mybatis 使用resultMap实现关联数据的查询（association 和collection ）

<?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">

<!-- namespace的名字需要跟接口的类名一致 -->
<mapper namespace="cn.bdqn.dao.UserMapper">
    <!-- 
    1、resultMap属性：type为java实体类；id为此resultMap的标识
    2、resultMap的子元素：
        id – 一般对应到数据库中该行的ID,设置此项可以提高Mybatis性能.
        result – 映射到JavaBean 的某个“简单类型”属性,String,int等.
        association – 映射到JavaBean 的某个“复杂类型”属性,其他JavaBean类.
        collection –复杂类型集合 (演示示例2)
     -->
     
    <!--根据roleId获取用户列表: 当数据库中的字段信息与对象的属性不一致时需要通过resultMap来映射 -->
    <!-- <resultMap type="User" id="seachUserResult">
        <result property="id" column="id"/>
        <result property="userCode" column="userCode"/>
        <result property="userName" column="userName"/>
        <result property="roleId" column="roleId"/>
        <result property="roleName" column="roleName"/>
    </resultMap>
    
    <select id="getUserListByRoleId" parameterType="Role" resultMap="seachUserResult">
        select u.*,r.roleName as roleName from user u,role r where u.roleId = r.id and u.roleId = #{id}
    </select> -->
    
    <!-- 根据roleId获取用户列表 association start-->
    <resultMap type="User" id="seachUserResult">
        <result property="id" column="id"/>
        <result property="userCode" column="userCode" />
        <result property="userName" column="userName" />
        <result property="roleId" column="roleId" />
　　　　//property=“属性名” javaType=“属性名的类型” ----（一对一）

        <!-- <association property="role" javaType="Role" >
            <result property="id" column="id"/>
            <result property="roleCode" column="roleCode"/>
            <result property="roleName" column="roleName"/>
        </association> -->
        <association property="role" javaType="Role" resultMap="roleMap"/>
    </resultMap>
    
    <resultMap type="Role" id="roleMap">
        <result property="id" column="id"/> 
        <result property="roleCode" column="roleCode"/> 
        <result property="roleName" column="roleName"/> 
    </resultMap>
    
    <select id="getUserListByRoleId" parameterType="Role" resultMap="seachUserResult">
        select u.*,r.roleCode as roleCode,r.roleName as roleName from user u,role r where u.roleId = r.id and u.roleId = #{id}
    </select>
    
    <!-- association end-->
    
    <!-- 获取指定用户的地址列表(user表-address表：1对多关系) collection start-->
    <resultMap type="User" id="userMap">
        <id property="id" column="userId"/>
　　　　//property是属性名  ofType是List《Address》的类对象

        <collection property="addressList" ofType="Address">
            <id property="id" column="a_id"/>
            <result property="postCode" column="postCode"/>
            <result property="addressContent" column="addressContent"/>
        </collection>
    </resultMap>
    
    <select id="getAddressListByUserId" parameterType="User" resultMap="userMap">
        select *,a.id as a_id from user u,address a where u.id=a.userId and u.id=#{id}
    </select>
    <!-- collection end -->
    
    <select id="count" resultType="int">
        select count(1) from user
    </select>
    
    <insert id="add" parameterType="User">
        insert into user (userCode,userName,userPassword) 
            values (#{userCode},#{userName},#{userPassword})
    </insert>
    
    <update id="update" parameterType="User">
        update user set userCode=#{userCode},userName=#{userName},
            userPassword=#{userPassword} where id=#{id}
    </update>
    
    <delete id="delete" parameterType="User">
        delete from user where id=#{id}
    </delete>
    
    <select id="getUserList" resultType="User">
        select * from user
    </select>
</mapper>

接口 UserMapper 

public interface UserMapper {
    
    public int count();
    
    public void add(User user);
    
    public void update(User user);
    
    public void delete(User user);
    
    public List<User> getUserList();
    
    //根据roleId获取用户列表
    public List<User> getUserListByRoleId(Role role);
    
    //获取指定用户的地址列表(user表-address表：1对多关系)
    public User getAddressListByUserId(User user);
    
}

接口 RoleMapper 

public interface RoleMapper {
    
    public void add(Role role);
    
    public void update(Role role);
    
    public void delete(Role role);
    
    public List<Role> getRoleList();
}

<?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.bdqn.dao.RoleMapper">
    <select id="getRoleList" resultType="Role">
        select * from role
    </select>
    
    <insert id="add" parameterType="Role">
        insert into role (roleCode,roleName) 
            values (#{roleCode},#{roleName})
    </insert>
    
    <update id="update" parameterType="Role">
        update role set roleCode=#{roleCode},roleName=#{roleName}
            where id=#{id}
    </update>
    
    <delete id="delete" parameterType="Role">
        delete from role where id=#{id}
    </delete>

</mapper>

User.java

public class User {
    private Integer id;
    private String userName;
    private String userCode;
    private String userPassword;
    private Integer roleId;
    //private String roleName;
    
    //collection
    private List<Address> addressList;
    
    //association
    private Role role;
    
    
    public Role getRole() {
        return role;
    }
    public void setRole(Role role) {
        this.role = role;
    }
    public List<Address> getAddressList() {
        return addressList;
    }
    public void setAddressList(List<Address> addressList) {
        this.addressList = addressList;
    }
    public Integer getRoleId() {
        return roleId;
    }
    public void setRoleId(Integer roleId) {
        this.roleId = roleId;
    }
    /**
    public String getRoleName() {
        return roleName;
    }
    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }
    */
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getUserCode() {
        return userCode;
    }
    public void setUserCode(String userCode) {
        this.userCode = userCode;
    }
    public String getUserPassword() {
        return userPassword;
    }
    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }
    
}

address.java

public class Address {
    private Integer id;
    private Integer postCode;
    private String addressContent;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public Integer getPostCode() {
        return postCode;
    }
    public void setPostCode(Integer postCode) {
        this.postCode = postCode;
    }
    public String getAddressContent() {
        return addressContent;
    }
    public void setAddressContent(String addressContent) {
        this.addressContent = addressContent;
    }
    
}