Spring Mybatis 基本使用過(guò)程(推薦)

更新時(shí)間：2024年09月23日 11:27:18 作者：JOJO___

Mybatis是一個(gè)半自動(dòng)ORM（Object Relational Mapping）框架,它可以簡(jiǎn)化數(shù)據(jù)庫(kù)編程,讓開發(fā)者更專注于SQL本身,本文給大家介紹Spring Mybatis 基本使用過(guò)程,感興趣的朋友跟隨小編一起看看吧

1. 簡(jiǎn)介

Mybatis庫(kù)可以簡(jiǎn)化數(shù)據(jù)庫(kù)的操作，專注于sql語(yǔ)句。

2.搭建步驟

2.1 在pom.xml引入mybatis

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.11</version>
</dependency>

2.2 在resources下新建mybatis配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Mapper 3.0/EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
<!--        <setting name="logImpl" value="STDOUT_LOGGING"/>&lt;!&ndash; 開啟mybatis的日志輸出 &ndash;&gt;-->
        <setting name="mapUnderscoreToCamelCase" value="true"/><!-- 開啟駝峰式自動(dòng)映射 a_big => aBig -->
    </settings>
    <typeAliases>
        <typeAlias alias="goods" type="com.jojo.pojo.Goods"/><!-- 單獨(dú)設(shè)置別名 -->
        <package name="com.jojo.pojo"/><!-- 批量設(shè)置別名, com.jojo.pojo包下的所有類名的別名為類的首字母小寫-->
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>  <!-- 自動(dòng)開啟事務(wù) -->
            <dataSource type="POOLED"><!-- mybatis維護(hù)連接池 -->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis-example"/>
                <property name="username" value="root"/>
                <property name="password" value="a12345678"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 指定mapper xml文件的位置 -->
        <mapper resource="mappers/GoodsMapper.xml"/>
    </mappers>
</configuration>

2.3 在resources/mapper下新建mapper的xml配置文件:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0/EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jojo.mapper.GoodsMapper"><!-- 對(duì)應(yīng)Mapper的全限定符 -->
<!--    這里寫sql語(yǔ)句 -->
    <insert id="insert" useGeneratedKeys="true" keyColumn="id" keyProperty="id">
        insert into goods (name) value(#{name})
    </insert>
    <update id="update">
        update goods set name=#{name} where id=#{id}
    </update>
    <delete id="delete">
        delete from goods where id = #{id}
    </delete>
    <select id="selectById" resultType="goods">
        select * from goods where id = #{id}
    </select>
    <select id="selectAll" resultType="goods">
        select * from goods
    </select>
</mapper>

2.4 新建pojo類

import lombok.Data;
@Data//lombook插件的@Data標(biāo)簽可以自動(dòng)生成get和set以及toString方法
public class Goods {
    private Integer id;
    private String name;
}

2.5 新建mapper接口

public interface GoodsMapper {
    int insert(Goods goods);
    int update(Goods goods);
    int delete(Integer id);
    Goods selectById(Integer id);
    List<Goods> selectAll();
}

2.6 測(cè)試

public class MybatisTest {
    @Test
    public void test() throws IOException {
        //1.讀取外部配置文件
        InputStream ips = Resources.getResourceAsStream("mybatis-config.xml");
        //2.創(chuàng)建sqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(ips);
        //3.根據(jù)sqlSessionFactory創(chuàng)建sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //4.獲取接口的代理對(duì)象，調(diào)用代理對(duì)象的方法就會(huì)查找mapper接口的方法
        GoosdMapper mapper = sqlSession.getMapper(GoosdMapper.class);
        Goods goods = mapper.queryById(1);
        System.out.println(goods);
        //5.提交事務(wù)和釋放資源
        //sqlSession.commit();
        sqlSession.close();
    }
}

