Spring的拦截器

Spring的拦截器主要分两种，一个是HandlerInterceptor，一个是MethodInterceptor。

 

HandlerInterceptor拦截器

        HandlerInterceptor是springMVC项目中的拦截器，它拦截的目标是请求的地址，比MethodInterceptor先执行。实现一个HandlerInterceptor拦截器可以实现HandlerInterceptor接口，也可以继承HandlerInterceptorAdapter类。

 

自定义拦截器：

public class CustomInterceptor implements HandlerInterceptor {
	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
		System.out.println("在Controller方法调用之前执行：" + request.getRequestURI());
		
		//只有返回true才会继续向下执行，返回false取消当前请求
		return true;
	}

	@Override
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
			throws Exception {
		System.out.println("在Controller方法调用之后，视图被渲染之前执行：" + request.getRequestURI());
	}
	
	@Override
	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
			throws Exception {
		System.out.println("在视图被渲染之后执行：" + request.getRequestURI());
	}
}

 

创建WebMvcConfigurerAdapter的子类，将自定义拦截器加入到拦截器链中。

@Configuration
public class WebMvcConfig extends WebMvcConfigurerAdapter {
	@Override
	public void addInterceptors(InterceptorRegistry registry) {
		//将自定义拦截器加入到拦截器链中
		String[] excludes = {"/css/**", "/images/**", "/js/**"}; //忽略静态资源
		registry.addInterceptor(new CustomInterceptor()).addPathPatterns("/**").excludePathPatterns(excludes);
		
		super.addInterceptors(registry);
	}
}

 

MethodInterceptor拦截器

        MethodInterceptor是AOP项目中的拦截器，它拦截的目标是方法，即使不是controller中的方法。实现MethodInterceptor拦截器大致也分为两种，一种是实现MethodInterceptor接口，另一种利用AspectJ的注解或配置。

 

实现MethodInterceptor接口：

//自定义注解类
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface Log {
	
}

//方法拦截器
public class CustomMethodInterceptor implements MethodInterceptor{
	@Override
	public Object invoke(MethodInvocation invocation) throws Throwable {
		System.out.println("before...");
        Object object = invocation.proceed();
        System.out.println("after...");
        return object;
	}
}


@Configuration
public class AspectjAutoConfig {
	@Bean
    public DefaultPointcutAdvisor getDefaultPointcutAdvisor() {
        DefaultPointcutAdvisor pointcutAdvisor = new DefaultPointcutAdvisor();
        pointcutAdvisor.setOrder(Ordered.HIGHEST_PRECEDENCE + 500);
        
		//基于方法注解进行拦截
        AnnotationMatchingPointcut pointcut = new AnnotationMatchingPointcut(null, Log.class);
        CustomMethodInterceptor advice = new CustomMethodInterceptor();
        pointcutAdvisor.setPointcut(pointcut);
        pointcutAdvisor.setAdvice(advice);
        
        return pointcutAdvisor;
    }
}


public interface CountryMapper {
	void show();
}


@Component
public class CountryMapperImpl implements CountryMapper {
	//用自定义注解类标注方法，该方法会被自定义方法拦截器进行拦截处理
	@Log
	@Override
	public void show(){
		System.out.println("invoke show...");
	}
}

@SpringBootApplication()
@RestController
public class Main{
	@Autowired
	private CountryMapper countryMapper;
	
	public static void main(String[] args){
		SpringApplication.run(Main.class, args);
	}
	
	@GetMapping("/index")
	public String index(){
		countryMapper.show();
		return LocalDateTime.now().toString();
	}
}

  

 

Hessian服务调用： MethodInterceptor拦截器、Spring代理、工厂Bean的综合利用案例

        在Spring环境下调用Hessian服务可以通过HessianProxyFactoryBean类实现，HessianProxyFactoryBean类的继承结构如下：

BeanClassLoaderAware
	RemotingSupport - beanClassLoader
		RemoteAccessor - serviceInterface
			UrlBasedRemoteAccessor+MethodInterceptor - serviceUrl
				HessianClientInterceptor+FactoryBean
					HessianProxyFactoryBean
						|_ ProxyFactory

 

1、通过HessianProxyFactoryBean获取到的对象是Spring的ProxyFactory对象

2、ProxyFactory对象对服务接口进行动态代理

3、调用服务接口的方法时，会被HessianClientInterceptor拦截器进行拦截处理

4、HessianClientInterceptor拦截器中

         通过HessianProxyFactory创建服务接口的代理对象，HessianProxyFactory底层使用JDK动态代理生成代理类

         动态代理对应的Handler类是HessianProxy，其实现InvocationHandler接口

         HessianProxy负责打开HessianConnection，获取HessianOutput，写数据到服务端；然后获取HessianInput，读数据并返回