如何让struts2和servlet的共存
虽然现在大多数的项目都采用了 sturts2的架构，但是不可避免的有时候要跟旧项目模块的servlet合并共存。
但是我们会发现 当servlet单独存在时,采用<form name="form1" method="post" action="MessagesAction?action=loginRoom">时可以跳转运行的。
加入到sturts2架构后，会报错：
HTTP Status 404 - There is no Action mapped for namespace / and action nameMessagesAction
因为struts2会拦截一切来自浏览器的请求。struts2把servlet当成action了，因为servlet和action都是没有后缀的.
解决方法目前有四种：
方法1-给servlet加后缀
统一在servlet后面加上.servlet结尾（包括web.xml配置文件中和页面上使用servlet的地方）比如我以上的例子：
index.jsp
<form name="form1" method="post" action="MessagesAction.servlet?action=loginRoom">
package com.cheney.chat;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;
import java.util.Random;
import java.util.Vector;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
import org.jdom.output.Format;
import org.jdom.output.XMLOutputter;
public class MessagesAction extends HttpServlet {
/**
* Constructor of the object.
*/
public MessagesAction() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>MessagesAction</servlet-name>
<servlet-class>com.cheney.chat.MessagesAction</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MessagesAction</servlet-name>
<url-pattern>/MessagesAction.servlet</url-pattern>
</servlet-mapping>
方法2-给strust2加后缀
（比较通用奥）：
在struts.xml中的<struts>的节点下面添加struts2处理的请求后缀 常量：
<!--
该属性指定需要Struts 2处理的请求后缀，该属性的默认值是action，即所有匹配*.action的请求都由Struts 2处理。
如果用户需要指定多个请求后缀，则多个后缀之间以英文逗号（，）隔开。
-->
<constant name="struts.action.extension" value="action" />
jsp页面上 使用到action的地方 比如 login 变成 login.action
方法3-修改strust2的拦截配置自动加后缀
在web.xml中修改struts2拦截页面请求的配置：
原：
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
现：
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>*.action</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/user/*</url-pattern>
</filter-mapping>
servlet的请求路径不必改变
jsp页面上 使用到action的地方 比如 login 变成 login.action
方法4-写一个过滤器区分sturst2和servlet
自定义filter对servlet进行过滤：
##############################################
# 该类是定义了一个过滤器（随便你放在哪个包下面），当既用到struts2有用到servlet时，
# 必须用该过滤器对所有的servlet做一次过滤，否则servlet将无法正常运行。
# 同时在web.xml中，在定义struts的核心控制器的过滤器前面添加该过滤器，添加代码如下：
* <filter>
* <filter-name>redisp</filter-name>
* <filter-class>filters.ReDispatcherFilter（该过滤器的类名）</filter-class>
* <init-param>
* <param-name>includeServlets</param-name>
* <param-value>所配置的servlet，注意是那url-pattern</param-value>
* </init-param>
* </filter>
* <filter-mapping>
* <filter-name>redisp</filter-name>
* <url-pattern>/*</url-pattern>
* </filter-mapping>
*该类也可以直接继承StrutsPrepareAndExecuteFilter的
###########################################################
public class ReDispatcherFilter implements Filter {
public void destroy() {
// TODO Auto-generated method stub
}
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException
{
HttpServletRequest request = (HttpServletRequest)req;
String target = request.getRequestURI();
target = target.lastIndexOf("?")>0
?target.substring(target.lastIndexOf("/")+1,target.lastIndexOf("?")-target.lastIndexOf("/"))
:target.substring(target.lastIndexOf("/")+1);
System.out.println(target);
if(this.includes.contains(target))
{
RequestDispatcher rdsp = request.getRequestDispatcher(target);
System.out.println("go..............."+rdsp);
rdsp.forward(req, resp);
}
else
chain.doFilter(req, resp);
}
private ArrayList<String> includes = new ArrayList<String>();
public void init(FilterConfig config) throws ServletException {
this.includes.addAll( Arrays.asList(config.getInitParameter("includeServlets").split(",")));
}
}
怕大家还是配置错误，给一个web.xml的配置实例。
<filter>
<filter-name>redisp</filter-name>
<filter-class>
com.xheditor.servlet.ReDispatcherFilter</filter-class>
<init-param>
<param-name>includeServlets</param-name>
<param-value>UploadFileServlet</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>redisp</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!-- struts2拦截页面请求的配置 -->
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!-- servlet的配置 -->
<servlet>
<servlet-name>ImageServlet</servlet-name>
<servlet-class>com.servlets.ImageServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ImageServlet</servlet-name>
<url-pattern>/myImageServlet/*</url-pattern>
</servlet-mapping>