编译器加载的AOP实现

public class MapClassLoader extends ClassLoader
{
    private Map<String, byte[]> classes;
    
    public MapClassLoader(Map<String, byte[]> classes)
    {
        this.classes = classes;
    }
    
    protected Class<?> findClass(String name)
        throws ClassNotFoundException
    {
        byte[] classBytes = classes.get(name);
        if (classBytes == null)
            throw new ClassNotFoundException(name);
        Class<?> cl = this.defineClass(name, classBytes, 0, classBytes.length);
        if (cl == null)
            throw new ClassNotFoundException(name);
        return cl;
    }
}

 

package compile;



public abstract class ButtonFrame extends JFrame
{
    private static final long serialVersionUID = 1L;
    
    protected JPanel panel;
    
    public static final int DEFAULT_WIDTH = 300;
    
    public static final int DEFAULT_HEIGHT = 200;
    
    protected JButton yellowButton;
    
    protected JButton blueButton;
    
    protected JButton redButton;
    
    public ButtonFrame()
    {
        this.setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
        panel = new JPanel();
        add(panel);
        yellowButton = new JButton("Yellow");
        blueButton = new JButton("Blue");
        redButton = new JButton("Red");
        
        panel.add(yellowButton);
        panel.add(blueButton);
        panel.add(redButton);
        addEventHandlers();
    }
    
    protected abstract void addEventHandlers();
}

 StringBuilderJavaSource 

//字符串源文件类，源文件类的重构
public class StringBuilderJavaSource extends SimpleJavaFileObject
{
    private StringBuilder code;
    
    public StringBuilderJavaSource(String name)
    {
        super(URI.create("string:////" + name.replace('.', '/') + Kind.SOURCE.extension), Kind.SOURCE);
        code = new StringBuilder();
    }
    
    public CharSequence getCharContent(boolean ignoreEncodingErrors)
    {
        return code;
    }
    
    public void append(String str)
    {
        code.append(str);
        code.append("\n");
    }
}

 

ByteArrayJavaClass

package compile;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;

import javax.tools.SimpleJavaFileObject;

//字节源文件构造
public class ByteArrayJavaClass extends SimpleJavaFileObject
{
    private ByteArrayOutputStream stream;
    
    protected ByteArrayJavaClass(String name)
    {
        super(URI.create("byte:///" + name), Kind.CLASS);
        this.stream = new ByteArrayOutputStream();
    }
    
    public OutputStream openOutputStream()
        throws IOException
    {
        return stream;
    }
    
    public byte[] getBytes()
    {
        return stream.toByteArray();
    }
    
}

 

action.properties文件内容   

  

yellowButton=panel.setBackground(java.awt.Color.YELLOW);   

blueButton=panel.setBackground(java.awt.Color.BLUE);   

redButton=panel.setBackground(java.awt.Color.RED);   

 

编译器测试类

public class CompilerTest
{
    public static void main(String[] args)
        throws IOException
    {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        final List<ByteArrayJavaClass> classFileObjects = new ArrayList<ByteArrayJavaClass>();
        DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
        JavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);
        
        fileManager = new ForwardingJavaFileManager<JavaFileManager>(fileManager)
        {
            
            @Override
            public JavaFileObject getJavaFileForOutput(Location location, String className, Kind kind,
                FileObject sibling)
                throws IOException
            {
                if (className.startsWith("x."))
                {
                    ByteArrayJavaClass fileObject = new ByteArrayJavaClass(className);
                    classFileObjects.add(fileObject);
                    return fileObject;
                }
                else
                    return super.getJavaFileForOutput(location, className, kind, sibling);
            }
        };
        JavaFileObject source = buildSource("compile.ButtonFrame");
        JavaCompiler.CompilationTask task = compiler.getTask(null,
            fileManager,
            diagnostics,
            null,
            null,
            Arrays.asList(source));
        Boolean result = task.call();
        for (Diagnostic<? extends JavaFileObject> d : diagnostics.getDiagnostics())
            System.out.println(d.getKind() + ": " + d.getMessage(null));
        fileManager.close();
        if (!result)
        {
            System.out.println("Compilation failed");
            System.exit(1);// 退出系统运行，挺有意思的，虽然我做的东西不经常用。。。
        }
        EventQueue.invokeLater(new Runnable()
        {
            
            public void run()
            {
                try
                {
                    Map<String, byte[]> byteCodeMap = new HashMap<String, byte[]>();
                    for (ByteArrayJavaClass cl : classFileObjects)
                        byteCodeMap.put(cl.getName().substring(1), cl.getBytes());
                    ClassLoader loader = new MapClassLoader(byteCodeMap);
                    Class<?> cl = loader.loadClass("x.Frame");
                    JFrame frame = (JFrame)cl.newInstance();
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setTitle("CompilerTest");
                    frame.setVisible(true);
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                }
                
            }
            
        });
    }
    
    // 建立源文件类
    static JavaFileObject buildSource(String superclassName)
        throws IOException
    {
        StringBuilderJavaSource source = new StringBuilderJavaSource("x.Frame");
        source.append("package x;\n");
        source.append("public class Frame extends " + superclassName + " {");
        source.append("protected void addEventHandlers(){");
        Properties props = new Properties();
        props.load(new FileReader("src\\compile\\action.properties"));
        for (Map.Entry<Object, Object> e : props.entrySet())
        {
            String beanName = (String)e.getKey();
            String eventCode = (String)e.getValue();
            source.append(beanName + ".addActionListener(new java.awt.event.ActionListener(){");
            source.append("public void actionPerformed(java.awt.event.ActionEvent event){");
            source.append(eventCode);
            source.append("}});");
        }
        source.append("}}");
        return source;
    }
}