JAVA 中的代码生成包 CGLIB （Code Generation Library）

// InvocationHandlerImpl 实现了 InvocationHandler 接口，并能实现方法调用从代理类到委托类的分派转发
// 其内部通常包含指向委托类实例的引用，用于真正执行分派转发过来的方法调用
InvocationHandler handler = new InvocationHandlerImpl(..); 

// 通过 Proxy 为包括 Interface 接口在内的一组接口动态创建代理类的类对象
Class clazz = Proxy.getProxyClass(classLoader, new Class[] { Interface.class, ... }); 

// 通过反射从生成的类对象获得构造函数对象
Constructor constructor = clazz.getConstructor(new Class[] { InvocationHandler.class }); 

// 通过构造函数对象创建动态代理类实例
Interface Proxy = (Interface)constructor.newInstance(new Object[] { handler });

// InvocationHandlerImpl 实现了 InvocationHandler 接口，并能实现方法调用从代理类到委托类的分派转发
InvocationHandler handler = new InvocationHandlerImpl(..); 

// 通过 Proxy 直接创建动态代理类实例
Interface proxy = (Interface)Proxy.newProxyInstance( classLoader, 
     new Class[] { Interface.class }, 
     handler );

public class DynamicProxy {
    interface IHello{
        void sayHello();
    }

    static class Hello implements IHello{
        public void sayHello() {
            System.out.println("hello world");
        }
    }

    static class DynamicProxyTest implements InvocationHandler{
        Object originalObj;
        Object bind(Object originalObj){
            this.originalObj = originalObj;
            return Proxy.newProxyInstance(originalObj.getClass().getClassLoader(),
                    originalObj.getClass().getInterfaces(), this);
        }
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            System.out.println("Welcome");
            return method.invoke(originalObj, args);
        }
    }

    public static void main(String[] args){
        //设置这个值，在程序运行完成后，可以生成代理类
        System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
        IHello hello = (IHello) new DynamicProxyTest().bind(new Hello());
        hello.sayHello();
    }
}

<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>2.2.2</version>
</dependency>

public class SampleClass {
    public void test(){
        System.out.println("hello world");
    }

    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(SampleClass.class);
        enhancer.setCallback(new MethodInterceptor() {
            @Override
            public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
                System.out.println("before method run...");
                Object result = proxy.invokeSuper(obj, args);
                System.out.println("after method run...");
                return result;
            }
        });
        SampleClass sample = (SampleClass) enhancer.create();
        sample.test();
    }
}

public class SampleClass {
    public String test(String input){
        return "hello world";
    }
}

@Test
public void testFixedValue(){
    Enhancer enhancer = new Enhancer();
    enhancer.setSuperclass(SampleClass.class);
    enhancer.setCallback(new FixedValue() {
        @Override
        public Object loadObject() throws Exception {
            return "Hello cglib";
        }
    });
    SampleClass proxy = (SampleClass) enhancer.create();
    System.out.println(proxy.test(null)); //拦截test，输出Hello cglib
    System.out.println(proxy.toString()); 
    System.out.println(proxy.getClass());
    System.out.println(proxy.hashCode());
}

public void testInvocationHandler() throws Exception{
    Enhancer enhancer = new Enhancer();
    enhancer.setSuperclass(SampleClass.class);
    enhancer.setCallback(new InvocationHandler() {
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if(method.getDeclaringClass() != Object.class && method.getReturnType() == String.class){
                return "hello cglib";
            }else{
                throw new RuntimeException("Do not know what to do");
            }
        }
    });
    SampleClass proxy = (SampleClass) enhancer.create();
    Assert.assertEquals("hello cglib", proxy.test(null));
    Assert.assertNotEquals("Hello cglib", proxy.toString());
}

