今天我们来学习Servlet文件上传下载

Servlet文件上传主要是使用了ServletInputStream读取流的方法，其读取方法与普通的文件流相同。

一.文件上传相关原理

第一步，构建一个upload.jsp文件

  1. <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
  2. <%
  3. String path = request.getContextPath();
  4. String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
  5. %>
  6.  
  7. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
  8. <html>
  9.   <head>
  10.     <base href="<%=basePath%>">
  11.  
  12.     <title>My JSP 'index.jsp' starting page</title>
  13. 	<meta http-equiv="pragma" content="no-cache">
  14. 	<meta http-equiv="cache-control" content="no-cache">
  15. 	<meta http-equiv="expires" content="0">
  16. 	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
  17. 	<meta http-equiv="description" content="This is my page">
  18. 	<!--
  19. 	<link rel="stylesheet" type="text/css" href="styles.css">
  20. 	-->
  21.   </head>
  22.   <body>
  23.     <form enctype="application/x-www-form-urlencoded" action="${pageContext.request.contextPath }/servlet/UploadServlet1" method="post">
  24.     <input type="text" name="name" value="name" /><br/>
  25.     <div id="div1">
  26.     <div>
  27.     <input type="file" name="photo" />
  28.     </div>
  29.     </div>
  30.     <input type="submit" name="上传" /><br/>
  31.     </form>
  32.   </body>
  33. </html>

第二步，构建一个servlet UploadServlet1.java

  1. package com.zk.upload;
  2.  
  3. import java.io.IOException;
  4. import java.io.PrintWriter;
  5.  
  6. import javax.servlet.ServletException;
  7. import javax.servlet.ServletInputStream;
  8. import javax.servlet.http.HttpServlet;
  9. import javax.servlet.http.HttpServletRequest;
  10. import javax.servlet.http.HttpServletResponse;
  11.  
  12. public class UploadServlet1 extends HttpServlet {
  13. 	public void doGet(HttpServletRequest request, HttpServletResponse response)
  14. 			throws ServletException, IOException {
  15. 			String name=request.getParameter("name");
  16. 			String photo=request.getParameter("photo");
  17.  
  18. 			ServletInputStream inputstream=request.getInputStream();
  19. 			int len=0;
  20. 			byte[] b=new byte[1024];
  21. 			while((len=inputstream.read(b))!=-1){
  22. 				System.out.println(new String(b,0,len));
  23. 			}
  24. 			inputstream.close();
  25. 	}
  26. 	public void doPost(HttpServletRequest request, HttpServletResponse response)
  27. 			throws ServletException, IOException {
  28. 		ServletInputStream inputstream=request.getInputStream();
  29. 		int len=0;
  30. 		byte[] b=new byte[1024];
  31. 		while((len=inputstream.read(b))!=-1){
  32. 			System.out.println(new String(b,0,len));
  33. 		}
  34. 		inputstream.close();
  35. 	}
  36.  
  37. 	/**
  38. 	 * Initialization of the servlet. <br>
  39. 	 *
  40. 	 * @throws ServletException if an error occurs
  41. 	 */
  42. 	public void init() throws ServletException {
  43. 		// Put your code here
  44. 	}
  45.  
  46. }

最后执行UploadServlet1.java之后，输出上传文件的信息。

这里涉及到文件上传的相关原理，在我本地浏览器中调试显示信息如下：

这是一些有关文件上传的相关信息。

二.文件上传

接下来，我们开始进行文件上传的工作。

第一部，创建jsp

这里的form表单需要更改一下enctype属性，这个属性是规定在发送到服务器之前应该如何对表单数据进行编码。

  1. <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
  2. <%
  3. String path = request.getContextPath();
  4. String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
  5. %>
  6.  
  7. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
  8. <html>
  9.   <head>
  10.     <base href="<%=basePath%>">
  11.  
  12.     <title>My JSP 'index.jsp' starting page</title>
  13. 	<meta http-equiv="pragma" content="no-cache">
  14. 	<meta http-equiv="cache-control" content="no-cache">
  15. 	<meta http-equiv="expires" content="0">
  16. 	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
  17. 	<meta http-equiv="description" content="This is my page">
  18.   </head>
  19.   <body>
  20.      <form enctype="multipart/form-data" action="${pageContext.request.contextPath }/servlet/UploadServlet2" method="post">
  21.     <input type="text" name="name" value="name" /><br/>
  22.     <div id="div1">
  23.     <div>
  24.     <input type="file" name="photo" />
  25.     </div>
  26.     </div>
  27.     <input type="submit" name="上传" /><br/>
  28.     </form>
  29.   </body>
  30. </html>

