td>
+            <td class="text-align:right">
+              <h2>CheckStyle Audit</h2>
+            </td>
+          </tr>
+          <tr>
+            <td class="text-align:right">Designed for use with <a
+                href='http://checkstyle.sourceforge.net/'>CheckStyle</a>.</td>
+          </tr>
+        </table>
+        <hr size="1" />
+
+        <!-- Summary part -->
+        <xsl:apply-templates select="." mode="summary" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- Package List part -->
+        <xsl:apply-templates select="." mode="filelist" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- For each package create its part -->
+        <xsl:for-each select="file">
+          <xsl:sort select="@name" />
+			  <xsl:apply-templates select="." />
+			  <p />
+			  <p />
+        </xsl:for-each>
+        <hr size="1" width="100%" align="left" />
+
+
+      </body>
+    </html>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="filelist">
+    <h3>Files</h3>
+		<table class="log" border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Name</th>
+        <th>Errors</th>
+      </tr>
+      <xsl:for-each select="file">
+        <xsl:sort select="@name" />
+				<xsl:variable name="errorCount" select="count(error)" />				
+				<tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <a href="#f-{@name}">
+              <xsl:value-of select="@name" />
+            </a>
+          </td>
+          <td>
+            <xsl:value-of select="$errorCount" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+  </xsl:template>
+
+
+  <xsl:template match="file">
+    <a name="f-{@name}"></a>
+    <h3>File <xsl:value-of select="@name" /></h3>
+    
+    <table class="log"
+      border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Error Description</th>
+        <th>Line</th>
+      </tr>
+      <xsl:for-each select="error">
+        <tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <xsl:value-of select="@message" />
+          </td>
+          <td>
+            <xsl:value-of select="@line" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+    <a
+      href="#top">Back to top</a>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="summary">
+    <h3>Summary</h3>
+		<xsl:variable name="fileCount" select="count(file)" />
+		<xsl:variable
+      name="errorCount" select="count(file/error)" />
+		<table class="log" border="0" cellpadding="5"
+      cellspacing="2" width="100%">
+      <tr>
+        <th>Files</th>
+        <th>Errors</th>
+      </tr>
+      <tr>
+        <xsl:call-template name="alternated-row" />
+        <td>
+          <xsl:value-of select="$fileCount" />
+        </td>
+        <td>
+          <xsl:value-of select="$errorCount" />
+        </td>
+      </tr>
+    </table>
+  </xsl:template>
+
+  <xsl:template name="alternated-row">
+    <xsl:attribute name="class">
+      <xsl:if test="position() mod 2 = 1">a</xsl:if>
+      <xsl:if test="position() mod 2 = 0">b</xsl:if>
+    </xsl:attribute>
+  </xsl:template>
+</xsl:stylesheet>
\ No newline at end of file
diff --git a/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/readme.txt b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/readme.txt
new file mode 100644
index 00000000000..adc8c3d80c2
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/htm/readme.txt
@@ -0,0 +1 @@
+This file should be skipped by the scan in CheckstyleXsltModule.
