Spring-JDBCTemplate操作数据库（查询）

jdbcTemplate操作数据库（查询）

一、查询返回某个值

查询表里面有多少条记录，返回是某个值

queryForObject(String sql, Class<T> requiredType)

第一个参数：sql语句

第二个参数：返回类型Class

二、查询返回对象

queryForObject(String sql, RowMapper  rowMapper, Object... args)

　第一个参数：sql语句

　第二个参数：RowMapper，是接口，返回不同类型数据，使用这个接口里面实现类完成数据封装

　第三个参数：sql语句值

三、查询返回集合

query(String sql, RowMapper<T> rowMapper, @Nullable Object... args)

第一个参数：sql
第二个参数：RowMapper，是接口，返回不同类型数据，使用这个接口里面实现类完成数据封装
第三个参数：sql语句值

package com.orzjiangxiaoyu.spring.dao;

import com.orzjiangxiaoyu.spring.entity.User;

import java.util.List;

/**
 * @author orz
 * @create 2020-08-18 9:36
 */
public interface UserDao {

    public int findCount();

    public User findUserInfo(int id);

    public List<User> findUserListInfo();

}

package com.orzjiangxiaoyu.spring.dao;

import com.orzjiangxiaoyu.spring.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

import java.util.Arrays;
import java.util.List;

/**
 * @author orz
 * @create 2020-08-18 9:37
 */
@Repository
public class UserDaoImpl implements UserDao {

    //注入JdbcTemplate
    @Autowired
    private JdbcTemplate jdbcTemplate;


    @Override
    public int findCount() {
        //1.创建sql语句
        String sql = "select count(*) from t_user";
        //2.调用方法实现

        Integer count = jdbcTemplate.queryForObject(sql, Integer.class);

        return count;
    }

    @Override
    public User findUserInfo(int id) {

        //1.创建sql语句
        String sql = "select * from t_user where user_id=?";
        //2.调用方法实现

        User user = jdbcTemplate.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class), id);
        return user;

    }

    @Override
    public List<User> findUserListInfo() {
        //1.创建sql语句
        String sql = "select * from t_user ";
        //2.调用方法实现

        List<User> list = jdbcTemplate.query(sql, new BeanPropertyRowMapper<User>(User.class));


        return list;
    }

   
}

package com.orzjiangxiaoyu.spring.service;

import com.orzjiangxiaoyu.spring.dao.UserDao;
import com.orzjiangxiaoyu.spring.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

/**
 * @author orz
 * @create 2020-08-18 9:36
 */
@Service
public class UserService {
    //注入dao
    @Autowired
    private UserDao userDao;

    //查询表记录数
    public int selectCount()
    {
        int i=userDao.findCount();
        return i;
    }

    //查询返回对象
    public User findUser(int id)
    {

        return userDao.findUserInfo(id);

    }

    //查询返回集合
    public List<User> findUserList()
    {
        return userDao.findUserListInfo();
    }


    
}

package com.orzjiangxiaoyu.spring.mysqltestdemo;

import com.orzjiangxiaoyu.spring.entity.User;
import com.orzjiangxiaoyu.spring.service.UserService;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.util.ArrayList;
import java.util.List;

/**
 * @author orz
 * @create 2020-08-18 10:20
 */
public class Test2 {

    //查询返回某个值
    @Test
    public void test4()
    {
        ApplicationContext context=new ClassPathXmlApplicationContext("jdbcbean.xml");

        UserService userService = context.getBean("userService", UserService.class);

        int i = userService.selectCount();
        System.out.println(i);
    }

    //查询返回对象
    @Test
    public void test5()
    {
        ApplicationContext context=new ClassPathXmlApplicationContext("jdbcbean.xml");

        UserService userService = context.getBean("userService", UserService.class);

        User user = userService.findUser(1);
        System.out.println(user);
    }

    //查询返回集合
    @Test
    public void test6()
    {
        ApplicationContext context=new ClassPathXmlApplicationContext("jdbcbean.xml");

        UserService userService = context.getBean("userService", UserService.class);

        List<User> userList = userService.findUserList();
        System.out.println(userList);
    }

  

}

Spring-JDBCTemplate操作数据库（查询）

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