本篇内容主要讲解“Spring中AOP的概念和JDK动态代理的实现方式”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“Spring中AOP的概念和JDK动态代理的实现方式”吧!
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AOP的概念
AOP：Aspect-Oriented Programming（面向切面编程），维基百科的解释如下：Aspect是一种新的模块化机制，用来描述分散在对象、类或者函数中的横切关注点，从关注点中分离出横切关注点是面向切面的程序设计的核心概念。分离关注点使解决特定领域问题的代码从业务逻辑中独立出来，业务逻辑的代码中不在含有针对特定领域问题的代码的调用，业务逻辑同特定领域问题的关系通过切面来封装、维护，这样原本分散在整个应用程序中的变动就可以很好地管理起来。从AOP的角度，应用可以分为横切关注点和业务逻辑代码，实际开发中，这些横切关注点往往会直接嵌入到业务逻辑代码中，面向切面编程就是要解决把横切关注点与业务逻辑相分离
实现方式：
Spring默认使用 JDK 动态代理作为AOP的代理，缺陷是目标类的类必须实现接口，否则不能使用JDK动态代理。如果需要代理的是类而不是接口，那么Spring会默认使用CGLIB代理，关于两者的区别：jdk动态代理是通过java的反射机制来实现的,目标类必须要实现接口，cglib是针对类来实现代理的，他的原理是动态的为指定的目标类生成一个子类，并覆盖其中方法实现增强，但因为采用的是继承，所以不能对final修饰的类进行代理。
JDK动态代理
Jdk动态代理是在程序运行过程中，根据目标类实现的接口来动态生成代理类的class文件,使用主要涉及两个类：
InvocationHandler接口： 它提供了一个invoke(Object obj,Method method, Object[] args)方法供实现者提供相应的代理逻辑的实现。可以对实际的实现进行一些特殊的处理其中参数
Object obj ：被代理的目标类
Method method： 需要执行的目标类的方法
Object[] args ：目标方法的参数
Proxy类：提供一个方法newProxyInstance (ClassLoader loader, Class[] interfaces, InvocationHandler h)来获得动态代理类
示例代码：
public interface OrderService {
public void createOrder();
}public class OrderServiceImpl implements OrderService {
@Override
public void createOrder() {
System.out.println("creating order");
}
}public class OrderLogger {
public void beforeCreateOrder(){
System.out.println("before create order");
}
public void afterCreateOrder(){
System.out.println("after create order");
}
}package com.sl.aop;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
public class ServiceProxy implements InvocationHandler {
private Object targetClass;
private OrderLogger orderLogger;
public ServiceProxy(Object targetClass,OrderLogger orderLogger) {
this.targetClass = targetClass;
this.orderLogger = orderLogger;
}
//获取代理
public Object GetDynamicProxy()
{
return Proxy.newProxyInstance(targetClass.getClass().getClassLoader(), //通过这个ClassLoader生成代理对象
targetClass.getClass().getInterfaces(),//代理类已实现的接口
this); //动态代理调用方法是关联的InvocationHandler,最终通过此InvocationHandler的invoke方法执行真正的方法
}
//实现相应的代理逻辑
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
this.orderLogger.beforeCreateOrder();
Object result= method.invoke(targetClass, args);
this.orderLogger.afterCreateOrder();
return result;
}
}测试类：
package com.sl.aop;
import org.junit.Test;
public class AopTest {
@Test
public void Testdynamicproxy() {
OrderServiceImpl serviceImpl = new OrderServiceImpl();
OrderLogger logger = new OrderLogger();
OrderService service = (OrderService) new ServiceProxy(serviceImpl, logger).GetDynamicProxy();
service.createOrder();
}
}运行结果：
到这个其实还是有点困惑，Proxy.newProxyInstance（）这个返回的是什么？ Invoke方法在哪里调用的？我们看一下JDK源码：看看DK动态代理的过程是什么样的：
根据源码内部的函数调用Proxy.newProxyInstance()->Proxy.getProxyClass0()->WeakCache.get() ，先定位到
WeakCache.class:
public V get(K key, P parameter) {
Objects.requireNonNull(parameter);
expungeStaleEntries();
Object cacheKey = CacheKey.valueOf(key, refQueue);
// lazily install the 2nd level valuesMap for the particular cacheKey
ConcurrentMap> valuesMap = map.get(cacheKey);
if (valuesMap == null) {
ConcurrentMap> oldValuesMap
= map.putIfAbsent(cacheKey,
valuesMap = new ConcurrentHashMap<>());
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}
// create subKey and retrieve the possible Supplier stored by that
// subKey from valuesMap
Object subKey = Objects.requireNonNull(subKeyFactory.apply(key, parameter));
Supplier supplier = valuesMap.get(subKey);
Factory factory = null;
while (true) {
if (supplier != null) {
// supplier might be a Factory or a CacheValue instance
V value = supplier.get();
if (value != null) {
