06CGLIB
CGLIB
public class CglibTest {
public void function(){
System.out.println("hello world");
}
@Test
public void test1() {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(CglibTest.class);
/**
enhancer.setCallbackFilter();
enhancer.setCallbacks();
enhancer.setInterfaces();
//生成策略
enhancer.setStrategy();
**/
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;
}
});
CglibTest test = (CglibTest) enhancer.create();
test.function();
/**
* before method run...
* hello world
* after method run...
*/
}
/**
* ImmutableBean允许创建一个原来对象的包装类，这个包装类是不可变的，
* 任何改变底层对象的包装类操作都会抛出IllegalStateException。
* 但是我们可以通过直接操作底层对象来改变包装类对象。
*/
@Test
public void testImmutableBean(){
Simple bean = new Simple();
bean.setValue("Hello world");
Simple immutableBean = (Simple) ImmutableBean.create(bean); //创建不可变类
System.out.println(immutableBean.getValue());
bean.setValue("Hello world, again"); //可以通过底层对象来进行修改
System.out.println(immutableBean.getValue());
try {
immutableBean.setValue("Hello cglib"); //直接修改将throw exception
} catch (Exception e) {
System.out.println(e);
}
/**
* Hello world
* Hello world, again
* java.lang.IllegalStateException: Bean is immutable
*/
}
/**
* Bean generator
* cglib提供的一个操作bean的工具，使用它能够在运行时动态的创建一个bean。
*/
@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");
System.out.println("getter.invoke(myBean) = " + getter.invoke(myBean));
/**
* getter.invoke(myBean) = Hello cglib
*/
}
/**
* Bean Copier
* cglib提供的能够从一个bean复制到另一个bean中，
* 而且其还提供了一个转换器，
* 用来在转换的时候对bean的属性进行操作。
*/
@Test
public void testBeanCopier() throws Exception{
BeanCopier copier = BeanCopier.create(Simple.class, Simple2.class, true);//设置为true，则使用converter
Simple myBean = new Simple();
myBean.setValue("Hello cglib");
Simple2 otherBean = new Simple2();
copier.copy(myBean, otherBean, new Converter(){
@Override
public Object convert(Object value, Class target, Object context) {
return value+" convert";
}
}); //设置为true，则传入converter指明怎么进行转换
System.out.println("otherBean.getValue() = " + otherBean.getValue());
//otherBean.getValue() = Hello cglib convert
}
/**
* BeanMap
* BeanMap类实现了Java Map，
* 将一个bean对象中的所有属性转换为一个String-to-Obejct的Java Map
*/
@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);
System.out.println("map.get(\"username\") = " + map.get("username"));
System.out.println("map.get(\"password\") = " + map.get("password"));
}
/**
* keyFactory
* keyFactory类用来动态生成接口的实例，
* 接口需要只包含一个newInstance方法，返回一个Object。
* keyFactory为构造出来的实例动态生成了Object.equals和Object.hashCode方法，
* 能够确保相同的参数构造出的实例为单例的。
*
*/
@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);
System.out.println("key = " + key+" "+key.hashCode());
System.out.println("key1 = " + key1+" "+key1.hashCode());
/**
* key = foo, 42 -1181409833
* key1 = foo, 42 -1181409833
*/
}
/**
* Interface Maker
* 正如名字所言，Interface Maker用来创建一个新的Interface
*/
@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();
System.out.println("iface.getMethods().length = " + iface.getMethods().length);
System.out.println("iface.getMethods()[0].getName() = " + iface.getMethods()[0].getName());
System.out.println("iface.getMethods()[0].getReturnType() = " + iface.getMethods()[0].getReturnType());
/**
* iface.getMethods().length = 1
* iface.getMethods()[0].getName() = foo
* iface.getMethods()[0].getReturnType() = double
*
*/
}
}Enhancer-CallBack
Callback-MethodInterceptor
- 方法拦截器
Object intercept(Object obj, java.lang.reflect.Method method, Object[] args, MethodProxy proxy) throws Throwable- MethodProxy proxy参数一般是用来调用原来的对应方法的。比如可以proxy.invokeSuper(obj, args)。那么为什么不能像InvocationHandler那样用method来调用呢？因为如果用method调用会再次进入拦截器。为了避免这种情况，应该使用接口方法中第四个参数methodProxy调用invokeSuper方法。
Callback-NoOp
- 这个回调相当简单，就是啥都不干的意思
Callback-LazyLoader
- LazyLoader是cglib用于实现懒加载的callback。当被增强bean的方法初次被调用时，会触发回调，之后每次再进行方法调用都是对LazyLoader第一次返回的bean调用。
public class EnhancerTest {
public static void main(String[] args) {
CarFactory factory = new CarFactory();
System.out.println("factory built");
System.out.println(factory.car.getName());
System.out.println(factory.car.getName());
}
static class Car {
String name;
Car() {
}
String getName() {
return name;
}
}
static class CarFactory {
