Provides an Ant Class loader.

This class loader allows a Java task to be run with a separate classpath
without requiring a new java instance to be created.


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@267798 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/AntClassLoader.java

@@ -0,0 +1,226 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 1999 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant;
+
+import java.util.*;
+import java.util.zip.*;
+import java.io.*;
+
+/**
+ * Used to load classes within ant with a different claspath from that used to start ant.
+ * Note that it is possible to force a class into this loader even when that class is on the
+ * system classpath by using the forceLoadClass method. Any subsequent classes loaded by that
+ * class will then use this loader rather than the system class loader.
+ *
+ * @author Conor MacNeill
+ */
+public class AntClassLoader  extends ClassLoader {
+    private Path classpath;
+    
+    private Project project;
+
+    private Vector components = null;
+    
+    public AntClassLoader(Project project, Path classpath) {
+        this.project = project;
+        this.classpath = classpath;
+    }
+
+    /**
+     * Set up this classloader for the first time. 
+     */
+    private void setup() {
+        // We iterate through the class path, resolving each element. 
+        components = new Vector();
+        
+        String[] pathElements = classpath.list();
+        for (int i = 0; i < pathElements.length; ++i) {
+            File element = project.resolveFile(pathElements[i]);
+            components.addElement(element);
+        }
+    }
+
+    /**
+     * Load a class through this class loader even if that class is available on the
+     * system classpath.
+     */
+    public Class forceLoadClass(String classname) throws ClassNotFoundException {
+        Class theClass = findLoadedClass(classname);
+
+        if (theClass == null) {
+            theClass = findClass(classname);
+        }
+        
+        return theClass;
+    }
+
+    public InputStream getResourceAsStream(String name) {
+        if (components == null) {
+            // we haven't set up the list of directories and jars yet.
+            setup();
+        }
+
+        // we need to search the components of the path to see if we can find the 
+        // class we want. 
+        InputStream stream = null;
+
+        for (Enumeration e = components.elements(); e.hasMoreElements() && stream == null; ) {
+            File pathComponent = (File)e.nextElement();
+            stream = getResourceStream(pathComponent, name);
+        }
+
+        return stream;
+    }
+
+    private InputStream getResourceStream(File file, String resourceName) {
+        try {
+            if (file.isDirectory()) {
+                File resource = new File(file, resourceName); 
+                if (resource.exists()) {   
+                    return new FileInputStream(resource);
+                }
+            }
+            else {
+                ZipFile zipFile = new ZipFile(file);
+        
+                ZipEntry entry = zipFile.getEntry(resourceName);
+                if (entry != null) {
+                    return zipFile.getInputStream(entry);
+                }
+            }
+        }
+        catch (Exception e) {
+            e.printStackTrace();
+        }
+        
+        return null;   
+    }
+
+    protected Class loadClass(String classname, boolean resolve) throws ClassNotFoundException {
+        
+        Class theClass = findLoadedClass(classname);
+        if (theClass == null) {
+            try {
+                theClass = findSystemClass(classname);
+            }
+            catch (ClassNotFoundException cnfe) {
+                theClass = findClass(classname);
+            }
+        }
+            
+        if (resolve) {
+            resolveClass(theClass);
+        }
+        
+        return theClass;
+    }
+
+    private String getClassFilename(String classname) {
+        return classname.replace('.', '/') + ".class";
+    }
+
+    
+    private Class getClassFromStream(InputStream stream, String classname) 
+                throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        int bytesRead = -1;
+        byte[] buffer = new byte[1024];
+        
+        while ((bytesRead = stream.read(buffer, 0, 1024)) != -1) {
+            baos.write(buffer, 0, bytesRead);
+        }
+        
+        byte[] classData = baos.toByteArray();
+
+        return defineClass(classname, classData, 0, classData.length); 
+    }
+
+
+    public Class findClass(String name) throws ClassNotFoundException {
+        if (components == null) {
+            // we haven't set up the list of directories and jars yet.
+            setup();
+        }
+
+        // we need to search the components of the path to see if we can find the 
+        // class we want. 
+        InputStream stream = null;
+        String classFilename = getClassFilename(name);
+        try {
+            for (Enumeration e = components.elements(); e.hasMoreElements() && stream == null; ) {
+                File pathComponent = (File)e.nextElement();
+                stream = getResourceStream(pathComponent, classFilename);
+            }
+        
+            if (stream == null) {
+                throw new ClassNotFoundException();
+            }
+                
+            return getClassFromStream(stream, name);
+        }
+        catch (IOException ioe) {
+            ioe.printStackTrace();
+            throw new ClassNotFoundException();
+        }
+        finally {
+            try {
+                if (stream != null) {
+                    stream.close();
+                }
+            }
+            catch (IOException e) {}
+        }
+    }
+}

src/main/org/apache/tools/ant/taskdefs/Java.java

@@ -188,8 +188,16 @@ public class Java extends Exec {
      */
     protected void run(String classname, Vector args) throws BuildException {
         try {
+            Class c = null;
+            if (classpath == null) {
+                c = Class.forName(classname);
+            } 
+            else {
+                AntClassLoader loader = new AntClassLoader(project, classpath);
+                c = loader.forceLoadClass(classname);
+            }
+        
             Class[] param = { Class.forName("[Ljava.lang.String;") };
-            Class c = Class.forName(classname);
             Method main = c.getMethod("main", param);
             Object[] a = { array(args) };
             main.invoke(null, a);