• 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;
        }
        
    }
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  • 原文地址:https://www.cnblogs.com/xuerong/p/5000233.html
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