Maven doesn't use Java 7

Question

I want to package a maven-(multi)module, the parent POM includes:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>2.3.2</version>
  <configuration>
    <source>${maven.compiler.source}</source>
    <target>${maven.compiler.target}</target>
    <encoding>${project.build.sourceEncoding}</encoding>
  </configuration>
</plugin>

I'm using Java 1.7 and the properties are specified as follows:

<properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <maven.compiler.source>1.7</maven.compiler.source>
  <maven.compiler.target>1.7</maven.compiler.target>
  <slf4j.version>1.6.1</slf4j.version>
</properties>

The Maven version is 2.2.1:

johannes@luna:~/workspace/treetank/bundles/treetank-core$ mvn -version
Apache Maven 2.2.1 (rdebian-6)
Java version: 1.7.0
Java home: /usr/lib/jvm/jdk1.7.0/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux" version: "3.0.0-14-generic" arch: "amd64" Family: "unix"

I have no clue why it doesn't use Java version 1.7. When invoking mvn package I get the error (use -source 7 or higher to enable diamond operator) for instance. Do you know why it tries using 1.6?

The effective POM is:

  <plugin>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>2.3.2</version>
    <executions>
      <execution>
        <id>default-testCompile</id>
        <phase>test-compile</phase>
        <goals>
          <goal>testCompile</goal>
        </goals>
        <configuration>
          <source>1.7</source>
          <target>1.7</target>
          <encoding>UTF-8</encoding>
        </configuration>
      </execution>
      <execution>
        <id>default-compile</id>
        <phase>compile</phase>
        <goals>
          <goal>compile</goal>
        </goals>
        <configuration>
          <source>1.7</source>
          <target>1.7</target>
          <encoding>UTF-8</encoding>
        </configuration>
      </execution>
    </executions>
    <configuration>
      <source>1.7</source>
      <target>1.7</target>
      <encoding>UTF-8</encoding>
    </configuration>
  </plugin>

Answer 1

This may not work in maven 2.2.1, but with Maven 3.0.4, simply adding the two properties to the pom's properties enables Java 7 for me:

<properties>
  <maven.compiler.source>1.7</maven.compiler.source>
  <maven.compiler.target>1.7</maven.compiler.target>
</properties>

Answer 2

perfectly nice explanation on the compatibility issue of jdk 1.7 with maven 2.2.1 given by Mark Peters Maven "could not parse error message" (Java 7 + Maven 2)