转载请注明出处：https://blog.csdn.net/feng2147685/article/details/80515371

简介：
        最近项目中需要做一个批量打包ZIP下载，以前做过，但是没有记录下来。
于是又开始烧脑进行开发，本次也记录下来方便大家参考。直接上代码：
第一步：
    列表选择需要下载的图片，将ID发送至后台。
		//下载
		function downloadat(id) {
			document.location=encodeURI("../baseInfo/downloadAttachments.do?uuids="+id);
		}
		
		//批量下载
		function downloadpl() {
			var rows = $("#tt").datagrid("getSelections");
			if (rows.length == 0) {
				alertInfo(" 请先选择要下载的附件！");
			} else {
				var id2 = new Array();
				for (var int = 0; int < rows.length; int++) {
					id2[int] = rows[int].uuid;
				}
			document.location=encodeURI("../baseInfo/downloadAttachments.do?uuids="+id2);
			}
		}
		
第二步：
    接收参数，ID为数组。

	@RequestMapping("/downloadAttachments.do")
	public void downloadAttachments(@RequestParam(value = "uuids")String[] uuids,HttpServletRequest request, HttpServletResponse response, PrintWriter pw) {
		// map 接收返回信息
		Map<String, String> map = new HashMap<>();
		// 如果uuids不为空，则下载
		if (uuids.length > 0) {
			try {
				attachmentService.downloadAttachments(response,request,uuids);
				map.put("msg", "下载成功！");
			} catch (Exception e) {
				e.printStackTrace();
			}
		}else{
			map.put("msg", "下载异常！");
		}
		//返回结果转json
		Gson gson = new Gson();
		String json = gson.toJson(map);
		try{
			 if(pw!=null){
				 pw.write(json);
			 }
		 }finally{
			 if(pw!=null){
				 pw.flush();
				 pw.close();
			 }
		 }
	}
第三步：
	/**
	 * 下载单个矿企附件
	 */
	@Override
	public List<Baseattachment> queryAttachments(String epcode) {
		List<Baseattachment> list = new ArrayList<Baseattachment>();
		
		try {
			// 根据矿企标识查询附件列表
			list = baseattachmentMapper.selectByEpcode(epcode);
			for (Baseattachment attachment : list) {
				//改变文件名编码，防止乱码
				String oldName = attachment.getFileoldname();
				String fileName = new String (oldName.getBytes("UTF-8"),"ISO-8859-1");
				attachment.setFileoldname(fileName);
				//更改文件大小单位
				attachment.setFilesize(FileUtil.getHumanReadableSize(Long.valueOf(attachment.getFilesize())));
				
				// 遍历附件列表，如果有图片文件，复制到临时文件夹内，并将图片路径返回。
				String fileFormat = attachment.getFileformat();
				if (fileFormat.equals("jpg") || fileFormat.equals("png") || fileFormat.equals("bmp")) {
					attachment.setFilepath(ConfigConstants.IMAGEPATH + new String (attachment.getFilepath().getBytes("UTF-8"),"ISO-8859-1"));
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return list;
	}
	/**
	 * 打包下载矿企附件
	 */
	@Override
	public void downloadAttachments(HttpServletResponse response,HttpServletRequest request,String[] uuids) {
		if (uuids.length<2) {//单独下载
				String uuid = uuids[0];
				//查询附件信息,将URL和名称放置对应数组
				Baseattachment attachment = baseattachmentMapper.selectByPrimaryKey(uuid);//查询出附件信息
				String filePath = ConfigConstants.IMAGEPATH + attachment.getFilepath();//拼接URL
				try {
					DownLoadUtil.urldownload(filePath, attachment.getFileoldname()+"."+attachment.getFileformat(), response);
				} catch (IOException e) {
					e.printStackTrace();
				}
		}else{//打包下载
			//循环查询出所有的附件路径
			List<String> lstStr = new ArrayList<>();
			List<String> fileNamelst = new ArrayList<>();
			for (String string : uuids) {
				//循环查询附件信息,将URL和名称放置对应数组
				Baseattachment selectByPrimaryKey = baseattachmentMapper.selectByPrimaryKey(string);
				lstStr.add( ConfigConstants.IMAGEPATH+selectByPrimaryKey.getFilepath());
				fileNamelst.add(selectByPrimaryKey.getFileoldname()+"."+selectByPrimaryKey.getFileformat());
			}
			try {
				//调用工具类实现导出
				DownLoadUtil.urldownloadZip(fileNamelst,lstStr,response);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		 
	}


