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Chapter 8. Annotation Processor (EXPERIMENTAL)

8.1. Prerequisites
8.2. Features
8.3. Options
8.4. Using the Annotation Processor
8.4.1. Command line builds
8.4.2. IDE builds
8.5. Known issues

Have you ever caught yourself by unintentionally doing things like

Then the Hibernate Validator Annotation Processor is the right thing for you. It helps preventing such mistakes by plugging into the build process and raising compilation errors whenever constraint annotations are incorrectly used.


A first version of the Hibernate Validator Annotation Processor is part of Hibernate Validator since release 4.1. It is currently still under development and should therefore be considered as an experimental feature. Some known issues can be found at the end of this chapter. In case any problems arise when using the processor feel free to ask for help at the forum or create an issue within JIRA.

The Hibernate Validator Annotation Processor is based on the "Pluggable Annotation Processing API" as defined by JSR 269. This API is part of the Java Platform since Java 6. So be sure to use this or a later version.

As of Hibernate Validator 4.1 the Hibernate Validator Annotation Processor checks that:

The behavior of the Hibernate Validator Annotation Processor can be controlled using the processor options listed in tableTable 8.1, “Hibernate Validator Annotation Processor options”:

This section shows in detail how to integrate the Hibernate Validator Annotation Processor into command line builds (javac, Ant, Maven) as well as IDE-based builds (Eclipse, IntelliJ IDEA, NetBeans).

When compiling on the command line using javac, specify the following JARs using the "processorpath" option:

  • validation-api-1.0.0.GA.jar

  • hibernate-validator-annotation-processor-4.1.0.Final.jar

The following listing shows an example. The processor will be detected automatically by the compiler and invoked during compilation.

There are several options for integrating the annotation processor with Apache Maven. Generally it is sufficient to add the Hibernate Validator Annotation Processor as dependency to your project:

The processor will then be executed automatically by the compiler. This basically works, but comes with the disadavantage that in some cases messages from the annotation processor are not displayed (see MCOMPILER-66).

Another option is using the Maven Annotation Plugin. At the time of this writing the plugin is not yet available in any of the well-known repositories. Therefore you have to add the project's own repository to your settings.xml or pom.xml:

Now disable the standard annotation processing performed by the compiler plugin and configure the annotation plugin by specifying an execution and adding the Hibernate Validator Annotation Processor as plugin dependency (that way the AP is not visible on the project's actual classpath):

Do the following to use the annotation processor within the Eclipse IDE:

  • Right-click your project, choose "Properties"

  • Go to "Java Compiler" and make sure, that "Compiler compliance level" is set to "1.6". Otherwise the processor won't be activated

  • Go to "Java Compiler - Annotation Processing" and choose "Enable annotation processing"

  • Go to "Java Compiler - Annotation Processing - Factory Path" and add the following JARs:

    • validation-api-1.0.0.GA.jar

    • hibernate-validator-annotation-processor-4.1.0.Final.jar

  • Confirm the workspace rebuild

You now should see any annotation problems as regular error markers within the editor and in the "Problem" view:

The following steps must be followed to use the annotation processor within IntelliJ IDEA (version 9 and above):

  • Go to "File", then "Settings",

  • Expand the node "Compiler", then "Annotation Processors"

  • Choose "Enable annotation processing" and enter the following as "Processor path": /path/to/validation-api-1.0.0.GA.jar:/path/to/hibernate-validator-annotation-processor-4.1.0.Final.jar

  • Add the processor's fully qualified name org.hibernate.validator.ap.ConstraintValidationProcessor to the "Annotation Processors" list

  • If applicable add you module to the "Processed Modules" list

Rebuilding your project then should show any erronous constraint annotations:

Starting with version 6.9, also the NetBeans IDE supports using annotation processors within the IDE build. To do so, do the following:

  • Right-click your project, choose "Properties"

  • Go to "Libraries", tab "Processor", and add the following two JARs:

    • validation-api-1.0.0.GA.jar

    • hibernate-validator-annotation-processor-4.1.0.Final.jar

  • Go to "Build - Compiling", select "Enable Annotation Processing" and "Enable Annotation Processing in Editor". Add the annotation processor by specifying its fully qualified name org.hibernate.validator.ap.ConstraintValidationProcessor

Any constraint annotation problems will then be marked directly within the editor:

The following known issues exist as of May 2010:

  • HV-308: Additional validators registered for a constraint using XML are not evaluated by the annotation processor.

  • Sometimes custom constraints can't be properly evaluated when using the processor within Eclipse. Cleaning the project can help in these situations. This seems to be an issue with the Eclipse JSR 269 API implementation, but further investigation is required here.