Add maven toolchains

README.md

@@ -15,7 +15,11 @@ Our latest source of PMD can be found on [GitHub]. Fork us!
 
 ### How to build PMD?
 
-Simply use maven in the top-level directory:
+You'll need to have a `~/.m2/toolchains.xml` file setup with jdk 1.6 (for pmd 5.3.x), jdk 1.7 (for pmd 5.4.x and pmd 5.5.x)
+and jdk 1.8 (for some features in pmd 5.5.x). See [maven toolchains](https://maven.apache.org/guides/mini/guide-using-toolchains.html).
+A example file can be found here: [example-toolchains.xml](https://github.com/pmd/pmd/blob/master/example-toolchains.xml).
+
+Use maven in the top-level directory:
 
     mvn clean package
 

example-toolchains.xml

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF8"?>
+<toolchains>
+  <!-- place this file in ${user.home}/.m2/toolchains.xml -->
+
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <version>1.6</version>
+    </provides>
+    <configuration>
+      <jdkHome>/path/to/jdk/1.6</jdkHome>
+    </configuration>
+  </toolchain>
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <version>1.7</version>
+    </provides>
+    <configuration>
+      <jdkHome>/path/to/jdk/1.7</jdkHome>
+    </configuration>
+  </toolchain>
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <version>1.8</version>
+    </provides>
+    <configuration>
+      <jdkHome>/path/to/jdk/1.8</jdkHome>
+    </configuration>
+  </toolchain>
+</toolchains>

pom.xml

@@ -387,6 +387,25 @@
                         <runOrder>alphabetical</runOrder>
                     </configuration>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-toolchains-plugin</artifactId>
+                    <version>1.1</version>
+                    <executions>
+                        <execution>
+                            <goals>
+                                <goal>toolchain</goal>
+                            </goals>
+                        </execution>
+                    </executions>
+                    <configuration>
+                        <toolchains>
+                            <jdk>
+                                <version>${java.version}</version>
+                            </jdk>
+                        </toolchains>
+                    </configuration>
+                </plugin>
                 <plugin>
                     <groupId>org.codehaus.mojo</groupId>
                     <artifactId>build-helper-maven-plugin</artifactId>
@@ -557,6 +576,10 @@
                     <suppressionsFile>${checkstyle.suppressionsFile}</suppressionsFile>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-toolchains-plugin</artifactId>
+            </plugin>
         </plugins>
     </build>
 
@@ -897,6 +920,31 @@
                 <module>pmd-scala</module>
             </modules>
         </profile>
+
+        <profile>
+          <id>travis</id>
+          <activation>
+            <!-- https://github.com/travis-ci/travis-ci/issues/2727 -->
+            <!-- http://docs.travis-ci.com/user/ci-environment/#Environment-variables -->
+            <!-- from: https://github.com/marschall/jdeps-maven-plugin/blob/master/pom.xml -->
+            <property>
+              <name>env.TRAVIS</name>
+              <value>true</value>
+            </property>
+          </activation>
+          <build>
+            <plugins>
+              <plugin>
+                <artifactId>maven-toolchains-plugin</artifactId>
+                <executions>
+                  <execution>
+                    <phase>none</phase>
+                  </execution>
+                </executions>
+              </plugin>
+            </plugins>
+          </build>
+        </profile>
     </profiles>
 
     <modules>