filter的执行顺序

一直没有仔细去研究下filter ，最近系统的测试了下：

先看代码吧

Java代码

1. FirstFilter.java  
2. ==================  
3. package com.test.filter;  
5. import java.io.IOException;  
7. import javax.servlet.Filter;  
8. import javax.servlet.FilterChain;  
9. import javax.servlet.FilterConfig;  
10. import javax.servlet.ServletException;  
11. import javax.servlet.ServletRequest;  
12. import javax.servlet.ServletResponse;  
14. public class FirstFilter implements Filter {  
16. @Override
17. public void destroy() {  
19.     }  
21. @Override
22. public void doFilter(ServletRequest request, ServletResponse response,  
23.             FilterChain chain) throws IOException, ServletException {  
24.         System.out.println("before invoke firstFilter's chain.doFilter() ..");  
25.         chain.doFilter(request, response);  
26.         System.out.println("after invoke firstFilter's chain.doFilter() ..");  
27.     }  
29. @Override
30. public void init(FilterConfig arg0) throws ServletException {  
31.         System.out.println("firstFilter init()...");  
33.     }  
35. }  
38. ============  
40. SecondFilter.java  
41. ==============  
43. package com.test.filter;  
45. import java.io.IOException;  
47. import javax.servlet.Filter;  
48. import javax.servlet.FilterChain;  
49. import javax.servlet.FilterConfig;  
50. import javax.servlet.ServletException;  
51. import javax.servlet.ServletRequest;  
52. import javax.servlet.ServletResponse;  
54. public class SecondFilter implements Filter {  
56. @Override
57. public void destroy() {  
59.     }  
61. @Override
62. public void doFilter(ServletRequest request, ServletResponse response,  
63.             FilterChain chain) throws IOException, ServletException {  
64.         System.out.println("before invoke secondFilter's chain.doFilter() ..");  
65.         chain.doFilter(request, response);  
66.         System.out.println("after invoke secondFilter's chain.doFilter() ..");  
67.     }  
69. @Override
70. public void init(FilterConfig filterConfig) throws ServletException {  
71.         System.out.println("secondFilter init()...");  
72.     }  
74. }  
75. ==========  
77. FirstServlet.java  
78. =============  
79. package com.test.servlet;  
81. import java.io.IOException;  
83. import javax.servlet.ServletException;  
84. import javax.servlet.http.HttpServlet;  
85. import javax.servlet.http.HttpServletRequest;  
86. import javax.servlet.http.HttpServletResponse;  
88. public class FirstServlet extends HttpServlet {  
90. @Override
91. protected void doGet(HttpServletRequest req, HttpServletResponse resp)  
92. throws ServletException, IOException {  
93.         System.out.println("servlet doGet be invoked...");  
94.         req.getRequestDispatcher("test.jsp").forward(req, resp);  
95.     }  
97. @Override
98. protected void doPost(HttpServletRequest req, HttpServletResponse resp)  
99. throws ServletException, IOException {  
100. // TODO Auto-generated method stub
101.         doGet(req, resp);  
102.     }  
104. }  
106. =========  
108. web.xml  
110. ===========  
111. <?xml version="1.0" encoding="UTF-8"?>  
112. <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
113.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
114.     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
115.     http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
116.     <welcome-file-list>  
117.         <welcome-file>index.jsp</welcome-file>  
118.     </welcome-file-list>  
119.     <filter>  
120.         <filter-name>firstFilter</filter-name>  
121.         <filter-class>com.test.filter.FirstFilter</filter-class>  
122.     </filter>  
123.     <filter>  
124.         <filter-name>secondFilter</filter-name>  
125.         <filter-class>com.test.filter.SecondFilter</filter-class>  
126.     </filter>  
127.     <filter-mapping>  
128.         <filter-name>secondFilter</filter-name>  
129.         <url-pattern>/*</url-pattern>  
130.     </filter-mapping>  
131.     <filter-mapping>  
132.         <filter-name>firstFilter</filter-name>  
133.         <url-pattern>/*</url-pattern>  
134.     </filter-mapping>  
136.     <servlet>  
137.         <servlet-name>firstServlet</servlet-name>  
138.         <servlet-class>com.alimama.servlet.FirstServlet</servlet-class>  
139.     </servlet>  
140.     <servlet-mapping>  
141.         <servlet-name>firstServlet</servlet-name>  
142.         <url-pattern>/firstServlet</url-pattern>  
143.     </servlet-mapping>  
144. </web-app>  
146. ============ 

