SpringBoot中過濾器、監聽器以及攔截器

屬於javax.servlet所提供的Api

攔截器原理

簡單來講是通過動態代理實現，被訪問的目標方法通過代理類（方法）來執行，這樣我們就可以在真正要執行的方法執行前、后做一些處理；
通過攔截器這種方式，使得代碼可以進行更高度的抽象。

過濾器初始化、銷毀

package com.example.demo.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

/**
 * Created by flyme
 * on 2017/11/6 19:30
 */
@WebFilter(filterName = "myfilter", urlPatterns = "/*")
public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) {
        System.out.println("過濾器初始化");
    }

    @Override
    public void destroy() {
        System.out.println("過濾器銷毀");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("執行過濾操作");
        filterChain.doFilter(servletRequest, servletResponse);
    }
}

監聽器 ServletContex初始化、ServletContex銷毀

package com.example.demo.listener;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

/**
 * Created by flyme
 * on 2017/11/6 19:37
 * //
 */
@WebListener
public class MyServletContextListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("ServletContex初始化");
        System.out.println(servletContextEvent.getServletContext().getServerInfo());
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        System.out.println("ServletContex銷毀");
    }


}

監聽器 ServletContex初始化、Session被創建

package com.example.demo.listener;

import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

/**
 * Created by flyme
 * on 2017/11/6 19:39
 */
@WebListener
public class MyHttpSessionLister implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        System.out.println("Session被創建");
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        System.out.println("ServletContex初始化");
    }
}

攔截器

實現自定義攔截器只需要3步：

1、創建我們自己的攔截器類並實現 HandlerInterceptor接口。
2、創建一個Java類繼承WebMvcConfigurerAdapter，並重寫 addInterceptors 方法。
2、實例化我們自定義的攔截器，然后將對像手動添加到攔截器鏈中（在addInterceptors方法中添加）

第一個攔截器

package com.example.demo.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * Created by flyme
 * on 2017/11/6 20:04
 *
 */
public class MyInterceptor1 implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println(">>>MyInterceptor1>>>>>>>在請求處理之前進行調用（Controller方法調用之前）");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println(">>>MyInterceptor1>>>>>>>請求處理之后進行調用，但是在視圖被渲染之前（Controller方法調用之后）");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println(">>>MyInterceptor1>>>>>>>在整個請求結束之后被調用，也就是在DispatcherServlet 渲染了對應的視圖之后執行（主要是用於進行資源清理工作）");
    }
}

第二個攔截器

package com.example.demo.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Created by flyme
 * on 2017/11/6 20:27
 */
public class MyInterceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println(">>>MyInterceptor2>>>>>>>在請求處理之前進行調用（Controller方法調用之前）");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println(">>>MyInterceptor2>>>>>>>請求處理之后進行調用，但是在視圖被渲染之前（Controller方法調用之后）");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println(">>>MyInterceptor2>>>>>>>在整個請求結束之后被調用，也就是在DispatcherServlet 渲染了對應的視圖之后執行（主要是用於進行資源清理工作）");
    }
}

將自定義的攔截器手動添加到攔截器鏈

package com.example.demo;

import com.example.demo.interceptor.MyInterceptor1;
import com.example.demo.interceptor.MyInterceptor2;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

/**
 * Created by flyme
 * on 2017/11/6 20:28
 */
@Configuration
public class MyWebAppConfigurer extends WebMvcConfigurerAdapter {
    public void addInterceptors(InterceptorRegistry registry){
        // 多個攔截器組成一個攔截器鏈
        // addPathPatterns 用於添加攔截規則
        // excludePathPatterns 用戶排除攔截
        registry.addInterceptor(new MyInterceptor1()).addPathPatterns("/**");
        registry.addInterceptor(new MyInterceptor2()).addPathPatterns("/**");
        super.addInterceptors(registry);
    }
}