servlet和struts2一起使用，实现绝对路径下的图片输出到jsp页面

如果我们在web.xml中配置的struts2的接收请求的路径为：

<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

是可以用struts2中使用servlet的，只是必须让struts2的action来转发到servlet的url-pattern中的地址就可以了。我们简单的举例如下：

例如定义了一个servlet：

<servlet>
<servlet-name>Snippet</servlet-name>
<servlet-class>com.social.util.Snippet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>Snippet</servlet-name>
<url-pattern>/Snippet</url-pattern>
</servlet-mapping>

其中Snippet是显示图片的servlet，代码如下：

import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;

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

public class Snippet extends HttpServlet{
   public void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {

           this.doPost(req, resp);
        }

   @Override
   protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

       resp.setContentType("text/html; charset=UTF-8");
            resp.setContentType("image/jpeg");    //设置图片格式格式，这里可以忽略

            FileInputStream fis = new FileInputStream("E:/tomcat/temp/1350558335484.jpg");
            OutputStream os = resp.getOutputStream();

            try {
                int count = 0;
                byte[] buffer = new byte[1024*1024];
                while ( (count = fis.read(buffer)) != -1 )
                    os.write(buffer, 0, count);
            } catch (IOException e){
               e.printStackTrace();

             }finally {

       if(os!=null)

                os.close();

                if(fis != null)

       fis.close();
            }
   }

}

如果你在页面中使用该servlet，则要用action转发到<url-pattern>/Snippet</url-pattern>的路径/Snippet.

如你的页面里有个<img>元素来显示图片，使用<img src="Snippet" width="60" height="20"/>是肯定不行的，你必须定义一个action 如：

package com.social.action;

import com.opensymphony.xwork2.Action;

public class GetImg implements Action{
public String execute(){
return SUCCESS;
}

}

然后在该struts2中配置该Action

<action name="image" class="com.social.action.GetImg">
<result>/Snippet</result>
</action>

最终那个img中这么使用<img src="image" width="60" height="20"/>这样就可以用servlet了。

在同一个项目中，如果既用到servlet又用了struts框架，运行项目时可能无法正常使用
servlet，解决办法如下：
该类是定义了一个过滤器，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>所有配置的servlet名字</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>redisp</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

package filters;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher; import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
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(",")));
}
}

最终web.xml中的配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<servlet>
<servlet-name>Snippet</servlet-name>
<servlet-class>com.social.util.Snippet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>Snippet</servlet-name>
<url-pattern>/Snippet</url-pattern>
</servlet-mapping>

<filter>

<filter-name>redisp</filter-name>

<filter-class>filters.ReDispatcherFilter</filter-class>

<init-param>

<param-name>includeServlets</param-name>

<param-value>Snippet</param-value>

</init-param>

</filter>

<filter-mapping>

<filter-name>redisp</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

<filter>
<filter-name>struts2</filter-name>

<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>