代理的作用主要是某个方法在执行前后做一定的特殊处理；
静态代理：
package com.thinkgem.jeesite.proxy.handler;
import com.thinkgem.jeesite.proxy.UserOneService;
import com.thinkgem.jeesite.proxy.entity.User;
import org.springframework.aop.framework.AopProxyUtils;
import org.springframework.lang.Nullable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* Description：
*
* @Author： leo.xiong
* @CreateDate： 2020/08/11 09:57
* @Email： [email protected]
* @Since：
*/
public class MyInvocationHandler {
private UserOneService userOneService;
//传入需要代理的对象
public MyInvocationHandler(UserOneService userOneService) {
this.userOneService = userOneService;
}
//增强代理属性
public void staticProxy(String userId) {
System.out.println("开始静态代理");
userOneService.getUserName(userId);
System.out.println("静态代理结束");
}
}
package com.thinkgem.jeesite.proxy;
import com.thinkgem.jeesite.proxy.handler.MyInvocationHandler;
import com.thinkgem.jeesite.proxy.impl.UserOneOneServiceImpl;
import com.thinkgem.jeesite.proxy.impl.UserTwoServiceImpl;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
/**
* Description：
*
* @Author： leo.xiong
* @CreateDate： 2020/08/11 10:03
* @Email： [email protected]
* @Since：
*/
public class MainTest {
public static void main(String[] args) {
UserOneService userOneService = new UserOneOneServiceImpl();
MyInvocationHandler invocationOneHandler = new MyInvocationHandler(userOneService);
invocationOneHandler.staticProxy("1");
}
}
静态代理只能对某个类进行增强，一个类有多个方法，增强类也得写多个方法，多个类需要些多个增强类，效率极低。
动态代理：
java反射可以使用Method方法点invoke调用当前方法，动态代理就是基于 method.invoke(obj,args)实现的；
package com.thinkgem.jeesite.proxy.handler;
import com.thinkgem.jeesite.proxy.entity.User;
import org.springframework.lang.Nullable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* Description：
*
* @Author： leo.xiong
* @CreateDate： 2020/08/11 09:57
* @Email： [email protected]
* @Since：
*/
public class MyInvocationHandler implements InvocationHandler {
private Object object;
public MyInvocationHandler(Object object) {
this.object = object;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
/**
* public final User getUserName(String var1) throws {
* try {
* return (User)super.h.invoke(this, m3, new Object[]{var1});
* } catch (RuntimeException | Error var3) {
* throw var3;
* } catch (Throwable var4) {
* throw new UndeclaredThrowableException(var4);
* }
* }
* super.h就是当前的InvocationHandler对象
* 如果method.invoke(object, args);使用proxy代理对象，则调用(User)super.h.invoke(this, m3, new Object[]{var1});
* 之后invocationHandler.invoke(this, m3, new Object[]{var1})又调用当前方法，死循环，所有需要使用原始对象
*/
//method是动态代理的方法名，object实现类，args参数，执行object的，方法为method的方法，实质就是原始为增强的方法。
User user = (User) method.invoke(object, args);
if (user != null) {
System.out.println(user);
}
return user;
}
/**
* 生成代理对象
* @param classLoader
* @param clazzs
* @return
*/
public Object getProxy(@Nullable ClassLoader classLoader, Class<?>[] clazzs) {
return Proxy.newProxyInstance(classLoader, clazzs, this);
}
}
package com.thinkgem.jeesite.proxy;
import com.thinkgem.jeesite.proxy.handler.MyInvocationHandler;
import com.thinkgem.jeesite.proxy.impl.UserOneOneServiceImpl;
import com.thinkgem.jeesite.proxy.impl.UserTwoServiceImpl;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
/**
* Description：
*
* @Author： leo.xiong
* @CreateDate： 2020/08/11 10:03
* @Email： [email protected]
* @Since：
*/
public class MainTest {
public static void main(String[] args) {
//是否生成代理文件，文件路径当前项目/com/sun/proxy路径下,默认不生成
System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
//需要代理的对象，包含它实现的所有接口的实现方法
UserOneService userOneService = new UserOneOneServiceImpl();
//自定义的代理增强类，传入代理对象，相当于静态代理的传入的代理对象
MyInvocationHandler invocationOneHandler = new MyInvocationHandler(userOneService);
try {
//获取代理对象
UserThreeService userThreeService = (UserThreeService) invocationOneHandler.getProxy(UserOneService.class.getClassLoader(), new Class[]{UserOneService.class, UserThreeService.class});
//执行方法
userThreeService.getId("7");
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
}
生成的代理类
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package com.sun.proxy;
import com.thinkgem.jeesite.proxy.UserOneService;
import com.thinkgem.jeesite.proxy.UserThreeService;
import com.thinkgem.jeesite.proxy.entity.User;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
public final class $Proxy0 extends Proxy implements UserOneService, UserThreeService {
private static Method m1;
private static Method m3;
private static Method m2;
private static Method m4;
private static Method m0;
public $Proxy0(InvocationHandler var1) throws {
