mybatis练习

发布时间：2024年01月16日

mybatis练习

一.环境准备

1.数据库实始化

-- 创建tb_brand表 

create table tb_brand ( 

/*id 主键*/

id int primary key auto_increment,

/* 品牌名称*/

brand_name varchar(20), 

/* 企业名称 */

company_name varchar(20), 

/* 排序字段*/ ordered int,

/* 描述信息*/ description varchar(100), 

/* 状态：0：禁用 1：启用*/ status int );

-- 添加数据 

insert into tb_brand (brand_name, company_name, ordered, description, status) values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0), ('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界', 1), ('小米', '小米科技有限公司', 50, 'are you ok', 1);

2.mybatis.xml配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--根元素-->
<configuration>
    <!--加载外部配置文件-->
    <properties resource="jdbc.properties"></properties>
    <!--开启驼峰映射：把数据表中的带有下划线的字段，变为java的驼峰命名方式。user_name->username userName-->
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <!--设置别名-->
    <typeAliases>
        <!--扫描指定的名,所包下的所有的类，都起了别名，别名格式：全部小写或驼峰命名-->
        <package name="com.itheima.pojo"/>
        <!--        <typeAlias type="com.itheima.pojo.User" alias="User"></typeAlias>-->
    </typeAliases>
    <!--配置数据源（数据库连接）-->
    <environments default="dev">
        <!--开发环境-->
        <environment id="dev">
            <!--事务管理器：按照jdbc默信的事务-->
            <transactionManager type="JDBC"/>
            <!--数据源(数据库连接池) mybatis有自带数据库连接池-->
            <dataSource type="POOLED">
                <!--连接数据库需要的4个参数：驱动、URL、登录名、密码-->
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <!--测试环境-->
        <environment id="test">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/hsp_db02?useUnicode=true&amp;characterEncoding=utf-8&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <!--映射映射相关文件-->
    <mappers>

        <!--方案1：指定关联的映射文件，通过映射文件在关联mapper接口-->
        <!--        <mapper resource="com/itheima/dao/UserMapper.xml"/>-->
        <!--方案1：指定关联的mapper接口（通过mapper接口关联映射文件）
            要求：
                1.映射文件名和mapper接口必须相同
                2.映射文件和mapper接口存储在相同的路径下
        -->
        <!--指定要扫描的所有mapper接口的包路径-->
        <package name="com.itheima.dao"/>
    </mappers>
</configuration>

3.pojo类

public class Brand {
    private Integer id;
    private String brandName;
    private String companyName;
    private Integer ordered;
    private String description;
    private Integer status;

    public Brand() {
    }

    public Brand(Integer id, String brandName, String companyName, Integer ordered, String description, Integer status) {
        this.id = id;
        this.brandName = brandName;
        this.companyName = companyName;
        this.ordered = ordered;
        this.description = description;
        this.status = status;
    }

    public Integer getId() {
        return id;
    }

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

    public String getBrandName() {
        return brandName;
    }

    public void setBrandName(String brandName) {
        this.brandName = brandName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    public Integer getOrdered() {
        return ordered;
    }

    public void setOrdered(Integer ordered) {
        this.ordered = ordered;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "BrandDao{" +
                "id=" + id +
                ", brandName='" + brandName + '\'' +
                ", companyName='" + companyName + '\'' +
                ", ordered=" + ordered +
                ", description='" + description + '\'' +
                ", status=" + status +
                '}';
    }
}

4.BrandMapper接口

package com.itheima.dao;

import com.itheima.pojo.Brand;

import java.util.List;

public interface BrandMapper {
    /**
     * 查询所有品牌
     * @return
     */
    public List<Brand> findAllBrand();
}

5.BrandMapper.xml

<?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">
<!--利用namespace属性，绑定当前映射文件和mapper接口映射关联-->
<mapper namespace="com.itheima.dao.BrandMapper">
    <!--使用resultMap解决查询结果中的字段名和java实体类中不一致问题-->
    <resultMap id="brandMap" type="com.itheima.pojo.Brand" autoMapping="true">
        <!--id标签：配置数据表的主键和实体类中的属性映射-->
        <id column="id" property="id"></id>
        <!--result标签：配置数据表中非主键字段和实体类的属性映射-->
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>
    <sql id="brandFields">
        id,
       brand_name,
       company_name,
       ordered,
       description,
       status
    </sql>
    <select id="findAllBrand" resultMap="brandMap">
        select <include refid="brandFields"/> from tb_brand

