day05-18-CRUD增删改查

CRUD增删改查，封装执行sql的方法

package day05.jdbc;
/*
crud 增删改查

 */

import com.google.common.collect.Lists;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

public class Demo05 {
    public static void main(String[] args) throws Exception{
        delete();
        //update();
        // insert();
        //query();
    }
    public static void delete(){
        String sql ="delete from auth_group where id =?";
        ex_sql(sql, Lists.newArrayList(1));

    }
    public static int ex_sql(String sql, List<Object> params){
        try(Connection conn = MysqlUtil.getConn();) {

            PreparedStatement ps = conn.prepareStatement(sql);
            for (int i =0;i<params.size();i++){
                // 这里是i+1，不是i，因为jdbc是从1开始数的
                ps.setObject(i+1,params.get(i));}
            int n = ps.executeUpdate();
            return n;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return -1;
    }


    public static void query() throws Exception{
        Connection conn = MysqlUtil.getConn();
        String sql ="select * from auth_group";
        PreparedStatement ps = conn.prepareStatement(sql);
        ResultSet resultSet = ps.executeQuery();
        while (resultSet.next()){
            long id = resultSet.getLong(1);
            String name = resultSet.getString(2);
            System.out.println(String.format("id:%d,name:%s", id, name));
        }
        MysqlUtil.close(conn);

    }
    public static void insert() throws Exception{
        Connection conn = MysqlUtil.getConn();
        String sql ="insert into auth_group values(?,?)";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setLong(1,1);
        ps.setString(2,"miaojiang");
        // 除了查询用executeQuery(),其他的增删改用executeUpdate()
        // 这里得到的int n是影响了多少行数据
        int n = ps.executeUpdate();
        System.out.println("n = " + n);
        MysqlUtil.close(conn);}

    public static void update() throws Exception{
        Connection conn = MysqlUtil.getConn();
        String sql ="update auth_group set name=? where id =?";
        PreparedStatement ps = conn.prepareStatement(sql);
        // parameterIndex代表？的下标
        ps.setString(1,"shuai");
        ps.setLong(2,1);
        // 除了查询用executeQuery(),其他的增删改用executeUpdate()
        // 这里得到的int n是影响了多少行数据
        int n = ps.executeUpdate();
        System.out.println("n = " + n);
        MysqlUtil.close(conn);



        }
}