super(var1);
}
public final boolean equals(Object var1) throws {
try {
return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final User getUserName(String var1) throws {
try {
return (User)super.h.invoke(this, m3, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final String toString() throws {
try {
return (String)super.h.invoke(this, m2, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
//代理类调用某方法super.h是InvocationHandler对象，调用invoke方法
public final User getId(String var1) throws {
try {
return (User)super.h.invoke(this, m4, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final int hashCode() throws {
try {
return (Integer)super.h.invoke(this, m0, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
static {
try {
m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
m3 = Class.forName("com.thinkgem.jeesite.proxy.UserOneService").getMethod("getUserName", Class.forName("java.lang.String"));
m2 = Class.forName("java.lang.Object").getMethod("toString");
m4 = Class.forName("com.thinkgem.jeesite.proxy.UserThreeService").getMethod("getId", Class.forName("java.lang.String"));
m0 = Class.forName("java.lang.Object").getMethod("hashCode");
} catch (NoSuchMethodException var2) {
throw new NoSuchMethodError(var2.getMessage());
} catch (ClassNotFoundException var3) {
throw new NoClassDefFoundError(var3.getMessage());
}
}
}
生成代理类：
@CallerSensitive
public static Object newProxyInstance(ClassLoader loader,
Class<?>[] interfaces,
InvocationHandler h)
throws IllegalArgumentException
{
Objects.requireNonNull(h);
final Class<?>[] intfs = interfaces.clone();
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
/*
* 生成并获取代理类Class
*/
Class<?> cl = getProxyClass0(loader, intfs);
/*
* Invoke its constructor with the designated invocation handler.
*/
try {
if (sm != null) {
checkNewProxyPermission(Reflection.getCallerClass(), cl);
}
//根据参数获取构造方法
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
//判断构造方法修饰符是否public，如果不是设置为可操作
if (!Modifier.isPublic(cl.getModifiers())) {
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
cons.setAccessible(true);
return null;
}
});
}
//根据构造方法获取对象
return cons.newInstance(new Object[]{h});
} catch (IllegalAccessException|InstantiationException e) {
throw new InternalError(e.toString(), e);
} catch (InvocationTargetException e) {
Throwable t = e.getCause();
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
} else {
throw new InternalError(t.toString(), t);
}
} catch (NoSuchMethodException e) {
throw new InternalError(e.toString(), e);
}
}private static Class<?> getProxyClass0(ClassLoader loader,
Class<?>... interfaces) {
if (interfaces.length > 65535) {
throw new IllegalArgumentException("interface limit exceeded");
}
//通过loader去缓存中获取是否存在class对象，不存在生成（弱引用），当内存不足时，GC自动回收
return proxyClassCache.get(loader, interfaces);
}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<Object, Supplier<V>> valuesMap = map.get(cacheKey);
if (valuesMap == null) {
ConcurrentMap<Object, Supplier<V>> oldValuesMap
= map.putIfAbsent(cacheKey,
valuesMap = new ConcurrentHashMap<>());
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}
// 生成key
Object subKey = Objects.requireNonNull(subKeyFactory.apply(key, parameter));
Supplier<V> supplier = valuesMap.get(subKey);
Factory factory = null;
while (true) {
if (supplier != null) {
// supplier might be a Factory or a CacheValue<V> 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);
}
}
}
}返回Supplier对象，之后调用get方法
@Override
public synchronized V get() { // serialize access
// re-check
Supplier<V> 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 {
//生成class对象
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<V> cacheValue = new CacheValue<>(value);
// put into reverseMap
reverseMap.put(cacheValue, Boolean.TRUE);
// try replacing us with CacheValue (this should always succeed)
if (!valuesMap.replace(subKey, this, cacheValue)) {
throw new AssertionError("Should not reach here");
}
// successfully replaced us with new CacheValue -> return the value
// wrapped by it
return value;
}
}private static final class ProxyClassFactory
implements BiFunction<ClassLoader, Class<?>[], Class<?>>
{
// prefix for all proxy class names
private static final String proxyClassNamePrefix = "$Proxy";
// next number to use for generation of unique proxy class names
private static final AtomicLong nextUniqueNumber = new AtomicLong();
@Override
public Class<?> apply(ClassLoader loader, Class<?>[] interfaces) {
Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