return value;
}
}
// else no supplier in cache
// or a supplier that returned null (could be a cleared CacheValue
// or a Factory that wasn't successful in installing the CacheValue)
// lazily construct a Factory
if (factory == null) {
factory = new Factory(key, parameter, subKey, valuesMap);
}
if (supplier == null) {
supplier = valuesMap.putIfAbsent(subKey, factory);
if (supplier == null) {
// successfully installed Factory
supplier = factory;
}
// else retry with winning supplier
} else {
if (valuesMap.replace(subKey, supplier, factory)) {
// successfully replaced
// cleared CacheEntry / unsuccessful Factory
// with our Factory
supplier = factory;
} else {
// retry with current supplier
supplier = valuesMap.get(subKey);
}
}
}
}可以看到函数return value; 而 V value = supplier.get(); 继续往下读可以发现 supper=factory,实际上是一个Factory对象,那么继续查看Factory.get()方法
public synchronized V get() { // serialize access
// re-check
Supplier supplier = valuesMap.get(subKey);
if (supplier != this) {
// something changed while we were waiting:
// might be that we were replaced by a CacheValue
// or were removed because of failure ->
// return null to signal WeakCache.get() to retry
// the loop
return null;
}
// else still us (supplier == this)
// create new value
V value = null;
try {
value = Objects.requireNonNull(valueFactory.apply(key, parameter));
} finally {
if (value == null) { // remove us on failure
valuesMap.remove(subKey, this);
}
}
// the only path to reach here is with non-null value
assert value != null;
// wrap value with CacheValue (WeakReference)
CacheValue cacheValue = new CacheValue<>(value);
// try replacing us with CacheValue (this should always succeed)
if (valuesMap.replace(subKey, this, cacheValue)) {
// put also in reverseMap
reverseMap.put(cacheValue, Boolean.TRUE);
} else {
throw new AssertionError("Should not reach here");
}
// successfully replaced us with new CacheValue -> return the value
// wrapped by it
return value;
}Return value；那么直接查看赋值语句：value = Objects.requireNonNull(valueFactory.apply(key, parameter));
valueFactory又什么鬼？
public WeakCache(BiFunction subKeyFactory,
BiFunction valueFactory) {
this.subKeyFactory = Objects.requireNonNull(subKeyFactory);
this.valueFactory = Objects.requireNonNull(valueFactory);
}
private static final WeakCache[], Class> proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory());
可以知道valueFactory是ProxyClassFactory类型对象，直接查看ProxyClassFactory. Apply()方法
public Class apply(ClassLoader loader, Class[] interfaces) {
Map, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
for (Class intf : interfaces) {
/*
* Verify that the class loader resolves the name of this
* interface to the same Class object.
*/
Class interfaceClass = null;
try {
interfaceClass = Class.forName(intf.getName(), false, loader);
} catch (ClassNotFoundException e) {
}
if (interfaceClass != intf) {
throw new IllegalArgumentException(
intf + " is not visible from class loader");
}
/*
* Verify that the Class object actually represents an
* interface.
*/
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
/*
* Verify that this interface is not a duplicate.
*/
if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
throw new IllegalArgumentException(
"repeated interface: " + interfaceClass.getName());
}
}
String proxyPkg = null; // package to define proxy class in
int accessFlags = Modifier.PUBLIC | Modifier.FINAL;
/*
* Record the package of a non-public proxy interface so that the
* proxy class will be defined in the same package. Verify that
* all non-public proxy interfaces are in the same package.
