Spring 自定义注解（上）

首先定义一个简单的Service：

public interface IDemoService {

    void add(int a, int b);

}
@Service
public class DemoServiceImpl implements IDemoService {

    @Log
    public void add(int a, int b) {
        System.out.println(Thread.currentThread().getName());
        System.out.println(a + b);

    }

}复制代码

假设@Log注解能够用来记录每一个函数的执行状况：

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Log {

}复制代码

使用BeanPostProcesser来生成自定义的代理对象：

@Service
public class LogAnnotationBeanPostProcesser extends AbstractBeanFactoryAwareAdvisingPostProcessor {

    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
        super.setBeanFactory(beanFactory);
        LogAnnotationAdvisor advisor = new LogAnnotationAdvisor();
        advisor.setBeanFactory(beanFactory);
        this.advisor = advisor;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) {
        Method[] methods = ReflectionUtils.getAllDeclaredMethods(bean.getClass());
        for (Method method : methods) {
            if (method.isAnnotationPresent(Log.class)) {
                ProxyFactory proxyFactory = prepareProxyFactory(bean, beanName);
                if (!proxyFactory.isProxyTargetClass()) {
                    evaluateProxyInterfaces(bean.getClass(), proxyFactory);
                }
                proxyFactory.addAdvisor(this.advisor);
                customizeProxyFactory(proxyFactory);
                return proxyFactory.getProxy(getProxyClassLoader());
            }
        }
        return bean;

    }

}复制代码

LogAnnotationAdvisor用来处理切面:

public class LogAnnotationAdvisor implements BeanFactoryAware,Advisor{

    private Advice advice;

    public LogAnnotationAdvisor(){

        this.advice=new LogAnnotationInterceptor();
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {


    }

    @Override
    public Advice getAdvice() {


        return this.advice;
    }

    @Override
    public boolean isPerInstance() {
        // TODO Auto-generated method stub
        return false;
    }

}复制代码

固然实例处理交给了：

public class LogAnnotationInterceptor implements MethodInterceptor, Ordered{

    @Override
    public int getOrder() {



        return Ordered.HIGHEST_PRECEDENCE;
    }

    @Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
        System.out.println("开始执行");
        invocation.proceed();

        System.out.println("结束执行");
        return null;
    }

}复制代码

使用：

public class Main {
    public static void main(String[] args) {
        @SuppressWarnings("resource")
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("application-context.xml");    
         IDemoService demoService = context.getBean(IDemoService.class);    
// AsyncAnnotationBeanPostProcessor 
        demoService.add(1, 2);

    }
}复制代码

输出：
开始执行 main 3 结束执行
源代码地址：github.com/slowlizard/…
解决了若是有一个方法加了@Log注解，那么这个类全部的方法都会执行Log的状况。
至于原理嘛。。下篇讲述。。
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