feat(null): adding operators ISNULL and NOTNULL (#32)

* feat(isnull-operator): implement ISNULL operator

querydsl-postgrest/pom.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <parent>
         <groupId>fr.ouestfrance.querydsl</groupId>
@@ -13,7 +14,7 @@
         <dependency>
             <groupId>fr.ouestfrance.querydsl</groupId>
             <artifactId>querydsl</artifactId>
-            <version>1.2.0</version>
+            <version>1.3.0</version>
         </dependency>
     </dependencies>
 </project>

querydsl-postgrest/src/main/java/fr/ouestfrance/querydsl/postgrest/mappers/IsNullMapper.java

@@ -0,0 +1,18 @@
+package fr.ouestfrance.querydsl.postgrest.mappers;
+
+import fr.ouestfrance.querydsl.FilterOperation;
+import fr.ouestfrance.querydsl.postgrest.model.Filter;
+import fr.ouestfrance.querydsl.postgrest.model.impl.QueryFilter;
+
+public class IsNullMapper extends AbstractMapper {
+
+    @Override
+    public Filter getFilter(String field, Object value) {
+        return QueryFilter.of(field, Boolean.TRUE.equals(value) ? Operators.IS : Operators.IS_NOT, null);
+    }
+
+    @Override
+    public Class<? extends FilterOperation> operation() {
+        return FilterOperation.ISNULL.class;
+    }
+}

querydsl-postgrest/src/main/java/fr/ouestfrance/querydsl/postgrest/mappers/Operators.java

@@ -56,6 +56,10 @@ public final class Operators {
      * is operation
      */
     public static final String IS = "is";
+    /**
+     * is not operation
+     */
+    public static final String IS_NOT = "not.is";
     /**
      * Contains operation for JSON/Range datatype
      */

querydsl-postgrest/src/test/java/fr/ouestfrance/querydsl/postgrest/mappers/IsNullMapperTest.java

@@ -0,0 +1,30 @@
+package fr.ouestfrance.querydsl.postgrest.mappers;
+
+import fr.ouestfrance.querydsl.FilterOperation;
+import fr.ouestfrance.querydsl.model.SimpleFilter;
+import fr.ouestfrance.querydsl.postgrest.builders.QueryFilterVisitor;
+import fr.ouestfrance.querydsl.postgrest.model.Filter;
+import org.junit.jupiter.api.Test;
+
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+class IsNullMapperTest {
+
+    @Test
+    void shouldMapIsNull() {
+        IsNullMapper mapper = new IsNullMapper();
+        assertNotNull(mapper.operation());
+        Stream.of(Boolean.TRUE, Boolean.FALSE).forEach(value -> {
+            Filter result = mapper.map(new SimpleFilter("name", FilterOperation.ISNULL.class, false, null), value);
+            assertNotNull(result);
+            QueryFilterVisitor visitor = new QueryFilterVisitor();
+            result.accept(visitor);
+            assertNotNull(visitor.getValue());
+            assertEquals(Boolean.TRUE.equals(value) ? "is.null" : "not.is.null", visitor.getValue());
+        });
+
+    }
+}