FirstFilter.java
==================
package com.test.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;

public class FirstFilter implements Filter {

	@Override
	public void destroy() {

	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		System.out.println("before invoke firstFilter's chain.doFilter() ..");
		chain.doFilter(request, response);
		System.out.println("after invoke firstFilter's chain.doFilter() ..");
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		System.out.println("firstFilter init()...");

	}

}


============

SecondFilter.java
==============

package com.test.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;

public class SecondFilter implements Filter {

	@Override
	public void destroy() {

	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		System.out.println("before invoke secondFilter's chain.doFilter() ..");
		chain.doFilter(request, response);
		System.out.println("after invoke secondFilter's chain.doFilter() ..");
	}

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

}
==========

FirstServlet.java
=============
package com.test.servlet;

import java.io.IOException;

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

public class FirstServlet extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		System.out.println("servlet doGet be invoked...");
		req.getRequestDispatcher("test.jsp").forward(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(req, resp);
	}
	
}

=========

web.xml

===========
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
	<filter>
		<filter-name>firstFilter</filter-name>
		<filter-class>com.test.filter.FirstFilter</filter-class>
	</filter>
	<filter>
		<filter-name>secondFilter</filter-name>
		<filter-class>com.test.filter.SecondFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>secondFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
	<filter-mapping>
		<filter-name>firstFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

	<servlet>
		<servlet-name>firstServlet</servlet-name>
		<servlet-class>com.alimama.servlet.FirstServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>firstServlet</servlet-name>
		<url-pattern>/firstServlet</url-pattern>
	</servlet-mapping>
</web-app>

============

然后发布，发现打印的日志如下：

。。。

firstFilter init()...
secondFilter init()...

。。。

2008-10-23 11:36:43 org.apache.catalina.startup.Catalina start
信息: Server startup in 3665 ms

这里过滤器初始化好了。

当我们访问我们的 应用：http://127.0.0.1:8080/appName

发现打印日记如下：

before invoke secondFilter's chain.doFilter() ..
before invoke firstFilter's chain.doFilter() ..
after invoke firstFilter's chain.doFilter() ..
after invoke secondFilter's chain.doFilter() ..

当我们将web.xml中filter的位置进行调整后：

Xml代码

1. <?xml version="1.0" encoding="UTF-8"?>
2. <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   
5.     http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
6. <welcome-file-list>
7. <welcome-file>index.jsp</welcome-file>
8. </welcome-file-list>
9. <filter>
10. <filter-name>firstFilter</filter-name>
11. <filter-class>com.test.filter.FirstFilter</filter-class>
12. </filter>
13. <filter>
14. <filter-name>secondFilter</filter-name>
15. <filter-class>com.test.filter.SecondFilter</filter-class>
16. </filter>
17. <SPAN style="COLOR: #ff0000"> <filter-mapping>
18. <filter-name>firstFilter</filter-name>
19. <url-pattern>/*</url-pattern>
20. </filter-mapping>
22. <filter-mapping>
23. <filter-name>secondFilter</filter-name>
24. <url-pattern>/*</url-pattern>
25. </filter-mapping></SPAN>
27. <servlet>
28. <servlet-name>firstServlet</servlet-name>
29. <servlet-class>com.alimama.servlet.FirstServlet</servlet-class>
30. </servlet>
31. <servlet-mapping>
32. <servlet-name>firstServlet</servlet-name>
33. <url-pattern>/firstServlet</url-pattern>
34. </servlet-mapping>
35. </web-app>

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
	<filter>
		<filter-name>firstFilter</filter-name>
		<filter-class>com.test.filter.FirstFilter</filter-class>
	</filter>
	<filter>
		<filter-name>secondFilter</filter-name>
		<filter-class>com.test.filter.SecondFilter</filter-class>
	</filter>
             <filter-mapping>
		<filter-name>firstFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

	<filter-mapping>
		<filter-name>secondFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
	
	<servlet>
		<servlet-name>firstServlet</servlet-name>
		<servlet-class>com.alimama.servlet.FirstServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>firstServlet</servlet-name>
		<url-pattern>/firstServlet</url-pattern>
	</servlet-mapping>
</web-app>

  然后在启动应用，会看到打印：

before invoke firstFilter's chain.doFilter() ..

before invoke secondFilter's chain.doFilter() ..
after invoke secondFilter's chain.doFilter() ..

after invoke firstFilter's chain.doFilter() ..

总结：

filter的执行顺序是按照web.xml中定义的顺序进行执行的（当多个filter都匹配的时候），执行顺序如下图表示。（PS图取自http://hi.baidu.com/cathy_200182/blog/item/1f686238df10eb22b8998fe3.html  感谢之）

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