第四步：
转载请注明出处：https://blog.csdn.net/feng2147685/article/details/80515371
下面是一个导出工具类，本工具类可自行修改。
package com.yutu.util;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

import javax.servlet.http.HttpServletResponse;

import com.yutu.config.ConfigConstants;
/**
 * 工具类，下载
* <p>Title: DownLoadUtil</p>
* <p>Description: </p>
* @author ccf
* @date 2018-5-30
 */
public class DownLoadUtil{  
    /**
     * 单个文件下载
     * @param urlstring URL
     * @param fileName 文件名称
     * @param response
     * @throws IOException
     */
    public static void urldownload(String urlstring,String fileName,HttpServletResponse response) throws IOException{ 
    	fileName = new String (fileName.getBytes("UTF-8"),"ISO-8859-1");
        response.reset();
    	response.setContentType("application/force-download");
		response.addHeader("Content-Disposition","attachment;fileName=" + fileName);
		response.setContentType("application/octet-stream;charset=utf-8");
		URL url = new URL(urlstring);
		URLConnection conn = url.openConnection();
		InputStream inputStream = conn.getInputStream();
		int length = conn.getContentLength();
		response.setHeader("Content-Length", ""+length);
		BufferedInputStream output = new BufferedInputStream(inputStream);
		OutputStream outputStream = response.getOutputStream();
		byte[] buff = new byte[1024*10];
		int len = 0;
		while ((len=output.read(buff))>-1) {
			outputStream.write(buff,0,len);
		}
        //释放资源  
		output.close();  
		output.close();  
    }

    /**
     * 打包ZIP下载,图片不是本地,而是URL路径
     * @param fileNamelst 文件名称list
     * @param lstStr 文件URLlist
     * @param response
     * @throws Exception
     */
	public static void urldownloadZip(List<String> fileNamelst,List<String> lstStr,
			HttpServletResponse response) throws Exception {
		//ConfigConstants.ZIPNAME为项目中配置的URL路径
		String fileName =new String(ConfigConstants.ZIPNAME.getBytes("UTF-8"),"UTF-8");  
		//响应头的设置 
        response.reset();
    	response.setContentType("application/force-download");
		response.addHeader("Content-Disposition","attachment;fileName=" + fileName);
		response.setContentType("application/octet-stream;charset=utf-8");
		 //设置压缩流：直接写入response，实现边压缩边下载  
        ZipOutputStream zipos = null;
        zipos = new ZipOutputStream(new BufferedOutputStream(response.getOutputStream()));  
        //设置压缩方法   
        zipos.setMethod(ZipOutputStream.DEFLATED); 
        DataOutputStream os = null;
        try { 
        	//循环将文件写入压缩流  
        	for (int i = 0; i < lstStr.size(); i++) {
            	URL url = new URL(lstStr.get(i));
        		URLConnection conn = url.openConnection();
        		InputStream inputStream = conn.getInputStream();
        		//添加ZipEntry，并ZipEntry中写入文件流  
        		zipos.putNextEntry(new ZipEntry(fileNamelst.get(i)));  
        		os = new DataOutputStream(zipos);  
        		byte[] buff = new byte[1024*10];
        		int len = 0;
        		//循环读写
        		while ((len=inputStream.read(buff))>-1) {
        			os.write(buff,0,len);
        		}
        		//关闭此文件流
        		inputStream.close();
        		//关闭当前ZIP项，并将流放置到写入的位置。下一个条目。
        		zipos.closeEntry();  
        	}
	        //释放资源
	        os.flush();
	        os.close();
	        zipos.close();
        } catch (IOException e) {  
        	e.printStackTrace();  
        }finally{
        	//释放资源
        	os.close();
        	zipos.close();  
        }
	}
}