*/
for (Class intf : interfaces) {
int flags = intf.getModifiers();
if (!Modifier.isPublic(flags)) {
accessFlags = Modifier.FINAL;
String name = intf.getName();
int n = name.lastIndexOf('.');
String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
if (proxyPkg == null) {
proxyPkg = pkg;
} else if (!pkg.equals(proxyPkg)) {
throw new IllegalArgumentException(
"non-public interfaces from different packages");
}
}
}
if (proxyPkg == null) {
// if no non-public proxy interfaces, use com.sun.proxy package
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}
/*
* Choose a name for the proxy class to generate.
*/
long num = nextUniqueNumber.getAndIncrement();
String proxyName = proxyPkg + proxyClassNamePrefix + num;
/*
* Generate the specified proxy class.
*/
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces, accessFlags);
try {
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
} catch (ClassFormatError e) {
/*
* A ClassFormatError here means that (barring bugs in the
* proxy class generation code) there was some other
* invalid aspect of the arguments supplied to the proxy
* class creation (such as virtual machine limitations
* exceeded).
*/
throw new IllegalArgumentException(e.toString());
}
}
}直接画重点：
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces, accessFlags);
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
调用ProxyGenerator.generateProxyClass最终动态生成一个代理类，但是似乎并未找到何处调用了invoke方法；参考CSDN: https://www.jb51.net/article/118935.htm这篇文章，尝试将这个动态生成的二进制字节码输出到本地，并反编译出来一看究竟，测试代码如下：
public class AopTest {
@Test
public void Testdynamicproxy() {
OrderServiceImpl serviceImpl = new OrderServiceImpl();
OrderLogger logger = new OrderLogger();
OrderService service = (OrderService) new ServiceProxy(serviceImpl, logger).GetDynamicProxy();
service.createOrder();
//输出动态代理类字节码
createProxyClassFile();
}
private static void createProxyClassFile(){
String name = "ProxyObject";
byte[] data = ProxyGenerator.generateProxyClass(name,new Class[]{OrderService.class});
FileOutputStream out =null;
try {
out = new FileOutputStream(name+".class");
System.out.println((new File("hello")).getAbsolutePath());
out.write(data);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if(null!=out) try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}使用java Decompiler工具将这个二进制class文件反编译查看：
具体动态代理类ProxyObject.java：
import com.sl.aop.OrderService;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
public final class ProxyObject
extends Proxy
implements OrderService
{
private static Method m1;
private static Method m2;
private static Method m3;
private static Method m0;
public ProxyObject(InvocationHandler paramInvocationHandler)
{
super(paramInvocationHandler);
}
public final boolean equals(Object paramObject)
{
try
{
return ((Boolean)this.h.invoke(this, m1, new Object[] { paramObject })).booleanValue();
}
catch (Error|RuntimeException localError)
{
throw localError;
}
catch (Throwable localThrowable)
{
throw new UndeclaredThrowableException(localThrowable);
}
}
public final String toString()
{
try
{
return (String)this.h.invoke(this, m2, null);
}
catch (Error|RuntimeException localError)
{
throw localError;
}
catch (Throwable localThrowable)
{
throw new UndeclaredThrowableException(localThrowable);
}
}
public final void createOrder()
{
try
{
this.h.invoke(this, m3, null);
return;
}
catch (Error|RuntimeException localError)
{
throw localError;
}
catch (Throwable localThrowable)
{
throw new UndeclaredThrowableException(localThrowable);
}
}
public final int hashCode()
{
try
{
return ((Integer)this.h.invoke(this, m0, null)).intValue();
}
catch (Error|RuntimeException localError)
{