for (Class<?> intf : interfaces) {
/*
* 获取接口类
*/
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;
/*
* 生成代理类字节码
*/
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces, accessFlags);
try {
//加载字节码为class对象
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());
}
}
}public static byte[] generateProxyClass(final String var0, Class<?>[] var1, int var2) {
ProxyGenerator var3 = new ProxyGenerator(var0, var1, var2);
final byte[] var4 = var3.generateClassFile();
//是否生成代理类class，默认不生成，可以通过设置 System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");修改
if (saveGeneratedFiles) {
//默认路径ReflectUtil.PROXY_PACKAGE + "."+ proxyPkg + proxyClassNamePrefix + nextUniqueNumber.getAndIncrement();
//com.sun.proxy+"."+""+$proxy+自增数
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
try {
int var1 = var0.lastIndexOf(46);
Path var2;
if (var1 > 0) {
Path var3 = Paths.get(var0.substring(0, var1).replace('.', File.separatorChar));
Files.createDirectories(var3);
var2 = var3.resolve(var0.substring(var1 + 1, var0.length()) + ".class");
} else {
var2 = Paths.get(var0 + ".class");
}
Files.write(var2, var4, new OpenOption[0]);
return null;
} catch (IOException var4x) {
throw new InternalError("I/O exception saving generated file: " + var4x);
}
}
});
}
return var4;
}JDK动态代理
/**
* 获取代理对象，this表示JdkDynamicAopProxy的实现类
**/
@Override
public Object getProxy(@Nullable ClassLoader classLoader) {
if (logger.isDebugEnabled()) {
logger.debug("Creating JDK dynamic proxy: target source is " + this.advised.getTargetSource());
}
//查找需要增强的接口类
Class<?>[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true);
//过滤equals和hashCode方法
findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
//创建代理类
return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
}@Override
@Nullable
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
MethodInvocation invocation;
Object oldProxy = null;
boolean setProxyContext = false;
//获取需要增强的对象信息，包装于advise的TargetSouce中
TargetSource targetSource = this.advised.targetSource;
Object target = null;
try {
//如果是equals方法，直接执行
if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
// The target does not implement the equals(Object) method itself.
return equals(args[0]);
}
//如果是hashCode方法，直接执行
else if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
// The target does not implement the hashCode() method itself.
return hashCode();
}
else if (method.getDeclaringClass() == DecoratingProxy.class) {
// 委派给代理执行
return AopProxyUtils.ultimateTargetClass(this.advised);
}
else if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&
method.getDeclaringClass().isAssignableFrom(Advised.class)) {
// Service invocations on ProxyConfig with the proxy config...
return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);
}
Object retVal;
//是否需要开放内部代理功能，内部this.method是不会增强的,可以开启此处，之后通过AopContext.currentProxy()获取增强类，之后this.调用本类方法也可以进行增强
if (this.advised.exposeProxy) {
// Make invocation available if necessary.
oldProxy = AopContext.setCurrentProxy(proxy);
setProxyContext = true;
}
//获取需要增强的类
target = targetSource.getTarget();
Class<?> targetClass = (target != null ? target.getClass() : null);
// 获取增强调用链
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
// 如果调用链为空，直接反射调用原始类方法
if (chain.isEmpty()) {
// We can skip creating a MethodInvocation: just invoke the target directly
// Note that the final invoker must be an InvokerInterceptor so we know it does
// nothing but a reflective operation on the target, and no hot swapping or fancy proxying.
Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
}
else {
// 创建爱你调用链增强类
invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
// 执行增强方法，获取返回值
retVal = invocation.proceed();
}
Class<?> returnType = method.getReturnType();
if (retVal != null && retVal == target &&
returnType != Object.class && returnType.isInstance(proxy) &&
!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
// Special case: it returned "this" and the return type of the method
// is type-compatible. Note that we can't help if the target sets
// a reference to itself in another returned object.
retVal = proxy;
}
else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {
throw new AopInvocationException(
"Null return value from advice does not match primitive return type for: " + method);
}
return retVal;
}
finally {
if (target != null && !targetSource.isStatic()) {
// Must have come from TargetSource.
targetSource.releaseTarget(target);
}
if (setProxyContext) {
// Restore old proxy.
AopContext.setCurrentProxy(oldProxy);
}
}
}