总结：
耗时4个小时，由于循环内没有调用zipos.closeEntry();，所以导出的ZIP会报错，未正确结尾。
转载请注明出处：https://blog.csdn.net/feng2147685/article/details/80515371

HttpClient 通过资源URL下载资源
 
使用富文本编辑器写文章什么的，从第三方拷贝过来的图文，里面的资源内容都是第三方的，如果第三方删除该资源，导致该文章也无法访问，故需要把文章中的第三方资源通过http下载到本地服务器，永久保存。
 用到了以下三种方法：
 
1、纯IO写文件
 
/**
 * 根据url下载文件，保存到filepath中
 * @param url
 * @param filepath
 * @return
 */
public static void download(String url, String filepath) {
    try {
        HttpClient client = HttpClients.createDefault();
        HttpGet httpGet = new HttpGet(url);
        //设置请求
        /**
         * setConnectTimeout：设置连接超时时间，单位毫秒。
         *
         * setConnectionRequestTimeout：设置从connect Manager(连接池)获取Connection 超时时间，单位毫秒。这个属性是新加的属性，因为目前版本是可以共享连接池的。
         *
         * setSocketTimeout：请求获取数据的超时时间(即响应时间)，单位毫秒。 如果访问一个接口，多少时间内无法返回数据，就直接放弃此次调用。
         */
        RequestConfig requestConfig = RequestConfig.custom()
                .setConnectTimeout(5000).setConnectionRequestTimeout(1000)
                .setSocketTimeout(3000).build();
        httpGet.setConfig(requestConfig);
        HttpResponse response = client.execute(httpGet);
        HttpEntity entity = response.getEntity();

        InputStream is = entity.getContent();
        File file = new File("C:\\Users\\XXX\\Downloads\\io");
        FileOutputStream fileout = new FileOutputStream(file);
        /**
         * 根据实际运行效果 设置缓冲区大小
         */
        byte[] buffer = new byte[cache];
        int ch = 0;
        while ((ch = is.read(buffer)) != -1) {
            fileout.write(buffer, 0, ch);
        }
        is.close();
        fileout.flush();
        fileout.close();

    } catch (Exception e) {
        e.printStackTrace();
    }

}
 
注：由于该资源是网页使用，此处没有考虑文件类型，无文件格式后缀的文件，浏览器已然可以正常解析
 
2、使用HttpEntity自带工具
 
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
    /**
     * 使用httpClient自带的工具类
     * @param url
     */
public static void downloadByWriteTo(String url){
    try {
        RequestConfig requestConfig = RequestConfig.custom()
                .setConnectTimeout(5000)
                .setConnectionRequestTimeout(1000)
                .setSocketTimeout(3000).build();
        CloseableHttpClient client = HttpClientBuilder.create()
                .setDefaultRequestConfig(requestConfig).build();
        CloseableHttpResponse response = client.execute(new HttpGet(new URL(url).toURI()));
        HttpEntity entity = response.getEntity();
        File file = new File("C:\\Users\\XXX\\Downloads\\WriteTo");
        entity.writeTo(new FileOutputStream(file));
    } catch (Exception e) {
        e.printStackTrace();
    }
}
 
3、使用nio工具类拷贝
 
public static void downloadByFilesCopy(String url){
   try {
       HttpClient client = HttpClients.createDefault();
       HttpResponse response = client.execute(new HttpGet(url));
       HttpEntity entity = response.getEntity();
       File file = new File("C:\\Users\\XXX\\Downloads\\FilesCopy");
       Files.copy(entity.getContent(),file.toPath(), StandardCopyOption.REPLACE_EXISTING);
   } catch (Exception e) {
       e.printStackTrace();
   }
}
 
以上操作均需要导入HttpClient 包
 
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
	<groupId>org.apache.httpcomponents</groupId>
	<artifactId>httpclient</artifactId>
	<version>4.5.6</version>
</dependency>

 
java从url下载文件
 

  

  

 
 
Today we will learn how to download a file from URL in java. We can use java.net.URL openStream() method to download file from URL in java program. We can use Java NIO Channels or Java IO InputStream to read data from the URL open stream and then save it to file.
 
