Hamcrest Feature Matcher Generator


annotation-processors-2.0.1 (Jun 11, 2017)
Oct 19, 2014
Jun 11, 2017 (Retired)
Yandex QATools (yandex-qatools)
Vladislav Bauer (vbauer)
Kirill Merkushev (lanwen)
QATools CI (qatools-ci)
Max Dobler (maxdobler)
Dmitriy Shibaev (DarkFelex)
Yannik Hampe (yankee42)
Source code


Hamcrest Feature Matcher Generator for POJOs

Inspired by lot of dummy work to create matchers for fields in auto-generated beans to write POJO-based tests.

Generates Hamcrest's Feature Matchers for every field annotated with @GenerateMatcher annotation (ru.yandex.qatools.processors.matcher.gen.annotations.GenerateMatcher).

Useful for testing auto-generated unmarshalled beans with help of jsonschema2pojo + Gson or JAXB

Usage Guide

1. Add dependency from Maven Central

    <!-- 'provided' scope because this is only needed during compilation -->

2. Generate (or write) beans

@GenerateMatcher // works with class level annotations as every field with same annotation
public class Owner {
    private String email;
    private String uid;
    @DoNotGenerateMatcher // excludes field from generation of matchers for class level @GenerateMatcher annotation
    private String name;

    public String getEmail() {
        return email;

    public String getUid() {
        return uid;

Beans MUST have getters with named get[Field]() to generate working matchers

3. Compile

Run mvn clean compile


  • Can use any other annotation to process if override system property matcher.gen.annotations.
  • Can use multiply annotations comma-separated.

For example we have @Expose annotation (com.google.gson.annotations.Expose) by Gson and want to generate matchers for fields with such annotation.

  • Run compilation with
mvn clean compile -Dmatcher.gen.annotations=ru.yandex.qatools.processors.matcher.gen.annotations.GenerateMatcher,com.google.gson.annotations.Expose
  • Or put in classpath matchers.gen.properties with content

4. See generated matchers

You can find result in ${project.build.directory}/generated-sources/annotations/*.
For each class with such fields will be generated class *Matchers with public static methods looks like:

 * Matcher for {@link ru.yandex.qatools.beans.Owner#email}
public static org.hamcrest.Matcher<ru.yandex.qatools.beans.Owner> withEmail(org.hamcrest.Matcher<java.lang.String> matcher) {
    return new org.hamcrest.FeatureMatcher<ru.yandex.qatools.beans.Owner, java.lang.String>(matcher, "email", "email") {
        protected java.lang.String featureValueOf(ru.yandex.qatools.beans.Owner actual) {
            return actual.getEmail();

5. Use it in your tests!

assertThat(someOwner, withEmail(containsString("@"))); 

// OR combined: 

assertThat(someOwner, both(withEmail(containsString("@"))).and(withUid(is(uid))); 

How to produce matchers in test scope for JAXB generated classes

There are 2 ways:

  1. Generate as usually in separate module and just add as dependency in test scope
  2. Generate all classes as test sources.

Generating JAXB classes and matchers as test sources

  1. Add one more execution for maven-jaxb2-plugin:
          <!--bunch of plugins that can be different from original configuration-->
          <arg>-Xxew:instantiate lazy</arg>
          <arg>-Xequals</arg> <!--in tests it will be useful to have to strings, equals...-->
  1. If you want to add toString, equals etc methods, don't forget to add also dependency to test scope:
  1. Add dependency to annotaion processor to <scope>test</scope>
  2. Add matchers.gen.properties file to src/test/resources/ with content:

How to debug Annotation Processors

With remote debugger on maven build

  1. Run in shell export MAVEN_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8000,suspend=n"
  2. Run mvn clean compile
  3. Connect with remote debugger to port 8000

With Intellij IDEA

  1. Open "Maven Projects" view
  2. Disclose "Yandex QATools Annotation Processors" element
  3. Right-click on Maven phase "package"
  4. Click on "Debug 'annotation-processors'"

It will create a new launcher configuration which can be used to debug project.


Not supported: EmptyClass -> EmptyStaticNested -> StaticNestedWithFields