Mybatis完成基于POJO类对象的增删改查-----Mybatis框架-EW帮帮网

java中使用pojo类给sql语句传值,大括号内写pojo类的属性值
MYBATIS框架实质上是使用Get方法取出该值的
如果使用pojo传值的话,大括号内的写的是get方法的属性名把第一个字母改小写
getUserName()改为userName
通过XML解析取出需要的属性名字,拼接为getXX方法,通过反射机制执行方法
也就是说mybatis在底层给sql的?传值的时候调用了pojo对象的getXX方法
Update实现也是通过Bean(POJO)类的get方法取值并拼接到sql语句之上实现的
需求根据ID进行查询的话,需要指定resultType="com.powernode.mybatis.pojo.Car"的值
用来告知框架,我们要把查询出来的信息封装成什么类型的POJO对象
如果查询出来的数据库结果的字段名字与类的属性名不一样,就没法赋值
select语句执行的时候将结果以AS的形式转换为我们POJO的属性名
selectOne和SelectList方法都是指定返回值类型
SelectList方法本身就会返回一个list集合的,但是集合对象的类型就需要我们指明

java中使用pojo类给sql语句传值,大括号内写pojo类的属性值
MYBATIS框架实质上是使用Get方法取出该值的
如果使用pojo传值的话,大括号内的写的是get方法的属性名把第一个字母改小写
getUserName()改为userName
通过XML解析取出需要的属性名字,拼接为getXX方法,通过反射机制执行方法
也就是说mybatis在底层给sql的?传值的时候调用了pojo对象的getXX方法
Update实现也是通过Bean(POJO)类的get方法取值并拼接到sql语句之上实现的
需求根据ID进行查询的话,需要指定resultType="com.powernode.mybatis.pojo.Car"的值
用来告知框架,我们要把查询出来的信息封装成什么类型的POJO对象
如果查询出来的数据库结果的字段名字与类的属性名不一样,就没法赋值
select语句执行的时候将结果以AS的形式转换为我们POJO的属性名
selectOne和SelectList方法都是指定返回值类型
SelectList方法本身就会返回一个list集合的,但是集合对象的类型就需要我们指明

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="abc">
    <!--    这个id是这条SQL语句的唯一标识,这个ID就代表了这条SQL语句-->
    <insert id="insertCar">
        insert into
            t_car(id,car_num,brand,guide_price,produce_time,car_type)
        values
            (null,#{car_num},#{brand},#{guide_price},#{produce_time},#{car_type})
--         底层调用map集合的get方法
    </insert>
    <insert id="insertCar1">
        insert into
            t_car(id,car_num,brand,guide_price,produce_time,car_type)
        values
            (null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType});
        <!--    大括号里面写Pojo类的属性名字-->
    </insert>
    <delete id="deleteById">
-- 一个占位符可以随便写,它能够识别
        delete from
            t_car
        where
            id = #{id};
    </delete>
    <update id="updateById">
        update
            t_car
        set
            car_num = #{carNum},
            brand = #{brand},
            guide_price = #{guidePrice},
            produce_time = #{produceTime},
            car_type = #{carType}
        where
            id = #{id};
        <!--    Update同理-->
    </update>
    <select id="selectById" resultType="com.powernode.mybatis.pojo.Car">
        select
            id,
            car_num as carNum,
            brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>

</mapper>

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="abc">
    <!--    这个id是这条SQL语句的唯一标识,这个ID就代表了这条SQL语句-->
    <insert id="insertCar">
        insert into
            t_car(id,car_num,brand,guide_price,produce_time,car_type)
        values
            (null,#{car_num},#{brand},#{guide_price},#{produce_time},#{car_type})
--         底层调用map集合的get方法
    </insert>
    <insert id="insertCar1">
        insert into
            t_car(id,car_num,brand,guide_price,produce_time,car_type)
        values
            (null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType});
        <!--    大括号里面写Pojo类的属性名字-->
    </insert>
    <delete id="deleteById">
-- 一个占位符可以随便写,它能够识别
        delete from
            t_car
        where
            id = #{id};
    </delete>
    <update id="updateById">
        update
            t_car
        set
            car_num = #{carNum},
            brand = #{brand},
            guide_price = #{guidePrice},
            produce_time = #{produceTime},
            car_type = #{carType}
        where
            id = #{id};
        <!--    Update同理-->
    </update>
    <select id="selectById" resultType="com.powernode.mybatis.pojo.Car">
        select
            id,
            car_num as carNum,
            brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>

