java开发在线下载功能，自动打开浏览器下载功能下载网络文件或图片

因为业务的需要，公司产品要求商品详情页面有个下载的功能

找了很多的方法，发现有的需要打开一个新窗口，而且在某些浏览器上不适用，所以继续寻找更好的方法

跟同事沟通后发现他那里有个下载的方法，不过是C#写的，改了改发现有些地方不太通用，所以继续百度。

后来找到一段可以用的代码，用了自己的前端js代码，加上百度的java代码修改后，发现可以达到自己的需求

于是，更新博客，留作以后使用。

本套代码示例基于springMVC 开发；

Java代码如下：

1.首先编写cotroller进行调用；

@RequestMapping(value="downLoadFromUrl")
    public void  downLoadFromUrl(HttpServletRequest request,HttpServletResponse response) throws IOException{  
        DownloadUtils.downLoadFromUrl(request, response);
    }

2.下载功能的实现代码DownloadUtils；

package com.utils;

import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

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

/**
 * 在线下载图片功能*/
public class DownloadUtils {
    public static void  downLoadFromUrl(HttpServletRequest request,HttpServletResponse response) throws IOException{  
        String downloadUrl = request.getParameter("fileName");
        URL url = new URL(downloadUrl);    
        HttpURLConnection conn = (HttpURLConnection)url.openConnection();    
                //设置超时间为3秒  
        conn.setConnectTimeout(3*1000);  
        //防止屏蔽程序抓取而返回403错误  
        conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");  
        //得到输入流  
        InputStream inputStream = conn.getInputStream();  
        try {
            String[] fileNameParts = downloadUrl.split("/");
            String fileName = fileNameParts[fileNameParts.length - 1];
//            String fileName = "aaa.jpg";
            fileName = new String(fileName.getBytes("UTF-8"),"ISO8859-1");
            response.setContentType("application/octet-stream");
            response.addHeader("Content-Disposition", "attachment;filename="+fileName);
            String len = String.valueOf(inputStream.available()/1000+"k");
            response.setHeader("Content-Length", len);
            OutputStream out = response.getOutputStream();
            byte[] getData = readInputStream(inputStream);      
            out.write(getData);
            inputStream.close();
            out.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
        
    
    /** 
     * 从输入流中获取字节数组 
     * @param inputStream 
     * @return 
     * @throws IOException 
     */  
    public static  byte[] readInputStream(InputStream inputStream) throws IOException {    
        byte[] buffer = new byte[1024];    
        int len = 0;    
        ByteArrayOutputStream bos = new ByteArrayOutputStream();    
        while((len = inputStream.read(buffer)) != -1) {    
            bos.write(buffer, 0, len);    
        }    
        bos.close();    
        return bos.toByteArray();    
    }  
}

3.js代码如下；

function downloadFile() {
    var pic=$("input[name='pic']
    window.location = "/product_big/downLoadFromUrl?fileName="+pic;
}

 最后感谢万能的百度

下面这个是打包下载文件的java代码,上面的是直接下载图片的，下面这个可以实现批量打包下载

@RequestMapping(value = "/downLoadImage", method = RequestMethod.GET)
    public void downLoadImage(HttpServletRequest request, HttpServletResponse response) throws Exception {
        List<String> urls = Lists.newArrayList();
        String path = request.getParameter("pictureUrl");
        urls.add(path);
        Map<String, InputStream> isMap = Maps.newHashMap();
        for (String urlStr : urls) {
            String[] fileNameParts = urlStr.split("/");
            String fileName = fileNameParts[fileNameParts.length - 1];
            try {
                URL url = new URL(urlStr);
                URLConnection con = url.openConnection();
                // 设置超时间为3秒
                con.setConnectTimeout(3 * 1000);
                // 防止屏蔽程序抓取而返回403错误
                con.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
                InputStream is = con.getInputStream();
                isMap.put(fileName, is);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        String[] fileNameParts = path.split("/");
        String fileNames = fileNameParts[fileNameParts.length - 1];
        response.setContentType("application/octet-stream");
        String filename = URLEncoder.encode(fileNames, "UTF-8");
        response.setHeader("Content-Disposition", "attachment; filename=" + filename + ".zip");
        ZipOutputStream zipOut = new ZipOutputStream(response.getOutputStream());
        for (Entry<String, InputStream> is : isMap.entrySet()) {
            String fileName = is.getKey();
            InputStream value = is.getValue();
            try {
                addToZip(value, zipOut, fileName);
                
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        zipOut.flush();
        zipOut.close();

    }
 
    private void addToZip(InputStream is,ZipOutputStream zipOut, String fileName) throws IOException {
        fileName = URLEncoder.encode(fileName, "UTF-8");
        ZipEntry entry = new ZipEntry(fileName);
        zipOut.putNextEntry(entry);
        int len;
        byte[] buffer = new byte[1024];
        while ((len = is.read(buffer)) > 0) {
            
            zipOut.write(buffer, 0, len);
        }
        zipOut.closeEntry();
        is.close();
    }