\ No newline at end of file
diff --git a/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/html/noframes-copy.xml b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/html/noframes-copy.xml
new file mode 100644
index 00000000000..b9c5e7106d1
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/html/noframes-copy.xml
@@ -0,0 +1,199 @@
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
+  <xsl:output method="html" indent="yes" />
+  <xsl:decimal-format decimal-separator="." grouping-separator="," />
+
+  <!-- Checkstyle XML Style Sheet by Stephane Bailliez <sbailliez@apache.org>         -->
+  <!-- Part of the Checkstyle distribution found at http://checkstyle.sourceforge.net -->
+  <!-- Usage (generates checkstyle_report.html):                                      -->
+  <!--    <checkstyle failonviolation="false" config="${check.config}">               -->
+  <!--      <fileset dir="${src.dir}" includes="**/*.java"/>                          -->
+  <!--      <formatter type="xml" toFile="${doc.dir}/checkstyle_report.xml"/>         -->
+  <!--    </checkstyle>                                                               -->
+  <!--    <style basedir="${doc.dir}" destdir="${doc.dir}"                            -->
+  <!--            includes="checkstyle_report.xml"                                    -->
+  <!--            style="${doc.dir}/checkstyle-noframes.xsl"/>                        -->
+
+  <xsl:template match="checkstyle">
+    <html>
+      <head>
+        <style type="text/css">
+          .bannercell {
+          border: 0px;
+          padding: 0px;
+          }
+          body {
+          margin-left: 10;
+          margin-right: 10;
+          font:normal 80% arial,helvetica,sanserif;
+          background-color:#FFFFFF;
+          color:#000000;
+          }
+          .a td {
+          background: #efefef;
+          }
+          .b td {
+          background: #fff;
+          }
+          th, td {
+          text-align: left;
+          vertical-align: top;
+          }
+          th {
+          font-weight:bold;
+          background: #ccc;
+          color: black;
+          }
+          table, th, td {
+          font-size:100%;
+          border: none
+          }
+          table.log tr td, tr th {
+
+          }
+          h2 {
+          font-weight:bold;
+          font-size:140%;
+          margin-bottom: 5;
+          }
+          h3 {
+          font-size:100%;
+          font-weight:bold;
+          background: #525D76;
+          color: white;
+          text-decoration: none;
+          padding: 5px;
+          margin-right: 2px;
+          margin-left: 2px;
+          margin-bottom: 0;
+          }
+        </style>
+      </head>
+      <body>
+        <a name="top"></a>
+        <!-- jakarta logo -->
+        <table border="0" cellpadding="0" cellspacing="0" width="100%">
+          <tr>
+            <td class="bannercell" rowspan="2">
+              <!--a
+              href="http://jakarta.apache.org/">
+          <img src="http://jakarta.apache.org/images/jakarta-logo.gif" alt="http://jakarta.apache.org"
+              align="left" border="0"/>
+          </a-->
+            </td>
+            <td class="text-align:right">
+              <h2>CheckStyle Audit</h2>
+            </td>
+          </tr>
+          <tr>
+            <td class="text-align:right">Designed for use with <a
+                href='http://checkstyle.sourceforge.net/'>CheckStyle</a>.</td>
+          </tr>
+        </table>
+        <hr size="1" />
+
+        <!-- Summary part -->
+        <xsl:apply-templates select="." mode="summary" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- Package List part -->
+        <xsl:apply-templates select="." mode="filelist" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- For each package create its part -->
+        <xsl:for-each select="file">
+          <xsl:sort select="@name" />
+			  <xsl:apply-templates select="." />
+			  <p />
+			  <p />
+        </xsl:for-each>
+        <hr size="1" width="100%" align="left" />
+
+
+      </body>
+    </html>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="filelist">
