simplified a bit

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@15750 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/JDK.java

@@ -101,12 +101,7 @@ public final class JDK extends ToolInstallation implements NodeSpecific<JDK> {
     }
 
     public JDK forNode(Node node) {
-        String newHome = ToolLocationNodeProperty.getToolHome(node, this);
-        if (newHome != null) {
-            return new JDK(getName(), newHome);
-        } else {
-            return this;
-        }
+        return new JDK(getName(),ToolLocationNodeProperty.getToolHome(node, this));
     }
 
     /**

core/src/main/java/hudson/tasks/Ant.java

@@ -402,12 +402,7 @@ public class Ant extends Builder {
 		}
 
         public AntInstallation forNode(Node node) {
-            String newHome = ToolLocationNodeProperty.getToolHome(node, this);
-            if (newHome != null) {
-                return new AntInstallation(getName(), newHome);
-            } else {
-                return this;
-            }
+            return new AntInstallation(getName(),ToolLocationNodeProperty.getToolHome(node, this));
         }
 
         @Extension

core/src/main/java/hudson/tasks/Maven.java

@@ -429,12 +429,7 @@ public class Maven extends Builder {
 		}
 
         public MavenInstallation forNode(Node node) {
-            String newHome = ToolLocationNodeProperty.getToolHome(Computer.currentComputer().getNode(), this);
-            if (newHome != null) {
-                return new MavenInstallation(getName(), newHome);
-            } else {
-                return this;
-            }
+            return new MavenInstallation(getName(),ToolLocationNodeProperty.getToolHome(node,this));
         }
 
         @Extension

core/src/main/java/hudson/tools/ToolInstallation.java

@@ -27,9 +27,11 @@ package hudson.tools;
 import hudson.DescriptorExtensionList;
 import hudson.Extension;
 import hudson.ExtensionPoint;
+import hudson.EnvVars;
 import hudson.model.Describable;
 import hudson.model.EnvironmentSpecific;
 import hudson.model.Hudson;
+import hudson.model.Node;
 import hudson.slaves.NodeSpecific;
 
 import java.io.Serializable;
@@ -52,7 +54,9 @@ import java.io.Serializable;
  * </ul>
  *
  * <p>
- * Implementation of this class should consider implementing {@link NodeSpecific} and {@link EnvironmentSpecific}.
+ * Implementations of this class are strongly encouraged to also implement {@link NodeSpecific}
+ * (by using {@link ToolLocationNodeProperty#getToolHome(Node, ToolInstallation)}) and
+ * {@link EnvironmentSpecific} (by using {@link EnvVars#expand(String)}.)
  *
  * <p>
  * To contribute an extension point, put {@link Extension} on your {@link ToolDescriptor} class.

core/src/main/java/hudson/tools/ToolLocationNodeProperty.java

@@ -31,6 +31,7 @@ import hudson.model.Hudson;
 import hudson.model.Node;
 import hudson.slaves.NodeProperty;
 import hudson.slaves.NodePropertyDescriptor;
+import hudson.slaves.NodeSpecific;
 import org.kohsuke.stapler.DataBoundConstructor;
 
 import java.util.Arrays;
@@ -71,12 +72,22 @@ public class ToolLocationNodeProperty extends NodeProperty<Node> {
         return null;
     }
 
+    /**
+     * Checks if the location of the tool is overridden for the given node, and if so,
+     * return the node-specific home directory. Otherwise return {@code installation.getHome()}
+     *
+     * <p>
+     * This is the core logic behind {@link NodeSpecific#forNode(Node)} for {@link ToolInstallation}.
+     *
+     * @return
+     *      never null.
+     */
     public static String getToolHome(Node node, ToolInstallation installation) {
         ToolLocationNodeProperty property = node.getNodeProperties().get(ToolLocationNodeProperty.class);
         if (property != null) {
             return property.getHome(installation);
         }
-        return null;
+        return installation.getHome();
     }
 
     @Extension