敲了两天了，还是解决不了错误，心碎了，请大神们帮帮忙
index.jsp
<%--
Created by IntelliJ IDEA.
User: LeoLi
Date: 2021/3/24
Time: 19:18
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录页面</title>
</head>
<body>
<h1 style="text-align: center">文件上传与下载系统</h1>
<form method="post" action="login.do">
姓名：<input type="text" name="username"><br>
<input type="submit" value="登录" />
</form>
</body>
</html>
welcome.jsp
<%--
Created by IntelliJ IDEA.
User: LeoLi
Date: 2021/3/24
Time: 9:24
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>文件上传与下载系统</title>
</head>
<body>
<h1 style="text-align: center">文件上传与下载系统</h1>
<h3>你好：<%=request.getAttribute("username")%></h3>
<form method="post" action="UploadServlet" enctype="multipart/form-data">
选择一个文件:
<input type="file" name="uploadFile" />
<br/><br/>
<input type="submit" value="上传" />
</form>
</body>
</html>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<context-param>
<description>Location to store uploaded file</description>
<param-name>file-upload</param-name>
<param-value>
C:\Program Files (x86)\tomcat-10.0.2\webapps\data\
</param-value>
</context-param>
<servlet>
<servlet-name>UploadServlet</servlet-name>
<servlet-class>UploadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UploadServlet</servlet-name>
<url-pattern>/UploadServlet</url-pattern>
</servlet-mapping>
</web-app>
doLoginServlet.java
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/login.do")
public class doLoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取客户端传来的参数
String username = request.getParameter("username");
request.setAttribute("username", username);
request.getRequestDispatcher("welcome.jsp").forward(request,response);
//request.getSession().setAttribute("username", username);
//response.sendRedirect("welcome.jsp");
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
// response.setHeader("refresh", "2;url=" + request.getContextPath() + "/WelcomeServlet");
}
}
UploadServlet.java
// 导入必需的 java 库
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.util.Iterator;
import java.util.List;
public class UploadServlet extends HttpServlet {
private boolean isMultipart;
private String filePath;
private int maxFileSize = 50 * 1024;
private int maxMemSize = 4 * 1024;
private File file ;
public void init( ){
// 获取文件将被存储的位置
filePath =
getServletContext().getInitParameter("file-upload");
}
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, java.io.IOException {
// 检查我们有一个文件上传请求
isMultipart = ServletFileUpload.isMultipartContent(request);
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter( );
if( !isMultipart ){
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet upload</title>");
out.println("</head>");
out.println("<body>");
out.println("<p>No file uploaded</p>");
out.println("</body>");
out.println("</html>");
return;
}
DiskFileItemFactory factory = new DiskFileItemFactory();
// 文件大小的最大值将被存储在内存中
factory.setSizeThreshold(maxMemSize);
// Location to save data that is larger than maxMemSize.
factory.setRepository(new File("c:\temp"));
// 创建一个新的文件上传处理程序
ServletFileUpload upload = new ServletFileUpload(factory);
// 允许上传的文件大小的最大值
upload.setSizeMax( maxFileSize );
try{
// 解析请求，获取文件项
List fileItems = upload.parseRequest(request);
// 处理上传的文件项
Iterator i = fileItems.iterator();
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet upload</title>");
out.println("</head>");
out.println("<body>");
while ( i.hasNext () )
{
FileItem fi = (FileItem)i.next();
if ( !fi.isFormField () )
{
// 获取上传文件的参数
String fieldName = fi.getFieldName();
String fileName = fi.getName();
String contentType = fi.getContentType();
boolean isInMemory = fi.isInMemory();
long sizeInBytes = fi.getSize();
// 写入文件
if( fileName.lastIndexOf("\\") >= 0 ){
file = new File( filePath +
fileName.substring( fileName.lastIndexOf("\\"))) ;
}else{
file = new File( filePath +
fileName.substring(fileName.lastIndexOf("\\")+1)) ;
}
fi.write( file ) ;
out.println("Uploaded Filename: " + fileName + "<br>");
}
}
out.println("</body>");
out.println("</html>");
}catch(Exception ex) {
System.out.println(ex);
}
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, java.io.IOException {
throw new ServletException("GET method used with " +
getClass( ).getName( )+": POST method required.");
}
}
1.首先你确定一下是否加了没有登录用户拦截 。2.打个断点 看一下 UploadServlet能否执行进入，如果断点可以进来跟踪调试一下。
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控制台的错误信息是什么，打个断点，看看到哪儿报的错误