Aop
jdk中的动态代理
接口类：
public interface IDateServices {
public void save(String data);
public int update(String data);
}接口实现类
public class DateService implements IDateServices{
@Override
public void save(String data) {
System.out.println("sava data "+data);
}
@Override
public int update(String data) {
System.out.println("update data "+data);
return 0;
}
}主类
@Data
@AllArgsConstructor
public class DynamicDemo1 implements InvocationHandler {
public DateService dateService;
public static void main(String[] args) {
IDateServices o = (IDateServices)Proxy.newProxyInstance(DynamicDemo1.class.getClassLoader(),
new Class[]{IDateServices.class},
new DynamicDemo1(new DateService()));
o.update("Dong");
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("before");
Object result = method.invoke(dateService,args);
System.out.println("after and result is "+result.toString());
return result;
}
}结果：
before
update data Dong
after and result is 0
动态代理的本质是将被代理类变化成代理类并加入内存，我们尝试将代理类打印出来，show code：
public class DynamicDemo2 {
public static void main(String[] args) throws Exception{
new DynamicDemo2().createProxyClass();
}
public void createProxyClass() throws Exception{
String classFileName = "D:\\java\\demo-total\\spring\\src\\main\\java\\com\\decy\\springboot\\mylearn\\of0901\\dynamic\\$proxy0.class";
byte[] classFile = ProxyGenerator.generateProxyClass("$proxy0", new Class[]{IDateServices.class});
FileOutputStream out = new FileOutputStream(classFileName);
out.write(classFile);
out.close();
}
}
反编译后的代码结果是：
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
import com.decy.springboot.mylearn.of0901.dynamic.IDateServices;
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 IDateServices {
private static Method m1;
private static Method m4;
private static Method m2;
private static Method m3;
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 void save(String var1) throws {
try {
super.h.invoke(this, m4, 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);
}
}
public final int update(String var1) throws {
try {
return (Integer)super.h.invoke(this, m3, 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"));
m4 = Class.forName("com.decy.springboot.mylearn.of0901.dynamic.IDateServices").getMethod("save", Class.forName("java.lang.String"));
m2 = Class.forName("java.lang.Object").getMethod("toString");
m3 = Class.forName("com.decy.springboot.mylearn.of0901.dynamic.IDateServices").getMethod("update", 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());
}
}
}
所有的方法都是反射，用的是h，本类继承的Proxy,Proxy类中有属性H
/**
* the invocation handler for this proxy instance.
* @serial
*/
protected InvocationHandler h;在源码方法中，newProxyInstance将实现类直接加入进去了
/**
* Returns an instance of a proxy class for the specified interfaces
* that dispatches method invocations to the specified invocation
* handler.
*
* <p>{@code Proxy.newProxyInstance} throws
* {@code IllegalArgumentException} for the same reasons that
* {@code Proxy.getProxyClass} does.
*
* @param loader the class loader to define the proxy class
* @param interfaces the list of interfaces for the proxy class
* to implement
* @param h the invocation handler to dispatch method invocations to
* @return a proxy instance with the specified invocation handler of a
* proxy class that is defined by the specified class loader
* and that implements the specified interfaces
* @throws IllegalArgumentException if any of the restrictions on the
* parameters that may be passed to {@code getProxyClass}
* are violated
* @throws SecurityException if a security manager, <em>s</em>, is present
* and any of the following conditions is met:
* <ul>
* <li> the given {@code loader} is {@code null} and
* the caller's class loader is not {@code null} and the
* invocation of {@link SecurityManager#checkPermission
* s.checkPermission} with
* {@code RuntimePermission("getClassLoader")} permission
* denies access;</li>
* <li> for each proxy interface, {@code intf},
* the caller's class loader is not the same as or an
* ancestor of the class loader for {@code intf} and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to {@code intf};</li>
* <li> any of the given proxy interfaces is non-public and the
* caller class is not in the same {@linkplain Package runtime package}
* as the non-public interface and the invocation of
* {@link SecurityManager#checkPermission s.checkPermission} with
* {@code ReflectPermission("newProxyInPackage.{package name}")}
* permission denies access.</li>
* </ul>
* @throws NullPointerException if the {@code interfaces} array
* argument or any of its elements are {@code null}, or
* if the invocation handler, {@code h}, is
* {@code null}
*/
@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);
}
/*
* Look up or generate the designated proxy class.
*/
Class<?> cl = getProxyClass0(loader, intfs);
/*
* Invoke its constructor with the designated invocation handler.
*/
try {
if (sm != null) {
checkNewProxyPermission(Reflection.getCallerClass(), cl);
}
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
if (!Modifier.isPublic(cl.getModifiers())) {
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
cons.setAccessible(true);
return null;
}
});
}
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);
}
}