One of the mybatis relationship mappings is one-to-many and one-to-one.

I. Introduction:

This example describes how to use a customer and an order: a customer can have multiple orders, and an order only corresponds to one customer.

Ii. Example:

1. code structure:

2. Table creation statement:

CREATE DATABASE test;  USE test;CREATE TABLE person(  personId VARCHAR(36) PRIMARY KEY,  personName VARCHAR(64),  personAddress VARCHAR(128),  personTel VARCHAR(11));CREATE TABLE orders(  orderId VARCHAR(36) PRIMARY KEY,  orderNumber VARCHAR(20),  orderPrice INT,  pid VARCHAR(36));INSERT INTO person VALUES('001', 'Jack', 'Wuhan', '1234567');INSERT INTO orders VALUES('O_00001', '00001', 100, '001');INSERT INTO orders VALUES('O_00002', '00002', 200, '001');SELECT p.*, o.*FROM person p   JOIN orders o ON (p.personId=o.pid)WHERE p.personId = '001'

3. Customer entity:

/*** Customer entity */public class person {private string ID; private string name; private string address; private string Tel; private list <order> orders; @ overridepublic string tostring () {return "{ID:" + ID + ", name:" + name + ", address:" + address + ", tel: "+ Tel + "}";}}

4. Order entity:

/*** Order entity */public class order {private string ID; private string number; private int price; private person; @ overridepublic string tostring () {return "{ID: "+ ID +", number: "+ number +", price: "+ Price + "}";}}

5. One-to-Multiple object configuration: person. xml

<? XML version = "1.0" encoding = "UTF-8"?> <! Doctype mapperpublic "-// mybatis.org//dtd mapper 3.0 //" http://mybatis.org/dtd/mybatis-3-mapper.dtd "> <mapper namespace =" com. zdp. domain. person "> <resultmap type =" person "id =" personbean "> <ID column =" personid "property =" ID "/> <result column =" personname "property =" name "/> <result column =" personaddress "property =" Address "/> <result column =" persontel "property =" tel "/> <! -- One-to-many relationship --> <! -- Property: the value of the Set property. oftype: indicates the type of elements in the collection --> <collection property = "orders" oftype = "order"> <ID column = "orderid" property = "ID"/> <result Column = "ordernumber" property = "Number"/> <result column = "orderprice" property = "price"/> </collection> </resultmap> <! -- Query person by ID and query orders by Association --> <select id = "selectpersonbyid" parametertype = "string" resultmap = "personbean"> select P. *, O. * From person P, orders O where p. personid = O. PID and P. personid =#{ ID} </SELECT> </mapper>

6. Multiple-to-one instance Configuration:

<? XML version = "1.0" encoding = "UTF-8"?> <! Doctype mapperpublic "-// mybatis.org//dtd mapper 3.0 //" http://mybatis.org/dtd/mybatis-3-mapper.dtd "> <mapper namespace =" com. zdp. domain. order "> <resultmap type =" order "id =" orderbean "> <ID column =" orderid "property =" ID "/> <result column =" ordernumber "property =" number "/> <result column =" orderprice "property =" price "/> <! -- Multi-to-one relationship --> <! -- Property: indicates the property value. javatype: indicates the property type --> <association property = "person" javatype = "person"> <ID column = "personid" property = "ID"/> <result column =" personname "property =" name "/> <result column =" personaddress "property =" Address "/> <result column =" persontel "property =" tel "/> </Association> </resultmap> <! -- Query order by ID and associate the query by person --> <select id = "selectorderbyid" parametertype = "string" resultmap = "orderbean"> select P. *, O. * From person P, orders O where p. personid = O. PID and O. orderid =#{ ID} </SELECT> </mapper>

7. Total configuration: sqlmapconfig. xml

<? XML version = "1.0" encoding = "UTF-8"?> <! Doctype configurationpublic "-// mybatis.org//dtd config 3.0 //" http://mybatis.org/dtd/mybatis-3-config.dtd "> <configuration> <typealiases> <typealias type =" com. zdp. domain. person "alias =" person "/> <typealias type =" com. zdp. domain. order "alias =" order "/> </typealiases> <environments default =" development "> <environment id =" development "> <transactionmanager type =" JDBC "/> <datasource type = "pooled"> <property n Ame = "driver" value = "com. mySQL. JDBC. driver "/> <property name =" url "value =" JDBC: mysql: // localhost/test "/> <property name =" username "value =" root "/> <property name =" password "value =" root "/> </datasource> </environment> </environments> <mappers> <! -- Ing file location --> <mapper resource = "com/zdp/domain/person. XML "/> <mapper resource =" com/zdp/domain/order. XML "/> </mappers> </configuration>

8. Test file:

/*** Test one-to-many and multiple-to-one */public class mybatistest {private sqlsessionfactory SSF; @ beforepublic void initsf () throws exception {string resource = "sqlmapconfig. XML "; inputstream = resources. getresourceasstream (Resource); SSF = new sqlsessionfactorybuilder (). build (inputstream) ;}@ test // One-to-multiple association query public void selectpersonbyid () throws exception {sqlsession session = SSF. opensession (); person = session. selectone ("com. zdp. domain. person. selectpersonbyid "," 001 "); system. out. println (person. getorders () ;}@ test // public void selectorderbyid () throws exception {sqlsession session = SSF. opensession (); Order order = session. selectone ("com. zdp. domain. order. selectorderbyid "," o_00001 "); system. out. println (Order. getperson (). getname ());}}

One of the mybatis relationship mappings is one-to-many and one-to-one.