1、配置 Mavan 依赖

pom.xml
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<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.2.2</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.25</version>
    </dependency>
</dependencies>

在 IntelliJ IDEA 中，还需要配置如下代码，否则不会编译 xml ，导致找不到配置文件 （这里踩坑了）

pom.xml
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<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include>
            </includes>
        </resource>
    </resources>
</build>

2、MyBatis 配置文件

mybatis_config.xml
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<?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">
<configuration>
    <environments default="mysql">
        <environment id="mysql">
            <!-- 配置事务处理，一般用JDBC -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置数据源 -->
            <dataSource type="POOLED">
                <!-- mysql数据库的配置信息 -->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/store"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
    	<!-- 单文件形式注册 Mapper -->
        <mapper resource="net/crazykid/mapper/categoryMapper.xml"/>
        <mapper resource="net/crazykid/mapper/productMapper.xml"/>

         <!--package方式注册，该包下所有mapper自动注册-->
        <package name="net.crazykid.mapper"/>
    </mappers>
</configuration>

3、pojo类

Category.java
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package net.crazykid.bean;

import java.util.List;

public class Category {
    private String cid;
    private String cname;
    private List<Product> products;


    public Category(){}

    public Category(String cid, String cname, List<Product> products) {
        this.cid = cid;
        this.cname = cname;
        this.products = products;
    }

    public String getCid() {
        return cid;
    }

    public void setCid(String cid) {
        this.cid = cid;
    }

    public String getCname() {
        return cname;
    }

    public void setCname(String cname) {
        this.cname = cname;
    }

    public List<Product> getProducts() {
        return products;
    }

    public void setProducts(List<Product> products) {
        this.products = products;
    }

    @Override
    public String toString() {
        return "Category{" +
                "cid='" + cid + '\'' +
                ", cname='" + cname + '\'' +
                ", products=" + products +
                '}';
    }
}

4、Mapper 的编写

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<?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="net.crazykid.mapper.categoryMapper">
    <!-- 这里写内容... -->
</mapper>

4.1 插入语句

  • parameterType: 传入参数的类型
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<insert id="Insert" parameterType="net.crazykid.bean.Category">
	INSERT INTO category (cid, cname) VALUES (#{cid}, #{cname});
</insert>

4.2 删除语句

注: parameterType 为 String 时，用 #{_parameter}

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<delete id="deleteCategoryById" parameterType="String">
	DELETE FROM category WHERE cid = #{_parameter};
</delete>

4.3 查询语句

  • resultType: 返回结果的类型
查询全部内容
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<select id="selectAllCategory" resultType="net.crazykid.bean.Category">
    SELECT * from category;
</select>
根据 ID 查询
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<select id="selectCategoryById" parameterType="Int" resultType="net.crazykid.bean.Category">
    SELECT * FROM category WHERE cid = #{cid}
</select>
多条件查询
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<select id="selectMultiCategoryById" resultType="net.crazykid.bean.Category">
    SELECT * FROM category WHERE cid IN
    <foreach item="item" index="index" collection="list"
             open="(" separator="," close=")">
        #{item}
    </foreach>
</select>
动态查询语句
categoryMapper.xml
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<!-- 定义一个结果集合 -->
<resultMap id="categoryMap" type="net.crazykid.bean.Category">
    <id column="cid" property="cid"/>
    <result column="cname" property="cname"/>

    <!-- 一对多关联查询 -->
    <collection column="cid" property="products" ofType="net.crazykid.bean.Product" select="net.crazykid.mapper.productMapper.selectProductByCId">
    </collection>
</resultMap>

<!--动态查询语句-->
<!-- resultMap 指定自定义的结果集合名称 -->
<select id="selectCategory" parameterType="java.util.Properties" resultType="net.crazykid.bean.Category" resultMap="categoryMap" >
    SELECT * FROM category
    <where>
        <if test="cid != null">
            AND cid = #{cid}
        </if>
        <if test="cname != null">
            AND cname = #{cname}
        </if>
    </where>
</select>

多对一关联查询….(这是另一个类另一个mapper)