</mapper>

package com.powernode.mybatis.pojo;

public class Car
{
    //这是一个封装汽车相关信息的普通的java类,数据库表中的字段应该和属性一一对应
    //为什么使用包装类,因为当我们查值的时候,返回值有可能是null
    //避免数据不兼容
    private Long id;
    private String carNum;
    private String brand;
    private Double guidePrice;
    private String produceTime;
    private String carType;
    public Car(){};

    public Car(Long id, String carNum, String brand, Double guidePrice, String produceTime, String carType) {
        this.id = id;
        this.carNum = carNum;
        this.brand = brand;
        this.guidePrice = guidePrice;
        this.produceTime = produceTime;
        this.carType = carType;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getCarNum() {
        return carNum;
    }

    public void setCarNum(String carNum) {
        this.carNum = carNum;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public Double getGuidePrice() {
        return guidePrice;
    }

    public void setGuidePrice(Double guidePrice) {
        this.guidePrice = guidePrice;
    }

    public String getProduceTime() {
        return produceTime;
    }

    public void setProduceTime(String produceTime) {
        this.produceTime = produceTime;
    }

    public String getCarType() {
        return carType;
    }

    public void setCarType(String carType) {
        this.carType = carType;
    }

    @Override
    public String toString() {
        return "Car{" +
                "id=" + id +
                ", carNum='" + carNum + '\'' +
                ", brand='" + brand + '\'' +
                ", guidePrice=" + guidePrice +
                ", produceTime='" + produceTime + '\'' +
                ", carType='" + carType + '\'' +
                '}';
    }
}

package com.powernode.mybatis.pojo;

public class Car
{
    //这是一个封装汽车相关信息的普通的java类,数据库表中的字段应该和属性一一对应
    //为什么使用包装类,因为当我们查值的时候,返回值有可能是null
    //避免数据不兼容
    private Long id;
    private String carNum;
    private String brand;
    private Double guidePrice;
    private String produceTime;
    private String carType;
    public Car(){};

    public Car(Long id, String carNum, String brand, Double guidePrice, String produceTime, String carType) {
        this.id = id;
        this.carNum = carNum;
        this.brand = brand;
        this.guidePrice = guidePrice;
        this.produceTime = produceTime;
        this.carType = carType;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getCarNum() {
        return carNum;
    }

    public void setCarNum(String carNum) {
        this.carNum = carNum;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public Double getGuidePrice() {
        return guidePrice;
    }

    public void setGuidePrice(Double guidePrice) {
        this.guidePrice = guidePrice;
    }

    public String getProduceTime() {
        return produceTime;
    }

    public void setProduceTime(String produceTime) {
        this.produceTime = produceTime;
    }

    public String getCarType() {
        return carType;
    }

    public void setCarType(String carType) {
        this.carType = carType;
    }

    @Override
    public String toString() {
        return "Car{" +
                "id=" + id +
                ", carNum='" + carNum + '\'' +
                ", brand='" + brand + '\'' +
                ", guidePrice=" + guidePrice +
                ", produceTime='" + produceTime + '\'' +
                ", carType='" + carType + '\'' +
                '}';
    }
}

package com.powernode.mybatis.test;

