Maven Resources Plugin

http://maven.apache.org/plugins/maven-resources-plugin/examples/copy-resources.html

Maven Resources Plugin

The Resources Plugin handles the copying of project resources to the output directory. There are two different kinds of resources: main resources and test resources. The difference is that the main resources are the resources associated to the main source code while the test resources are associated to the test source code.

Thus, this allows the separation of resources for the main source code and its unit tests.

Starting with version 2.3 this plugin uses the Maven Filtering shared component for filtering resources.

Filtering

Variables can be included in your resources. These variables, denoted by the ${...} delimiters, can come from the system properties, your project properties, from your filter resources and from the command line.

For example, if we have a resource src/main/resources/hello.txt containing

Hello ${name}

And a POM like this

<project>
  ...
  <name>My Resources Plugin Practice Project</name>
  ...
  <build>
    ...
    <resources>
      <resource>
        <directory>src/main/resources</directory>
      </resource>
      ...
    </resources>
    ...
  </build>
  ...
</project>

Upon calling

mvn resources:resources

This will create a resource output in target/classes/hello.txt which contains exactly the same text.

Hello ${name}

However, if we add a <filtering> tag to our POM and set it to true like this:

      ...
      <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
      </resource>
      ...

Our target/classes/hello.txt after calling

mvn resources:resources

would be

Hello My Resources Plugin Practice Project

That's because the name variable was replaced by the value of the project's name (which was specified in the POM).

Moreover, we can also assign values through the command line using the "-D" option. For example, to change the value for the variable name to "world", we can simply invoke this command:

mvn resources:resources -Dname="world"

And the output in target/classes/hello.txt would be

Hello world

Furthermore, we are not limited to use pre-defined project variables. We can specify our own variables and their values in the <properties> element. For example, if we want to change the variable from "name" to "your.name", we can do so by adding a <your.name> element within the <properties> element.

<project>
  ...
  <properties>
    <your.name>world</your.name>
  </properties>
  ...
</project>

But to organize your project, you may want to put all your variables and their values in a separate file so that you will not have to rewrite your POM, or set their values all the time with every build. This can be done by adding a filter.

<project>
  ...
  <name>My Resources Plugin Practice Project</name>
  ...
  <build>
    ...
    <filters>
      <filter> [a filter property] </filter>
    </filters>
    ...
  </build>
  ...
</project>

For example, we can separate "your.name" from the POM by specifying a filter file my-filter-values.properties containing:

your.name = world

and adding that to our POM

    ...
    <filters>
      <filter>my-filter-values.properties</filter>
    </filters>
    ...

Warning: Do not filter files with binary content like images! This will most likely result in corrupt output. If you have both text files and binary files as resources, you need to declare two mutually exclusive resource sets. The first resource set defines the files to be filtered and the other resource set defines the files to copy unaltered as illustrated below:

<project>
  ...
  <build>
    ...
    <resources>
      <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
        <includes>
          <include>**/*.xml</include>
        </includes>
      </resource>
      <resource>
        <directory>src/main/resources</directory>
        <filtering>false</filtering>
        <excludes>
          <exclude>**/*.xml</exclude>
        </excludes>
      </resource>
      ...
    </resources>
    ...
  </build>
  ...
</project>