SpringBoot 拦截器、过滤器、监听器

时间  2019-12-05
标签 springboot 拦截 过滤器 监听器 栏目 Spring 繁體版
原文   原文链接

  在工做中使用Web框架，老是避免不了与这些概念打交道，作一下总结，一口气说完拦截器、过滤器、监听器。java

GitHub源码地址git

1. 拦截器、过滤器、监听器区别

  • 拦截器(interceptor)：依赖于web框架，基于Java的反射机制，属于AOP的一种应用。一个拦截器实例在一个controller生命周期内能够屡次调用。只能拦截Controller的请求。
  • 过滤器(Filter)：依赖于Servlet容器，基于函数回掉，能够对几乎全部请求过滤，一个过滤器实例只能在容器初使化调用一次。
  • 监听器(Listener)：web监听器是Servlet中的特殊的类，用于监听web的特定事件，随web应用启动而启动，只初始化一次。

2. 有什么用

  • 拦截器(interceptor)：在一个请求进行中的时候，你想干预它的进展，甚至控制是否终止。这是拦截器作的事。
  • 过滤器(Filter)：当有一堆东西，只但愿选择符合的东西。定义这些要求的工具，就是过滤器。
  • 监听器(Listener)：一个事件发生后，只但愿获取这些事个事件发生的细节，而不去干预这个事件的执行过程，这就用到监听器

3. 启动顺序

监听器 >  过滤器 > 拦截器
复制代码

4.SpringBoot中的具体实现

（1） 拦截器

  1. 拦截器经常使用有两种方式实现
    • 实现HandlerInterceptor接口
    • 继承HandlerInterceptorAdapter 抽象类
  2. 区别和联系
  • HandlerInterceptorAdapter 实现AsyncHandlerInterceptor接口，AsyncHandlerInterceptor接口 继承HandlerInterceptor接口.
  • AsyncHandlerInterceptor接口多了一个afterConcurrentHandlingStarted方法
  1. 具体方法
  • preHandle //请求过来以后首先走的方法 return true 继续往下执行
  • postHandle //请求以后返回以前
  • afterCompletion //处理完成以后
  • afterConcurrentHandlingStarted //若是返回一个current类型的变量，会启用一个新的线程。执行完preHandle方法以后当即会调用afterConcurrentHandlingStarted,而后新线程再以次执行preHandle,postHandle,afterCompletion
  1. 代码实现

【注】如下代码基于springboot2.0github

(1)拦截器web

MyInterceptor1 继承 HandlerInterceptorAdapterspring

MyInterceptor2 实现 HandlerInterceptor接口springboot

public class MyInterceptor1 extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        request.setAttribute("startTime", System.currentTimeMillis());
        System.out.println(">>>>> MyInterceptor1 preHandle >>>>>>>>>>>>>>>>>>>>>>");
        return super.preHandle(request, response, handler);
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        long startTime = (long) request.getAttribute("startTime");
        System.out.println("MyInterceptor1 执行:" + (System.currentTimeMillis() - startTime));
        System.out.println(">>>>> MyInterceptor1 postHandle >>>>>>>>>>>>>>>>>>>>>>");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        request.removeAttribute("startTime");
        System.out.println(">>>>> MyInterceptor1 afterCompletion >>>>>>>>>>>>>>>>>>>>>>");
    }

    @Override
    public void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        super.afterConcurrentHandlingStarted(request, response, handler);
        System.out.println(">>>>> MyInterceptor1 afterConcurrentHandlingStarted >>>>>>>>>>>>>>>>>>>>>>");
    }
}
复制代码
public class MyInterceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        request.setAttribute("startTime", System.currentTimeMillis());
        System.out.println(">>>>> MyInterceptor2 preHandle >>>>>>>>>>>>>>>>>>>>>>");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        long startTime = (long) request.getAttribute("startTime");
        System.out.println("MyInterceptor2 执行:" + (System.currentTimeMillis() - startTime));
        System.out.println(">>>>> MyInterceptor2 postHandle >>>>>>>>>>>>>>>>>>>>>>");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        request.removeAttribute("startTime");
        System.out.println(">>>>> MyInterceptor2 afterCompletion >>>>>>>>>>>>>>>>>>>>>>");
    }
}
复制代码

(2)配置app

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor1()).addPathPatterns("/**");
        registry.addInterceptor(new MyInterceptor2()).addPathPatterns("/**");
    }
}
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(3)请求框架

@RestController
@SpringBootApplication
public class SpringbootInterceptorApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootInterceptorApplication.class, args);
    }