+    <h3>Files</h3>
+		<table class="log" border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Name</th>
+        <th>Errors</th>
+      </tr>
+      <xsl:for-each select="file">
+        <xsl:sort select="@name" />
+				<xsl:variable name="errorCount" select="count(error)" />				
+				<tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <a href="#f-{@name}">
+              <xsl:value-of select="@name" />
+            </a>
+          </td>
+          <td>
+            <xsl:value-of select="$errorCount" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+  </xsl:template>
+
+
+  <xsl:template match="file">
+    <a name="f-{@name}"></a>
+    <h3>File <xsl:value-of select="@name" /></h3>
+    
+    <table class="log"
+      border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Error Description</th>
+        <th>Line</th>
+      </tr>
+      <xsl:for-each select="error">
+        <tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <xsl:value-of select="@message" />
+          </td>
+          <td>
+            <xsl:value-of select="@line" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+    <a
+      href="#top">Back to top</a>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="summary">
+    <h3>Summary</h3>
+		<xsl:variable name="fileCount" select="count(file)" />
+		<xsl:variable
+      name="errorCount" select="count(file/error)" />
+		<table class="log" border="0" cellpadding="5"
+      cellspacing="2" width="100%">
+      <tr>
+        <th>Files</th>
+        <th>Errors</th>
+      </tr>
+      <tr>
+        <xsl:call-template name="alternated-row" />
+        <td>
+          <xsl:value-of select="$fileCount" />
+        </td>
+        <td>
+          <xsl:value-of select="$errorCount" />
+        </td>
+      </tr>
+    </table>
+  </xsl:template>
+
+  <xsl:template name="alternated-row">
+    <xsl:attribute name="class">
+      <xsl:if test="position() mod 2 = 1">a</xsl:if>
+      <xsl:if test="position() mod 2 = 0">b</xsl:if>
+    </xsl:attribute>
+  </xsl:template>
+</xsl:stylesheet>
\ No newline at end of file
diff --git a/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/html/noframes.xml b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/html/noframes.xml
new file mode 100644
index 00000000000..b9c5e7106d1
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/checkstyle-xslt/html/noframes.xml
@@ -0,0 +1,199 @@
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
+  <xsl:output method="html" indent="yes" />
+  <xsl:decimal-format decimal-separator="." grouping-separator="," />
+
+  <!-- Checkstyle XML Style Sheet by Stephane Bailliez <sbailliez@apache.org>         -->
+  <!-- Part of the Checkstyle distribution found at http://checkstyle.sourceforge.net -->
+  <!-- Usage (generates checkstyle_report.html):                                      -->
+  <!--    <checkstyle failonviolation="false" config="${check.config}">               -->
+  <!--      <fileset dir="${src.dir}" includes="**/*.java"/>                          -->
+  <!--      <formatter type="xml" toFile="${doc.dir}/checkstyle_report.xml"/>         -->
+  <!--    </checkstyle>                                                               -->
+  <!--    <style basedir="${doc.dir}" destdir="${doc.dir}"                            -->
+  <!--            includes="checkstyle_report.xml"                                    -->
+  <!--            style="${doc.dir}/checkstyle-noframes.xsl"/>                        -->
+
+  <xsl:template match="checkstyle">
+    <html>
+      <head>
+        <style type="text/css">
+          .bannercell {
+          border: 0px;
+          padding: 0px;
+          }
+          body {
+          margin-left: 10;
+          margin-right: 10;
+          font:normal 80% arial,helvetica,sanserif;
+          background-color:#FFFFFF;
+          color:#000000;
+          }
+          .a td {
+          background: #efefef;
+          }
+          .b td {
+          background: #fff;
+          }
+          th, td {
+          text-align: left;
+          vertical-align: top;
+          }
