About the use of collection in mapper file Resultmap in MyBatis

There are two types of Resultmap and select for collection, and you must manually specify a

1. Entity classes:

1  PackageCom.mrlu.mybatis.domain;2 3 Importjava.util.List;4 5 /**6 * Created by Stefan on 15-12-31.7  */8  Public classUser {9     PrivateInteger ID;Ten     PrivateString name; One     PrivateList<account>accounts; A  -      PublicInteger getId () { -         returnID; the     } -  -      Public voidsetId (Integer id) { -          This. ID =ID; +     } -  +      PublicString GetName () { A         returnname; at     } -  -      Public voidsetName (String name) { -          This. Name =name; -     } -  in @Override -      PublicString toString () { to         return"User{" + +"id=" + ID + -", Name= ' + name + ' + ' + the", accounts=" + accounts + *‘}‘; $     }Panax Notoginseng  -      PublicList<account>getaccounts () { the         returnaccounts; +     } A  the      Public voidSetaccounts (list<account>accounts) { +          This. accounts =accounts; -     } $  $}

 PackageCom.mrlu.mybatis.domain;/*** Created by Stefan on 15-12-31.*/ Public classAccount {PrivateInteger ID; PrivateInteger userId; PrivateString num;  PublicInteger getId () {returnID; }     Public voidsetId (Integer id) { This. ID =ID; }     PublicInteger getUserId () {returnuserId; }     Public voidSetuserid (Integer userId) { This. UserId =userId; }     PublicString Getnum () {returnnum; }     Public voidsetnum (String num) { This. num =num; } @Override PublicString toString () {return"account{" + "id=" + ID + ", userid=" + UserId + ", num= '" + num + "+ ‘}‘; }}

2. DAO:

 package   Com.mrlu.mybatis.dao;  import   Com.mrlu.mybatis.domain.User;  import   java.util.List;  /**   * Created by Stefan on 15-12-31.  */ public  interface   Userdao { void   insert (user user);  public  list<user> SelectAll ();}  

 Package Com.mrlu.mybatis.dao; Import Com.mrlu.mybatis.domain.Account; /**  */Publicinterface  Accountdao    {publicvoid  Insert (account account);}

3. Mapper.xml

<?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= "Com.mrlu.mybatis.dao.AccountDao" >       <insert id= "Insert" usegeneratedkeys= "true" keyproperty= "id" > INSERT into account              (user_id, num) VALUES (                #{userid}, #{num}              )       </ Insert></mapper>

Resultmap:

1<?xml version= "1.0" encoding= "UTF-8"?>2<! DOCTYPE Mapper Public "-//mybatis.org//dtd mapper 3.0//en" "Http://mybatis.org/dtd/mybatis-3-mapper.dtd" >3<mapper namespace= "Com.mrlu.mybatis.dao.UserDao" >4<resultmap id= "Baseresultmap" type= "Com.mrlu.mybatis.domain.User" >5<result column= "id" property= "id"/>6<result column= "name" property= "name"/>7<collection property= "Accounts" oftype= "Com.mrlu.mybatis.domain.Account" javatype= "Java.util.ArrayList" resultmap= "Accountmap" >8<result column= "id" property= "id"/>9<result column= "user_id" property= "UserId"/>Ten<result column= "num" property= "num"/> One</collection> A</resultMap> -<resultmap id= "Accountmap" type= "Com.mrlu.mybatis.domain.Account" > -<result column= "id" property= "id"/> the<result column= "user_id" property= "UserId"/> -<result column= "num" property= "num"/> -</resultMap> -<insert id= "Insert" keyproperty= "id" usegeneratedkeys= "true" > + INSERT into User (name) VALUES ( - #{name} +               ) A</insert> at  -<select id= "SelectAll" resultmap= "Baseresultmap" > - SELECT a.id,a.user_id,a.num from user T -Right JOIN account A on t.id=a.user_id -</select> -</mapper>

Select

1<?xml version= "1.0" encoding= "UTF-8"?>2<! DOCTYPE Mapper Public "-//mybatis.org//dtd mapper 3.0//en" "Http://mybatis.org/dtd/mybatis-3-mapper.dtd" >3<mapper namespace= "Com.mrlu.mybatis.dao.UserDao" >4<resultmap id= "Baseresultmap" type= "Com.mrlu.mybatis.domain.User" >5<result column= "id" property= "id"/>6<result column= "name" property= "name"/>7<collection property= "Accounts" column= "id" select= "selectaccount" >8<result column= "id" property= "id"/>9<result column= "user_id" property= "UserId"/>Ten<result column= "num" property= "num"/> One</collection> A</resultMap> -<insert id= "Insert" keyproperty= "id" usegeneratedkeys= "true" > - INSERT into User (name) VALUES ( the #{name} -               ) -</insert> -  +<select id= "SelectAll" resultmap= "Baseresultmap" > -SELECT *From user T +</select> A  at<select id= "Selectaccount" resulttype= "Com.mrlu.mybatis.domain.Account" > -SELECT * from Account -WHERE user_id =#{id} -</select> -</mapper>

The fields marked are required and are not marked as optional.

About the use of collection in mapper file Resultmap in MyBatis