　　UploadServlet2.java

  1. package com.zk.upload;
  2.  
  3. import java.io.File;
  4. import java.io.FileOutputStream;
  5. import java.io.IOException;
  6. import java.io.InputStream;
  7. import java.io.PrintWriter;
  8. import java.io.UnsupportedEncodingException;
  9. import java.text.SimpleDateFormat;
  10. import java.util.Date;
  11. import java.util.List;
  12. import java.util.UUID;
  13.  
  14. import javax.servlet.ServletException;
  15. import javax.servlet.http.HttpServlet;
  16. import javax.servlet.http.HttpServletRequest;
  17. import javax.servlet.http.HttpServletResponse;
  18.  
  19. import org.apache.commons.fileupload.FileItem;
  20. import org.apache.commons.fileupload.FileUploadBase;
  21. import org.apache.commons.fileupload.FileUploadException;
  22. import org.apache.commons.fileupload.disk.DiskFileItemFactory;
  23. import org.apache.commons.fileupload.servlet.ServletFileUpload;
  24. import org.apache.commons.io.FilenameUtils;
  25.  
  26. public class UploadServlet2 extends HttpServlet {
  27.  
  28. 	/**
  29. 	 * Constructor of the object.
  30. 	 */
  31. 	public UploadServlet2() {
  32. 		super();
  33. 	}
  34.  
  35. 	/**
  36. 	 * Destruction of the servlet. <br>
  37. 	 */
  38. 	public void destroy() {
  39. 		super.destroy(); // Just puts "destroy" string in log
  40. 		// Put your code here
  41. 	}
  42.  
  43. 	/**
  44. 	 * The doGet method of the servlet. <br>
  45. 	 *
  46. 	 * This method is called when a form has its tag value method equals to get.
  47. 	 *
  48. 	 * @param request the request send by the client to the server
  49. 	 * @param response the response send by the server to the client
  50. 	 * @throws ServletException if an error occurred
  51. 	 * @throws IOException if an error occurred
  52. 	 */
  53. 	public void doGet(HttpServletRequest request, HttpServletResponse response)
  54. 			throws ServletException, IOException {
  55. 		//优先级不高
  56. 		request.setCharacterEncoding("UTF-8");
  57.  
  58. 		//要执行文件上传的操作
  59. 		//判断表单是否支持文件上传
  60. 		boolean isMultipartContent=ServletFileUpload.isMultipartContent(request);
  61. 		if(!isMultipartContent){
  62. 			throw new RuntimeException("your form is not multipart/form-data");
  63. 		}
  64. 		//创建一个DiskFileItemFactory工厂类
  65. 		DiskFileItemFactory factory=new DiskFileItemFactory();
  66. 		//创建一个ServletFileUpload核心对象
  67. 		ServletFileUpload sfu=new ServletFileUpload(factory);
  68. 		//解决上传表单乱码的问题
  69. 		sfu.setHeaderEncoding("UTF-8");
  70. 		try {
  71. 			//限制上传文件的大小
  72. 			//sfu.setFileSizeMax(1024);
  73. 			//sfu.setSizeMax(6*1024*1024);
  74. 		    //解析requst对象，得到一个表单项的集合
  75. 			List<FileItem> fileitems=sfu.parseRequest(request);
  76. 			//遍历表单项数据
  77. 			for(FileItem fileItem:fileitems){
  78. 				if(fileItem.isFormField()){
  79. 					//普通表单项
  80. 					processFormField(fileItem);
  81. 				}
  82. 				else{
  83. 					//上传表单项
  84. 					processUploadField(fileItem);
  85. 				}
  86. 			}
  87. 		} catch(FileUploadBase.FileSizeLimitExceededException e){
  88. 			throw new RuntimeException("文件过大");
  89. 		}catch (FileUploadException e) {
  90. 			// TODO Auto-generated catch block
  91. 			e.printStackTrace();
  92. 		}
  93. 	}
  94. 	private void processUploadField(FileItem fileItem) {
  95. 		// TODO Auto-generated method stub
  96. 		//得到上传的名字
  97. 		String filename=fileItem.getName();
  98. 		//得到文件流
  99. 		try {
  100. 			InputStream is=fileItem.getInputStream();