+          th {
+          font-weight:bold;
+          background: #ccc;
+          color: black;
+          }
+          table, th, td {
+          font-size:100%;
+          border: none
+          }
+          table.log tr td, tr th {
+
+          }
+          h2 {
+          font-weight:bold;
+          font-size:140%;
+          margin-bottom: 5;
+          }
+          h3 {
+          font-size:100%;
+          font-weight:bold;
+          background: #525D76;
+          color: white;
+          text-decoration: none;
+          padding: 5px;
+          margin-right: 2px;
+          margin-left: 2px;
+          margin-bottom: 0;
+          }
+        </style>
+      </head>
+      <body>
+        <a name="top"></a>
+        <!-- jakarta logo -->
+        <table border="0" cellpadding="0" cellspacing="0" width="100%">
+          <tr>
+            <td class="bannercell" rowspan="2">
+              <!--a
+              href="http://jakarta.apache.org/">
+          <img src="http://jakarta.apache.org/images/jakarta-logo.gif" alt="http://jakarta.apache.org"
+              align="left" border="0"/>
+          </a-->
+            </td>
+            <td class="text-align:right">
+              <h2>CheckStyle Audit</h2>
+            </td>
+          </tr>
+          <tr>
+            <td class="text-align:right">Designed for use with <a
+                href='http://checkstyle.sourceforge.net/'>CheckStyle</a>.</td>
+          </tr>
+        </table>
+        <hr size="1" />
+
+        <!-- Summary part -->
+        <xsl:apply-templates select="." mode="summary" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- Package List part -->
+        <xsl:apply-templates select="." mode="filelist" />
+        <hr size="1" width="100%" align="left" />
+
+        <!-- For each package create its part -->
+        <xsl:for-each select="file">
+          <xsl:sort select="@name" />
+			  <xsl:apply-templates select="." />
+			  <p />
+			  <p />
+        </xsl:for-each>
+        <hr size="1" width="100%" align="left" />
+
+
+      </body>
+    </html>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="filelist">
+    <h3>Files</h3>
+		<table class="log" border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Name</th>
+        <th>Errors</th>
+      </tr>
+      <xsl:for-each select="file">
+        <xsl:sort select="@name" />
+				<xsl:variable name="errorCount" select="count(error)" />				
+				<tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <a href="#f-{@name}">
+              <xsl:value-of select="@name" />
+            </a>
+          </td>
+          <td>
+            <xsl:value-of select="$errorCount" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+  </xsl:template>
+
+
+  <xsl:template match="file">
+    <a name="f-{@name}"></a>
+    <h3>File <xsl:value-of select="@name" /></h3>
+    
+    <table class="log"
+      border="0" cellpadding="5" cellspacing="2" width="100%">
+      <tr>
+        <th>Error Description</th>
+        <th>Line</th>
+      </tr>
+      <xsl:for-each select="error">
+        <tr>
+          <xsl:call-template name="alternated-row" />
+          <td>
+            <xsl:value-of select="@message" />
+          </td>
+          <td>
+            <xsl:value-of select="@line" />
+          </td>
+        </tr>
+      </xsl:for-each>
+    </table>
+    <a
+      href="#top">Back to top</a>
+  </xsl:template>
+
+
+  <xsl:template match="checkstyle" mode="summary">
+    <h3>Summary</h3>
+		<xsl:variable name="fileCount" select="count(file)" />
+		<xsl:variable
+      name="errorCount" select="count(file/error)" />
+		<table class="log" border="0" cellpadding="5"
+      cellspacing="2" width="100%">
+      <tr>
+        <th>Files</th>
+        <th>Errors</th>
+      </tr>
+      <tr>
+        <xsl:call-template name="alternated-row" />
+        <td>
+          <xsl:value-of select="$fileCount" />
+        </td>
+        <td>
+          <xsl:value-of select="$errorCount" />
+        </td>
+      </tr>
+    </table>
+  </xsl:template>
+
+  <xsl:template name="alternated-row">
+    <xsl:attribute name="class">