    </select>
    <!--根据id查询一行数据-->
    <select id="findBrandById" resultType="com.itheima.pojo.Brand" parameterType="int">
        SELECT
            id,
            brand_name as brandName,
            company_name as companyName,
            ordered,
            description,
            status
        FROM tb_brand
        where id=#{id}
    </select>

</mapper>

6.测试代码

public class MybatisTest {
    @Test
    public void testFindAllBrand(){
        //使用SqlSessionFactory工厂类，创建SqlSession
        SqlSession sqlSession = MybatisUtil.openSession();

        //利用sqlSession，创建一个代理对象
        BrandMapper sessionMapper = sqlSession.getMapper(BrandMapper.class);

        //使用代理对象和方法查询用户数据
        List<Brand> brandList = sessionMapper.findAllBrand();
        //释放资源
        MybatisUtil.closeSqlSession(sqlSession);
        //测试用户数据
        for (Brand brand:brandList){
            System.out.println(brand);
        }
    }
}

二.mybatis占位符

参数占位符详解：

mybatis提供了两种参数占位符：

${key}：在核心配置文件中获取外部配置文件中的数据;在映射文件中做为sql的占位符参数使用（注意细节：需要使用@Param(“参数”))

#{key}:在映射文件中做为sql的占位符参数使用

#{key}和${key}的区别

#{}：底层使用的是 PreparedStatement 对sql进行预编译，使用占位符。好处：防止SQL注入

2024-01-15 17:57:11.300 [DEBUG]  com.itheima.dao.BrandMapper.findBrandById [main] : ==>  Preparing: SELECT id, brand_name as brandName, company_name as companyName, ordered, description, status FROM tb_brand where id=? 
2024-01-15 17:57:11.398 [DEBUG]  com.itheima.dao.BrandMapper.findBrandById [main] : ==> Parameters: 3(Integer)
2024-01-15 17:57:11.437 [TRACE]  com.itheima.dao.BrandMapper.findBrandById [main] : <==    Columns: id, brandName, companyName, ordered, description, status
2024-01-15 17:57:11.437 [TRACE]  com.itheima.dao.BrandMapper.findBrandById [main] : <==        Row: 3, 小米, 小米科技有限公司, 50, are you ok, 1
2024-01-15 17:57:11.441 [DEBUG]  com.itheima.dao.BrandMapper.findBrandById [main] : <==      Total: 1

${} ：底层使用的是 Statement，拼接SQL，会存在SQL注入问题

2024-01-15 17:58:37.816 [DEBUG]  com.itheima.dao.BrandMapper.findBrandById [main] : ==>  Preparing: SELECT id, brand_name as brandName, company_name as companyName, ordered, description, status FROM tb_brand where id=3 
2024-01-15 17:58:37.922 [DEBUG]  com.itheima.dao.BrandMapper.findBrandById [main] : ==> Parameters: 
2024-01-15 17:58:37.966 [TRACE]  com.itheima.dao.BrandMapper.findBrandById [main] : <==    Columns: id, brandName, companyName, ordered, description, status
2024-01-15 17:58:37.968 [TRACE]  com.itheima.dao.BrandMapper.findBrandById [main] : <==        Row: 3, 小米, 小米科技有限公司, 50, are you ok, 1
2024-01-15 17:58:37.976 [DEBUG]  com.itheima.dao.BrandMapper.findBrandById [main] : <==      Total: 1

三.条件查询

1.-Map集合作为SQL参数

brandMapper.xml

<!--根据条件查询品牌数据-->
<select id="findBrandByCondition" resultMap="brandMap">
    SELECT
        id,
        brand_name,
        company_name,
        ordered,
        description,
        status
    FROM tb_brand
    WHERE brand_name=#{brandName}
        AND
          company_name=#{companyName}
        AND
          status=#{status}
</select>
<select id="findBrandByCondition2" resultMap="brandMap">
    SELECT
        id,
        brand_name,
        company_name,
        ordered,
        description,
        status
    FROM tb_brand
    WHERE brand_name=#{brandName}
      AND
        company_name=#{companyName}
      AND
        status=#{status}
</select>
<select id="findBrandByCondition3" resultMap="brandMap">
    SELECT
        id,
        brand_name,
        company_name,
        ordered,
        description,
        status
    FROM tb_brand
    WHERE brand_name=#{brandname}
      AND
        company_name=#{companyname}
      AND
        status=#{status}
</select>

brandMapper接口

/**
 * 根据条件，查询品牌数据
 * @param brandName  品牌名称
 * @param companyName  公司名称
 * @param status    状态
 * @return 返回的数据
 */
//当方法中传递的参数有2个或以上时，需要使用@Param注解声明占位符参数
public List<Brand> findBrandByCondition(
        @Param("brandName") String brandName,
        @Param("companyName") String companyName,
        @Param("status") int status);

public List<Brand> findBrandByCondition2(Brand brand);
public List<Brand> findBrandByCondition3(Map paramMap);//mpa[key=value]

