core technology

• java web servlet: HttpServlet class, configuration of Servlet class based on @WebServlet() comment
• tomcat project deployment
• mysql database
• jdbc
• druid database connection pool
• html

Software used

• java web integrated development environment: IntelliJ IDEA
• Server: tomcat
• Visualization interface for mysql: SQLyog

jar packages used

• The jar packages required for the project: druid-1.0.9.jar, mysql-connector-java-5.1.48-bin.jar
• druid-1.0.9.jar: Druid database connection pool driver package for Alibaba
• mysql-connector-java-5.1.48-bin.jar: driver package for database connection of jdbc

Case Requirements

• A simple web project that enables login operations with specified account passwords and displays login results
• Implement registration and login functions
• Store registered accounts in mysql database
• Using druid database connection pool technology

Configuration of project jar packages and databases

• The jar package for a web project is first placed in the WEB-INF directory under the web directory
  
• Right-click the libs folder to select Add as Library
  
• Add the two jar packages in tomcat's lib directory (otherwise the web project will not find the class when the browser runs)
• The configuration file druid.properties for the database connection pool Druid is placed in the src folder
  
• Configuration information for druid.properties

  # Driver directory for jdbc,class.forName();
  driverClassName=com.mysql.jdbc.Driver
  # url of database
  url=jdbc:mysql://127.0.0.1:3306/city
  # Account to connect to
  username=root
  # Password for the account to be linked 
  password=root
  # Number of connection objects in the initial connection pool
  initialSize=5
  # Maximum number of connection objects
  maxActive=10
  # Maximum Wait Time
  maxWait=3000
  

• Create users table in mysql database

  CREATE TABLE users (
  USER VARCHAR(30) UNIQUE NOT NULL,
  PASSWORD VARCHAR(50) NOT NULL
  );
  

Writing druid tool classes

• Requirements: Implement the Get Connection Object method, implement the close method of PreparedStatement,ResultSet,Connection Object
• DruidUtils class code

  package cn.web.jdbc;
  
  
  import com.alibaba.druid.pool.DruidDataSourceFactory;
  
  import javax.sql.DataSource;
  import java.io.InputStream;
  import java.sql.Connection;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.util.Properties;
  
  public class DruidUtils {
  
      private static DataSource dataSource;
  
      static {
          Properties properties = new Properties();
          ClassLoader classLoader = DruidUtils.class.getClassLoader();
          InputStream inputStream = classLoader.getResourceAsStream("druid.properties");
          try {
              properties.load(inputStream);
              dataSource = DruidDataSourceFactory.createDataSource(properties);
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
      public static DataSource getDataSource() {
          return dataSource;
      }
  
      public static Connection getConnection() {
          try {
              return dataSource.getConnection();
          } catch (SQLException e) {
              e.printStackTrace();
          }
          return null;
      }
  
      public static void close(PreparedStatement preparedStatement) {
          if(preparedStatement != null) {
              try {
                  preparedStatement.close();
              } catch (SQLException e) {
                  e.printStackTrace();
              }
          }
      }
  
      public static void close(Connection connection) {
          if(connection != null) {
              try {
                  connection.close();
              } catch (SQLException e) {
                  e.printStackTrace();
              }
          }
      }
  
      public static void close(ResultSet resultSet) {
          if(resultSet != null) {
              try {
                  resultSet.close();
              } catch (SQLException e) {
                  e.printStackTrace();
              }
          }
      }
  
      public static void close(PreparedStatement preparedStatement, Connection connection, ResultSet resultSet) {
          close(preparedStatement);
          close(resultSet);
          close(connection);
      }
  
      public static void close(PreparedStatement preparedStatement, Connection connection) {
          close(preparedStatement);
          close(connection);
      }
  }
  
  

Write UserManager classes (manage user objects)