Car car;
CarFactory() {
car = carLazyProxy();
}
Car carLazyProxy() {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(Car.class);
enhancer.setCallback(new LazyLoader() {
@Override
public Object loadObject() throws Exception {
System.out.println("prepare loading");
Car car = new Car();
car.name = "this is a car";
System.out.println("after loading");
return car;
}
});
return ((Car) enhancer.create());
}
}
}
/**
factory built
prepare loading
after loading
this is a car
this is a car
**/Callback-Dispatcher
- Dispatcher和LazyLoader作用很相似，区别是用Dispatcher的话每次对增强bean进行方法调用都会触发回调。
public class EnhancerTest {
public static void main(String[] args) {
CarFactory factory = new CarFactory();
System.out.println("factory built");
System.out.println(factory.car.getName());
System.out.println(factory.car.getName());
}
static class Car {
String name;
Car() {
}
String getName() {
return name;
}
}
static class CarFactory {
Car car;
CarFactory() {
car = carLazyProxy();
}
Car carLazyProxy() {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(Car.class);
enhancer.setCallback(new Dispatcher() {
@Override
public Object loadObject() throws Exception {
System.out.println("prepare loading");
Car car = new Car();
car.name = "this is a car";
System.out.println("after loading");
return car;
}
});
return ((Car) enhancer.create());
}
}
}
/**
factory built
prepare loading
after loading
this is a car
prepare loading
after loading
this is a car
**/Callback-InvocationHandler
- 如果对参数中的method再次调用，会重复进入InvocationHandler。
public class EnhancerTest {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(Car.class);
enhancer.setCallback(new InvocationHandler() {
@Override
public Object invoke(Object obj, Method method, Object[] args) throws Throwable {
if (method.getReturnType() == void.class) {
System.out.println("hack");
}
return null;
}
});
Car car = (Car) enhancer.create();
car.print();
}
static class Car {
void print() {
System.out.println("I am a car");
}
}
}Callback-FixedValue
- FixedValue一般用于替换方法的返回值为回调方法的返回值，但必须保证返回类型是兼容的，否则会出转换异常。
public class EnhancerTest {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(Car.class);
enhancer.setCallback(new FixedValue() {
@Override
public Object loadObject() throws Exception {
return "hack!";
}
});
Car car = (Car) enhancer.create();
System.out.println(car.print1());
System.out.println(car.print2());
}
static class Car {
String print1() {
return "car1";
}
String print2() {
return "car2";
}
}
}CallbackFilter
- 上面都是为增强bean配置了一种代理callback，但是当需要作一些定制化的时候，CallbackFilter就派上用处了。
- 当通过设置CallbackFilter增强bean之后，bean中原方法都会根据设置的filter与一个特定的callback映射。我们通常会使用cglib中CallbackFilter的默认实现CallbackHelper，它的getCallbacks方法可以返回生成的callback数组。
///被代理的类
public class ConcreteClassNoInterface {
public String getConcreteMethodA(String str){
System.out.println("ConcreteMethod A ... "+str);
return str;
}
public int getConcreteMethodB(int n){
System.out.println("ConcreteMethod B ... "+n);
return n+10;
}
public int getConcreteMethodFixedValue(int n){
System.out.println("getConcreteMethodFixedValue..."+n);
return n+10;
}
}
//CallbackFilter
public class ConcreteClassCallbackFilter implements CallbackFilter{
public int accept(Method method) {
if("getConcreteMethodB".equals(method.getName())){
return 0;//Callback callbacks[0]--->interceptor
}else if("getConcreteMethodA".equals(method.getName())){
return 1;//Callback callbacks[1]--->noOp
}else if("getConcreteMethodFixedValue".equals(method.getName())){
return 2;//Callback callbacks[2]--->fixedValue
}
return 1;//Callback callbacks[1]--->noOp
}
}
//
Enhancer enhancer=new Enhancer();
enhancer.setSuperclass(ConcreteClassNoInterface.class);
CallbackFilter filter=new ConcreteClassCallbackFilter();
enhancer.setCallbackFilter(filter);
Callback interceptor=new ConcreteClassInterceptor();
Callback noOp=NoOp.INSTANCE;
Callback fixedValue=new ConcreteClassFixedValue();
Callback[] callbacks=new Callback[]{interceptor,noOp,fixedValue};
enhancer.setCallbacks(callbacks);
ConcreteClassNoInterface proxyObject=(ConcreteClassNoInterface)enhancer.create();
06CGLIB
https://jiajun.xyz/2020/10/10/java/spring/06CGLIB/