@Test
public void testCallbackFilter() throws Exception{
    Enhancer enhancer = new Enhancer();
    CallbackHelper callbackHelper = new CallbackHelper(SampleClass.class, new Class[0]) {
        @Override
        protected Object getCallback(Method method) {
            if(method.getDeclaringClass() != Object.class && method.getReturnType() == String.class){
                return new FixedValue() {
                    @Override
                    public Object loadObject() throws Exception {
                        return "Hello cglib";
                    }
                };
            }else{
                return NoOp.INSTANCE;
            }
        }
    };
    enhancer.setSuperclass(SampleClass.class);
    enhancer.setCallbackFilter(callbackHelper);
    enhancer.setCallbacks(callbackHelper.getCallbacks());
    SampleClass proxy = (SampleClass) enhancer.create();
    Assert.assertEquals("Hello cglib", proxy.test(null));
    Assert.assertNotEquals("Hello cglib",proxy.toString());
    System.out.println(proxy.hashCode());
}

Interface Callable<V>

import java.util.Random;
import java.util.concurrent.Callable;

public class CallableExample  implements Callable {
    @Override
    public Object call() throws Exception {
        Random generator = new Random();
        Integer randomNumber = generator.nextInt(5);
        Thread.sleep(randomNumber * 1000);
        return randomNumber;
    }
}

@Test
public void callabledTest(){
    ExecutorService executorService = Executors.newCachedThreadPool();
    CallableExample callableExample = new CallableExample();
    Future<Object> future = executorService.submit(callableExample);
    executorService.shutdown();
    try{
        System.out.println(future.get());
    }catch (Exception e){
        e.printStackTrace();
    }
}

public interface Callback { }

 public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {

   for (int i = 0; i < callbacks.length; i++) {
      if (callbacks[i] instanceof TextOutputCallback) {

          // display the message according to the specified type
          TextOutputCallback toc = (TextOutputCallback)callbacks[i];
          switch (toc.getMessageType()) {
          case TextOutputCallback.INFORMATION:
              System.out.println(toc.getMessage());
              break;
          case TextOutputCallback.ERROR:
              System.out.println("ERROR: " + toc.getMessage());
              break;
          case TextOutputCallback.WARNING:
              System.out.println("WARNING: " + toc.getMessage());
              break;
          default:
              throw new IOException("Unsupported message type: " +
                                  toc.getMessageType());
          }

      } else if (callbacks[i] instanceof NameCallback) {

          // prompt the user for a username
          NameCallback nc = (NameCallback)callbacks[i];

          // ignore the provided defaultName
          System.err.print(nc.getPrompt());
          System.err.flush();
          nc.setName((new BufferedReader
                  (new InputStreamReader(System.in))).readLine());

      } else if (callbacks[i] instanceof PasswordCallback) {

          // prompt the user for sensitive information
          PasswordCallback pc = (PasswordCallback)callbacks[i];
          System.err.print(pc.getPrompt());
          System.err.flush();
          pc.setPassword(readPassword(System.in));

      } else {
          throw new UnsupportedCallbackException
                  (callbacks[i], "Unrecognized Callback");
      }
   }
 }

 // Reads user password from given input stream.
 private char[] readPassword(InputStream in) throws IOException {
    // insert code to read a user password from the input stream
 }

import java.util.List;

public interface CallBackInterface {
    Object process(List<String> list);
}

import lombok.Data;

import java.util.ArrayList;
import java.util.List;
@Data
public class WorldListHandler {
    List<String> stringList = new ArrayList<>();
    public void execute(CallBackInterface callBackInterface){
        Object process = callBackInterface.process(stringList);
        System.out.println(process);
    }

}

@Test
public void callableTest2(){
    List<String> list = Arrays.asList("123","asd","1432","fsd","543","987","tre");
    WorldListHandler worldListHandler = new WorldListHandler();
    worldListHandler.setStringList(list);
    worldListHandler.execute(new CallBackInterface() {
        @Override
        public Object process(List<String> list) {
            List<String> collect = list.stream().filter(e -> e.contains("1")).collect(Collectors.toList());
            worldListHandler.setStringList(collect);
            return true;
        }
    });
    worldListHandler.getStringList().forEach(e-> System.out.println(e));
}

public class SampleBean {
    private String value;

    public SampleBean() {
    }

    public SampleBean(String value) {
        this.value = value;
    }
    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

