Merge pull request #11 from rsalvador/PMDASTClassLoader

Reuse PMDASMClassLoader instance across all compilation units analyzed.

pmd/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/ClassTypeResolver.java

@@ -134,7 +134,7 @@ public class ClassTypeResolver extends JavaParserVisitorAdapter {
 	}
 
 	public ClassTypeResolver(ClassLoader classLoader) {
-		pmdClassLoader = new PMDASMClassLoader(classLoader);
+		pmdClassLoader = PMDASMClassLoader.getInstance(classLoader);
 	}
 
 	// FUTURE ASTCompilationUnit should not be a TypeNode.  Clean this up accordingly.

pmd/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/PMDASMClassLoader.java

@@ -30,16 +30,32 @@ import org.objectweb.asm.ClassReader;
  * then the resource foo/Bar.class will not exist, too.
  */
 public class PMDASMClassLoader extends ClassLoader {
+    
+    private static PMDASMClassLoader cachedPMDASMClassLoader;
+    private static ClassLoader cachedClassLoader;
+    
+    /**
+     * A new PMDASMClassLoader is created for each compilation unit, this method allows to reuse the same
+     * PMDASMClassLoader across all the compilation units.
+     */
+    public static synchronized PMDASMClassLoader getInstance(ClassLoader parent) {
+        if (parent == cachedClassLoader) return cachedPMDASMClassLoader;
+        cachedClassLoader = parent;
+        cachedPMDASMClassLoader = new PMDASMClassLoader(parent);
+        return cachedPMDASMClassLoader;
+    }
+    
+    //
 
-    public PMDASMClassLoader(ClassLoader parent) {
+    private PMDASMClassLoader(ClassLoader parent) {
     	super(parent);
     }
 
     /** Caches the names of the classes that we can't load or that don't exist. */
-    private Set<String> dontBother = Collections.synchronizedSet(new HashSet<String>());
+    private final Set<String> dontBother = new HashSet<String>();
 
     @Override
-    public Class<?> loadClass(String name) throws ClassNotFoundException {
+    public synchronized Class<?> loadClass(String name) throws ClassNotFoundException {
 	if (dontBother.contains(name)) {
 	    throw new ClassNotFoundException(name);
 	}

pmd/src/test/java/net/sourceforge/pmd/typeresolution/PMDASMClassLoaderTest.java

@@ -17,7 +17,7 @@ public class PMDASMClassLoaderTest {
     
     @Before
     public void setUp() throws Exception {
-        cl = new PMDASMClassLoader(getClass().getClassLoader());
+        cl = PMDASMClassLoader.getInstance(getClass().getClassLoader());
     }
 
     /**
@@ -78,7 +78,7 @@ public class PMDASMClassLoaderTest {
     @Test
     public void testCachingOfNotFoundClasses() throws Exception {
 	MockedClassLoader mockedClassloader = new MockedClassLoader();
-	PMDASMClassLoader cl = new PMDASMClassLoader(mockedClassloader);
+	PMDASMClassLoader cl = PMDASMClassLoader.getInstance(mockedClassloader);
 	String notExistingClassname = "that.clazz.doesnot.Exist";
 	try {
 	    cl.loadClass(notExistingClassname);
@@ -116,7 +116,7 @@ public class PMDASMClassLoaderTest {
     @Test
     public void testCachingMemoryConsumption() throws Exception {
 	MockedClassLoader mockedClassLoader = new MockedClassLoader();
-	PMDASMClassLoader cl = new PMDASMClassLoader(mockedClassLoader);
+	PMDASMClassLoader cl = PMDASMClassLoader.getInstance(mockedClassLoader);
 
 	Runtime runtime = Runtime.getRuntime();
 	System.gc();