throw localError;
}
catch (Throwable localThrowable)
{
throw new UndeclaredThrowableException(localThrowable);
}
}
static
{
try
{
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
m3 = Class.forName("com.sl.aop.OrderService").getMethod("createOrder", new Class[0]);
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
return;
}
catch (NoSuchMethodException localNoSuchMethodException)
{
throw new NoSuchMethodError(localNoSuchMethodException.getMessage());
}
catch (ClassNotFoundException localClassNotFoundException)
{
throw new NoClassDefFoundError(localClassNotFoundException.getMessage());
}
}终于看到关于invoke的部分了：
public final void createOrder()
{
try
{
this.h.invoke(this, m3, null);
return;
}
catch (Error|RuntimeException localError)
{
throw localError;
}
catch (Throwable localThrowable)
{
throw new UndeclaredThrowableException(localThrowable);
}
}实际上动态代理类继承自Proxy，并且实现了目标类继承的接口，在createOrder方法中调用了invoke方法，实现了切面逻辑的植入，这里也回答了一个问题，为什么JDK动态代理的目标类必须是实现接口的，因为代理类其实是针对接口代理，而不是针对类来代理的，动态代理类自己继承自Proxy,Java也不允许多重继承。动态代理类和目标类其实是各自实现了接口，代理类通过InvocationHandler.invoke实现对目标类方法的调用。
CGLIB动态代理
CGLIB代理是通过使用一个字节码处理框架ASM，来转换字节码并生成新的类，并在子类中采用方法拦截的技术拦截所有父类方法的调用，实现织如如横切逻辑 ，效率上比使用反射技术的JDK动态代理要高，但是由于CGLIB的原理是动态为目标类生成子类代理类，所以不能为声明为final的方法进行代理。其使用主要涉及两个类：
MethodInterceptor接口：该接口提供一个方法intercept(Object arg0, Method arg1, Object[] arg2, MethodProxy arg3)主要用于拦截目标类方法的调用
Object arg0, ：被代理的目标类
Method arg1, 委托方法
Object[] arg2, 方法参数
MethodProxy arg3 ：代理方法的MethodProxy对象
Enhancer类：用于创建代理类
示例：
实现MethodInterceptor接口，代理类在调用方法时，CGLIB会回调MethodInterceptor接口intercept方法，从而织入切面逻辑。
package com.sl.aop;
import java.lang.reflect.Method;
import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;
public class CglibServiceProxy implements MethodInterceptor {
private Object targetClass;
private OrderLogger orderLogger;
public CglibServiceProxy(Object targetClass,OrderLogger orderLogger) {
this.targetClass = targetClass;
this.orderLogger = orderLogger;
}
/**
* 创建代理对象
*
*/
public Object getInstance() {
Enhancer enhancer = new Enhancer();
//设置目标类（需要被代理的类）
enhancer.setSuperclass(this.targetClass.getClass());
// 回调方法
enhancer.setCallback(this);
// 创建代理对象
return enhancer.create();
}
/**
* 拦截所有目标类方法的调用
*
*/
@Override
public Object intercept(Object arg0, Method arg1, Object[] arg2, MethodProxy arg3) throws Throwable {
orderLogger.beforeCreateOrder();
Object o1 = arg3.invokeSuper(arg0, arg2);
orderLogger.afterCreateOrder();
return o1;
}
}测试方法：
public void Testdynamicproxy() {
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\\class");
OrderServiceImpl serviceImpl = new OrderServiceImpl();
OrderLogger logger = new OrderLogger();
CglibServiceProxy proxy = new CglibServiceProxy(serviceImpl,logger);
//通过生成子类的方式创建代理类
OrderServiceImpl proxyImp = (OrderServiceImpl)proxy.getInstance();
proxyImp.createOrder();
}结果：
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\\class");将cglib动态代理类输出到指定目录，反编译查看一下代理类真面目：
package com.sl.aop;
import com.sl.aop.OrderServiceImpl;
import java.lang.reflect.Method;
import org.springframework.cglib.core.ReflectUtils;
import org.springframework.cglib.core.Signature;
import org.springframework.cglib.proxy.Callback;
import org.springframework.cglib.proxy.Factory;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;
public class OrderServiceImpl$$EnhancerByCGLIB$$17779aa4 extends OrderServiceImpl implements Factory {
private boolean CGLIB$BOUND;
public static Object CGLIB$FACTORY_DATA;
private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
private static final Callback[] CGLIB$STATIC_CALLBACKS;
private MethodInterceptor CGLIB$CALLBACK_0;
private static Object CGLIB$CALLBACK_FILTER;