  101. 			String dictory=this.getServletContext().getRealPath("/upload");
  102. 			System.out.println(dictory);
  103. 			//创建一个存盘的路径
  104. 			File storeDirecctory=new File(dictory);//既代表文件又代表目录
  105. 			if(!storeDirecctory.exists()){
  106. 				storeDirecctory.mkdirs();//创建一个指定目录
  107. 			}
  108. 			//处理文件名
  109. 			filename=filename.substring(filename.lastIndexOf(File.separator)+1);
  110. 			if(filename!=null){
  111. 				filename=FilenameUtils.getName(filename);
  112. 			}
  113. 			//解决文件同名的问题
  114. 			filename=UUID.randomUUID()+"_"+filename;
  115.  
  116. 			//目录打散
  117. 			//String childDirectory=makeChildDirectory(storeDictory);//2015-10-
  118. 			String childDirectory=makeChildDirectory2(storeDirecctory,filename);
  119. 			//System.out.println(childDirectory);
  120. 			//上传文件,自动删除临时文件
  121. 			fileItem.write(new File(storeDirecctory,childDirectory+File.separator+filename));
  122.  
  123. 		} catch (IOException e) {
  124. 			// TODO Auto-generated catch block
  125. 			e.printStackTrace();
  126. 		} catch (Exception e) {
  127. 			// TODO Auto-generated catch block
  128. 			e.printStackTrace();
  129. 		}
  130.  
  131. 	}
  132.  
  133. 	//上传表单项
  134. 	private void processUploadField1(FileItem fileItem) {
  135. 		// TODO Auto-generated method stub
  136.  
  137. 		//得到上传的名字
  138. 		String filename=fileItem.getName();
  139. 		//得到文件流
  140. 		try {
  141. 			//得到文件流
  142. 			InputStream is=fileItem.getInputStream();
  143.  
  144. 			String dictory=this.getServletContext().getRealPath("/upload");
  145. 			System.out.println(dictory);
  146. 			//创建一个存盘的路径
  147. 			File storeDictory=new File(dictory);//既代表文件又代表目录
  148. 			if(!storeDictory.exists()){
  149. 				storeDictory.mkdirs();//创建一个指定目录
  150. 			}
  151. 			//处理文件名
  152. 			filename=filename.substring(filename.lastIndexOf(File.separator)+1);
  153. 			if(filename!=null){
  154. 				filename=FilenameUtils.getName(filename);
  155. 			}
  156. 			//解决文件同名的问题
  157. 			filename=UUID.randomUUID()+"_"+filename;
  158.  
  159. 			//目录打散
  160. 			//String childDirectory=makeChildDirectory(storeDictory);//2015-10-
  161. 			String childDirectory2=makeChildDirectory2(storeDictory,filename);
  162. 			//System.out.println(childDirectory);
  163. 			//在storeDictory目录下创建完整的文件
  164. 			//File file=new File(storeDictory,filename);
  165. 			//File file=new File(storeDictory,childDirectory+File.separator+filename);
  166. 			File file2=new File(storeDictory,childDirectory2+File.separator+filename);
  167.  
  168. 			//通过文件输出流将上传的文件保存到磁盘
  169. 			//FileOutputStream fos=new FileOutputStream(file);
  170. 			FileOutputStream fos2=new FileOutputStream(file2);
  171.  
  172. 			int len=0;
  173. 			byte[] b=new byte[1024];
  174. 			while((len=is.read(b))!=-1){
  175. 			//	fos.write(b,0,len);
  176. 				fos2.write(b,0,len);
  177. 			}
  178. 			//fos.close();
  179. 			fos2.close();
  180. 			is.close();
  181. 			System.out.println("success");
  182. 			//删除临时文件
  183. 			fileItem.delete();
  184. 		} catch (IOException e) {
  185. 			// TODO Auto-generated catch block
  186. 			e.printStackTrace();
  187. 		}
  188.  
  189. 	}
  190. 	//目录打散
  191. 	private String makeChildDirectory(File storeDictory) {
  192. 		// TODO Auto-generated method stub
  193. 		SimpleDateFormat sm=new SimpleDateFormat("yyyy-MM-dd");
  194. 		String date=sm.format(new Date());
  195. 		//创建目录
  196. 		File file=new File(storeDictory,date);
