Fileupload 处理表单问题

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>测试</title>
</head>
<body>
    <center>
        <!-- <form action="/Foods/IndexServlet" method="post"> -->
        <form action="/Foods/IndexServlet" method="post" enctype="multipart/form-data">
            <table>
                <tr>
                    <td>用户名</td>
                    <td>
                        <input type="text" name="username">
                    </td>
                </tr>
                <tr>
                    <td>密码</td>
                    <td>
                        <input type="text" name="password">
                    </td>
                </tr>
                <tr>
                    <td>性别</td>
                    <td>
                        <input type="radio" name="sex" value="男">男
                        <input type="radio" name="sex" value="女">女
                    </td>
                </tr>
                <tr>
                    <td>
                        <input type="submit" value="提交">
                        <input type="reset" value="重置">
                    </td>
                </tr>
            </table>
        </form>
    </center>
</body>
</html>

package com.imooc.servlet;
 
import java.io.IOException;
import java.util.List;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
 
/**
 * Servlet implementation class IndexServlet
 */
@WebServlet("/IndexServlet")
public class IndexServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
        
     
    public IndexServlet() {
        
    }
 
     
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         
        DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
         
        ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
         
        try {
            List<FileItem> list = (List<FileItem>)servletFileUpload.parseRequest(request);
             
            for(FileItem fileItem : list){
                if(fileItem.isFormField()){//普通表单项
                    String name = fileItem.getFieldName();
                    String value = fileItem.getString("utf-8");
                    System.out.println("name:"+name);
                    System.out.println("value:"+value);
                    if(value == ""){
                        System.out.println("1");
                    }else if(value == null){
                        System.out.println("2");
                    }else{
                        System.out.println("3");
                    }
                }
            }
        } catch (FileUploadException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         
        /*String username = request.getParameter("username");
        String password = request.getParameter("password");
        String sex = request.getParameter("sex");
        System.out.println("username:"+username);
        System.out.println("password:"+password);
        System.out.println("sex:"+sex);
        if(username == ""){
            System.out.println("1");
        }else if(username == null){
            System.out.println("2");
        }else{
            System.out.println("3");
        }
         
        if(password == ""){
            System.out.println("4");
        }else if(password == null){
            System.out.println("5");
        }else{
            System.out.println("6");
        }*/
    }
 
     
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
 
}
 
//表单提交问题，使用最基本的表单提交时，如果什么都不填写，直接点击提交，在servlet处理的时候，request.getParameter("username")和request.getparameter("password"),对应的打印值为"",性别选择的打印值为null。而在使用fileupload提交表单时，表单什么也不写，对应的fileItem.getString("UTF-8")打印，既不是""也不是null，麻烦帮忙看一下。

慕粉3355010 2018-11-26

源自：项目：登录注册功能 3-2 接收表单普通项的参数

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1回答

提问者慕粉3355010 2018-11-26 10:02:29

问题补充，使用fileupload提交表单时，<input text="radio" 这个标签如果不选择的话，根本就不会打印值。

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chrismorgen #1

请问同学的疑问点是什么呢，如果没有值，返回的就是空字符串，所以就不会打印值，祝学习愉快~

2018-11-26 15:03:44
提问者慕粉3355010 回复 chrismorgen #2

就是两种表单提交的方式，普通的提交表单，如果没有输入，servlet接收到name对应的value是“”。但是使用fileupload提交空表单，则servlet接收到对应的value的值既不是“”也不是null 那应该是什么怎么判断才对，不知道你有没有理解我说的。

2018-11-26 15:08:59
chrismorgen 回复提问者慕粉3355010 #3

我明白同学的意思，value输出的是空字符串，也就是“”，你可以用.equals("")方法来判断他是否为空，祝学习愉快~

2018-11-26 17:02:42