Require Java Version

This rule enforces certain Java JDK versions. The rule uses the Enforcer version range syntax to define allowed versions.

The following parameters are supported by this rule:

• message - an optional message to the user if the rule fails.
• version - range of allowed JDKs.
• display - flag to display the normalized JDK version.

  For JDK 1.8 you can also use simple 8 as version - it will be internally changed to 1.8

The JDK version is retrieved and the following processing occurs before being checked:

1. Drop all non-numeric characters preceding the first number. (build 1.5.0_07-b03 becomes 1.5.0_07-b03)
2. Replace all '_' and '-' with '.' (1.5.0_07-b03 becomes 1.5.0.07.b03)
3. Remove all non digit characters "[^0-9] and convert each section using Integer.parseInt() (1.5.0_07-b03 becomes 1.5.0.7.3)
4. Split the string on '.' and take the first 3 sections, separated by '.' and add '-' followed by the fourth section (1.5.0.7.3 becomes 1.5.0-7)

This preprocessing normalizes various JDK version strings into a standard x.y.z-b version number. Your required range should therefore use the x.y.z-b format for comparison. There is an easy way to see how your current JDK string will be normalized, you can enable display option.

Sample Plugin Configuration:

<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>3.5.0</version>
        <executions>
          <execution>
            <id>enforce-java</id>
            <goals>
              <goal>enforce</goal>
            </goals>
            <configuration>
              <rules>
                <requireJavaVersion>
                  <version>1.6.0</version>
                </requireJavaVersion>
              </rules>    
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
  [...]
</project>

If you would like to enforce a certain vendor string for the JDK, you would use the RequireJavaVendor rule