JDBCCRUD操作

Posted 2022-12-23 huowuyan

JDBC的CRUD操作

• 向数据库中保存记录
• 修改数据库中的记录
• 删除数据库中的记录
• 查询数据库中的记录

保存代码的实现

package demo1;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

public class JDBCDemo3 
    
    @Test
    /**
     * 保存代码的实现
     */
    public void demo3() 
        Connection conn = null;
        Statement stmt = null;
        
        try 
            //注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //获得连接
            conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");
            //获得执行SQL语句的对象
            stmt = conn.createStatement();
            //编写SQL
            String sql = "insert user values(null,'ddd','444','赵六')";
            //执行SQL
            int i = stmt.executeUpdate(sql);
            if(i > 0) 
                System.out.println("保存成功！");
            
        catch(Exception e) 
            e.printStackTrace();
        finally
            //释放资源
            if(stmt != null) 
                try 
                    stmt.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                stmt = null;
            
            if(conn != null) 
                try 
                    conn.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                conn = null;
            
        
    

修改代码的实现

package demo1;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

public class JDBCDemo3 
    
    @Test
    /**
     * 修改代码的实现
     */
    public void demo2() 
        Connection conn = null;
        Statement stmt = null;
        
        try 
            //注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //获得连接
            conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");
            //获得执行SQL语句的对象
            stmt = conn.createStatement();
            //编写SQL
            String sql = "update user set username='qqq',password='1234',name='或无言' where uid=4";
            //执行SQL
            int i = stmt.executeUpdate(sql);
            if(i > 0) 
                System.out.println("修改成功！");
            
        catch(Exception e) 
            e.printStackTrace();
        finally
            //释放资源
            if(stmt != null) 
                try 
                    stmt.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                stmt = null;
            
            if(conn != null) 
                try 
                    conn.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                conn = null;
            
        
    

删除代码的实现

package demo1;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

public class JDBCDemo3 
    
    @Test
    /**
     * 删除代码的实现
     */
    public void demo1() 
        Connection conn = null;
        Statement stmt = null;
        
        try 
            //注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //获得连接
            conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");
            //获得执行SQL语句的对象
            stmt = conn.createStatement();
            //编写SQL
            String sql = "delete from user where uid=4";
            //执行SQL
            int i = stmt.executeUpdate(sql);
            if(i > 0) 
                System.out.println("删除成功！");
            
        catch(Exception e) 
            e.printStackTrace();
        finally
            //释放资源
            if(stmt != null) 
                try 
                    stmt.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                stmt = null;
            
            if(conn != null) 
                try 
                    conn.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                conn = null;
            
        
    

查询代码的实现

package demo1;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

public class JDBCDemo1 
    
    @Test
    /**
     * 查询代码的实现
     */
    public void demo1() 
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try 
            //1.加载驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            
            //2.获得连接
            conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");
            
            //3创建执行SQL语句的对象，并且执行SQL
            //3.1创建执行SQL语句的对象
            String sql = "select * from user";
            stmt = conn.createStatement();
            //3.2执行SQL
            rs = stmt.executeQuery(sql);
            while(rs.next()) 
                int uid = rs.getInt("uid");
                String username = rs.getString("username");
                String password = rs.getString("password");
                String name = rs.getString("name");
                
                System.out.println(uid + "-" + username + "-" + password + "-" + name);
            
         catch (Exception e) 
            e.printStackTrace();
         finally 
            //释放资源
            if(rs != null) 
                try 
                    rs.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                rs = null;
            
            if(stmt != null) 
                try 
                    stmt.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                stmt = null;
            
            if(conn != null) 
                try 
                    conn.close();
                 catch (SQLException e) 
                    e.printStackTrace();
                
                conn = null;