文件下载

Servlet实现

目录结构

DownLoadServlet.java

package com.ghq.controller;

import java.io.File;
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 DownLoadServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doPost(request, response);
    }

    
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        String imageRP = this.getServletContext().getRealPath("/images");
        //获取被下载的文件的名字
        String oldfileName = request.getParameter("fn");
        
        //代表要下载的文件
        File sourceFile = new File(imageRP, oldfileName);
        //被下载文件对应的输入流
        FileInputStream fin = new FileInputStream(sourceFile);
        //将文件名进行重新编码，解决下载中文文件名时，出现乱码的情况
        oldfileName = new String(oldfileName.getBytes(),"ISO8859-1");
        //设置响应头，表示是下载文件，不是给浏览器输出
        response.addHeader("Content-Disposition", "attachment;filename="+oldfileName);
        
        OutputStream out = response.getOutputStream();
        
        byte[] bs = new byte[1024];
        int count = 0;
        while((count = fin.read(bs))!= -1){
            out.write(bs, 0, count);
        }
        if (out != null) {
            out.close();
        }
        if (fin != null) {
            fin.close();
        }
        
    }

}

web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>DownLoadFile</display-name>
  <servlet>
    <servlet-name>DownLoadServlet</servlet-name>
    <servlet-class>com.ghq.controller.DownLoadServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>DownLoadServlet</servlet-name>
    <url-pattern>/DownLoadServlet</url-pattern>
  </servlet-mapping>
</web-app>

jsp页面

<body>
    <a href="<%=path%>/DownLoadServlet?fn=测试.png">测试.png </a>
</body>

Struts2的文件下载

项目的目录结构

DownLoadAction.java

package com.ghq.action;

import java.io.InputStream;
import java.io.UnsupportedEncodingException;

import javax.servlet.ServletContext;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class DownLoadAction extends ActionSupport {
    private String filename;

    public String getFilename() {
        //解决被下载文件的名字是中文时乱码的情况
        try {
            filename=new String(filename.getBytes(),"ISO8859-1");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return filename;
    }
    
    public void setFilename(String filename) {
        this.filename = filename;
    }

    public InputStream getTargetFile() throws Exception{
        //获取ServletContext的对象
              ServletContext application = ServletActionContext.getServletContext();
        InputStream fin = application.getResourceAsStream("/images/"+filename);
        return fin;
    }
    
}

struts.xml

　　tatgetFile和DownLoadAction.java中的下载文件的方法名getTargetFile()对应

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>

    <constant name="struts.enable.DynamicMethodInvocation" value="false" />
    <constant name="struts.devMode" value="true" />
    <constant name="struts.action.extension" value="action"/>
    
    <package name="default" namespace="/" extends="struts-default">
        <action name="DownLoadAction_*" class="com.ghq.action.DownLoadAction" method="{1}">
            <result type="stream">
                <param name="inputName">targetFile</param>
                <!-- attachment用于指定是下载文件，而不是解析文件 -->
                <param name="contentDisposition">attachment;filename=${filename}</param>
            </result>
        </action>
    </package>
</struts>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>struts2_DownLoadFile</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  <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>*.action</url-pattern>
  </filter-mapping>
 
</web-app>

jsp页面

<body>
    JavaEE项目开发实践.jpg&nbsp;&nbsp;<a href="<%=path %>/DownLoadAction.action?filename=JavaEE项目开发实践.jpg">下载</a><br>
    1.jpg&nbsp;&nbsp;<a href="<%=path %>/DownLoadAction.action?filename=1.jpg">下载</a>
</body>