=========================
MyBatis关联映射之添加详情
=========================

1 详情表

create table t_detail(
    detailid int primary key auto_increment,
    address varchar(50) not null,
    telephone varchar(11) not null,
    description varchar(200),
    userid int not null unique, <- 唯一
    constraint FK_USER foreign key(userid) reference t_user(id)
);                     \_________________/           \________/
                                |                         |
                               外键                     主键
                                \_________________________/
                                             |
                                          物理关联

比物理关联更好的方式是通过业务代码建立逻辑关联：

create table t_detail(
    detailid int primary key auto_increment,
    address varchar(50) not null,
    telephone varchar(11) not null,
    description varchar(200),
    userid int not null unique
);

2 实体类

在/src/main/java/cn.tedu.association.pojo目录下创建Detail.java文件：

@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class Detail {
    private int detailid;
    private String address;
    private String telephone;
    private String description;
    private int userid;
}

3 添加详情

3.1 定义接口

在/src/main/java/cn.tedu.association.dao目录下创建DetailDao.java文件：

public interface DetailDao {
    public int addDetail(Detail detail);
}

3.2 配置映射

在/src/main/resources/mappers目录下创建DetailMapper.xml文件：

<?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="cn.tedu.association.dao.DetailDao">
    <insert id="addDetail">
        insert into t_detail(address, telephone, description, userid)
        values(#{address}, #{telephone}, #{description}, #{userid})
    </insert>
</mapper>

在/src/main/resources/mybatis-config.xml文件中添加：

<configuration>
    ...
    <mappers>
        ...
        <mapper resource="mappers/DetailMapper.xml" />
        ...
    </mappers>
    ...
</configuration>

3.3 单元测试

在/src/test/java/cn.tedu.association.dao/UserDaoTest.java文件中修改：

public class UserDaoTest {
    @Test
    public void testAddUser() {
        SqlSession session = MyBatisUtil.getSession();

        try {
            UserDao userDao = session.getMapper(UserDao.class);
            User user = new User(0, "zhangfei", "111111", "张飞", "001.jpg");
            assertEquals(1, userDao.addUser(user));

            DetailDao detailDao = session.getMapper(DetailDao.class);
            Detail detail = new Detail(0, "北京市海淀区", "13910110072", "我思故我在", user.getId());
            assertEquals(1, detailDao.addDetail(detail));

            session.commit();
        }
        catch (Exception e) {
            e.printStackTrace();
            session.rollback();
        }
    }
}

运行测试用例。

4 查询用户信息

在/src/main/java/cn.tedu.association.dao/UserDao.java文件中添加：

public interface UserDao {
    ...
    public User getUser(String username);
    ...
}

在/src/main/resources/mybatis-config.xml文件中添加：

<configuration>
    ...
    <typeAliases>
        ...
        <typeAlias type="cn.tedu.association.pojo.User" alias="User" />
        ...
    </typeAliases>
    ...
</configuration>

在/src/main/resources/mappers/UserMapper.xml文件中添加：

<mapper namespace="cn.tedu.association.dao.UserDao">
    ...
    <select id="getUser" resultType="User">
        select id, username, password, realname, image from t_user
        where username = #{username}
    </select>
    ...
</mapper>

在/src/main/java/cn.tedu.association.dao/DetailDao.java文件中添加：

public interface DetailDao {
    ...
    public Detail getDetail(int userid);
    ...
}

在/src/main/resources/mybatis-config.xml文件中添加：

<configuration>
    ...
    <typeAliases>
        ...
        <typeAlias type="cn.tedu.association.pojo.Detail" alias="Detail" />
        ...
    </typeAliases>
    ...
</configuration>


在/src/main/resources/mappers/DetailMapper.xml文件中添加：

<mapper namespace="cn.tedu.association.dao.DetailDao">
    ...
    <select id="getDetail" resultType="Detail">
        select detailid, address, telephone, description, userid from t_detail
        where userid = #{userid}
    </select>
    ...
</mapper>

在/src/test/java/cn.tedu.association.dao/UserDaoTest.java文件中添加：

public class UserDaoTest {
    ...
    @Test
    public void testGetUser() {
        UserDao userDao = MyBatisUtil.getMapper(UserDao.class);
        User user = userDao.getUser("zhangfei");
        assertNotEquals(null, user);
        System.out.println(user);

        DetailDao detailDao = MyBatisUtil.getMapper(DetailDao.class);
        Detail detail = detailDao.getDetail(user.getId());
        assertNotEquals(null, detail);
        System.out.println(detail);
    }
    ...
}

运行测试用例。

例程：Association