测试代码

@Test
public void testFindBrandByCondition3(){
    //使用SqlSessionFactory工厂类，创建SqlSession
    SqlSession sqlSession = MybatisUtil.openSession();

    //利用sqlSession，创建一个代理对象
    BrandMapper sessionMapper = sqlSession.getMapper(BrandMapper.class);

    //使用代理对象和方法查询用户数据
    Map map=new HashMap();
    map.put("brandname","华为");
    map.put("companyname","华为技术有限公司");
    map.put("status",1);
    List<Brand> brandList = sessionMapper.findBrandByCondition3(map);
    //释放资源
    MybatisUtil.closeSqlSession(sqlSession);
    for (Brand brand2:brandList){
        System.out.println(brand2);
    }
}
@Test
public void testFindBrandByCondition2(){
    //使用SqlSessionFactory工厂类，创建SqlSession
    SqlSession sqlSession = MybatisUtil.openSession();

    //利用sqlSession，创建一个代理对象
    BrandMapper sessionMapper = sqlSession.getMapper(BrandMapper.class);

    //使用代理对象和方法查询用户数据
    Brand brand=new Brand();
    brand.setBrandName("华为");
    brand.setCompanyName("华为技术有限公司");
    brand.setStatus(1);
    List<Brand> brandList = sessionMapper.findBrandByCondition2(brand);
    //释放资源
    MybatisUtil.closeSqlSession(sqlSession);
    for (Brand brand2:brandList){
        System.out.println(brand2);
    }
}
@Test
public void testFindBrandByCondition(){
    //使用SqlSessionFactory工厂类，创建SqlSession
    SqlSession sqlSession = MybatisUtil.openSession();

    //利用sqlSession，创建一个代理对象
    BrandMapper sessionMapper = sqlSession.getMapper(BrandMapper.class);

    //使用代理对象和方法查询用户数据
    List<Brand> brandList = sessionMapper.findBrandByCondition("华为","华为技术有限公司",1);
    //释放资源
    MybatisUtil.closeSqlSession(sqlSession);
    for (Brand brand:brandList){
        System.out.println(brand);
    }
}

2.动态SQL

2.1 if

<!--根据条件查询品牌数据-->
<select id="findBrandByCondition" resultMap="brandMap">
    SELECT
        id,
        brand_name,
        company_name,
        ordered,
        description,
        status
    FROM tb_brand
    WHERE 1=1
    <if test="brandName !=null ">
        AND brand_name=#{brandName}
    </if>
    <if test="companyName !=null ">
        AND company_name=#{companyName}
    </if>
    <if test="status !=null ">
        AND status=#{status}
    </if>
</select>

2.2 where

where标签：代替sql语句中的where关键字可以自动去除sql语句中的where 条件里面多余的or或and

<select id="findBrandByCondition2" resultMap="brandMap">
    SELECT
        id,
        brand_name,
        company_name,
        ordered,
        description,
        status
    FROM tb_brand
    <where>
        <if test="brandName !=null ">
            AND brand_name=#{brandName}
        </if>
        <if test="companyName !=null ">
            AND company_name=#{companyName}
        </if>
        <if test="status !=null ">
            AND status=#{status}
        </if>
    </where>
</select>

2.3 choose

<select id="findBrandByCondition3" resultMap="brandMap">
    SELECT
        id,
        brand_name,
        company_name,
        ordered,
        description,
        status
    FROM tb_brand
    <where>
        <choose>
            <when test="brandname!=null">
                brand_name=#{brandname}
            </when>
            <when test="companyname!=null">
                company_name=#{companyname}
            </when>
            <when test="status!=null">
                status=#{status}
            </when>
        </choose>
    </where>
</select>

2.4添加

xml:

<insert id="addBrand" parameterType="com.itheima.pojo.Brand">
    insert into tb_brand (brand_name, company_name, ordered, description, status)
    values (#{brandName}, #{companyName}, #{ordered}, #{description}, #{status})
</insert>

接口：

/**
 * 添加品牌
 * @param brand 品牌对象
 * @return 受影响的行数
 */
public  int addBrand(Brand brand);

