FileDownload.java：文件下载工具类

2017-04-25·Mr.Xia

4489 次浏览

文件下载功能的工具类

JavaWeb工具类目录 [http://baike.xsoftlab.net/view/1059.html](http://baike.xsoftlab.net/view/1059.html)

基础版本：

```java

package com.zhenzhigu.commons.util;

import java.io.File;

import java.io.FileInputStream;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.URLEncoder;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* 下载文件 创建人：Master.Xia 创建时间：2014年06月08日

*

* @version

*/

public class FileDownload {

/**

* @param request

* @param response

* @param fileAbsPath 文件绝对路径(包括文件名和扩展名)

* @param showName 下载后看到的文件名

* @return 文件名

*/

public static void execute(HttpServletRequest request,HttpServletResponse response, InputStream input,long length, String showName)throws Exception {

String info = request.getHeader("User-Agent").toLowerCase();

if (info.contains("firefox")) { // Firefox

showName = new String(showName.getBytes(), "ISO-8859-1");

} else { // IE,Chrome

showName = URLEncoder.encode(showName, "UTF-8");

}

response.reset(); // 响应重置

response.setHeader("Content-Disposition", "attachment; filename=\""+ showName + "\"");

response.addHeader("Content-Length", ""+length);

response.setContentType("application/octet-stream;charset=UTF-8");

OutputStream out = response.getOutputStream();

int len = 0;

byte[] buffer = new byte[1024*8];

while ((len = input.read(buffer)) != -1) {

out.write(buffer,0,len);

}

input.close();

response.flushBuffer();

}

public static void execute(HttpServletRequest request,

HttpServletResponse response, File file, String showName)

throws Exception {

execute(request, response, new FileInputStream(file), file.length(), showName);

}

public static void execute(HttpServletRequest request, HttpServletResponse response, String fileAbsPath, String showName) throws Exception{

execute(request, response, new File(fileAbsPath), showName);

}

}

```

支持断点续传的升级版本：

```java

package com.itshidu.commons.web.utils;

import java.io.File;

import java.io.FileInputStream;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.URLEncoder;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* 下载文件

* @author Master.Xia

* @version 1.0 (2014.07.16)

* @version 1.1 (2018.02.16)

* @version 1.2 (2018.09.30)

*/

public class FileDownload {

/**

* 请求转发到一个指定的文件，就像浏览器直接访问这个文件一样，不会弹框提示

* @param request (请求)

* @param response (响应)

* @param file (访问的文件)

* @throws Exception (异常)

*/

public static void forward(HttpServletRequest request,HttpServletResponse response,File file)throws Exception {

forward(request, response, file, null, false);

}

/**

* 请求转发到一个指定的文件，就像浏览器直接访问这个文件一样，如果遇到浏览器不认识的文件类型，则会下载它，支持断点续传。

* 当isAttachment为true时会有下载提示框

* @param request (请求)

* @param response (响应)

* @param file (访问的文件)

* @param name (下载时在浏览器显示的名字)

* @param isAttachment (浏览器是否弹出下载框，true弹框，false不弹框)

* @throws Exception (异常)

*/

public static void forward(HttpServletRequest request,HttpServletResponse response,File file,String name,boolean isAttachment)throws Exception {

Path path = Paths.get(file.getAbsolutePath());

int length = (int)file.length();

int start = 0;

int end = length - 1;

String range = request.getHeader("Range");

if(range!=null&&range.length()>0) {

range = range.toLowerCase(); //RANGE:BYTES=100-500

range = range.replaceAll("\\s*", ""); //去除字符串中所有的不可见字符

if(range.contains("bytes=")) {//bytes=100

if(range.contains("-")) {

String a = range.substring(6, range.indexOf("-"));

start = Integer.parseInt(a);

if(range.charAt(range.length()-1)!='-') {

String b = range.substring(range.indexOf("-")+1);

end = Integer.parseInt(b);

}

}else {

String a = range.substring(6);

start = Integer.parseInt(a);

}

}

}

int contentLength = end - start + 1;

response.reset();

response.setHeader("Accept-Ranges", "bytes");

response.setContentType(Files.probeContentType(path));

response.setHeader("Content-Range",String.format("bytes %s-%s/%s", start, end, length));

response.setHeader("Content-Length", String.format("%s", contentLength));

response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);

if(isAttachment) {

//如果是下载，则弹框提示，解决乱码问题

String info = request.getHeader("User-Agent").toLowerCase();

String showName = file.getName();

if(name!=null&&name.length()>0)showName=name;

if (info.contains("firefox")) { // Firefox

showName = new String(showName.getBytes(), "ISO-8859-1");

} else { // IE,Chrome

showName = URLEncoder.encode(showName, "UTF-8");

}

response.setHeader("Content-Disposition", "attachment; filename=\""+ showName + "\"");

}

//数据传输

InputStream in = null;

try{

in = new FileInputStream(file);

int len,remain = contentLength;

byte[] buffer = new byte[1024*8];

OutputStream out = response.getOutputStream();

int plan = start;

while(plan>0){

plan -= in.skip(plan);

}

while((len=in.read(buffer))!=-1 && remain > 0) {

out.write(buffer, 0, (remain

}

}catch (Exception e) {

throw e;

}finally {

try {in.close(); } catch (Exception e2) { }

}

}

}

```