+      <xsl:if test="position() mod 2 = 1">a</xsl:if>
+      <xsl:if test="position() mod 2 = 0">b</xsl:if>
+    </xsl:attribute>
+  </xsl:template>
+</xsl:stylesheet>
\ No newline at end of file
diff --git a/contrib/checkstyle/test/resources/non-compatible/src/blocks/ArrayTrailingComma.java b/contrib/checkstyle/test/resources/non-compatible/src/blocks/ArrayTrailingComma.java
new file mode 100644
index 00000000000..eef26be6246
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/src/blocks/ArrayTrailingComma.java
@@ -0,0 +1,39 @@
+package blocks;
+
+// https://checkstyle.org/checks/blocks/avoidnestedblocks.html#ArrayTrailingComma
+public class ArrayTrailingComma {
+
+    public class Example1 {
+        int[] numbers = {1, 2, 3};
+        boolean[] bools = {
+            true,
+            true,
+            false  // violation
+        };
+
+        String[][] text = {{},{},};
+
+        double[][] decimals = {
+            {0.5, 2.3, 1.1,},
+            {1.7, 1.9, 0.6},
+            {0.8, 7.4, 6.5}  // violation
+        };
+
+        char[] chars = {'a', 'b', 'c'
+        };
+
+        String[] letters = {
+            "a", "b", "c"};
+
+        int[] a1 = new int[]{
+            1,
+            2
+            ,
+        };
+
+        int[] a2 = new int[]{
+            1,
+            2
+            ,};
+    }
+}
diff --git a/contrib/checkstyle/test/resources/non-compatible/src/coding/EmptyStatement.java b/contrib/checkstyle/test/resources/non-compatible/src/coding/EmptyStatement.java
new file mode 100644
index 00000000000..6937cd0bcaa
--- /dev/null
+++ b/contrib/checkstyle/test/resources/non-compatible/src/coding/EmptyStatement.java
@@ -0,0 +1,17 @@
+package coding;
+
+// https://checkstyle.org/checks/coding/emptystatement.html#EmptyStatement
+public class EmptyStatement {
+
+    public class Example1 {
+        public void foo() {
+            int i = 5;
+            if(i > 3); // violation
+            i++;
+            for (i = 0; i < 5; i++); // violation
+            i++;
+            while (i > 10)
+                i++;
+        }
+    }
+}
diff --git a/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleModuleTest.scala b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleModuleTest.scala
new file mode 100644
index 00000000000..162e1562f57
--- /dev/null
+++ b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleModuleTest.scala
@@ -0,0 +1,208 @@
+package mill
+package contrib.checkstyle
+
+import mainargs.Leftover
+import mill.scalalib.{JavaModule, ScalaModule}
+import mill.testkit.{TestBaseModule, UnitTester}
+import utest._
+
+object CheckstyleModuleTest extends TestSuite {
+
+  def tests: Tests = Tests {
+
+    val resources: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+
+    // violations (for version 10.18.1) in "non-compatible" module
+    val violations: Seq[String] =
+      Seq.fill(2)("Array should contain trailing comma") ++
+        Seq.fill(2)("Empty statement")
+
+    test("arguments") {
+
+      test("check") {
+
+        intercept[RuntimeException](
+          testJava(resources / "non-compatible", check = true)
+        )
+      }
+
+      test("stdout") {
+
+        assert(
+          testJava(resources / "non-compatible", violations = violations, stdout = true)
+        )
+      }
+
+      test("sources") {
+
+        assert(
+          testJava(
+            resources / "non-compatible",
+            violations = violations.take(2),
+            sources = Seq("src/blocks")
+          ),
+          testJava(
+            resources / "non-compatible",
+            violations = violations.take(2) ++ violations.take(2),
+            sources = Seq("src/blocks", "src/blocks/ArrayTrailingComma.java")
+          ),
+          testJava(
+            resources / "non-compatible",
+            violations = violations,
+            sources = Seq("src/blocks", "src/coding")
+          )
+        )
+
+        intercept[UnsupportedOperationException](
+          testJava(resources / "non-compatible", sources = Seq("hope/this/path/does/not/exist"))
+        )
+      }
+    }
+
+    test("settings") {
+
+      test("format") {
