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>

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);

}

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>

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;
}

}

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;
}

}