3.常用mapper語(yǔ)句

3.1 傳入值

<!-- #{id} = 使用占位符？，防止sql注入攻擊，但不能替代表名表項(xiàng)-->
<!-- ${id} = 不使用占位符？，不能防止sql注入攻擊，但可以替代表名表項(xiàng)-->
<select id="queryById" resultType="com.jojo.pojo.Employee">
    select emp_id empId,emp_name empName, emp_salary empSalary from t_emp where emp_id = #{id}
</select>
<delete id="deleteById">
    delete from t_emp where emp_id = #{id} <!-- 傳入Integer類型，id可以改寫成任意字符串-->
</delete>
<select id="queryBySalary" resultType="com.jojo.pojo.Employee">
    select emp_id empId,emp_name empName, emp_salary empSalary from t_emp where empSalary = #{salary} <!-- 傳入Double類型，salary可以改寫成任意字符串-->
</select>
<insert id="insertEmp">
    insert into t_emp (emp_name, emp_salary) values (#{empName},#{empSalary});<!-- 傳入對(duì)象時(shí)，要寫傳入對(duì)象的屬性 -->
</insert>
<select id="queryByNameAndSalary" resultType="com.jojo.pojo.Employee">
    select emp_id empId,emp_name empName, emp_salary empSalary from t_emp where empSalary = #{a} and empName = # <!-- 傳入兩個(gè)基本類型，根據(jù)接口中的@Param("名稱")來(lái)指定-->
</select>
<select id="queryByNameAndSalary" resultType="com.jojo.pojo.Employee">
    select emp_id empId,emp_name empName, emp_salary empSalary from t_emp where empSalary = #{arg0} and empName = #{arg1} <!-- 法2：傳入兩個(gè)基本類型，可以根據(jù)順序來(lái)取arg0...arg1...-->
</select>
<select id="queryByNameAndSalary" resultType="com.jojo.pojo.Employee">
    select emp_id empId,emp_name empName, emp_salary empSalary from t_emp where empSalary = #{param1} and empName = #{param2} <!-- 法3：傳入兩個(gè)基本類型，可以根據(jù)順序來(lái)取param1...param2...-->
</select>
<insert id="insertEmpMap">
    insert into t_emp (emp_name, emp_salary) values (#{name},#{salary});<!-- 傳入Map時(shí)，要寫傳入Map的key -->
</insert>

3.2 返回值

<select id="queryNameById" resultType="string"><!-- resultType指定返回的類型，寫類的全限定符或者mybatis提供的別名(在mybatis官網(wǎng)查)-->
    select emp_name from t_emp where emp_id = #{id} 
</select>
<select id="queryById" resultType="employee"> <!-- resultType指定返回的為對(duì)象時(shí)，select的行需要起別名來(lái)與類的屬性完全一致-->
    select emp_id empId,emp_name empName, emp_salary empSalary from t_emp where emp_id = #{id} 
</select>
<select id="queryById" resultType="employee"><!-- resultType指定返回的為對(duì)象時(shí)，開啟駝峰映射(mapUnderscoreToCamelCase)后，select的行不再需要起別名來(lái)與類的屬性完全一致-->
    select * from t_emp where emp_id = #{id}  
</select>
<select id="selectEmpNameAndMaxSalary" resultType="map"> <!-- resultType返回的值沒有未定義類時(shí)，可以用map接值，map的每一項(xiàng)的key對(duì)應(yīng)一個(gè)列名 -->
    select emp_name 員工姓名, emp_salary 員工工資, (SELECT AVG(emp_salary) from t_emp) 部門平均工資 from t_emp where emp_salary=(select max(emp_salary) from t_emp)
</select>
<select id="queryNamesBySalary" resultType="string"><!--如果返回類型時(shí)List<String>，那么指定String即可-->
    select emp_name from t_emp where emp_salary > #{ salary};
</select>
<select id="queryAll" resultType="employee"><!--如果返回類型時(shí)List<Employee>，那么指定Employee即可-->
    select * from t_emp;
</select>
<insert id="insertEmp" useGeneratedKeys="true" keyColumn="emp_id" keyProperty="empId"><!-- 主鍵自增長(zhǎng)型：插入時(shí)，獲取插入的id放在empId中 -->
    insert into t_emp (emp_name, emp_salary) value(#{empName},#{empSalary});
</insert>
<insert id="insertTeacher">
    <selectKey order="BEFORE" resultType="string" keyProperty="tId">
        select replace(UUID(),'-',''); <!-- 插入前由數(shù)據(jù)庫(kù)生成uuid并放在tId中-->
    </selectKey>
    insert into teacher (t_id,t_name) value (#{tId},#{tName})
</insert>

