AOP
基于JDK和CGlib实现AOP
1、PointCut 切点表达式，ClassFilter定义类匹配类，用于切点找到给定的接口和目标类；MethodMatcher，方法匹配，找到表达式范围内匹配的目标类和方法；
public interface Pointcut {
/**
* Return the ClassFilter for this pointcut.
* @return the ClassFilter (never <code>null</code>)
*/
ClassFilter getClassFilter();
/**
* Return the MethodMatcher for this pointcut.
* @return the MethodMatcher (never <code>null</code>)
*/
MethodMatcher getMethodMatcher();
}
2、切点表达式类，负责对aspectJ包提供的表达式校验方法使用
public class AspectJExpressionPointcut implements Pointcut, ClassFilter, MethodMatcher {
private static final Set<PointcutPrimitive> SUPPORTED_PRIMITIVES = new HashSet<PointcutPrimitive>();
static {
SUPPORTED_PRIMITIVES.add(PointcutPrimitive.EXECUTION);
}
private final PointcutExpression pointcutExpression;
public AspectJExpressionPointcut(String expression) {
PointcutParser pointcutParser = PointcutParser.getPointcutParserSupportingSpecifiedPrimitivesAndUsingSpecifiedClassLoaderForResolution(SUPPORTED_PRIMITIVES, this.getClass().getClassLoader());
pointcutExpression = pointcutParser.parsePointcutExpression(expression);
}
@Override
public boolean matches(Class<?> clazz) {
return pointcutExpression.couldMatchJoinPointsInType(clazz);
}
@Override
public boolean matches(Method method, Class<?> targetClass) {
return pointcutExpression.matchesMethodExecution(method).alwaysMatches();
}
@Override
public ClassFilter getClassFilter() {
return this;
}
@Override
public MethodMatcher getMethodMatcher() {
return this;
}
}
3、包装切面通知消息
public class AdvisedSupport {
// 被代理的目标对象
private TargetSource targetSource;
// 方法拦截器
private MethodInterceptor methodInterceptor;
// 方法匹配器(检查目标方法是否符合通知条件)
private MethodMatcher methodMatcher;
// ...get/set
}
- AdvisedSupport，主要是用于把代理、拦截、匹配的各项属性包装到一个类中，方便在 Proxy 实现类进行使用。这和你的业务开发中包装入参是一个道理
- TargetSource，是一个目标对象，在目标对象类中提供 Object 入参属性，以及获取目标类 TargetClass 信息。
- MethodInterceptor，是一个具体拦截方法实现类，由用户自己实现 MethodInterceptor#invoke 方法，做具体的处理。像我们本文的案例中是做方法监控处理
- MethodMatcher，是一个匹配方法的操作，这个对象由 AspectJExpressionPointcut 提供服务。
4、代理抽象实现
public interface AopProxy {
Object getProxy();
}
动态代理，包含两个实现类，一个基于AOP实现AOPProxy和InvocationHandler，另一个基于cglib实现
public class JdkDynamicAopProxy implements AopProxy, InvocationHandler {
private final AdvisedSupport advised;
public JdkDynamicAopProxy(AdvisedSupport advised) {
this.advised = advised;
}
@Override
public Object getProxy() {
return Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), advised.getTargetSource().getTargetClass(), this);
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (advised.getMethodMatcher().matches(method, advised.getTargetSource().getTarget().getClass())) {
MethodInterceptor methodInterceptor = advised.getMethodInterceptor();
return methodInterceptor.invoke(new ReflectiveMethodInvocation(advised.getTargetSource().getTarget(), method, args));
}
return method.invoke(advised.getTargetSource().getTarget(), args);
}
}
Cglib实现
public class Cglib2AopProxy implements AopProxy {
private final AdvisedSupport advised;
public Cglib2AopProxy(AdvisedSupport advised) {
this.advised = advised;
}
@Override
public Object getProxy() {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(advised.getTargetSource().getTarget().getClass());
enhancer.setInterfaces(advised.getTargetSource().getTargetClass());
enhancer.setCallback(new DynamicAdvisedInterceptor(advised));
return enhancer.create();
}
private static class DynamicAdvisedInterceptor implements MethodInterceptor {
@Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
CglibMethodInvocation methodInvocation = new CglibMethodInvocation(advised.getTargetSource().getTarget(), method, objects, methodProxy);
if (advised.getMethodMatcher().matches(method, advised.getTargetSource().getTarget().getClass())) {
return advised.getMethodInterceptor().invoke(methodInvocation);
}
return methodInvocation.proceed();
}
}
private static class CglibMethodInvocation extends ReflectiveMethodInvocation {
@Override
public Object proceed() throws Throwable {
return this.methodProxy.invoke(this.target, this.arguments);
}
}
}