测试代码：

@Test
public void testAddBrand(){
    //使用SqlSessionFactory工厂类，创建SqlSession
    SqlSession sqlSession = MybatisUtil.openSession();

    //利用sqlSession，创建一个代理对象
    BrandMapper sessionMapper = sqlSession.getMapper(BrandMapper.class);
    Brand brand=new Brand();
    brand.setStatus(1);
    brand.setBrandName("测试1");
    brand.setCompanyName("测试1");
    brand.setDescription("测试1");
    brand.setOrdered(5);

    //插入数据
    int rowCount=sessionMapper.addBrand(brand);
    if(rowCount>0){
        System.out.println("插入数据成功");
    }
    //释放资源
    MybatisUtil.closeSqlSession(sqlSession);
}

2.5添加-主键返回

在mybatis的insert操作过程中，存在一各路扶桑术：主键回填，在向表中插入一行记录后，会自动把当前行的主键列下的数据值获取

2.5.1SQL

CREATE TABLE tb_order(
    id int primary key auto_increment,
    payment double,
    payment_type int,
    status int
	
);

create table tb_order_item
(
	id int primary key auto_increment,
	goods_name varchar(20),
	goods_price double,
	count varchar(32),
	order_id int
);

insert into tb_order(payment,payment_type,status)values(4887,1,2),(1975,1,1);

insert into tb_order_item(goods_name,goods_price,count,order_id)values('华为手机',3888,1,1),('华为Pad',999,1,1),('小米手机',888,2,2),('小米手环',199,1,2);

2.5.2pojo

package com.itheima.pojo;

public class Order {
    private Integer id;
    private Double payment;
    private Integer paymentType;
    private Integer status;

    public Order() {
    }

    public Order(Integer id, Double payment, Integer paymentType, Integer status) {
        this.id = id;
        this.payment = payment;
        this.paymentType = paymentType;
        this.status = status;
    }

    public Integer getId() {
        return id;
    }

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

    public Double getPayment() {
        return payment;
    }

    public void setPayment(Double payment) {
        this.payment = payment;
    }

    public Integer getPaymentType() {
        return paymentType;
    }

    public void setPaymentType(Integer paymentType) {
        this.paymentType = paymentType;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "Order{" +
                "id=" + id +
                ", payment=" + payment +
                ", paymentType=" + paymentType +
                ", status=" + status +
                '}';
    }
}

package com.itheima.pojo;

public class OrderItem {
    private Integer id;
    private String goodsName;
    private double goodsPrice;
    private String count;
    private Integer orderId;

    public OrderItem() {
    }

    public OrderItem(Integer id, String goodsName, double goodsPrice, String count, Integer orderId) {
        this.id = id;
        this.goodsName = goodsName;
        this.goodsPrice = goodsPrice;
        this.count = count;
        this.orderId = orderId;
    }

    public Integer getId() {
        return id;
    }

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

    public String getGoodsName() {
        return goodsName;
    }

    public void setGoodsName(String goodsName) {
        this.goodsName = goodsName;
    }

    public double getGoodsPrice() {
        return goodsPrice;
    }

    public void setGoodsPrice(double goodsPrice) {
        this.goodsPrice = goodsPrice;
    }

    public String getCount() {
        return count;
    }

    public void setCount(String count) {
        this.count = count;
    }

    public Integer getOrderId() {
        return orderId;
    }

    public void setOrderId(Integer orderId) {
        this.orderId = orderId;
    }

    @Override
    public String toString() {
        return "OrderItem{" +
                "id=" + id +
                ", goodsName='" + goodsName + '\'' +
                ", goodsPrice=" + goodsPrice +
                ", count='" + count + '\'' +
                ", orderId=" + orderId +
                '}';
    }
}

2.5.3orderMapper.xml

<?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">
<!--利用namespace属性，绑定当前映射文件和mapper接口映射关联-->
<mapper namespace="com.itheima.dao.OrderMapper">
    <!--添加订单-->
    <insert id="addOrder" parameterType="com.itheima.pojo.Order" useGeneratedKeys="true" keyProperty="id">
        insert into tb_order(payment,payment_type,status)
        values(#{payment},#{paymentType},#{status})
    </insert>
    <!--添加订单明细-->
    <insert id="addOrderItem" parameterType="com.itheima.pojo.OrderItem">
        insert into tb_order_item(goods_name,goods_price,count,order_id)
        values(#{goodsName},#{goodsPrice},#{count},#{orderId})
    </insert>
</mapper>

