链式-AOP

骑猪看日落 2021-09-20 02:48 244阅读 0赞

[2019独角兽企业重金招聘Python工程师标准>>> ][2019_Python_] ![hot3.png][]

链式-AOP 属于 责任链模式，eg: 我们可以将每个 Proxy 用一根链子串起来，形成一个 Proxy Chain。然后调用这个 Proxy Chain，让它去依次调用 Chain 中的每个 Proxy。

public interface Proxy { // 具体要串在链子上的东东
    
        void doProxy(ProxyChain proxyChain);
    }

public class ProxyChain { // 链子，用来串Proxy用的
    
        private List<Proxy> proxyList;
        private int currentProxyIndex = 0;
    
        private Class<?> targetClass; // 具体哪个类
        private Object targetObject;  // 的哪个对象
        private Method targetMethod;  // 的哪个方法
        private Object[] methodParams; // 有哪几个参数的方法
        private MethodProxy methodProxy;  // 方法代理对象
        private Object methodResult;  // 方法返回结果
    
        public ProxyChain(Class<?> targetClass, Object targetObject, Method targetMethod, Object[] methodParams, MethodProxy methodProxy, List<Proxy> proxyList) {
            this.targetClass = targetClass;
            this.targetObject = targetObject;
            this.targetMethod = targetMethod;
            this.methodParams = methodParams;
            this.methodProxy = methodProxy;
            this.proxyList = proxyList;
        }
    
        public Class<?> getTargetClass() {
            return targetClass;
        }
    
        public Object getTargetObject() {
            return targetObject;
        }
    
        public Method getTargetMethod() {
            return targetMethod;
        }
    
        public Object[] getMethodParams() {
            return methodParams;
        }
    
        public MethodProxy getMethodProxy() {
            return methodProxy;
        }
    
        public Object getMethodResult() {
            return methodResult;
        }
    
        public void doProxyChain() {
            if (currentProxyIndex < proxyList.size()) {
                proxyList.get(currentProxyIndex++).doProxy(this); // 调用链条上的某个Proxy的某个方法
            } else {
                try {
                    methodResult = methodProxy.invokeSuper(targetObject, methodParams);
                } catch (Throwable throwable) {
                    throw new RuntimeException(throwable);
                }
            }
        }
    }

public class ProxyManager { // 一个Proxy工厂，用来创建Proxy用的
    
        private Class<?> targetClass; // 具体要创建哪一个类的Proxy
        private List<Proxy> proxyList;
    
        public ProxyManager(Class<?> targetClass, List<Proxy> proxyList) {
            this.targetClass = targetClass;
            this.proxyList = proxyList;
        }
    
        @SuppressWarnings("unchecked")
        public <T> T createProxy() {
            return (T) Enhancer.create(targetClass, new MethodInterceptor() {
                @Override
                public Object intercept(Object target, Method method, Object[] args, MethodProxy proxy) throws Throwable {
                    ProxyChain proxyChain = new ProxyChain(targetClass, target, method, args, proxy, proxyList);
                    proxyChain.doProxyChain();
                    return proxyChain.getMethodResult();
                }
            });
        }
    }

上面的三个类 只是创建了一种链式模式，下面要利用这种链式模式 实现AOP：

// “模版方法模式”，就是定义一个抽象类 里面一些空方法 当模版
    public abstract class AbstractProxy implements Proxy { // 实现 Proxy 借口
    
        @Override
        public final void doProxy(ProxyChain proxyChain) {
            Class<?> cls = proxyChain.getTargetClass(); // 具体哪个类要增强
            Method method = proxyChain.getTargetMethod(); // 的具体哪个方法
            Object[] params = proxyChain.getMethodParams(); // 的方法参数
    
            begin(); // 所有方法执行前要干什么
            try {
                if (filter(cls, method, params)) {
                    before(cls, method, params); // 具体方法执行前要干什么
                    proxyChain.doProxyChain(); 
                    after(cls, method, params); // 具体方法执行后要干什么
                } else {
                    proxyChain.doProxyChain();
                }
            } catch (Throwable e) {
                error(cls, method, params, e);
            } finally {
                end(); // 所有方法执行完后要干什么
            }
        }
    
        public void begin() {
        }
    
        public boolean filter(Class<?> cls, Method method, Object[] params) {
            return true;
        }
    
        public void before(Class<?> cls, Method method, Object[] params) {
        }
    
        public void after(Class<?> cls, Method method, Object[] params) {
        }
    
        public void error(Class<?> cls, Method method, Object[] params, Throwable e) {
        }
    
        public void end() {
        }
    }

具体实现：

public class BeforeProxy extends AbstractProxy {
    
        @Override
        public void before(Class<?> cls, Method method, Object[] params) {
            System.out.println("Before");
        }
    }

public class AfterProxy extends AbstractProxy {
    
        @Override
        public void after(Class<?> cls, Method method, Object[] params) {
            System.out.println("After");
        }
    }

编写客户端代码：

public class Client {
    
        public static void main(String[] args) {
            List<Proxy> proxyList = new ArrayList<Proxy>();
            proxyList.add(new BeforeProxy());
            proxyList.add(new AfterProxy());
    
            ProxyManager proxyManager = new ProxyManager(GreetingImpl.class, proxyList);
            GreetingImpl greetingProxy = proxyManager.createProxy();
    
            greetingProxy.sayHello("Jack");
        }
    }

转载于:https://my.oschina.net/Business/blog/912267

[2019_Python_]: https://my.oschina.net/u/2663968/blog/3061697
[hot3.png]: /images/20210726/411e3db10e074aeb8293a212fb372b26.png