【JDBC】CRUD操作

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;
            }
        }
    }
}