Spring Mvc下实现以文件流方式下载文件的方法示例

项目中需要对一个点击事件进行下载操作，同时通过点击事件，已经可以从jsp页面获取到需要访问的url和下载的文件名（数据库获取，jsp页面显示）。点击事件js如下：

function downloadfile(filepath,filename){
 
 filename = filename.substr(0,filename.lastindexof("."));
 $.ajax({
   async : false, 
   cache:false, 
   type: 'get',
   datatype : "json", 
   url: rootpath() + "/checkdownload",//请求的action路径 
   data:{url:filepath},
   error: function () {//请求失败处理函数 
     alert("下载失败");
   }, 
   success:function(json) { //请求成功后处理函数。
   var code = json.code;
   if(code) {
    window.location.href = rootpath()+"/todownload?url="+filepath+"&name="+filename;
   }else {
    layer.alert(filename+' 文件不存在'); 
   }
   } 
 });
 
}

该ajax调用后台（checkdownload）方法，首先判断从该url能否获得指定下载的文件，如果获取不到，方法返回参数code=0，页面弹出“...文件不存在”。

 @requestmapping("/checkdownload")
 @responsebody
 public result checkdownload(string url,httpservletresponse response) {
 result result = result.createsuccessresult();
 httpurlconnection conn = null;
 try {
  url path = new url(url);
  conn = (httpurlconnection) path.openconnection();
  conn.setrequestmethod("get");
  conn.setconnecttimeout(5 * 1000);
  conn.getinputstream();// 通过输入流获取数据
 } catch (ioexception ex) {
  result.setcode(0);
  ex.printstacktrace();
 }finally {
  if(conn != null) {
  conn.disconnect();
  }
 }
 return result;
 }
    

如果checkdownload方法中能够正确获得资源，方法返回参数code=1，ajax成功执行：window.location.href = rootpath()+"/todownload?url="+filepath+"&name="+filename;   调用（todownload)方法，传入url和name，执行文件下载。

 @requestmapping("/todownload")
 @responsebody
 public void download(string url, string name, httpservletresponse response) {
 httpurlconnection conn = null;
 try {
  file file = new file(url);
  // 取得文件的后缀名。
  string ext = file.getname().substring(file.getname().lastindexof(".") + 1).tolowercase();
  stringbuffer buffername = new stringbuffer(name);
  string filename = buffername.append(".").append(ext).tostring();
 
  url path = new url(url);
  conn = (httpurlconnection) path.openconnection();
  conn.setrequestmethod("get");
  conn.setconnecttimeout(5 * 1000);
  inputstream fis = conn.getinputstream();// 通过输入流获取数据
 
  byte[] buffer = readinputstream(fis);
  if (null != buffer && buffer.length > 0) {
  // 清空response
  response.reset();
  // 设置response的header
  response.addheader("content-disposition","attachment;filename="+ new string((filename).getbytes("gbk"),"iso8859_1"));
  response.addheader("content-length", "" + buffer.length);
  outputstream toclient = response.getoutputstream();
  response.setcontenttype("application/octet-stream");
  toclient.write(buffer);
  toclient.flush();
  toclient.close();
  }
 
 } catch (ioexception ex) {
  ex.printstacktrace();
 }finally {
  if(conn != null) {
  conn.disconnect();
  }
 }
 }
 
  /** 
   * 从输入流中获取数据 
   * @param instream 输入流 
   * @return 
   * @throws exception 
   */ 
 private byte[] readinputstream(inputstream fis) throws ioexception {
  bytearrayoutputstream outstream = new bytearrayoutputstream(); 
     byte[] buffer = new byte[1024]; 
     int len = 0; 
     while( (len=fis.read(buffer)) != -1 ){ 
       outstream.write(buffer, 0, len); 
     } 
     fis.close(); 
     return outstream.tobytearray();
 } 

ps：spring mvc 文件流形式下载(返回)视频文件

import io.swagger.annotations.api;
import io.swagger.annotations.apioperation;
import org.springframework.stereotype.controller;
import org.springframework.web.bind.annotation.requestmapping;
import org.springframework.web.bind.annotation.requestmethod;
import org.springframework.web.bind.annotation.restcontroller;

import javax.servlet.http.httpservletresponse;
import java.io.file;
import java.io.fileinputstream;
import java.io.ioexception;
import java.io.outputstream;
import java.net.urlencoder;

/**
 * 文件流形式下载视频
 * @author front ng
 * @date 2019-05-23 09:25
 **/

@controller
@requestmapping(value = "/download")
@api(value = "下载", tags = "下载")
public class downloadcontroller {


  @apioperation(value = "下载视频")
  @requestmapping(method = requestmethod.get)
  public void download(httpservletresponse response) throws ioexception {

    file file = new file("/users/front/downloads/123.mp4");

    fileinputstream inputstream = new fileinputstream(file);
    byte[] data = new byte[(int) file.length()];
    int length = inputstream.read(data);
    inputstream.close();

    string filename = urlencoder.encode("文件流形式视频.mp4", "utf-8");

    response.setcontenttype("application/octet-stream;charset=utf-8");
    response.setheader("content-disposition", "attachment; filename=\"" + filename + "\"");
    response.addheader("content-length", "" + data.length);

    outputstream stream = response.getoutputstream();
    stream.write(data);
    stream.flush();
    stream.close();
  }
}

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