import com.powernode.mybatis.pojo.Car;
import com.powernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class CarMapperTest
{
    private static final Logger logger = LoggerFactory.getLogger(CarMapperTest.class);
    @Test
    public void TestSelectAll()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行SQL语句
        List<Object> selectAll = sqlSession.selectList("selectAll");
        for (int i = 0; i < selectAll.size(); i++)
        {
            logger.info(selectAll.toString());
        }
        Iterator iterator = selectAll.iterator();
        while (iterator.hasNext())
        {
            logger.info(iterator.next().toString());
        }
        selectAll.forEach(car -> logger.info(car.toString()));
        sqlSession.close();
    }
    @Test
    public void TestInsertCar()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //前端传过来数据了,用MAP封装
        Map<String,Object> map = new HashMap<>();
        map.put("car_num","1111");
        map.put("brand","比亚迪汉");
        map.put("guide_price","10.0");
        map.put("produce_time","2020-11-11");
        map.put("car_type","新能源");
        //执行sql语句,insert(sqlID,一个对象用来封装数据)
        //两个参数,一个是sqlId,一个是数据封装的对象
        //用这个封装了数据的对象来传值
        //这个对象就体现了ORM(对象关系映射)
        int insert = sqlSession.insert("insertCar",map);
        logger.info("" + insert);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestInsertCarByPOJO()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行SQL
        Car car = new Car(null,"3333","比亚迪秦",12.0,"2020-11-11","新能源");
        int insertCar = sqlSession.insert("insertCar1", car);
        //ORM对象,我们都是映射,要取值只能是调用get方法
        logger.info(insertCar == 1?"成功" : "失败");
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestDeleteById()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行SQL语句
        int deleteById = sqlSession.delete("deleteById", 2);
        logger.info(deleteById == 1?"成功" : "失败");
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestUpdateById()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        Car car = new Car(3L,"3333","比亚迪秦",12.0,"2020-11-11","新能源");
        int updateById = sqlSession.update("updateById", car);
        logger.info(updateById == 1?"成功" : "失败");
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestSelectById()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行DQL语句
        Car car = sqlSession.selectOne("selectById", 5);
        //mybatis底层执行了select后会返回一个ResultSet结果对象
        //接下来mybatis应该从ResultSet中取值封装成java对象
        //封装完成返回一个java对象
        logger.info(car.toString());
        sqlSession.close();
    }
}

package com.powernode.mybatis.test;

import com.powernode.mybatis.pojo.Car;
import com.powernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class CarMapperTest
{
    private static final Logger logger = LoggerFactory.getLogger(CarMapperTest.class);
    @Test
    public void TestSelectAll()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行SQL语句
        List<Object> selectAll = sqlSession.selectList("selectAll");
        for (int i = 0; i < selectAll.size(); i++)
        {
            logger.info(selectAll.toString());
        }
        Iterator iterator = selectAll.iterator();
        while (iterator.hasNext())
        {
            logger.info(iterator.next().toString());
        }
        selectAll.forEach(car -> logger.info(car.toString()));
        sqlSession.close();
    }
    @Test
    public void TestInsertCar()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //前端传过来数据了,用MAP封装
        Map<String,Object> map = new HashMap<>();
        map.put("car_num","1111");
        map.put("brand","比亚迪汉");
        map.put("guide_price","10.0");
        map.put("produce_time","2020-11-11");
        map.put("car_type","新能源");
        //执行sql语句,insert(sqlID,一个对象用来封装数据)
        //两个参数,一个是sqlId,一个是数据封装的对象
        //用这个封装了数据的对象来传值
        //这个对象就体现了ORM(对象关系映射)
        int insert = sqlSession.insert("insertCar",map);
        logger.info("" + insert);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestInsertCarByPOJO()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行SQL
        Car car = new Car(null,"3333","比亚迪秦",12.0,"2020-11-11","新能源");
        int insertCar = sqlSession.insert("insertCar1", car);
        //ORM对象,我们都是映射,要取值只能是调用get方法
        logger.info(insertCar == 1?"成功" : "失败");
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestDeleteById()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行SQL语句
        int deleteById = sqlSession.delete("deleteById", 2);
        logger.info(deleteById == 1?"成功" : "失败");
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestUpdateById()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        Car car = new Car(3L,"3333","比亚迪秦",12.0,"2020-11-11","新能源");
        int updateById = sqlSession.update("updateById", car);
        logger.info(updateById == 1?"成功" : "失败");
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void TestSelectById()
    {
        SqlSession sqlSession = SqlSessionUtil.openSqlSession();
        //执行DQL语句
        Car car = sqlSession.selectOne("selectById", 5);
        //mybatis底层执行了select后会返回一个ResultSet结果对象
        //接下来mybatis应该从ResultSet中取值封装成java对象
        //封装完成返回一个java对象
        logger.info(car.toString());
        sqlSession.close();
    }
}

Mybatis完成基于POJO类对象的增删改查-----Mybatis框架

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