2.5.4orderMapper接口

package com.itheima.dao;

import com.itheima.pojo.Order;
import com.itheima.pojo.OrderItem;

public interface OrderMapper {
    /**
     * 添加订单
     * @param order 订单对象
     * @return 返行行数
     */
    public int addOrder(Order order);

    /**
     * 添加订单明细
     * @param orderItem 订单明细对象
     * @return 返回行数
     */
    public int addOrderItem(OrderItem orderItem);
}

测试代码：

package com.itheima.test;

import com.itheima.dao.BrandMapper;
import com.itheima.dao.OrderMapper;
import com.itheima.pojo.Order;
import com.itheima.pojo.OrderItem;
import com.itheima.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class OrderMapperTest {
    @Test
    public void TestAddOrder(){
        //使用SqlSessionFactory工厂类，创建SqlSession
        SqlSession sqlSession = MybatisUtil.openSession();

        //利用sqlSession，创建一个代理对象
        OrderMapper orderMapper = sqlSession.getMapper(OrderMapper.class);

        Order order=new Order();
        order.setPayment(10000.0);
        order.setPaymentType(2); //2表示支付宝
        order.setStatus(1);

        int rowCount = orderMapper.addOrder(order);

        //订单对象
        OrderItem orderItem=new OrderItem();
        orderItem.setOrderId(order.getId());
        orderItem.setGoodsName("小米");
        orderItem.setGoodsPrice(1000);
        orderItem.setCount("10");
        int count2=orderMapper.addOrderItem(orderItem);
        if(rowCount>0 && count2>0){
            sqlSession.commit();
            System.out.println("插入数据成功");
        }
        //释放资源
        MybatisUtil.closeSqlSession(sqlSession);
    }
}

2.6修改所有字段

brandMapper.xml

    <update id="updateBrand">
        update tb_brand
        set brand_name=#{brandName},
            company_name=#{companyName},
            ordered=#{ordered},
            description=#{description},
            status=#{status}
        where id=#{id}
    </update>

2.7修改部份数据

brandMapper.xml

<!--修改数据-->
<update id="updateBrand">
    update tb_brand
    <set>
        <if test="brandName!=null">
            brand_name=#{brandName}
        </if>
        <if test="companyName!=null">
            company_name=#{companyName}
        </if>
        <if test="ordered!=null">
            ordered=#{ordered},
        </if>
        <if test="description!=null">
            description=#{description}
        </if>
        <if test="status!=null">
            status=#{status}
        </if>
    </set>
    where id=#{id}
</update>

brandMapper接口

/**
 * 修改品牌
 * @param brand 品牌对象
 * @return  受影响的行数
 */
public int updateBrand(Brand brand);

测试代码

@Test
public void testUpdateBrand(){
    //使用SqlSessionFactory工厂类，创建SqlSession
    SqlSession sqlSession = MybatisUtil.openSession();

    //利用sqlSession，创建一个代理对象
    BrandMapper sessionMapper = sqlSession.getMapper(BrandMapper.class);
    Brand brand=new Brand();
    brand.setStatus(1);
    brand.setBrandName("苹果");
    brand.setCompanyName("苹果股份");
    brand.setDescription("好用");
    brand.setOrdered(9);
    brand.setId(3);

    //插入数据
    int rowCount=sessionMapper.updateBrand(brand);
    if(rowCount>0){
        sqlSession.commit();
        System.out.println("修改数据成功");
    }
    //释放资源
    MybatisUtil.closeSqlSession(sqlSession);
}

2.8批量删除-动态SQL

brandMapper.xml

<delete id="deleteByIds">
    delete from tb_brand where id
    in(
    <foreach collection="ids" item="id" separator=",">
        #{id}
    </foreach>
    );
</delete>

brandMapper接口

/**
 * 批量删除品牌
 * @param ids
 * @return
 */
public int deleteByIds(@Param("ids") List<Integer>ids);

测试代码

@Test
public void testDeleteBrandByIds(){
    //使用SqlSessionFactory工厂类，创建SqlSession
    SqlSession sqlSession = MybatisUtil.openSession();

    //利用sqlSession，创建一个代理对象
    BrandMapper sessionMapper = sqlSession.getMapper(BrandMapper.class);

    List<Integer> ids=new ArrayList<>();
    Collections.addAll(ids,1,2,3);
    int count=sessionMapper.deleteByIds(ids);
    if(count>0){
        sqlSession.commit();
        System.out.println("删除成功");
    }
    //释放资源
    MybatisUtil.closeSqlSession(sqlSession);
}

文章来源:https://blog.csdn.net/lisus2007/article/details/135631931
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