需求：浏览器访问后台的http地址后，后台将多个网络文件打成压缩包返回给浏览器，用户可以通过浏览器直接下载压缩包。

实现：

根据文件链接把文件下载下来并且转成字节码  ，代码：

package com.zwy.blog.servelt;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class UrlFilesToZip {
// private static final Logger logger = LoggerFactory.getLogger(UrlFilesToZip.class);
//根据文件链接把文件下载下来并且转成字节码
public byte[] getImageFromURL(String urlPath) {
byte[] data = null;
InputStream is = null;
HttpURLConnection conn = null;
try {
URL url = new URL(urlPath);
conn = (HttpURLConnection) url.openConnection();
conn.setDoInput(true);
// conn.setDoOutput(true);
conn.setRequestMethod("GET");
conn.setConnectTimeout(6000);
is = conn.getInputStream();
if (conn.getResponseCode() == 200) {
data = readInputStream(is);
} else {
data = null;
}
} catch (MalformedURLException e) {
// logger.error("MalformedURLException", e);
} catch (IOException e) {
// logger.error("IOException", e);
} finally {
try {
if (is != null) {
is.close();
}
} catch (IOException e) {
// logger.error("IOException", e);
}
conn.disconnect();
}
return data;
}

public byte\[\] readInputStream(InputStream is) {  
    ByteArrayOutputStream baos = new ByteArrayOutputStream();  
    byte\[\] buffer = new byte\[1024\];  
    int length = -1;  
    try {  
        while ((length = is.read(buffer)) != -1) {  
            baos.write(buffer, 0, length);  
        }  
        baos.flush();  
    } catch (IOException e) {  

// logger.error("IOException", e);
}
byte[] data = baos.toByteArray();
try {
is.close();
baos.close();
} catch (IOException e) {
// logger.error("IOException", e);
}
return data;
}
}

新建DownFileServlet，调用上面的工具类，代码如下：

package com.zwy.blog.servelt;

import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

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

public class DownFileServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public DownFileServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
//String filename = new String("xx.zip".getBytes("UTF-8"), "ISO8859-1");//控制文件名编码
String fileName = URLEncoder.encode("证据材料.zip","UTF-8");
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ZipOutputStream zos = new ZipOutputStream(bos);
UrlFilesToZip s = new UrlFilesToZip();
String urls[]={"https://hr-minio.cas-air.cn/pdf-temp/001d535005784d3d8220e89d5ce4b3ab.pdf","https://hr-minio.cas-air.cn/pdf-temp/001ee146be864a848a04bef6abfb1a89.pdf"};
for (String oneFile : urls) {
String filename=oneFile.substring(oneFile.lastIndexOf("/")+1);
zos.putNextEntry(new ZipEntry(filename));
byte[] bytes = s.getImageFromURL(oneFile);
zos.write(bytes, 0, bytes.length);
zos.closeEntry();
}
zos.close();
response.setContentType("application/force-download");// 设置强制下载不打开
response.addHeader("Content-Disposition", "attachment;fileName=" + fileName);// 设置文件名
OutputStream os = response.getOutputStream();
os.write(bos.toByteArray());
os.close();
} catch (FileNotFoundException ex) {
// logger.error("FileNotFoundException", ex);
} catch (Exception ex) {
// logger.error("Exception", ex);
}
}

}

浏览器直接访问DownFileServlet的地址，即可直接下载压缩包。