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Record: solution of 404 error of servlet accessing database in dynamic web project

2022-07-06 13:00:00 【Non wind thought】

dynamic Web project servlet Access database 404 Error resolution

login.html
stay login.html Enter the user's password and click login on the page displayed in the browser , according to action/Web/login go to Web Under the project web.xml file .

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form action="/Web/login" method="post">
		 user name ：<input type="text" name="username"><br>
		 password ：<input type="password" name="password"><br>
		<input type="submit" value=" Sign in "><br>
	</form>
		
</body>
</html>

web.xml
stay xml In the document servlet-mapping In the tag url-pattern In the tag /login, find /login after , According to the above servlet-name Text in label LoginServlet Look for servlet In the label servlet-name The same text in the label LoginServlet, Then find the following servlet-class The text in the label login.LoginServlet, This text indicates to run .java The path of the file （ The bag where it is ）.

  <servlet>
    <description></description>
    <display-name>LoginServlet</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>login.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/login</url-pattern>
  </servlet-mapping>

LoginServlet.java
according to xml In the path （ The bag where it is ） To run the LoginServlet.java file , So as to operate the data in the database 

package login;

import java.io.IOException;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;

import domain.User;
import utils.DataSourceUtils;

public class LoginServlet extends HttpServlet {
    

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
		//1. Get user name and password 
		String username = request.getParameter("username");
		String password = request.getParameter("password");
		//2. Verify whether the user name and password are missing from the database 
		QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
		String sql = "select * from user where username=? and password=?";
		User user = null;
		try {
    
			user = runner.query(sql, new BeanHandler<User>(User.class), username,password);
		} catch (SQLException e) {
    
			// TODO  Automatically generated  catch  block 
			e.printStackTrace();
		}
		//3. Different display information is given to users according to the returned results 
		if (user!=null) {
    
			// User login successful 
			response.getWriter().write(user.toString());
		}else {
    
			// User login failed 
			response.getWriter().write("sorry your username or password is wriong!!!");
		}
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
		doGet(request, response);
	}
}

therefore web.xml Medium url-mapping Text /login Medium login Must be with form Labeled action=/Web/login Medium login The same name

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https://yzsam.com/2022/187/202207060914257053.html

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