 今天，我们将学习如何从Java中的URL下载文件。 我们可以使用java.net.URL openStream()方法从java程序中的URL下载文件。 我们可以使用Java NIO Channels或Java IO InputStream从URL打开流中读取数据，然后将其保存到文件中。 
 
 
 从URL下载Java文件 (Java Download File from URL)
 
 

 

  
 
 
 Here is the simple java download file from URL example program. It shows both ways to download file from URL in java.
 

 
  
 这是来自URL示例程序的简单Java下载文件。 它显示了从Java中的URL下载文件的两种方法。 
 
 

 
 
 
JavaDownloadFileFromURL.java
 
 JavaDownloadFileFromURL.java 
 
 
package com.journaldev.files;

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;

public class JavaDownloadFileFromURL {

    public static void main(String[] args) {
        String url = "https://www.journaldev.com/sitemap.xml";
        
        try {
            downloadUsingNIO(url, "/Users/pankaj/sitemap.xml");
            
            downloadUsingStream(url, "/Users/pankaj/sitemap_stream.xml");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void downloadUsingStream(String urlStr, String file) throws IOException{
        URL url = new URL(urlStr);
        BufferedInputStream bis = new BufferedInputStream(url.openStream());
        FileOutputStream fis = new FileOutputStream(file);
        byte[] buffer = new byte[1024];
        int count=0;
        while((count = bis.read(buffer,0,1024)) != -1)
        {
            fis.write(buffer, 0, count);
        }
        fis.close();
        bis.close();
    }

    private static void downloadUsingNIO(String urlStr, String file) throws IOException {
        URL url = new URL(urlStr);
        ReadableByteChannel rbc = Channels.newChannel(url.openStream());
        FileOutputStream fos = new FileOutputStream(file);
        fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
        fos.close();
        rbc.close();
    }

}
 
downloadUsingStream: In this method of java download file from URL, we are using URL openStream method to create the input stream. Then we are using a file output stream to read data from the input stream and write to the file.
 
 downloadUsingStream ：在这种从URL下载Java文件的方法中，我们使用URL openStream方法创建输入流。 然后，我们使用文件输出流从输入流中读取数据并写入文件。 
 
 

  

  

 
 
downloadUsingNIO: In this download file from URL method, we are creating byte channel from URL stream data. Then use the file output stream to write it to file.
 
 downloadUsingNIO ：在此从URL下载文件的方法中，我们正在从URL流数据创建字节通道。 然后使用文件输出流将其写入文件。 
 
 
You can use any of these methods to download the file from URL in java program. If you are looking for performance, then do some analysis by using both methods and see what suits your need.
 
 您可以使用这些方法中的任何一种从java程序中的URL下载文件。 如果您正在寻找性能，则可以使用这两种方法进行一些分析，然后找出适合您需求的方法。 
 
 

  

  

 
 

  GitHub Repository.
  GitHub存储库中签出更多Java IO示例。 
 
 

  
翻译自: https://www.journaldev.com/924/java-download-file-url
 
 
java从url下载文件

 
 
java根据http url下载图片
 
 
网络图片下载
 
工具代码
 
/**
	 * 网络图片下载
	 * @param url 图片url
	 * @param formatName 文件格式名称
	 * @param localFile 下载到本地文件
	 * @return 下载是否成功
	 */
	public static boolean downloadImage(String imageUrl, String formatName, File localFile) {
		boolean isSuccess = false;
		URL url = null;
		try {
			url = new URL(imageUrl);
			isSuccess = ImageIO.write(ImageIO.read(url), formatName, localFile);
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return isSuccess;
	}
 
测试代码
 
/**
	 * 测试图片下载
	 */
	@Test
	public void testDownloadImage() {
		String baiduLogoUrl = "https://www.baidu.com/img/bd_logo1.png";
		File localFile = new File(IMAGE_PATH + "bd_logo1.png");
		Assert.assertTrue(ImageUtil.downloadImage(baiduLogoUrl, ImageUtil.PNG, localFile));
	}
 
完整源码：https://github.com/ConstXiong/xtools
 
 
 
 
 

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