• Requirements: Enable registration and login functions
• UserManager class code

  package cn.web.user;
  
  import cn.web.jdbc.DruidUtils;
  
  import java.sql.Connection;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  
  public class UserManager {
  
      private static String REGISTER_SQL = "INSERT INTO users VALUES (?, ?)";
      private static String LOGIN_SQL = "SELECT * FROM users WHERE user = ? AND password = ?";
  
      private static Connection connection;
      private static PreparedStatement preparedStatement;
      private static ResultSet resultSet;
  
      private static void getConnection() {
          connection = DruidUtils.getConnection();
      }
  
      private static void getPreparedStatement(String sql) {
          try {
              preparedStatement = connection.prepareStatement(sql);
          } catch (SQLException e) {
              e.printStackTrace();
          }
      }
  
      private static void setPreparedStatement(String user, String password) {
          try {
              preparedStatement.setString(1, user);
              preparedStatement.setString(2,password);
          } catch (SQLException e) {
              e.printStackTrace();
          }
      }
  
      public static boolean login(String user, String password) {
          boolean count = true;
          getConnection();
          getPreparedStatement(LOGIN_SQL);
          setPreparedStatement(user, password);
  
          try {
              resultSet = preparedStatement.executeQuery();
          } catch (SQLException e) {
              e.printStackTrace();
          }
  
          try {
              if(!resultSet.next()) {
                  count = false;
              }
          } catch (SQLException e) {
              e.printStackTrace();
          }
  
          DruidUtils.close(preparedStatement, connection, resultSet);
  
          return count;
      }
  
  
      public static boolean register(String user, String password) {
          int count = -1;
          getConnection();
          getPreparedStatement(REGISTER_SQL);
          setPreparedStatement(user, password);
  
          try {
              count = preparedStatement.executeUpdate();
          } catch (SQLException e) {
              e.printStackTrace();
          }
  
          DruidUtils.close(preparedStatement, connection, resultSet);
          return count == 1 ? true : false;
      }
  }
  

A servlet class that implements registration and login

• Requirements: Return results for registration and login
• LoginServlet class code implementation

  package cn.web.net;
  
  import cn.web.user.UserManager;
  
  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 java.io.IOException;
  
  @WebServlet(urlPatterns = {"/login"})
  public class LoginServlet extends HttpServlet {
      @Override
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          doPost(request, response);
      }
      @Override
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          response.setContentType("text/html; charset=utf-8");
          boolean result = UserManager.login(request.getParameter("user"), request.getParameter("password"));
          if(result) {
              response.getWriter().write("Landing Success!");
          } else {
              response.getWriter().write("Logon Failure!");
          }
      }
  }
  
  

• Code implementation of RegisterServlet class

  package cn.web.net;
  
  import cn.web.jdbc.DruidUtils;
  import cn.web.user.UserManager;
  
  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 java.io.IOException;
  import java.sql.Connection;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  
  @WebServlet(urlPatterns = {"/register"})
  public class RegisterServlet extends HttpServlet {
      @Override
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          doPost(request, response);
      }
  
      @Override
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          response.setContentType("text/html; charset=utf-8");
          boolean result = UserManager.register(request.getParameter("user"), request.getParameter("password"));
          if(result == true) {
              response.getWriter().write("login was successful!");
          } else {
              response.getWriter().write("login has failed!");
          }
      }
  }
  
  

Write html files for landing and registration pages

Registration Page

• register.html

  <!DOCTYPE html>
  <html lang="en">
  <head>
      <meta charset="UTF-8">
      <title>register</title>
  </head>
  <body>
  developer:tom<br>
  <form action="/register" method="post">
      <input type="text" placeholder="user" name="user"><br>
      <input type="text" placeholder="password" name="password"><br>
      <input type="submit" name="register">
  </form>
  </body>
  </html>
  

• Page Effects
  

Landing Page

• login.html

  <!DOCTYPE html>
  <html lang="en">
  <head>
      <meta charset="UTF-8">
      <title>Land</title>
  </head>
  <body>
  <form action="/login" method="post">
      <input type="text" placeholder="user" name="user"><br>
      <input type="text" placeholder="password" name="password"><br>
      <input type="submit" value="Land">
  </form>
  </body>
  </html>
  

• Page Effects
  

Deployment of the project

Points stepped on in this project

• The lib file for the jar package is placed under web/WEB-INF
• The jar package should also be placed in the lib folder of tomcat
• Try not to have Chinese names for project paths. If there are Chinese names, use the java.net.URLDecoder.decode() method to re-encode them.
• The page uses the response.getWriter().write() method to scramble Chinese and response.setContentType("text/html; charset=utf-8") to set the encoding.

Project Source Download

• Link: https://pan.baidu.com/s/1nkdKUhrGlptmMBkcVKHbzw
• Extraction Code: n1p1