private static final Method CGLIB$createOrder$0$Method;
private static final MethodProxy CGLIB$createOrder$0$Proxy;
private static final Object[] CGLIB$emptyArgs;
private static final Method CGLIB$equals$1$Method;
private static final MethodProxy CGLIB$equals$1$Proxy;
private static final Method CGLIB$toString$2$Method;
private static final MethodProxy CGLIB$toString$2$Proxy;
private static final Method CGLIB$hashCode$3$Method;
private static final MethodProxy CGLIB$hashCode$3$Proxy;
private static final Method CGLIB$clone$4$Method;
private static final MethodProxy CGLIB$clone$4$Proxy;
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
Class var0 = Class.forName("com.sl.aop.OrderServiceImpl$$EnhancerByCGLIB$$17779aa4");
Class var1;
Method[] var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
CGLIB$equals$1$Method = var10000[0];
CGLIB$equals$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$1");
CGLIB$toString$2$Method = var10000[1];
CGLIB$toString$2$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$2");
CGLIB$hashCode$3$Method = var10000[2];
CGLIB$hashCode$3$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$3");
CGLIB$clone$4$Method = var10000[3];
CGLIB$clone$4$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$4");
CGLIB$createOrder$0$Method = ReflectUtils.findMethods(new String[]{"createOrder", "()V"}, (var1 = Class.forName("com.sl.aop.OrderServiceImpl")).getDeclaredMethods())[0];
CGLIB$createOrder$0$Proxy = MethodProxy.create(var1, var0, "()V", "createOrder", "CGLIB$createOrder$0");
}
final void CGLIB$createOrder$0() {
super.createOrder();
}
public final void createOrder() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if(this.CGLIB$CALLBACK_0 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if(var10000 != null) {
var10000.intercept(this, CGLIB$createOrder$0$Method, CGLIB$emptyArgs, CGLIB$createOrder$0$Proxy);
} else {
super.createOrder();
}
}
final boolean CGLIB$equals$1(Object var1) {
return super.equals(var1);
}
public final boolean equals(Object var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if(this.CGLIB$CALLBACK_0 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if(var10000 != null) {
Object var2 = var10000.intercept(this, CGLIB$equals$1$Method, new Object[]{var1}, CGLIB$equals$1$Proxy);
return var2 == null?false:((Boolean)var2).booleanValue();
} else {
return super.equals(var1);
}
}
final String CGLIB$toString$2() {
return super.toString();
}
public final String toString() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if(this.CGLIB$CALLBACK_0 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null?(String)var10000.intercept(this, CGLIB$toString$2$Method, CGLIB$emptyArgs, CGLIB$toString$2$Proxy):super.toString();
}
final int CGLIB$hashCode$3() {
return super.hashCode();
}
public final int hashCode() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if(this.CGLIB$CALLBACK_0 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if(var10000 != null) {
Object var1 = var10000.intercept(this, CGLIB$hashCode$3$Method, CGLIB$emptyArgs, CGLIB$hashCode$3$Proxy);
return var1 == null?0:((Number)var1).intValue();
} else {
return super.hashCode();
}
}
final Object CGLIB$clone$4() throws CloneNotSupportedException {
return super.clone();
}
protected final Object clone() throws CloneNotSupportedException {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if(this.CGLIB$CALLBACK_0 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null?var10000.intercept(this, CGLIB$clone$4$Method, CGLIB$emptyArgs, CGLIB$clone$4$Proxy):super.clone();
}
public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
String var10000 = var0.toString();
