Java 从服务器下载文件到本地(页面、后台、配置都有)

先来看实现效果:

有一个链接如下:

Java 从服务器下载文件到本地(页面、后台、配置都有)

点击链接下载文件:

Java 从服务器下载文件到本地(页面、后台、配置都有)

 第一种方法:Servlet实现

一、HTML页面部分:

1、HTML页面中的一个链接

<a id="downloadTemplate" style="color:blue" onclick="download();">下载导入模板</a>

2、引入JS

function download(){
downloadTemplate('downloadExel.downloadexcel', 'filename', 'project');
} /**
* 用于下载导入模板时的影藏form表单的提交,采用post方式提交
* @param action action映射地址
* @param type parameter的名称
* @param value parameter的值,这里为file的filename
*/
function downloadTemplate(action, type, value){
var form = document.createElement('form');
document.body.appendChild(form);
form.style.display = "none";
form.action = action;
form.id = 'excel';
form.method = 'post'; var newElement = document.createElement("input");
newElement.setAttribute("type","hidden");
newElement.name = type;
newElement.value = value;
form.appendChild(newElement); form.submit();
}

3、解释上面JS(不是正是代码)

相当于提交一个form,里面如下:

<input type=hidden name="filename" value = "project">

后台可以通过下面代码获得文件名:project

String filename = request.getParameter("filename");

(这段是上面js的翻译,不是正式的哦)

二、配置部分

配置前台页面和后台交互

1、web.xml配置

<?xml version="1.0" encoding="UTF-8"?>

<web-app id="WebApp_ID" 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>downloadServlet</servlet-name>
<servlet-class>
com.zit.rfid.app.prms.business.service.servlet.DownloadTemplateServlet
</servlet-class>
<load-on-startup></load-on-startup>
</servlet> <servlet-mapping>
<servlet-name>downloadServlet</servlet-name>
<url-pattern>*.downloadexcel</url-pattern>
</servlet-mapping>
</web-app>

我这个web.xml不是整个工程的web.xml,只是一个模块的,在你的web.xml加入上面servlet和servlet-mapping里的内容即可

如上:

(1)接受 *.downloadexcel 的Action

(2)HTML的JS里的Action,交给com.test.DownloadTemplateServlet这个类去处理

2、WebContent目录下新建file文件夹,存放project.xls文件   (Eclipse的Web工程有WebContent,MyEclipse好像是WebRoot)

Java 从服务器下载文件到本地(页面、后台、配置都有)

三、后台部分

1、新建一个servlet:  

DownloadTemplateServlet.java

package com.test;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.URLEncoder; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* @author 0223000218
* 主要用于下载导入模板,页面上传入的request中parameter中,filename代表了要下载的模板的名称
*/
public class DownloadTemplateServlet extends HttpServlet { /**
* serialVersionUID
*/
private static final long serialVersionUID = -4541729035831587727L; private final static String HOME_PATH = DownloadTemplateServlet.class.getResource("/").getPath();
private final static String DOWNLOAD_TEMP_FILE = HOME_PATH.subSequence(, HOME_PATH.indexOf("WEB-INF")) + "file/"; @Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doPost(req, resp);
} @Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String filename = req.getParameter("filename");
try{
resp.reset();// 清空输出流 String resultFileName = filename + System.currentTimeMillis() + ".xls";
resultFileName = URLEncoder.encode(resultFileName,"UTF-8");
resp.setCharacterEncoding("UTF-8");
resp.setHeader("Content-disposition", "attachment; filename=" + resultFileName);// 设定输出文件头
resp.setContentType("application/msexcel");// 定义输出类型
//输入流:本地文件路径
DataInputStream in = new DataInputStream(
new FileInputStream(new File(DOWNLOAD_TEMP_FILE + filename + ".xls")));
//输出流
OutputStream out = resp.getOutputStream();
//输出文件
int bytes = ;
byte[] bufferOut = new byte[];
while ((bytes = in.read(bufferOut)) != -) {
out.write(bufferOut, , bytes);
}
out.close();
in.close();
} catch(Exception e){
e.printStackTrace();
resp.reset();
try {
OutputStreamWriter writer = new OutputStreamWriter(resp.getOutputStream(), "UTF-8");
String data = "<script language='javascript'>alert(\"\\u64cd\\u4f5c\\u5f02\\u5e38\\uff01\");</script>";
writer.write(data);
writer.close();
} catch (IOException e1) {
e1.printStackTrace();
}
} } }

大致步骤:

1. 获取服务器文件所在路径

2. 输入服务器文件

3. 输出文件到本地

第二种方法:SpringMVC实现

这种方法比较简单

一、JSP页面部分

和上面一样

<a id="downloadTemplate" style="color:blue" onclick="download();">下载导入模板</a>
//导出模板下载
function download(){
//后台方法、文件类型、文件名
downloadTemplate('${pageContext.request.contextPath}/cardIssueVehicleInfo/exportVehicleInfo', 'filename', 'test');
} /**
* 用于下载导入模板时的影藏form表单的提交,采用post方式提交
* @param action 请求后台方法
* @param type 文件类型
* @param value 文件名
*/
function downloadTemplate(action, type, value){
var form = document.createElement('form');
document.body.appendChild(form);
form.style.display = "none";
form.action = action;
form.id = 'excel';
form.method = 'post'; var newElement = document.createElement("input");
newElement.setAttribute("type","hidden");
newElement.name = type;
newElement.value = value;
form.appendChild(newElement); form.submit();
}

二、后台部分

@RequestMapping("exportVehicleInfo")
public void exportVehicleInfo(HttpServletRequest req, HttpServletResponse resp) {
String filename = req.getParameter("filename");
DataInputStream in = null;
OutputStream out = null;
try{
resp.reset();// 清空输出流 String resultFileName = filename + System.currentTimeMillis() + ".xls";
resultFileName = URLEncoder.encode(resultFileName,"UTF-8");
resp.setCharacterEncoding("UTF-8");
resp.setHeader("Content-disposition", "attachment; filename=" + resultFileName);// 设定输出文件头
resp.setContentType("application/msexcel");// 定义输出类型
//输入流:本地文件路径
in = new DataInputStream(
new FileInputStream(new File(downloadPath + "test.xls")));
//输出流
out = resp.getOutputStream();
//输出文件
int bytes = ;
byte[] bufferOut = new byte[];
while ((bytes = in.read(bufferOut)) != -) {
out.write(bufferOut, , bytes);
}
} catch(Exception e){
e.printStackTrace();
resp.reset();
try {
OutputStreamWriter writer = new OutputStreamWriter(resp.getOutputStream(), "UTF-8");
String data = "<script language='javascript'>alert(\"\\u64cd\\u4f5c\\u5f02\\u5e38\\uff01\");</script>";
writer.write(data);
writer.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}finally {
if(null != in) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(null != out) {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
} }
上一篇:Java Web实现使用浏览器从服务器下载文件(后台)


下一篇:【FTP】C# System.Net.FtpClient库连接ftp服务器(下载文件)