@Test(expected = IllegalStateException.class)
public void testImmutableBean() throws Exception{
    SampleBean bean = new SampleBean();
    bean.setValue("Hello world");
    SampleBean immutableBean = (SampleBean) ImmutableBean.create(bean); //创建不可变类
    Assert.assertEquals("Hello world", immutableBean.getValue()); 
    bean.setValue("Hello world, again"); // 可以通过底层对象来进行修改
    Assert.assertEquals("Hello world, again", immutableBean.getValue());
    immutableBean.setValue("Hello cglib"); // 直接修改将throw exception
}

@Test
public void testBeanGenerator() throws Exception{
    BeanGenerator beanGenerator = new BeanGenerator();
    beanGenerator.addProperty("value", String.class);
    Object myBean = beanGenerator.create();
    Method setter = myBean.getClass().getMethod("setValue", String.class);
    setter.invoke(myBean, "Hello cglib");

    Method getter = myBean.getClass().getMethod("getValue");
    Assert.assertEquals("Hello cglib", getter.invoke(myBean));
}

public class OtherSampleBean {
    private String value;

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

@Test
public void testBeanCopier() throws Exception{
    BeanCopier copier = BeanCopier.create(SampleBean.class, OtherSampleBean.class, false); //设置为true，则使用converter
    SampleBean myBean = new SampleBean();
    myBean.setValue("Hello cglib");
    OtherSampleBean otherBean = new OtherSampleBean();
    copier.copy(myBean, otherBean, null); //设置为true，则传入converter指明怎么进行转换
    assertEquals("Hello cglib", otherBean.getValue());
}

@Test
public void testBulkBean() throws Exception{
    BulkBean bulkBean = BulkBean.create(SampleBean.class, new String[]{"getValue"}, new String[]{"setValue"}, new Class[]{String.class});
    SampleBean bean = new SampleBean();
    bean.setValue("Hello world");
    Object[] propertyValues = bulkBean.getPropertyValues(bean);
    assertEquals(1, bulkBean.getPropertyValues(bean).length);
    assertEquals("Hello world", bulkBean.getPropertyValues(bean)[0]);
    bulkBean.setPropertyValues(bean, new Object[]{"Hello cglib"});
    assertEquals("Hello cglib", bean.getValue());
}

@Test
public void testBeanMap() throws Exception{
    BeanGenerator generator = new BeanGenerator();
    generator.addProperty("username", String.class);
    generator.addProperty("password", String.class);
    Object bean = generator.create();
    Method setUserName = bean.getClass().getMethod("setUsername", String.class);
    Method setPassword = bean.getClass().getMethod("setPassword", String.class);
    setUserName.invoke(bean, "admin");
    setPassword.invoke(bean, "password");
    BeanMap map = BeanMap.create(bean);
    Assert.assertEquals("admin", map.get("username"));
    Assert.assertEquals("password", map.get("password"));
}

public interface SampleKeyFactory {
    Object newInstance(String first, int second);
}

@Test
public void testKeyFactory() throws Exception{
    SampleKeyFactory keyFactory = (SampleKeyFactory) KeyFactory.create(SampleKeyFactory.class);
    Object key = keyFactory.newInstance("foo", 42);
    Object key1 = keyFactory.newInstance("foo", 42);
    Assert.assertEquals(key,key1);//测试参数相同，结果是否相等
}

public class MixinInterfaceTest {
    interface Interface1{
        String first();
    }
    
    interface Interface2{
        String second();
    }

    class Class1 implements Interface1{
        @Override
        public String first() {
            return "first";
        }
    }

    class Class2 implements Interface2{
        @Override
        public String second() {
            return "second";
        }
    }

    interface MixinInterface extends Interface1, Interface2{

    }

    @Test
    public void testMixin() throws Exception{
        Mixin mixin = Mixin.create(new Class[]{Interface1.class, Interface2.class, MixinInterface.class}, new Object[]{new Class1(), new Class2()});
        MixinInterface mixinDelegate = (MixinInterface) mixin;
        assertEquals("first", mixinDelegate.first());
        assertEquals("second", mixinDelegate.second());
    }
}

