java上传文件到远程服务器(一)---HttpURLConnection方式

我们在之前的文章

JavaWeb静态资源分离思路

中已经了解到要把文件上传到静态资源服务器有三种方式:

java上传文件到ftp服务器(这个方案需要在静态资源服务器安装ftp服务)

java使用HttpURLConnection上传文件到远程服务器  (分为客户端和服务端，客户端负责上传，服务端负责接收文件)

java使用HttpClient通过Post上传文件到远程服务器  (分为客户端和服务端，客户端负责上传，服务端负责接收文件)

本章我们就来尝试HttpURLConnection上传文件到远程服务器。

我们在之前的文章中已经在SpringMVC基础框架的基础上应用了BootStrap的后台框架，在此基础上记录HttpURLConnection上传文件到远程服务器。

应用bootstrap模板

基础项目源码下载地址为:

SpringMVC+Shiro+MongoDB+BootStrap基础框架

我们在基础项目中已经做好了首页index的访问。
现在就在index.jsp页面和index的路由Controller上做修改，HttpURLConnection上传文件到远程服务器。

客户端

客户端HttpURLConnection上传文件到远程服务器的原理是通过构造参数模仿form提交文件的http请求，把文件提交到远程服务器的接收路由中。

index.jsp的代码为:

<%@ include file="./include/header.jsp"%>        <div id="page-wrapper">            <div id="page-inner">                <div class="row">                    <div class="col-md-12">                        <h1 class="page-header">                            HttpURLConnection <small>HttpURLConnection</small>                        </h1>                    </div>                </div>                <!-- /. ROW  -->     <form class="form-horizontal" name="upform" action="upload" method="post" enctype="multipart/form-data">                    <div class="form-group">                    <label for="sourceModule" class="col-sm-2 control-label">上传文件:</label>                    <div class="col-sm-10">                  <input type="file" name="filename"/><br/>  　　                                             <input type="submit" value="提交" /><br/>                     </div>                </div>           </form>                  <!-- /. ROW  -->            </div>            <!-- /. PAGE INNER  -->        </div>        <!-- /. PAGE WRAPPER  -->                     <%@ include file="./include/footer.jsp"%><script type="text/javascript">    $(document).ready(function () {       });</script></body></html>

当提交表单里包含文件上传的时候，即Form的enctype属性值为multipart/form-data时，后台是无法像普通表单那样通过request.getParameter来获取用户提交的数据的。

这时候，当然可以通过解析提交到服务器的数据流来得到数据了，但是这样不但麻烦而且容易出错。

最好的方式是使用第三方的jar包获取数据，这方面有很多现成的成熟优秀的jar包。最常用的时以下三个：

apache的commons-fileupload ： http://commons.apache.org/fileupload/

O'Reilly的cos： http://www.servlets.com/cos/index.html

jspsmart的SmartUpload：官方不提供下载了，google搜吧。

其中，据评测效率最高的是COS，最慢的是SmartUpload；最常用的是common-upload；文件太大时SmartUpland会崩溃。


我们这里使用commons-fileupload,需要引入两个jar包：commons-fileupload-1.3.1.jar和commons-io-2.4.jar。

下载地址:

http://central.maven.org/maven2/commons-fileupload/commons-fileupload/1.3.1/commons-fileupload-1.3.1.jar

http://central.maven.org/maven2/commons-io/commons-io/2.4/commons-io-2.4.jar

如果是maven项目,在pom.xml中增加:

<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload --><dependency>    <groupId>commons-fileupload</groupId>    <artifactId>commons-fileupload</artifactId>    <version>1.3.1</version></dependency><!-- https://mvnrepository.com/artifact/commons-io/commons-io --><dependency>    <groupId>commons-io</groupId>    <artifactId>commons-io</artifactId>    <version>2.4</version></dependency>

路由中upload方法接受form提交的file文件，并且上传到服务器:

IndexController.java代码如下:

package com.test.web.controller;import java.io.BufferedReader;import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.net.HttpURLConnection;import java.net.URL;import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;import javax.servlet.http.HttpServletRequest;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.apache.shiro.SecurityUtils;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.ResponseBody;import com.alibaba.fastjson.JSONObject;import com.test.web.message.response.JSONResult;/** * IndexController *  *  */@Controllerpublic class IndexController {private static final String FAR_SERVICE_DIR = "http://192.168.30.39:8080/receive";//远程服务器接受文件的路由private static final long yourMaxRequestSize = 10000000;@RequestMapping("/")public String index(Model model) throws IOException {return "/index";}@RequestMapping("/upload")public String upload(HttpServletRequest request) throws Exception {// 判断enctype属性是否为multipart/form-databoolean isMultipart = ServletFileUpload.isMultipartContent(request);if (!isMultipart)throw new IllegalArgumentException("上传内容不是有效的multipart/form-data类型.");// Create a factory for disk-based file itemsDiskFileItemFactory factory = new DiskFileItemFactory();// Create a new file upload handlerServletFileUpload upload = new ServletFileUpload(factory);// 设置上传内容的大小限制（单位：字节）upload.setSizeMax(yourMaxRequestSize);// Parse the requestList<?> items = upload.parseRequest(request);Iterator iter = items.iterator();while (iter.hasNext()) {FileItem item = (FileItem) iter.next();if (item.isFormField()) {// 如果是普通表单字段String name = item.getFieldName();String value = item.getString();// ...} else {// 如果是文件字段String fieldName = item.getFieldName();String fileName = item.getName();String contentType = item.getContentType();boolean isInMemory = item.isInMemory();long sizeInBytes = item.getSize();// ...//上传到远程服务器InputStream uploadedStream = item.getInputStream();HashMap<String, InputStream> files = new HashMap<String, InputStream>();files.put(fileName, uploadedStream);uploadToFarService(files);uploadedStream.close();}}return "redirect:/";}public void uploadToFarService(HashMap<String, InputStream> files) {try {String BOUNDARY = "---------7d4a6d158c9"; // 定义数据分隔线URL url = new URL(FAR_SERVICE_DIR);HttpURLConnection conn = (HttpURLConnection) url.openConnection();// 发送POST请求必须设置如下两行conn.setDoOutput(true);conn.setDoInput(true);conn.setUseCaches(false);conn.setRequestMethod("POST");conn.setRequestProperty("connection", "Keep-Alive");conn.setRequestProperty("user-agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");conn.setRequestProperty("Charsert", "UTF-8");conn.setRequestProperty("Content-Type","multipart/form-data; boundary=" + BOUNDARY);OutputStream out = new DataOutputStream(conn.getOutputStream());byte[] end_data = ("\r\n--" + BOUNDARY + "--\r\n").getBytes();// 定义最后数据分隔线Iterator iter = files.entrySet().iterator();int i=0;while (iter.hasNext()) {i++;Map.Entry entry = (Map.Entry) iter.next();String key = (String) entry.getKey();InputStream val = (InputStream) entry.getValue();String fname = key;File file = new File(fname);StringBuilder sb = new StringBuilder();sb.append("--");sb.append(BOUNDARY);sb.append("\r\n");sb.append("Content-Disposition: form-data;name=\"file" + i+ "\";filename=\"" + key + "\"\r\n");sb.append("Content-Type:application/octet-stream\r\n\r\n");byte[] data = sb.toString().getBytes();out.write(data);DataInputStream in = new DataInputStream(val);int bytes = 0;byte[] bufferOut = new byte[1024];while ((bytes = in.read(bufferOut)) != -1) {out.write(bufferOut, 0, bytes);}out.write("\r\n".getBytes()); // 多个文件时，二个文件之间加入这个in.close();}out.write(end_data);out.flush();out.close();// 定义BufferedReader输入流来读取URL的响应BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));String line = null;while ((line = reader.readLine()) != null) {System.out.println(line);}} catch (Exception e) {System.out.println("发送POST请求出现异常！" + e);e.printStackTrace();}}}

服务端

我们仍然在基础项目上fileController中实现接收文件。代码如下:

FileController.java

package com.test.web.controller;import java.io.File;import java.util.Iterator;import java.util.List;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;/** * IndexController *  *  */@Controllerpublic class FileController {//private static final String STORE_FILE_DIR="/usr/local/image/";//文件保存的路径private static final String STORE_FILE_DIR="D:\\";//文件保存的路径@RequestMapping("/receive")public String receive(HttpServletRequest request,HttpServletResponse response) throws Exception {// 判断enctype属性是否为multipart/form-databoolean isMultipart = ServletFileUpload.isMultipartContent(request);if (!isMultipart)throw new IllegalArgumentException("上传内容不是有效的multipart/form-data类型.");// Create a factory for disk-based file itemsDiskFileItemFactory factory = new DiskFileItemFactory();// Create a new file upload handlerServletFileUpload upload = new ServletFileUpload(factory);// Parse the requestList<?> items = upload.parseRequest(request);Iterator iter = items.iterator();while (iter.hasNext()) {FileItem item = (FileItem) iter.next();if (item.isFormField()) {// 如果是普通表单字段String name = item.getFieldName();String value = item.getString();// ...} else {// 如果是文件字段String fieldName = item.getFieldName();String fileName = item.getName();String contentType = item.getContentType();boolean isInMemory = item.isInMemory();long sizeInBytes = item.getSize();String filePath=STORE_FILE_DIR+fileName;//写入文件到当前服务器磁盘File uploadedFile = new File(filePath);// File uploadedFile = new File("D:\haha.txt");item.write(uploadedFile);}}response.setCharacterEncoding("UTF-8");   response.getWriter().println("上传成功");return null;}}

我们需要把服务端发布到 远程服务器上 使用tomcat等运行起来。

如果项目中有shiro拦截的话记得设置成  /receive = anon 。让接收文件的路由不被拦截。

然后运行客户端，选择文件就可以上传了。对安全有要求的，可以在客户端加一个key，服务器端接收到请求后验证key，没问题的话 再写入目录和文件。