JDBC database operation

Operate on this database

1, stay pom file dependencies Internal configuration dependency

		<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
		</dependency>

		<dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
            <scope>provided</scope>
        </dependency>

2, Writing user entity classes

// Here we use lombok The plug-in automatically generates for each property get and set Method , There are also parametric and nonparametric functions . Import code in “1”
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.experimental.Accessors;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
@Accessors(chain = true) // Chain programming 
public class User {
    
    private int id;
    private String userName;
    private String userPass;
}

3, Write user interface

public interface UserDao {
    
	// Insert 
    void insert(User user) throws Exception;
    // modify 
    int update(User user) throws Exception;
    // Delete 
    int delete(int id) throws Exception;
}

4, Implementation class

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

public class UserDaoImpl implements UserDao{
    
	// establish conection
    private final String url = "jdbc:mysql://localhost:3306/aad?useSSL=false&charactorEncoding=utf8";
    private final String user1 = "root";
    private final String password = "123456";
	// Insert 
    @Override
    public void insert(User user) throws Exception{
    
        // Load drive class 
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection(url,user1,password);
        // Intercostal statement object 
        String sql = "insert into admin(userName,userPass) values(?,?)";
        PreparedStatement pstm = con.prepareStatement(sql);
        // Set parameters 
        pstm.setString(1, user.getUserName());
        pstm.setString(2,user.getUserPass());
        // perform sql
        int r = pstm.executeUpdate();
        // Output 
        System.out.println(r);
        // close resource 
        pstm.close();
        con.close();
    }
    // modify 
    @Override
    public int update(User user) throws Exception {
    
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection(url,user1,password);
        String sql = "update admin set userName = ?, userPass = ? where id = ?";
        PreparedStatement pstm = con.prepareStatement(sql);
        pstm.setString(1,user.getUserName());
        pstm.setString(2,user.getUserPass());
        pstm.setInt(3,user.getId());
        int r = pstm.executeUpdate();
        pstm.close();
        con.close();
        return r;
    }
    // Delete 
    @Override
    public int delete(int id) throws Exception {
    
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection(url,user1,password);
        String sql = "delete from admin where id = ?";
        PreparedStatement pstm = con.prepareStatement(sql);
        pstm.setInt(1,id);
        int r = pstm.executeUpdate();
        return r;
    }
}

5, Use junit test

① Insert the test

import org.junit.Test;

public class UserDaoImplTest {
    
    // Insert the test 
    @Test
    public void testInsert() throws Exception{
    
        User user = new User()
                .setUserName(" wuhu ")
                .setUserPass("123456");
        UserDao userDao = new UserDaoImpl();
        userDao.insert(user);
    }
}

You can see the successful insertion

② Revision Test

// Revision Test 
    @Test
    public void testUpdate() throws Exception {
    
        User user = new User()
                .setId(1)
                .setUserName(" Xiao Ming ")
                .setUserPass("55555");
        userDao.update(user);
    }

You can see id by １ User modification of succeeded ！

③ Delete the test

 // Delete the test 
    @Test
    public void testDelete() throws Exception {
    
        int id = 2;
        userDao.delete(id);
    }

id by ２ The data is deleted

ps: The first time to write all the code that has a lot of repetition , The encapsulation will be modified later .

6, Improved encapsulation of duplicate code , Write a tool class

Create a jdbcutil class

public final class jdbcUtil01 {
    
    private static final String url = "jdbc:mysql://localhost:3306/aad?useSSL=false&charactorEncoding=utf8";
    private static final String user1 = "root";
    private static final String password = "123456";
    private jdbcUtil01() {
    
    }
    // Load drive class , Just execute it once , There is no need to return 
    static {
    
        try {
    
            Class.forName("com.mysql.jdbc.Driver");
        }catch (Exception e) {
    
            //e.printStackTrace();
            throw new RuntimeException(" Error loading drive class , The error message is " + e.getMessage());
        }
    }

    public static int  update(String sql, Object... params) {
    
        Connection con =null;
        PreparedStatement pstm = null;
        ResultSet rs = null;
        try {
    
            // Load drive class 
            Class.forName("com.mysql.jdbc.Driver");
            // Create connection objects 
            con = DriverManager.getConnection(url,user1,password);
            // Create execution sql Statement object 
            pstm = con.prepareStatement(sql);
            // Set parameters 
            for(int i = 0; i < params.length; i++) {
    
                pstm.setObject(i + 1,params[i]);
            }
            // perform sql
            return pstm.executeUpdate();
        }catch (Exception e) {
    
            e.printStackTrace();
            return 0;
        }finally {
    
            distory(con,pstm,rs);
        }
    }

    // A common way to free up resources .
    public static void distory(Connection con, PreparedStatement pstm, ResultSet rs) {
    
        // Release resources 
        if(rs != null) {
    
            try{
    
                rs.close();
            }catch (Exception e) {
    
                e.printStackTrace();
            }
        }
        if(pstm != null) {
    
            try{
    
                pstm.close();
            }catch (Exception e) {
    
                e.printStackTrace();
            }
        }
        if(con != null) {
    
            try{
    
                con.close();
            }catch (Exception e) {
    
                e.printStackTrace();
            }
        }
    }
}