@Test
public void testStringSwitcher() throws Exception{
    String[] strings = new String[]{"one", "two"};
    int[] values = new int[]{10,20};
    StringSwitcher stringSwitcher = StringSwitcher.create(strings, values, true);
    assertEquals(10, stringSwitcher.intValue("one"));
    assertEquals(20, stringSwitcher.intValue("two"));
    assertEquals(-1, stringSwitcher.intValue("three"));
}

@Test
public void testInterfaceMarker() throws Exception{
    Signature signature = new Signature("foo", Type.DOUBLE_TYPE, new Type[]{Type.INT_TYPE});
    InterfaceMaker interfaceMaker = new InterfaceMaker();
    interfaceMaker.add(signature, new Type[0]);
    Class iface = interfaceMaker.create();
    assertEquals(1, iface.getMethods().length);
    assertEquals("foo", iface.getMethods()[0].getName());
    assertEquals(double.class, iface.getMethods()[0].getReturnType());
}

interface BeanDelegate{
    String getValueFromDelegate();
}

@Test
public void testMethodDelegate()  throws Exception{
    SampleBean bean = new SampleBean();
    bean.setValue("Hello cglib");
    BeanDelegate delegate = (BeanDelegate) MethodDelegate.create(bean, "getValue", BeanDelegate.class);
    assertEquals("Hello cglib", delegate.getValueFromDelegate());
}

public interface DelegatationProvider {
    void setValue(String value);
}

public class SimpleMulticastBean implements DelegatationProvider {
    private String value;
    @Override
    public void setValue(String value) {
        this.value = value;
    }

    public String getValue() {
        return value;
    }
}

@Test
public void testMulticastDelegate() throws Exception{
    MulticastDelegate multicastDelegate = MulticastDelegate.create(DelegatationProvider.class);
    SimpleMulticastBean first = new SimpleMulticastBean();
    SimpleMulticastBean second = new SimpleMulticastBean();
    multicastDelegate = multicastDelegate.add(first);
    multicastDelegate  = multicastDelegate.add(second);

    DelegatationProvider provider = (DelegatationProvider) multicastDelegate;
    provider.setValue("Hello world");

    assertEquals("Hello world", first.getValue());
    assertEquals("Hello world", second.getValue());
}

interface SampleBeanConstructorDelegate{
    Object newInstance(String value);
}

/**
 * 对构造函数进行代理
 * @throws Exception
 */
@Test
public void testConstructorDelegate() throws Exception{
    SampleBeanConstructorDelegate constructorDelegate = (SampleBeanConstructorDelegate) ConstructorDelegate.create(
            SampleBean.class, SampleBeanConstructorDelegate.class);
    SampleBean bean = (SampleBean) constructorDelegate.newInstance("Hello world");
    assertTrue(SampleBean.class.isAssignableFrom(bean.getClass()));
    System.out.println(bean.getValue());
}

@Test
public void testParallelSorter() throws Exception{
    Integer[][] value = {
            {4, 3, 9, 0},
            {2, 1, 6, 0}
    };
    ParallelSorter.create(value).mergeSort(0);
    for(Integer[] row : value){
        int former = -1;
        for(int val : row){
            assertTrue(former < val);
            former = val;
        }
    }
}

@Test
public void testFastClass() throws Exception{
    FastClass fastClass = FastClass.create(SampleBean.class);
    FastMethod fastMethod = fastClass.getMethod("getValue",new Class[0]);
    SampleBean bean = new SampleBean();
    bean.setValue("Hello world");
    assertEquals("Hello world",fastMethod.invoke(bean, new Object[0]));
}