  197. 		if(!file.exists()){
  198. 			file.mkdirs();
  199. 		}
  200. 		return date;
  201. 	}
  202. 	//目录打散
  203. 	private String makeChildDirectory2(File storeDictory,String filename){
  204. 		int hashcode=filename.hashCode();
  205. 		System.out.println(hashcode);
  206. 		String code=Integer.toHexString(hashcode);
  207. 		String childDirectory=code.charAt(0)+File.separator+code.charAt(1);
  208. 		//创建指定目录
  209. 		File file=new File(storeDictory,childDirectory);
  210. 		if(!file.exists()){
  211. 			file.mkdirs();
  212. 		}
  213. 		return childDirectory;
  214. 	}
  215. 	//普通表单项
  216. 	private void processFormField(FileItem fileItem) {
  217. 		// TODO Auto-generated method stub
  218. 		String fieldname=fileItem.getFieldName();
  219.  
  220. 		try {
  221. 			String valuename=fileItem.getString("UTF-8");
  222. 		//	fieldname=new String(valuename.getBytes("iso-8859-1"),"utf-8");
  223. 			System.out.println(fieldname+":"+valuename);
  224. 		} catch (UnsupportedEncodingException e) {
  225. 			// TODO Auto-generated catch block
  226. 			e.printStackTrace();
  227. 		}
  228.  
  229. 	}
  230.  
  231. 	/**
  232. 	 * The doPost method of the servlet. <br>
  233. 	 *
  234. 	 * This method is called when a form has its tag value method equals to post.
  235. 	 *
  236. 	 * @param request the request send by the client to the server
  237. 	 * @param response the response send by the server to the client
  238. 	 * @throws ServletException if an error occurred
  239. 	 * @throws IOException if an error occurred
  240. 	 */
  241. 	public void doPost(HttpServletRequest request, HttpServletResponse response)
  242. 			throws ServletException, IOException {
  243. 		request.setCharacterEncoding("UTF-8");
  244. 		//要执行文件上传的操作
  245. 				//判断表单是否支持文件上传
  246. 				boolean isMultipartContent=ServletFileUpload.isMultipartContent(request);
  247. 				if(!isMultipartContent){
  248. 					throw new RuntimeException("your form is not multipart/form-data");
  249. 				}
  250. 				//创建一个DiskFileItemFactory工厂类
  251. 				DiskFileItemFactory factory=new DiskFileItemFactory();
  252. 				//产生临时文件
  253. 				factory.setRepository(new File("f:\\temp"));
  254. 				//创建一个ServletFileUpload核心对象
  255. 				ServletFileUpload sfu=new ServletFileUpload(factory);
  256. 				sfu.setHeaderEncoding("UTF-8");
  257. 				try {
  258. 					//限制上传文件的大小
  259. 					//sfu.setFileSizeMax(1024*1024*1024);
  260. 					//sfu.setSizeMax(6*1024*1024);
  261. 				    //解析requst对象，得到一个表单项的集合
  262. 					List<FileItem> fileitems=sfu.parseRequest(request);
  263. 					//遍历表单项数据
  264. 					for(FileItem fileItem:fileitems){
  265. 						if(fileItem.isFormField()){
  266. 							//普通表单项
  267. 							processFormField(fileItem);
  268. 						}
  269. 						else{
  270. 							//上传表单项
  271. 							processUploadField(fileItem);
  272. 						}
  273. 					}
  274. 				} catch(FileUploadBase.FileSizeLimitExceededException e){
  275. 					//throw new RuntimeException("文件过大");
  276. 					System.out.println("文件过大");
  277. 				}catch (FileUploadException e) {
  278. 					// TODO Auto-generated catch block
  279. 					e.printStackTrace();
  280. 				}
  281. 	}
  282.  
  283. 	/**
  284. 	 * Initialization of the servlet. <br>
  285. 	 *
  286. 	 * @throws ServletException if an error occurs
  287. 	 */
  288. 	public void init() throws ServletException {
  289. 		// Put your code here
  290. 	}
  291.  
  292. }

