Review validation of configuration properties and associated error messages

[brenuart]

Rules:

• Property must be validated eagerly by the corresponding setter method. An IllegalArgumentException should be thrown when the validation fails. A NullPointerException is currently thrown in most cases for not-null properties - an IllegalStateException should be used instead for consistency.

• The exception message often reports the name of the property which is not required. When Joran fails to set a property it already builds an error message itself reporting which property failed. For example:

10:15:07,901 |-WARN in ch.qos.logback.core.joran.util.PropertySetter@1ffe63b9 - Failed to set property [encoding] to value "foo".  ch.qos.logback.core.util.PropertySetterException: java.lang.reflect.InvocationTargetException
	at ch.qos.logback.core.util.PropertySetterException: java.lang.reflect.InvocationTargetException
	at 	at ch.qos.logback.core.joran.util.PropertySetter.setProperty(PropertySetter.java:133)
	at 	at ch.qos.logback.core.joran.util.PropertySetter.setProperty(PropertySetter.java:98)
...
Caused by: java.lang.IllegalArgumentException: Unknown encoding foo
	at 	at net.logstash.logback.composite.CompositeJsonFormatter.setEncoding(CompositeJsonFormatter.java:337)
	at 	at net.logstash.logback.encoder.CompositeJsonEncoder.setEncoding(CompositeJsonEncoder.java:234)
	at 	... 25 common frames omitted

Adding the name of the property in the exception message requires to keep the error message in sync with the name of the corresponding setter method - this may fail in case of refactoring.

• It may happen however the exception message must refer to one or more properties by their name. For instance:

Property [foo] cannot be used when property [bar] is set to "value".

In this case, property names must be enclosed between brackets ([...]) to follow the same Logback conventions.

Note: these rules apply to the validation of configuration properties. Other methods not directly used by Joran to set a property are free to use other conventions.