[原创]java WEB学习笔记49:文件上传基础,基于表单的文件上传,使用fileuoload 组件

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1.基于表单的文件上传java

  1)若是在表单中使用表单元素 <input type=“file” />,浏览器在解析表单时,会自动生成一个输入框和一个按钮,输入框可供用户填写本地文件的文件名和路径名,按钮可让浏览器打开一个文件选择框供用户选择文件:apache

        

 

  2)Enctype 属性浏览器

  ① 当表单须要上传文件时,需指定表单 enctype 的值为 multipart/form-data服务器

  ② 在 form 元素的语法中,enctype 属性指定将数据发送到服务器时浏览器使用的编码类型网络

  ③ enctype 属性取值:app

    > application/x-www-form-urlencoded:表单 enctype 属性的默认值。这种编码方案使用有限的字符集,当使用了非字母和数字时,必须用”%HH”代替(H 表明十六进制数字)。对于大容量的二进制数据或包含非 ASCII 字符的文原本说,这种编码不能知足要求jsp

    > multipart/form-data:form 设定了enctype=“multipart/form-data”属性后,表示表单以二进制传输数据 post

 

  3)总结:进行文件上传时,表单须要作的准备学习

   ① 请求请求方式为 post  :<form action="uploadServlet" method="post"   ....... >

   ② 使用file 表单域  File:<input type="file" name="file"/>

   ③ 使用请求编码方式 : enctype="multipart/form-data"

   ④ 在服务端不能再使用 request.getParameter() 等方式获取请求信息。获取不到,由于请求的编码方式已经为multipart/form-data ,以二进制的方式来提交请求信息,可使用输入流的方式来获取请求信息

 

upload.jsp

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2  pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     
11     <form action="uploadServlet" method="post" enctype="multipart/form-data">
12         File:<input type="file" name="file"/>
13         <br><br>
14         Desc:<input type="text" name="desc"/>
15         <br><br>
16         <input type="submit" value="submit"/>
17     </form>
18 
19 </body>
20 </html>

 

 

 

UploadServlet.java

 

 1 package com.jason.fileupload;  2 
 3 import java.io.BufferedReader;  4 import java.io.IOException;  5 import java.io.InputStream;  6 import java.io.InputStreamReader;  7 import java.io.Reader;  8 
 9 import javax.servlet.ServletException; 10 import javax.servlet.annotation.WebServlet; 11 import javax.servlet.http.HttpServlet; 12 import javax.servlet.http.HttpServletRequest; 13 import javax.servlet.http.HttpServletResponse; 14 
15 /**
16  * Servlet implementation class UploadServlet 17  */
18 @WebServlet("/uploadServlet") 19 public class UploadServlet extends HttpServlet { 20     private static final long serialVersionUID = 1L; 21 
22     /**
23  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) 24      */
25     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 26         //1.获取请求信息 27 // String file = request.getParameter("file"); 28 // String desc = request.getParameter("desc"); 29 //        
30 // System.out.println(file); 31 // System.out.println(desc); 32         
33         //以流的方式处理 上传的代码
34         InputStream in = request.getInputStream(); 35         
36         Reader reader = new InputStreamReader(in); 37         BufferedReader bufferedReader = new BufferedReader(reader); 38         
39         String str = null; 40         
41         while((str = bufferedReader.readLine()) != null){ 42  System.out.println(str); 43  } 44 
45  } 46 
47     
48     
49     
50 }

 

 

2.使用fileuoload 组件

  1)环境的搭建:加入jar包到 lib目录

  

  2)基本思想:

  ① commons-fileupload 能够解析请求,获得一个FileItem 对象组成的List

    ② commons-fileupload 把请求的信息都解析为FileItem 对象,不管是一个通常的文本域仍是一个文件域

  ③ 能够调用 FileItem 的 isFormField() 方法来判断是一个表单域 或不是表单域(则是一个文件域)

  ④ 进一步获取信息

    

1 // Process a regular form field
2 if (item.isFormField()) { 3     String name = item.getFieldName(); 4     String value = item.getString(); 5  ... 6 }

 

 

1 // Process a file upload
2 if (!item.isFormField()) { 3     String fieldName = item.getFieldName(); 4     String fileName = item.getName(); 5     String contentType = item.getContentType(); 6     boolean isInMemory = item.isInMemory(); 7     long sizeInBytes = item.getSize(); 8  ... 9 }

 

 

   3) 如何获得List<FileItem> 对象

简单方式:

1 // Create a factory for disk-based file items
2 FileItemFactory factory = new DiskFileItemFactory(); 3 
4 // Create a new file upload handler
5 ServletFileUpload upload = new ServletFileUpload(factory); 6 
7 // Parse the request
8 List /* FileItem */ items = upload.parseRequest(request);

 

 

复杂方式:能够对文件的上床加入限制条件和其余属性

 1 // Create a factory for disk-based file items
 2 DiskFileItemFactory factory = new DiskFileItemFactory();  3 
 4 // Set factory constraints
 5 factory.setSizeThreshold(yourMaxMemorySize);//设置内存中最多能够存放的上传的文件的大小,若超出则把文件写到一个临时文件夹中,以 byte 为单位  6 factory.setRepository(yourTempDirectory);//设置那个临时文件夹  7 
 8 // Create a new file upload handler
 9 ServletFileUpload upload = new ServletFileUpload(factory); 10 
11 // Set overall request size constraint
12 upload.setSizeMax(yourMaxRequestSize);//设置整个文件的大小 13 
14 // Parse the request
15 List /* FileItem */ items = upload.parseRequest(request);

 

 

 

 helloword.java测试

 

 1 package com.jason.fileupload;  2 
 3 import java.io.BufferedReader;  4 import java.io.File;  5 import java.io.FileOutputStream;  6 import java.io.IOException;  7 import java.io.InputStream;  8 import java.io.InputStreamReader;  9 import java.io.OutputStream; 10 import java.io.Reader; 11 import java.util.List; 12 
13 import javax.servlet.ServletException; 14 import javax.servlet.annotation.WebServlet; 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.FileUploadException; 21 import org.apache.commons.fileupload.disk.DiskFileItemFactory; 22 import org.apache.commons.fileupload.servlet.ServletFileUpload; 23 
24 /**
25  * Servlet implementation class UploadServlet 26  */
27 @WebServlet("/upload/uploadServlet") 28 public class UploadServlet extends HttpServlet { 29     private static final long serialVersionUID = 1L; 30 
31     /**
32  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse 33  * response) 34      */
35     protected void doPost(HttpServletRequest request, 36             HttpServletResponse response) throws ServletException, IOException { 37         // 1.获得FileIrem 的集合 items 38         // Create a factory for disk-based file items
39         DiskFileItemFactory factory = new DiskFileItemFactory(); 40 
41         // Set factory constraints
42         factory.setSizeThreshold(1024 * 500); 43         File tempDirectory = new File("e:\\tempDirectory"); 44  factory.setRepository(tempDirectory); 45 
46         // Create a new file upload handler
47         ServletFileUpload upload = new ServletFileUpload(factory); 48 
49         // Set overall request size constraint
50         upload.setSizeMax(1024 * 1024 * 5); 51 
52         // Parse the request
53         try { 54             List<FileItem> items = upload.parseRequest(request); 55             // 2.遍历items:如果通常表单域,打印信息
56             for (FileItem item : items) { 57                 if (item.isFormField()) { 58                     String name = item.getFieldName(); 59                     String value = item.getString(); 60                     System.out.println(name + " : " + value); 61                 } else { 62                     // 3.如果文件域则把文件保存到目录 files
63                     String fieldName = item.getFieldName(); 64                     String fileName = item.getName(); 65                     String contentType = item.getContentType(); 66                     long sizeInBytes = item.getSize(); 67 
68  System.out.println(fieldName); 69  System.out.println(fileName); 70  System.out.println(contentType); 71  System.out.println(sizeInBytes); 72 
73                     InputStream in = item.getInputStream(); 74                     byte[] buffer = new byte[1024]; 75                     int len = 0; 76                     fileName = "e:\\file\\" + fileName; 77  System.out.println(fileName); 78 
79                     OutputStream out = new FileOutputStream(fileName); 80                     while ((len = in.read(buffer)) != -1) { 81                         out.write(buffer, 0, len); 82  } 83  out.close(); 84  in.close(); 85  } 86  } 87 
88         } catch (FileUploadException e) { 89  e.printStackTrace(); 90  } 91 
92  } 93 
94 }

 

 

 upload.jsp

 

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2  pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     
11     <form action="uploadServlet" method="post" enctype="multipart/form-data">
12         File:<input type="file" name="file"/>
13         <br><br>
14         Desc:<input type="text" name="desc"/>
15         <br><br>
16         <input type="submit" value="submit"/>
17     </form>
18 
19 </body>
20 </html>
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