4.多表查詢

4.1 一對(duì)一

1對(duì)1關(guān)系：一個(gè)A類中包含一個(gè)B類：

public class A {
    private Integer Id;
    private String aName;
    private Integer bId;
    private B b;
}
public class B {
    private Integer bId;
    private String bName;
}

使用resultMap來(lái)裝數(shù)據(jù)：

<resultMap id="aMap" type="a">
    <!-- a的主鍵 id標(biāo)簽-->
    <id column="a_id" property="aId"/>
    <!-- order的普通列 custom標(biāo)簽-->
    <result column="a_name" property="aName"/>
    <result column="b_id" property="bId"/>
    <!-- 給第二層對(duì)象屬性賦值 -->
    <association property="b" javaType="b">
        <id column="b_id" property="bId"/>
        <result column="b_name"  property="bName"></result>
    </association>
</resultMap>
<select id="queryAById" resultMap="aMap">
    SELECT * FROM t_a ta join t_b tb on ta.b_id = tb.b_id where ta.a_id = #{id};
</select>

在config文件中加入：

<settings>
	<!-- 開啟駝峰式自動(dòng)映射 a_big => aBig -->
    <setting name="mapUnderscoreToCamelCase" value="true"/>
    <!-- 開啟自動(dòng)映射 a_big => aBig -->
    <setting name="autoMappingBehavior" value="FULL"/>
</settings>

后可省略主鍵以外的映射關(guān)系：

<resultMap id="aMap" type="a">
    <!-- a的主鍵 id標(biāo)簽-->
    <id column="a_id" property="aId"/>
    <!-- 給第二層對(duì)象屬性賦值 -->
    <association property="b" javaType="b">
        <id column="b_id" property="bId"/>
    </association>
</resultMap>
<select id="queryAById" resultMap="aMap">
    SELECT * FROM t_a ta join t_b tb on ta.b_id = tb.b_id where ta.a_id = #{id};
</select>

4.2 一對(duì)多

1對(duì)多關(guān)系：一個(gè)A類中包含多個(gè)B類（List）：

public class A {
    private Integer Id;
    private String aName;
    private Integer bId;
    private List<B> bList;
}
public class B {
    private Integer bId;
    private String bName;
}

使用resultMap來(lái)裝數(shù)據(jù)：

<resultMap id="aMap" type="a">
    <id column="a_id" property="aId"/>
    <result column="a_name" property="aName"/>
     <result column="b_id" property="bId"/>
    <!--針對(duì)List<A>屬性使用collection -->
    <collection property="bList" ofType="b">
        <id column="b_id" property="bId"></id>
        <result column="b_name" property="bName"/>
    </collection>
</resultMap>
<select id="queryAList" resultMap="aMap">
    select * from t_a ta join t_b tb on ta.customer_id = tb.customer_id
</select>

在config文件中加入：

<settings>
	<!-- 開啟駝峰式自動(dòng)映射 a_big => aBig -->
    <setting name="mapUnderscoreToCamelCase" value="true"/>
    <!-- 開啟自動(dòng)映射 a_big => aBig -->
    <setting name="autoMappingBehavior" value="FULL"/>
</settings>

后可省略主鍵以外的映射關(guān)系：

<resultMap id="aMap" type="a">
    <id column="a_id" property="aId"/>
    <!--針對(duì)List<A>屬性使用collection -->
    <collection property="bList" ofType="b">
        <id column="b_id" property="bId"></id>
    </collection>
</resultMap>
<select id="queryAList" resultMap="aMap">
    select * from t_a ta join t_b tb on ta.customer_id = tb.customer_id
</select>

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