　这里面加了文件大小限制、文件重命名、目录打散等方法。

最后，我们运行一下这个demo

我们在web-apps的目录下可以看到我们刚刚上传的文件

三.文件下载

现在我们进行文件下载

  1. package com.zk.upload;
  2.  
  3. import java.io.FileInputStream;
  4. import java.io.IOException;
  5. import java.io.PrintWriter;
  6. import java.net.URLEncoder;
  7.  
  8. import javax.servlet.ServletException;
  9. import javax.servlet.ServletOutputStream;
  10. import javax.servlet.http.HttpServlet;
  11. import javax.servlet.http.HttpServletRequest;
  12. import javax.servlet.http.HttpServletResponse;
  13.  
  14. public class DownloadServlet1 extends HttpServlet {
  15.  
  16. 	/**
  17. 	 * Constructor of the object.
  18. 	 */
  19. 	public DownloadServlet1() {
  20. 		super();
  21. 	}
  22.  
  23. 	/**
  24. 	 * Destruction of the servlet. <br>
  25. 	 */
  26. 	public void destroy() {
  27. 		super.destroy(); // Just puts "destroy" string in log
  28. 		// Put your code here
  29. 	}
  30.  
  31. 	/**
  32. 	 * The doGet method of the servlet. <br>
  33. 	 *
  34. 	 * This method is called when a form has its tag value method equals to get.
  35. 	 *
  36. 	 * @param request the request send by the client to the server
  37. 	 * @param response the response send by the server to the client
  38. 	 * @throws ServletException if an error occurred
  39. 	 * @throws IOException if an error occurred
  40. 	 */
  41. 	public void doGet(HttpServletRequest request, HttpServletResponse response)
  42. 			throws ServletException, IOException {
  43. 		//设置一个要下载的文件
  44. 		String filename="a.csv";
  45. 		filename=new String(filename.getBytes("UTF-8"),"iso-8859-1");
  46. 		//告知浏览器要下载文件
  47. 		response.setHeader("content-disposition", "attachment;filename="+filename);
  48. 		response.setContentType(this.getServletContext().getMimeType(filename));//根据文件明自动获取文件类型
  49. 		response.setCharacterEncoding("UTF-8");//告知文件用什么服务器编码
  50.  
  51. 		PrintWriter pw=response.getWriter();
  52. 		pw.write("Hello,world");
  53.  
  54. 	}
  55.  
  56. 	/**
  57. 	 * The doPost method of the servlet. <br>
  58. 	 *
  59. 	 * This method is called when a form has its tag value method equals to post.
  60. 	 *
  61. 	 * @param request the request send by the client to the server
  62. 	 * @param response the response send by the server to the client
  63. 	 * @throws ServletException if an error occurred
  64. 	 * @throws IOException if an error occurred
  65. 	 */
  66. 	public void doPost(HttpServletRequest request, HttpServletResponse response)
  67. 			throws ServletException, IOException {
  68. 		doGet(request,response);
  69. 	}
  70.  
  71. 	/**
  72. 	 * Initialization of the servlet. <br>
  73. 	 *
  74. 	 * @throws ServletException if an error occurs
  75. 	 */
  76. 	public void init() throws ServletException {
  77. 		// Put your code here
  78. 	}
  79.  
  80. }

　　首先指定一个需要下载的文件的文件名，然后告知浏览器需要下载文件，根据文件明自动获取文件类型，并告知文件用什么服务器编码。执行servlet后，会下载一个名为

a.csv的文件。

下载后，可以看到文件中存有Hello,world字符。

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