    @GetMapping(value = "/hello1")
    public ResponseEntity<String> hello() throws InterruptedException {
        Thread.sleep(500);
        return ResponseEntity.ok("HelloWorld");
    }

    @GetMapping(value = "/hello2")
    public StreamingResponseBody hello2() throws InterruptedException {
        Thread.sleep(500);
        return (OutputStream outputStream) -> {
            outputStream.write("success".getBytes());
            outputStream.flush();
            outputStream.close();
        };
    }

    @GetMapping(value = "/hello3")
    public Future<String> hello3() throws InterruptedException {
        Thread.sleep(500);
        return new AsyncResult<>("Hello");
    }
}
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(4) 运行结果ide

  1. 请求/hello1函数

    >>>>> MyInterceptor1 preHandle >>>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor2 preHandle >>>>>>>>>>>>>>>>>>>>>>
MyInterceptor2 执行:516
>>>>> MyInterceptor2 postHandle >>>>>>>>>>>>>>>>>>>>>
MyInterceptor1 执行:516
>>>>> MyInterceptor1 postHandle >>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor2 afterCompletion >>>>>>>>>>>>>>>>
>>>>> MyInterceptor1 afterCompletion >>>>>>>>>>>>>>>>
复制代码

    执行按preHandle > postHandle > afterCompletion

  2. 请求/hello2 或 /hello3

    >>>>> MyInterceptor1 preHandle >>>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor2 preHandle >>>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor1 afterConcurrentHandlingStarted >>>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor1 preHandle >>>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor2 preHandle >>>>>>>>>>>>>>>>>>>>>>
MyInterceptor2 执行:1
>>>>> MyInterceptor2 postHandle >>>>>>>>>>>>>>>>>>>>>>
MyInterceptor1 执行:1
>>>>> MyInterceptor1 postHandle >>>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor2 afterCompletion >>>>>>>>>>>>>>>>>>>>>>
>>>>> MyInterceptor1 afterCompletion >>>>>>>>>>>>>>>>>>>>>>
复制代码

    MyInterceptor1 执行顺序 preHandle > afterConcurrentHandlingStarted > preHandle > postHandle >afterCompletion

    MyInterceptor2 执行顺序 preHandle > preHandle > postHandle > afterCompletion

综上.对于concurrent类型的返回值，spring会启用一个新的线程来处理concurrent类型消息，在新的线程中会从新调用preHandle方法。

（2） 过滤器

(1) 过滤器

public class MyFilter1 implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println(filterConfig.getInitParameter("initParam"));
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("doFilter1 >>>>>>>>>>>");
        filterChain.doFilter(servletRequest, servletResponse);
    }
}
复制代码

(2) 配置

  • 第一种方式
@Bean
public FilterRegistrationBean<MyFilter1> filterRegistrationBean() {
    FilterRegistrationBean<MyFilter1> filterRegistrationBean = new FilterRegistrationBean<>();
    filterRegistrationBean.addUrlPatterns("/*");//过滤全部
    filterRegistrationBean.setFilter(new MyFilter1());
    filterRegistrationBean.setOrder(1);
    filterRegistrationBean.addInitParameter("initParam", "initOk");
    return filterRegistrationBean;
}
复制代码
  • 第二种方式
@Bean
public MyFilter1 myFilter() {
    return new MyFilter1();
}
复制代码
  • 第三种方式
@WebFilter("/test/*")
public class MyFilter2 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("MyFilter2");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        filterChain.doFilter(servletRequest, servletResponse);
        System.out.println("DoFilter 2");
    }
}
复制代码

经过@WebFilter("/test/*")注解，首先须要@ServletComponentScan("com.jiuxian")

Filter 全局拦截的配置(/*)和 Interceptor(/**)有所区别须要注意

（3） 监听器

(1) 监听器

public class MyListener1 implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("MyListener1 ... ");
    }
}
复制代码

(2) 配置方式和Filter相似

  • 第一种方式
@Bean
public ServletListenerRegistrationBean<MyListener1> registrationBean() {
    ServletListenerRegistrationBean<MyListener1> servletListenerRegistrationBean
            = new ServletListenerRegistrationBean<>();
    servletListenerRegistrationBean.setListener(new MyListener1());
    return servletListenerRegistrationBean;
}
复制代码
  • 第二种方式
@Bean
public MyListener1 myListener1() {
    return new MyListener1();
}
复制代码
  • 第三种方式
@WebListener
public class MyListener2 implements ServletRequestListener {

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        System.out.println("MyListener2");
    }
}
复制代码

使用@WebListener注解，首先须要@ServletComponentScan("com.jiuxian")

【注】以上代码基于springboot2.0

GitHub源码地址

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