https://github.com/lunaczp/java/blob/master/hello/src/com/lunac/learning/java/proxy/JDKProxy.java
package com.lunac.learning.java.proxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
public class JDKProxy {
public static void main(String[] args) {
InvocationHandler handler = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println(method);
if (method.getName().equals("drive")) {
System.out.println("let's drive " + args[0]);
}
return null;
}
};
Car car = (Car) Proxy.newProxyInstance(
Car.class.getClassLoader(),
new Class[] {Car.class},
handler
);
car.drive("cow");
}
}
interface Car {
void drive(String something);
}
//获取代理类
//通过ProxyGenerator动态生成了指定的interface的实现类
"main@1" prio=5 tid=0x1 nid=NA runnable
java.lang.Thread.State: RUNNABLE
at sun.misc.ProxyGenerator.generateClassFile(ProxyGenerator.java:570)
at sun.misc.ProxyGenerator.generateProxyClass(ProxyGenerator.java:339)
at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:639)
at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:557)
at java.lang.reflect.WeakCache$Factory.get(WeakCache.java:230)
- locked <0x20a> (a java.lang.reflect.WeakCache$Factory)
at java.lang.reflect.WeakCache.get(WeakCache.java:127)
at java.lang.reflect.Proxy.getProxyClass0(Proxy.java:419)
at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:719)
at com.lunac.learning.java.proxy.JDKProxy.main(JDKProxy.java:19)
//实例化代理类
"main@1" prio=5 tid=0x1 nid=NA runnable
java.lang.Thread.State: RUNNABLE
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:739)
at com.lunac.learning.java.proxy.JDKProxy.main(JDKProxy.java:19)
JDK源码（以JDK8为例，使用openJDK代码）
https://github.com/lunaczp/jdk/blob/jdk8-b120/jdk/src/share/classes/sun/misc/ProxyGenerator.java
/**
* Generate a class file for the proxy class. This method drives the
* class file generation process.
*/
private byte[] generateClassFile() {
/* ============================================================
* Step 1: Assemble ProxyMethod objects for all methods to
* generate proxy dispatching code for.
*/
/*
* Record that proxy methods are needed for the hashCode, equals,
* and toString methods of java.lang.Object. This is done before
* the methods from the proxy interfaces so that the methods from
* java.lang.Object take precedence over duplicate methods in the
* proxy interfaces.
*/
addProxyMethod(hashCodeMethod, Object.class);
addProxyMethod(equalsMethod, Object.class);
addProxyMethod(toStringMethod, Object.class);
/*
* Now record all of the methods from the proxy interfaces, giving
* earlier interfaces precedence over later ones with duplicate
* methods.
*/
for (Class<?> intf : interfaces) {
for (Method m : intf.getMethods()) {
addProxyMethod(m, intf);
}
}
/*
* For each set of proxy methods with the same signature,
* verify that the methods' return types are compatible.
*/
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
checkReturnTypes(sigmethods);
}
/* ============================================================
* Step 2: Assemble FieldInfo and MethodInfo structs for all of
* fields and methods in the class we are generating.
*/
try {
methods.add(generateConstructor());
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
for (ProxyMethod pm : sigmethods) {
// add static field for method's Method object
fields.add(new FieldInfo(pm.methodFieldName,
"Ljava/lang/reflect/Method;",
ACC_PRIVATE | ACC_STATIC));
// generate code for proxy method and add it
methods.add(pm.generateMethod());
}
}
methods.add(generateStaticInitializer());
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception", e);
}
if (methods.size() > 65535) {
throw new IllegalArgumentException("method limit exceeded");
}
if (fields.size() > 65535) {
throw new IllegalArgumentException("field limit exceeded");
}
/* ============================================================
* Step 3: Write the final class file.
*/
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getClass(dotToSlash(className));
cp.getClass(superclassName);
for (Class<?> intf: interfaces) {
cp.getClass(dotToSlash(intf.getName()));
}
/*
* Disallow new constant pool additions beyond this point, since
* we are about to write the final constant pool table.