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<resultMap id="productMap" type="net.crazykid.bean.Product" extends="baseMap">
    <association column="cid" property="category" javaType="net.crazykid.bean.Category" select="net.crazykid.mapper.categoryMapper.selectCategoryById">
    </association>
</resultMap>

5、Mapper 的实现类

categoryMapper.java
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public interface categoryMapper {
    //这是上面写好的 Mapper 的实现方法
    void Insert(Category category);
    List<Category> selectAllCategory();
    List<Category> selectCategory(Properties properties);
    void deleteCategoryById(String id);
    List<Category> selectMultiCategoryById(List list);

    //这是基于注解的方法，不用写 Mapper ...
    @Select("SELECT * FROM category where cid=#{cid}")
    List<Category> selectAllCategory2(String cid);

    //类似的注解还有 @Insert @Delete @Update....
}

6、测试类

categoryTest.java
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public class categoryTest {
    SqlSessionFactory sessionFactory = null;
    InputStream inputStream = null;

    @Before
    public void init(){
        try {
            inputStream = Resources.getResourceAsStream("mybatis_config.xml");
            sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Test
    public void testInsert() {
        SqlSession session = sessionFactory.openSession();
        categoryMapper CategoryMapper=session.getMapper(categoryMapper.class);

        Category category = new Category();
        category.setCid("123");
        category.setCname("阔落");
        
        CategoryMapper.Insert(category);
        session.commit();
        session.close();
    }

    @Test
    public void testSelectAllCategory() {
        SqlSession session = sessionFactory.openSession();
        categoryMapper CategoryMapper=session.getMapper(categoryMapper.class);

        List<Category> list = CategoryMapper.selectAllCategory();
        System.out.println(list);
    }

    @Test
    public void testSelectCategory() {
        SqlSession session = sessionFactory.openSession();
        categoryMapper CategoryMapper=session.getMapper(categoryMapper.class);

        Properties properties = new Properties();
        properties.setProperty("cid", "1");
        //properties.setProperty("cname", "aaaa");

        List<Category> list = CategoryMapper.selectCategory(properties);
        System.out.println(list);
    }

    @Test
    public void testDeleteCategoryById() {
        SqlSession session = sessionFactory.openSession();
        categoryMapper CategoryMapper=session.getMapper(categoryMapper.class);

        CategoryMapper.deleteCategoryById("aaa2");
    }

    @Test
    public void testSelectMultiCategoryById() {
        SqlSession session = sessionFactory.openSession();
        categoryMapper CategoryMapper=session.getMapper(categoryMapper.class);


        List li = new ArrayList();
        li.add(1);
        li.add(2);

        List<Category> list = CategoryMapper.selectMultiCategoryById(li);
        System.out.println(list);
    }

    @Test
    public void testSelectAllCategory2() {
        SqlSession session = sessionFactory.openSession();
        categoryMapper CategoryMapper=session.getMapper(categoryMapper.class);

        List<Category> list = CategoryMapper.selectAllCategory2("6");
        System.out.println(list);
    }
}

7、整合 Log4j

7.1 导入 Log4j 包

pom.xml
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<!-- https://mvnrepository.com/artifact/log4j/log4j -->
<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

7.2 引入 Log4j

踩坑记录： 必须按照指定的顺序放置标签，如 <setting> 不能放在 <environments> 或者 <mappers> 的后面，否则会报错！！

mybatis_config.xml
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<configuration>
    <!--集成Log4j-->
    <settings>
        <setting name="logImpl" value="LOG4J"/>
    </settings>
    
    <environments default="mysql">
        ...
    </environments>
    
    <mappers>
       ...
    </mappers>
</configuration>

7.3 Log4j 的配置文件

log4j.properties
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# 全局日志配置
log4j.rootLogger=ERROR, stdout
# 指定Mapper的日志配置
log4j.logger.net.crazykid.mapper.categoryMapper=TRACE
# 控制台输出
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

# 对于命名空间为 net.crazykid.mapper.categoryMapper 的 Mapper，日子级别为 Trace
# 其余的则为全局配置级别 Error, stdout