JSP的文件上传

程序员文章站 2022-06-03 09:06:37

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jsp页面使用form 标签一起使用来允许用户上传文件到服务器。上传的文件可以是文本文件或图像文件或任何文档。

1.需要用到的jar包

需要用到的jar包：commons-fileupload-1.3.2.jar,commons-io-2.5.jar

为大家准备好的jar包链接：https://pan.baidu.com/s/1GyOp2o0ID-4JeMNW1YSMrw 密码：tm8g

2.注意事项

1）表单 method 属性应该设置为 POST 方法，不能使用 GET 方法。

2）表单 enctype 属性应该设置为 multipart/form-data。

3）表单 enctype 属性设置为 multipart/form-data后，后台servlet接收表单中的数据时会接收不到。

解决方法一：用JavaScript重新url

    //先获取form表单的action属性
    var action = $form.attr("action");
    action = action + "?studentName=" + $("#studentName").val() + "&studentID" + $("#studentID").val();
    $form.attr("action",action);
    $form.submit();

注意中文乱码处理！！

解决方法二：像我这样写。

3.上代码

例：首先创建两个jsp页面，一个servlet负责后台操作

index页面代码：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>文件上传</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
</head>

<body>
	<h3>文件上传</h3>
	<form method="post" action="servlet/UploadServlet" enctype="multipart/form-data">
		<label>姓名：</label><input name="studentName" type="text"/><br>
		<label>学号：</label><input name="studentID" type="text" /><br>
		<label>选择一个照片: </label><input type="file" name="studentImg" /> <br>
		<input type="submit" value="上传" />
	</form>
</body>
</html>

message页面代码，负责展示上传的信息

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>消息</title>
    
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

  </head>
  
  <body>
  	<c:choose>
  		<c:when test="${!empty student}">
  			<table>
  				<tr>
  					<td>姓名：</td>
  					<td>${student.name}</td>
  				</tr>
  				<tr>
  					<td>学号：</td>
  					<td>${student.id}</td>
  				</tr>
  				<tr>
  					<td>照片：</td>
  					<td><img src="${student.img}" /></td>
  				</tr>
  			</table>
  		</c:when>
  		<c:otherwise>
  			<h3 style="text-align: center; color: red;">失败，没有任何信息</h3>
  		</c:otherwise>
  	</c:choose>
  </body>
</html>

后台的servlet

package top.liu15.controller;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
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 top.liu15.entity.Student;

public class UploadServlet extends HttpServlet {

    /**
     * 
     */
    private static final long serialVersionUID = -7106039161860356768L;

    /**
     * Constructor of the object.
     */
    public UploadServlet() {
        super();
    }
    // 上传文件存储目录
    private static final String UPLOAD_DIRECTORY = "upload";
 
    // 上传配置
    private static final int MEMORY_THRESHOLD   = 1024 * 1024 * 3;  // 3MB
    private static final int MAX_FILE_SIZE      = 1024 * 1024 * 40; // 40MB
    private static final int MAX_REQUEST_SIZE   = 1024 * 1024 * 50; // 50MB
    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 检测是否为多媒体上传
        if (!ServletFileUpload.isMultipartContent(request)) {
            // 如果不是则停止
            PrintWriter writer = response.getWriter();
            writer.println("Error: 表单必须包含 enctype=multipart/form-data");
            writer.flush();
            return;
        }
 
        // 配置上传参数
        DiskFileItemFactory factory = new DiskFileItemFactory();
        // 设置内存临界值 - 超过后将产生临时文件并存储于临时目录中
        factory.setSizeThreshold(MEMORY_THRESHOLD);
        // 设置临时存储目录
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
 
        ServletFileUpload upload = new ServletFileUpload(factory);
         
        // 设置最大文件上传值
        upload.setFileSizeMax(MAX_FILE_SIZE);
         
        // 设置最大请求值 (包含文件和表单数据)
        upload.setSizeMax(MAX_REQUEST_SIZE);
        
        // 中文处理
        upload.setHeaderEncoding("UTF-8"); 

        // 构造临时路径来存储上传的文件
        // 这个路径相对当前应用的目录
        String uploadPath = getServletContext().getRealPath("") + File.separator + UPLOAD_DIRECTORY;
       
         
        // 如果目录不存在则创建
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }
        //存放学生数据
        Student stu = null;
        try {
            // 解析请求的内容提取文件数据
            List<FileItem> formItems = upload.parseRequest(request);
            if (formItems != null && formItems.size() > 0) {
                stu =  new Student();
                // 迭代表单数据
                for (FileItem item : formItems) {
                    // 处理不在表单中的字段
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        String filePath = uploadPath + File.separator + fileName;
                        File storeFile = new File(filePath);
                        stu.setImg(request.getContextPath() + "/" + UPLOAD_DIRECTORY + "/" + fileName);
                        // 保存文件到硬盘
                        item.write(storeFile);
                        //判断字段名
                    } else{
                        //字段名
                        String name = item.getFieldName();
                        //对应的值
                        String value = new String(item.get(),"utf-8");
                        if("studentName".equals(name)){
                            stu.setName(value);
                        }else{
                            stu.setId(value);
                        }
                    }
                }
            }
        } catch (Exception ex) {
            request.setAttribute("message","错误信息: " + ex.getMessage());
        }
        request.setAttribute("student", stu);
        // 跳转到 message.jsp
        getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
    }

    /**
     * The doPost method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

}

运行结果如下：

index.jsp页面

JSP的文件上传

message页面

JSP的文件上传

希望本篇文章可以帮助到您！

JSP的文件上传

1.需要用到的jar包

2.注意事项

3.上代码

例：首先创建两个jsp页面，一个servlet负责后台操作

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