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连接数据库

程序员文章站 2022-06-19 11:33:27
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连接数据库连接数据库只能拿结果或者遍历
连接数据库连接数据库
提升作用域

package jdbcdemo.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class jdbcutils {
    //提升作用域
    private static String driver =null;
    private static String url =null;
    private static String username =null;
    private static String password =null;
    static{
        try{
         InputStream in = jdbcutils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);
            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");
            //加载驱动
            Class.forName(driver);
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    //获取连接
    public static Connection getConnection() throws SQLException {
         DriverManager.getConnection(url,username,password);
        return null;
    }

        //释放资源
    public static  void release(Connection conn, Statement st, ResultSet rs) throws SQLException {
        if(rs!=null){
            rs.close();
        }
        if(st!=null){
            st.close();
        }
        if(conn!=null){
            conn.close();
        }

    }
}

//db.properties
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/ssm?useUnicode=true&characterEncoding=utf8&useSSL=false
username=root
password=123

//增
package jdbcdemo;

import jdbcdemo.util.jdbcutils;

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

public class testinsert {
    public static void main(String[] args) throws SQLException {

        Connection conn=null;
        Statement st=null;
        ResultSet rs =null;
        try {
            conn = jdbcutils.getConnection();
            st=conn.createStatement();
            String sql="INSERT INTO `ssm`.`t-customer`" +
                    "            (`id`," +
                    "             `NAME`," +
                    "             `gender`," +
                    "             `telephone`," +
                    "             `address`)" +
                    "VALUES ('3'," +
                    "        '徐源'," +
                    "        '男'," +
                    "        '123456789'," +
                    "        '蓝田');";
            int i = st.executeUpdate(sql);
            if(i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            jdbcutils.release(conn,st,rs);
        }

    }
}
//改
package jdbcdemo;

import jdbcdemo.util.jdbcutils;

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

public class updata {
    public static void main(String[] args) {

        Connection conn=null;
        Statement st=null;
        ResultSet rs=null;

        try {
            conn= jdbcutils.getConnection();
            st=conn.createStatement();
            String sql="UPDATE `t-customer` SET `NAME`=\"李四\",`gender`=\"男\" WHERE id=1";
            int i = st.executeUpdate(sql);
            if(i>0){
                System.out.println("修改成功");
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally{
            try {
                jdbcutils.release(conn,st,rs);
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
}
//查
package jdbcdemo.util;

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

public class testselect {
    public static void main(String[] args) throws SQLException {
        Connection conn=null;
        Statement  st =null;
        ResultSet  rs =null;
        try {
            conn = jdbcutils.getConnection();
           st= conn.createStatement();
           //sql
            String sql="SELECT *FROM `t-customer`";
            rs = st.executeQuery(sql);
            while(rs.next()){
                System.out.println(rs.getString("NAME"));
            }

        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {rs.close();
            st.close();
            conn.close();

        }
    }
}

sql注入问题
连接数据库preparedStatement
连接数据库删除操作
连接数据库IDEr连接
找到databatis然后添加,找到
如果失败就是jar包的版本问题