*/
cp.setReadOnly();
ByteArrayOutputStream bout = new ByteArrayOutputStream();
DataOutputStream dout = new DataOutputStream(bout);
try {
/*
* Write all the items of the "ClassFile" structure.
* See JVMS section 4.1.
*/
// u4 magic;
dout.writeInt(0xCAFEBABE);
// u2 minor_version;
dout.writeShort(CLASSFILE_MINOR_VERSION);
// u2 major_version;
dout.writeShort(CLASSFILE_MAJOR_VERSION);
cp.write(dout); // (write constant pool)
// u2 access_flags;
dout.writeShort(accessFlags);
// u2 this_class;
dout.writeShort(cp.getClass(dotToSlash(className)));
// u2 super_class;
dout.writeShort(cp.getClass(superclassName));
// u2 interfaces_count;
dout.writeShort(interfaces.length);
// u2 interfaces[interfaces_count];
for (Class<?> intf : interfaces) {
dout.writeShort(cp.getClass(
dotToSlash(intf.getName())));
}
// u2 fields_count;
dout.writeShort(fields.size());
// field_info fields[fields_count];
for (FieldInfo f : fields) {
f.write(dout);
}
// u2 methods_count;
dout.writeShort(methods.size());
// method_info methods[methods_count];
for (MethodInfo m : methods) {
m.write(dout);
}
// u2 attributes_count;
dout.writeShort(0); // (no ClassFile attributes for proxy classes)
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception", e);
}
return bout.toByteArray();
}
https://github.com/lunaczp/java/blob/master/hello/src/com/lunac/learning/java/proxy/CglibProxy.java
package com.lunac.learning.java.proxy;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
public class CglibProxy implements MethodInterceptor {
@Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
System.out.println("before Intercept");
methodProxy.invokeSuper(o, objects);
System.out.println("after Intercept");
return null;
}
public static void main(String[] args) {
CCar cCar = Factory.getInstance(new CglibProxy());
cCar.drive();
}
}
class Factory {
public static CCar getInstance(CglibProxy proxy) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(CCar.class);
enhancer.setCallback(proxy);
return (CCar) enhancer.create();
}
}
class CCar {
public CCar() {
System.out.println("i'm in ccar constructor now");
}
public void drive() {
System.out.println("driving");
}
}
"main@1" prio=5 tid=0x1 nid=NA runnable
java.lang.Thread.State: RUNNABLE
at com.lunac.learning.java.proxy.CCar.<init>(CglibProxy.java:37)
at com.lunac.learning.java.proxy.CCar$$EnhancerByCGLIB$$f9118a4f.<init>(<generated>:-1)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(NativeConstructorAccessorImpl.java:-1)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at net.sf.cglib.core.ReflectUtils.newInstance(ReflectUtils.java:291)
at net.sf.cglib.proxy.Enhancer$EnhancerFactoryData.newInstance(Enhancer.java:448)
at net.sf.cglib.proxy.Enhancer.nextInstance(Enhancer.java:700)
at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:298)
at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:480)
at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:305)
at com.lunac.learning.java.proxy.Factory.getInstance(CglibProxy.java:30)
at com.lunac.learning.java.proxy.CglibProxy.main(CglibProxy.java:19)
"main@1" prio=5 tid=0x1 nid=NA runnable
java.lang.Thread.State: RUNNABLE
at com.lunac.learning.java.proxy.CCar.drive(CglibProxy.java:42)
at com.lunac.learning.java.proxy.CCar$$EnhancerByCGLIB$$f9118a4f.CGLIB$drive$0(<generated>:-1)
at com.lunac.learning.java.proxy.CCar$$EnhancerByCGLIB$$f9118a4f$$FastClassByCGLIB$$2d4d573.invoke(<generated>:-1)
at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228)
at com.lunac.learning.java.proxy.CglibProxy.intercept(CglibProxy.java:13)
at com.lunac.learning.java.proxy.CCar$$EnhancerByCGLIB$$f9118a4f.drive(<generated>:-1)
at com.lunac.learning.java.proxy.CglibProxy.main(CglibProxy.java:20)