+
+        assert(
+          testJava(resources / "non-compatible", "plain", violations = violations),
+          testJava(resources / "non-compatible", "sarif", violations = violations),
+          testJava(resources / "non-compatible", "xml", violations = violations),
+          testJava(resources / "compatible-java", "plain"),
+          testJava(resources / "compatible-java", "sarif"),
+          testJava(resources / "compatible-java", "xml"),
+          testScala(resources / "compatible-scala", "plain"),
+          testScala(resources / "compatible-scala", "sarif"),
+          testScala(resources / "compatible-scala", "xml")
+        )
+      }
+
+      test("options") {
+
+        assert(
+          testJava(resources / "compatible-java", options = Seq("-d"))
+        )
+      }
+
+      test("version") {
+
+        assert(
+          testJava(resources / "compatible-java", "plain", "6.3"),
+          testJava(resources / "compatible-java", "sarif", "8.43"),
+          testJava(resources / "compatible-java", "xml", "6.3")
+        )
+
+        intercept[UnsupportedOperationException](
+          testJava(resources / "compatible-java", "sarif", "8.42")
+        )
+      }
+    }
+
+    test("limitations") {
+
+      test("incompatible version generates report with unexpected violation") {
+        assert(
+          testJava(
+            resources / "compatible-java",
+            "plain",
+            "6.2",
+            violations = Seq("File not found")
+          ),
+          testJava(
+            resources / "compatible-java",
+            "xml",
+            "6.2",
+            violations = Seq("File not found")
+          )
+        )
+      }
+
+      test("cannot set options for legacy version") {
+        intercept[UnsupportedOperationException](
+          testJava(resources / "compatible-java", version = "6.3", options = Seq("-d"))
+        )
+      }
+    }
+  }
+
+  def testJava(
+      modulePath: os.Path,
+      format: String = "xml",
+      version: String = "10.18.1",
+      options: Seq[String] = Nil,
+      violations: Seq[String] = Seq.empty,
+      check: Boolean = false,
+      stdout: Boolean = false,
+      sources: Seq[String] = Seq.empty
+  ): Boolean = {
+
+    object module extends TestBaseModule with JavaModule with CheckstyleModule {
+      override def checkstyleFormat: T[String] = format
+      override def checkstyleOptions: T[Seq[String]] = options
+      override def checkstyleVersion: T[String] = version
+    }
+
+    testModule(
+      module,
+      modulePath,
+      violations,
+      CheckstyleArgs(check, stdout, Leftover(sources: _*))
+    )
+  }
+
+  def testScala(
+      modulePath: os.Path,
+      format: String = "xml",
+      version: String = "10.18.1",
+      options: Seq[String] = Nil,
+      violations: Seq[String] = Seq.empty,
+      check: Boolean = false,
+      stdout: Boolean = false,
+      sources: Seq[String] = Seq.empty
+  ): Boolean = {
+
+    object module extends TestBaseModule with ScalaModule with CheckstyleModule {
+      override def checkstyleFormat: T[String] = format
+      override def checkstyleOptions: T[Seq[String]] = options
+      override def checkstyleVersion: T[String] = version
+      override def scalaVersion: T[String] = sys.props("MILL_SCALA_2_13_VERSION")
+    }
+
+    testModule(
+      module,
+      modulePath,
+      violations,
+      CheckstyleArgs(check, stdout, Leftover(sources: _*))
+    )
+  }
+
+  def testModule(
+      module: TestBaseModule with CheckstyleModule,
+      modulePath: os.Path,
+      violations: Seq[String],
+      args: CheckstyleArgs
+  ): Boolean = {
+    val eval = UnitTester(module, modulePath)
+
+    eval(module.checkstyle(args)).fold(
+      {
+        case api.Result.Exception(cause, _) => throw cause
+        case failure => throw failure
+      },
+      numViolations => {
+
+        numViolations.value == violations.length && {
+
+          val Right(report) = eval(module.checkstyleOutput)
+
+          if (os.exists(report.value.path))
+            violations.isEmpty || {
+              val lines = os.read.lines(report.value.path)