switch(var10000.hashCode()) {
case -2138148221:
if(var10000.equals("createOrder()V")) {
return CGLIB$createOrder$0$Proxy;
}
break;
case -508378822:
if(var10000.equals("clone()Ljava/lang/Object;")) {
return CGLIB$clone$4$Proxy;
}
break;
case 1826985398:
if(var10000.equals("equals(Ljava/lang/Object;)Z")) {
return CGLIB$equals$1$Proxy;
}
break;
case 1913648695:
if(var10000.equals("toString()Ljava/lang/String;")) {
return CGLIB$toString$2$Proxy;
}
break;
case 1984935277:
if(var10000.equals("hashCode()I")) {
return CGLIB$hashCode$3$Proxy;
}
}
return null;
}
public OrderServiceImpl$$EnhancerByCGLIB$$17779aa4() {
CGLIB$BIND_CALLBACKS(this);
}
public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
CGLIB$THREAD_CALLBACKS.set(var0);
}
public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
CGLIB$STATIC_CALLBACKS = var0;
}
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
OrderServiceImpl$$EnhancerByCGLIB$$17779aa4 var1 = (OrderServiceImpl$$EnhancerByCGLIB$$17779aa4)var0;
if(!var1.CGLIB$BOUND) {
var1.CGLIB$BOUND = true;
Object var10000 = CGLIB$THREAD_CALLBACKS.get();
if(var10000 == null) {
var10000 = CGLIB$STATIC_CALLBACKS;
if(CGLIB$STATIC_CALLBACKS == null) {
return;
}
}
var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
}
}
public Object newInstance(Callback[] var1) {
CGLIB$SET_THREAD_CALLBACKS(var1);
OrderServiceImpl$$EnhancerByCGLIB$$17779aa4 var10000 = new OrderServiceImpl$$EnhancerByCGLIB$$17779aa4();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Callback var1) {
CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
OrderServiceImpl$$EnhancerByCGLIB$$17779aa4 var10000 = new OrderServiceImpl$$EnhancerByCGLIB$$17779aa4();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
CGLIB$SET_THREAD_CALLBACKS(var3);
OrderServiceImpl$$EnhancerByCGLIB$$17779aa4 var10000 = new OrderServiceImpl$$EnhancerByCGLIB$$17779aa4;
switch(var1.length) {
case 0:
var10000.();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
default:
throw new IllegalArgumentException("Constructor not found");
}
}
public Callback getCallback(int var1) {
CGLIB$BIND_CALLBACKS(this);
MethodInterceptor var10000;
switch(var1) {
case 0:
var10000 = this.CGLIB$CALLBACK_0;
break;
default:
var10000 = null;
}
return var10000;
}
public void setCallback(int var1, Callback var2) {
switch(var1) {
case 0:
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2;
default:
}
}
public Callback[] getCallbacks() {
CGLIB$BIND_CALLBACKS(this);
return new Callback[]{this.CGLIB$CALLBACK_0};
}
public void setCallbacks(Callback[] var1) {
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0];
}
static {
CGLIB$STATICHOOK1();
}
}上面的代码可以看到代理类OrderServiceImpl$$EnhancerByCGLIB$$17779aa4 继承目标类OrderServiceImpl并且实现了接口Factory,代理类中关于createorder生成了两个方法CGLIB$createOrder$0和createOrder：
CGLIB$createOrder$0方法内部直接调用目标类的supper.createOrder
createOrder方法内部首先盘点否实现了MethodInterceptor接口的callback，如果存在则调用MethodInterceptor接口拦截方法intercept,根据前面的实现intercept方法内部实现了对目标方法的调用Object o1 = arg3.invokeSuper(arg0, arg2) ，invokeSuper内部实际上是直接调用的代理类的CGLIB$createOrder$0()方法，最终调用了目标类createOrder。
两种代理对比
JDK动态代理：
代理类与委托类实现同一接口，主要是通过代理类实现InvocationHandler并重写invoke方法来进行动态代理的，在invoke方法中将对方法进行增强处理 优点：不需要硬编码接口，代码复用率高，缺点：只能够代理实现了接口的委托类
CGLIB动态代理：
代理类将委托类作为自己的父类并为其中的非final委托方法创建两个方法，一个是与委托方法签名相同的方法，它在方法中会通过super调用委托方法；另一个是代理类独有的方法。在代理方法中，它会判断是否存在实现了MethodInterceptor接口的对象，若存在则将调用intercept方法对委托方法进行代理 优点：可以在运行时对类或者是接口进行增强操作，且委托类无需实现接口，缺点：不能对final类以及final方法进行代理
到此，相信大家对“Spring中AOP的概念和JDK动态代理的实现方式”有了更深的了解，不妨来实际操作一番吧！这里是创新互联网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
本文题目：Spring中AOP的概念和JDK动态代理的实现方式
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