Mimic

A Mimic is a generated wrapper for an object with non-public fields. It offers type-safe accessors using Java reflection to get and set all object fields. This is useful to create custom serializers/deserializers for third-party classes or unit tests for example.

This repository contains a generic Annotation processor to create Mimics, and Maven and Gradle plugins for more comfort.

Maven plugin usage

<plugin>
	<groupId>dev.bodewig.mimic</groupId>
	<artifactId>mimic-maven-plugin</artifactId>
	<version>1.1.0</version>
	<executions>
		<execution>
			<goals>
				<goal>mimic</goal>
			</goals>
			<phase>generate-sources</phase><!-- default -->
			<configuration>
				<classes>
					<class>dev.bodewig.mimic.maven.test.MyTestClass</class>
				</classes>
				<outputDirectory>${project.build.directory}/generated-sources/mimic</outputDirectory><!-- default -->
				<packageName>dev.bodewig.mimic.maven.test.generated</packageName>
			</configuration>
		</execution>
	</executions>
</plugin>

Maven plugin configuration

Property	Default	Required	Description
classes		yes	List of fully qualified class names to create Mimics for. The classes must be loadable from the compile classpath.
outputDirectory	${project.build.directory}/generated-sources/mimic		Relative project path where the generated Mimics are written to. Will be added as additional compile source directory.
packageName		yes	Target package for the generated java classes

Gradle plugin usage (groovy)

Add the Mimic Annotation to your own class or configure third party classes via the plugin extension DSL. Each Mimic Annotation can be parameterized with a package name, the configured package name in the plugin extension is used as a fallback.

plugins {
	id 'dev.bodewig.mimic' version '1.1.0'
}
mimic {
	packageName = 'dev.bodewig.mimic.gradle.test.generated'
	classes = ['dev.bodewig.mimic.maven.test.MyTestClass']
}

If you use the dev.bodewig.mimic plugin, the Gradle Java plugin is applied automatically.

Gradle plugin configuration

Property	Description
classes	List of fully qualified class names to create Mimics for. The classes must be loadable from the compile classpath.
outputDirectory	Relative project path where the generated Mimics are written to. Will be added as a SourceSetDirectory to the main SourceSet.
packageName	The default target package for the generated java classes, fallback if no annotation with parameter is present

All properties are required, there are no defaults.

Annotation processor usage

Add the Mimic Annotation to your own class or configure third party classes via compileArgs. Each Mimic Annotation can be parameterized with a package name, the configured package name in the compileArgs is used as a fallback.

The annotation processor can be used with multiple build tools, e.g. with Maven:

<dependency>
	<groupId>dev.bodewig.mimic</groupId>
	<artifactId>mimic-annotation</artifactId>
	<version>1.1.0</version>
</dependency>
...
<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-compiler-plugin</artifactId>
	<configuration>
		<annotationProcessorPaths>
			<path>
				<groupId>dev.bodewig.mimic</groupId>
				<artifactId>mimic-annotation-processor</artifactId>
				<version>1.1.0</version>
			</path>
		</annotationProcessorPaths>
		<compilerArgs>
			<arg>-Amimic.packageName=dev.bodewig.mimic.annotation.test.generated.lang</arg>
			<arg>-Amimic.classes=my.test.class.One,my.test.class.Two</arg>
		</compilerArgs>
	</configuration>
</plugin>

Annotation processor configuration

CompilerArg	Description
mimic.classes	Comma-separated list of fully qualified class names to create Mimics for
mimic.packageName	The default target package for the generated java classes, fallback if no annotation with parameter is present

Example

public class MyTestClass {
  public int count = 1;
  private String name = "test";
}

MyTestClass has two fields, one public and one private.
This is the generated Mimic with getter and setter methods for both fields:

public class MyTestClassMimic {
  private final MyTestClass instance;

  public MyTestClassMimic(MyTestClass instance) {
    this.instance = instance;
  }

  public int getCount() {
    return instance.count;
  }

  public void setCount(int value) {
    instance.count = value;
  }

  public String getName() {
    try {
      Field f = MyTestClass.class.getDeclaredField("name");
      f.setAccessible(true);
      return (String) f.get(instance);
    } catch (NoSuchFieldException | IllegalAccessException e) {
      throw new RuntimeException(e);
    }
  }

  public void setName(String value) {
    try {
      Field f = MyTestClass.class.getDeclaredField("name");
      f.setAccessible(true);
      f.set(instance, value);
    } catch (NoSuchFieldException | IllegalAccessException e) {
      throw new RuntimeException(e);
    }
  }
}

Since count is a public field, reflection is not necessary and the Mimic offers type-safe reflective access to name.

MyTestClass orig = ...
System.out.println(orig.name); // not possible outside of MyTestClass!

MyTestClassMimic mimic = new MyTestClassMimic(orig);
System.out.println(mimic.getName()); // prints orig.name

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Run git config --add include.path ../.gitconfig to include the template config in your project config.