+              violations.forall(violation => lines.exists(_.contains(violation)))
+            }
+          else
+            args.stdout
+        }
+      }
+    )
+  }
+}
diff --git a/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleXsltModuleTest.scala b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleXsltModuleTest.scala
new file mode 100644
index 00000000000..b869d4a084b
--- /dev/null
+++ b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleXsltModuleTest.scala
@@ -0,0 +1,63 @@
+package mill
+package contrib.checkstyle
+
+import mainargs.Leftover
+import mill.scalalib.{JavaModule, ScalaModule}
+import mill.testkit.{TestBaseModule, UnitTester}
+import utest._
+
+object CheckstyleXsltModuleTest extends TestSuite {
+
+  def tests: Tests = Tests {
+
+    val resources: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+
+    test("checkstyle generates XSLT output reports") {
+
+      assert(
+        testJava(resources / "non-compatible"),
+        testScala(resources / "compatible-scala")
+      )
+    }
+
+    test("checkstyle succeeds when no XSLT files are found") {
+
+      assert(
+        testJava(resources / "compatible-java")
+      )
+    }
+  }
+
+  def testJava(modulePath: os.Path): Boolean = {
+
+    object module extends TestBaseModule with JavaModule with CheckstyleXsltModule
+
+    testModule(module, modulePath)
+  }
+
+  def testScala(modulePath: os.Path): Boolean = {
+
+    object module extends TestBaseModule with ScalaModule with CheckstyleXsltModule {
+      override def scalaVersion: T[String] = sys.props("MILL_SCALA_2_13_VERSION")
+    }
+
+    testModule(module, modulePath)
+  }
+
+  def testModule(module: TestBaseModule with CheckstyleXsltModule, modulePath: os.Path): Boolean = {
+    val eval = UnitTester(module, modulePath)
+
+    eval(module.checkstyle(CheckstyleArgs(sources = Leftover()))).fold(
+      {
+        case api.Result.Exception(cause, _) => throw cause
+        case failure => throw failure
+      },
+      _ => {
+
+        val Right(reports) = eval(module.checkstyleXsltReports)
+
+        reports.value.forall(report => os.exists(report.output.path))
+      }
+    )
+  }
+}
diff --git a/contrib/package.mill b/contrib/package.mill
index 3c5ee5bda6b..9dd33ac0bb7 100644
--- a/contrib/package.mill
+++ b/contrib/package.mill
@@ -235,4 +235,9 @@ object `package` extends RootModule {
     def buildInfoObjectName = "BuildInfo"
     def buildInfoMembers = Seq(BuildInfo.Value("errorProneVersion", Deps.RuntimeDeps.errorProneCore.version))
   }
+
+  object checkstyle extends ContribModule {
+    def compileModuleDeps = Seq(build.scalalib)
+    def testModuleDeps = super.testModuleDeps ++ Seq(build.scalalib)
+  }
 }
diff --git a/main/util/src/mill/util/Jvm.scala b/main/util/src/mill/util/Jvm.scala
index b026adabed8..ed39e68613d 100644
--- a/main/util/src/mill/util/Jvm.scala
+++ b/main/util/src/mill/util/Jvm.scala
@@ -24,7 +24,8 @@ object Jvm extends CoursierSupport {
       envArgs: Map[String, String] = Map.empty,
       mainArgs: Seq[String] = Seq.empty,
       workingDir: os.Path = null,
-      streamOut: Boolean = true
+      streamOut: Boolean = true,
+      check: Boolean = true
   )(implicit ctx: Ctx): CommandResult = {
 
     val commandArgs =
@@ -36,7 +37,23 @@ object Jvm extends CoursierSupport {
     val workingDir1 = Option(workingDir).getOrElse(ctx.dest)
     os.makeDir.all(workingDir1)
 
-    os.proc(commandArgs).call(cwd = workingDir1, env = envArgs)
+    os.proc(commandArgs).call(cwd = workingDir1, env = envArgs, check = check)
+  }
+
+  /**
+   * Runs a JVM subprocess with the given configuration and returns a
+   * [[os.CommandResult]] with it's aggregated output and error streams
+   */
+  def callSubprocess(
+      mainClass: String,
+      classPath: Agg[os.Path],
+      jvmArgs: Seq[String],
+      envArgs: Map[String, String],
+      mainArgs: Seq[String],
+      workingDir: os.Path,
+      streamOut: Boolean
+  )(implicit ctx: Ctx): CommandResult = {
+    callSubprocess(mainClass, classPath, jvmArgs, envArgs, mainArgs, workingDir, streamOut, true)
   }
 
   /**