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過濾器Filter

在src下建立com.example.filter包

• 建立 ServletFilter.java 實現 Filter 方法

package com.example.filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import
 
 javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;

/**
 * Servlet Filter implementation class ServletFilter
 * 註解註冊過濾器：實現 javax.servlet.Filter介面 
 * filterName 是過濾器的名字
 * urlPatterns 是需要過濾的請求 ，這裡只過濾servlet/* 下面的所有請求
 */
@WebFilter(filterName="ServletFilter",urlPatterns="/servlet/*"
 
)
public class ServletFilter implements Filter {

    /**
     * Default constructor. 
     */
    public ServletFilter() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        System.out.println("過濾器被銷燬。");
    }

    /**
     * @see
 
 Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        // place your code here
        System.out.println("過濾器正在執行...");
        // pass the request along the filter chain
        chain.doFilter(request, response);
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        System.out.println("初始化過濾器。");
    }

}

測試

控制檯輸出：

監聽器Listener

在src下建立com.example.listener包

• 建立 ContextListener.java 類

package com.example.listener;

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

/**
 * Application Lifecycle Listener implementation class ContextListener
 * @author LingDu
 */
@WebListener
public class ContextListener implements ServletContextListener {

    /**
     * Default constructor. 
     */
    public ContextListener() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see ServletContextListener#contextDestroyed(ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent arg0)  { 
         System.out.println("監聽器被銷燬");
    }

    /**
     * @see ServletContextListener#contextInitialized(ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent arg0)  { 
         System.out.println("監聽器初始化。");
    }

}

專案啟動的時候 監聽器是先被初始化的

攔截器Interceptor

建立攔截器

      在src下建立com.example.interceptor包，
建立MyInterceptor.java類，實現HandlerInterceptor介面，重寫裡面3個主要的方法。

• MyInterceptor.java

package com.example.interceptor;

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

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

/**
 * 1、建立攔截器類並實現 HandlerInterceptor 介面
 * @author LingDu
 */
public class MyInterceptor implements HandlerInterceptor {

    @Override
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        System.out.println("攔截器MyInterceptor------->3、請求結束之後被呼叫，主要用於清理工作。");

    }

    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        System.out.println("攔截器MyInterceptor------->2、請求之後呼叫，在檢視渲染之前，也就是Controller方法呼叫之後");

    }

    @Override
    public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
        System.out.println("攔截器MyInterceptor------->1、請求之前呼叫，也就是Controller方法呼叫之前。");
        return true;//返回true則繼續向下執行，返回false則取消當前請求
    }

}

註冊攔截器

      在src下建立com.example.interceptor包
建立InterceptorConfigurerAdapter類，繼承WebMvcConfigurerAdapter類，重寫addInterceptors方法

• InterceptorConfigurerAdapter.java

注意：需要加上@Configuration註解

package com.example.interceptor;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

/**
 * 建立java類繼承WebMvcConfigurerAdapter類，重寫addInterceptors方法
 * @author LingDu
 */
@Configuration
public class InterceptorConfigurerAdapter extends WebMvcConfigurerAdapter {
    /**
     * 該方法用於註冊攔截器
     * 可註冊多個攔截器，多個攔截器組成一個攔截器鏈
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // addPathPatterns 新增路徑
        // excludePathPatterns 排除路徑
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/*.*");
        super.addInterceptors(registry);
    }
}

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