java Filter的简单使用

Posted 2020-09-19 耗子的烂代码

java web中的过滤器的简单使用、直接上代码。
1、web.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3     xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
 4     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
 5     version="3.0">
 6     <display-name>testFilter</display-name>
 7     
 8     <filter>
 9         <filter-name>filter1</filter-name>
10         <filter-class>test_servlet_package.SimpleFilter1</filter-class>
11     </filter>
12     <filter-mapping>
13         <filter-name>filter1</filter-name>
14         <url-pattern>/*</url-pattern>
15     </filter-mapping>
16 
17     <filter>
18         <filter-name>filter2</filter-name>
19         <filter-class>test_servlet_package.SimpleFilter2</filter-class>
20     </filter>
21     <filter-mapping>
22         <filter-name>filter2</filter-name>
23         <url-pattern>/*</url-pattern>
24     </filter-mapping>
25 
26     <servlet>
27         <servlet-name>testServlet</servlet-name>
28         <servlet-class>test_servlet_package.test_servlet</servlet-class>
29         <init-param> 
30             <param-name>test</param-name> 
31             <param-value>test1</param-value> 
32         </init-param>
33         <load-on-startup>1</load-on-startup>
34     </servlet>
35     <servlet-mapping>
36         <servlet-name>testServlet</servlet-name>
37         <url-pattern>/testServlet</url-pattern>
38     </servlet-mapping>
39 </web-app>

2、test_servlet.java、SimpleFilter2.java、SimpleFilter1.java

 1 package test_servlet_package;
 2 import java.io.IOException;
 3 import javax.servlet.Filter;
 4 import javax.servlet.FilterChain;
 5 import javax.servlet.FilterConfig;
 6 import javax.servlet.ServletException;
 7 import javax.servlet.ServletRequest;
 8 import javax.servlet.ServletResponse;
 9 public class SimpleFilter1 implements Filter {
10     // 随着容器 一起 起来 。。。初始化。。。
11     @SuppressWarnings("unused")
12     private FilterConfig filterConfig;
13     public void init(FilterConfig config) throws ServletException {
14         this.filterConfig = config;
15     }
16     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {
17         try {
18             System.out.println("Within SimpleFilter1:Filtering the Request...");
19             chain.doFilter(request, response);// 把处理发送到下一个过滤器
20             System.out.println("Within SimpleFilter1:Filtering the Response...");
21         } catch (IOException ioe) {
22             ioe.printStackTrace();
23         } catch (ServletException se) {
24             se.printStackTrace();
25         }
26     }
27     public void destroy() {
28         this.filterConfig = null;
29     }
30 }

 1 package test_servlet_package;
 2 
 3 import java.io.IOException;
 4 import javax.servlet.Filter;
 5 import javax.servlet.FilterChain;
 6 import javax.servlet.FilterConfig;
 7 import javax.servlet.ServletException;
 8 import javax.servlet.ServletRequest;
 9 import javax.servlet.ServletResponse;
10 
11 public class SimpleFilter2 implements Filter {
12     @SuppressWarnings("unused")
13     private FilterConfig filterConfig;
14 
15     public void init(FilterConfig config) throws ServletException {
16         this.filterConfig = config;
17     }
18 
19     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {
20         try {
21             System.out.println("Within SimpleFilter2:Filtering the Request...");
22             chain.doFilter(request, response); // 把处理发送到下一个过滤器
23             System.out.println("Within SimpleFilter2:Filtering the Response...");
24         } catch (IOException ioe) {
25             ioe.printStackTrace();
26         } catch (ServletException se) {
27             se.printStackTrace();
28         }
29     }
30 
31     public void destroy() {
32         this.filterConfig = null;
33     }
34     /*
35      * Within SimpleFilter1:Filtering the Request... Within
36      * SimpleFilter2:Filtering the Request... Within SimpleFilter2:Filtering the
37      * Response... Within SimpleFilter1:Filtering the Response...
38      */
39 }

 1 package test_servlet_package;
 2 import java.io.IOException;
 3 import javax.servlet.ServletConfig;
 4 import javax.servlet.ServletContext;
 5 import javax.servlet.ServletException;
 6 import javax.servlet.http.HttpServlet;
 7 import javax.servlet.http.HttpServletRequest;
 8 import javax.servlet.http.HttpServletResponse;
 9 public class test_servlet extends HttpServlet {
10     private static final long serialVersionUID = 1L;
11     // servlet 第一次 请求 被初始化 ,对象 在 容器 里 只有 一个
12     // 但是 在 web.xml 配置 了 <load-on-startup>1</load-on-startup> 则 会 立刻 启动初始化
13     // 初始化
14     public void init(ServletConfig config) throws ServletException {
15         super.init(config);
16         // 从配置文件中获得初始化参数
17         String test = config.getInitParameter("test");
18         ServletContext context = this.getServletContext();
19         String filePath = context.getRealPath(test);
20         System.out.println("filePath：" + filePath);
21     }
22     protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
23         ServletConfig config = this.getServletConfig();
24         ServletContext servletContext =  this.getServletContext();
25         res.getWriter().println("test");
26         res.getWriter().close();
27     
28     }
29     protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
30         doGet(req, res);
31     }
32 }