注解式是真的好用！
一对一的关系：客户拥有一张身份证，而身份证也只有一个客户。
客户表中有身份证的cid，可以通过这个cid匹配身份证表中的cid，拿到那个具体的身份证信息
反之，身份证通过本身的cid匹配客户表中的cid，以此得到客户的信息。
/*
Navicat MySQL Data Transfer
Source Server : hc
Source Server Version : 50723
Source Host : localhost:3306
Source Database : cn
Target Server Type : MYSQL
Target Server Version : 50723
File Encoding : 65001
Date: 2018-11-07 15:32:01
*/
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `person`
-- ----------------------------
DROP TABLE IF EXISTS `person`;
CREATE TABLE `person` (
`perId` int(11) NOT NULL AUTO_INCREMENT,
`perName` varchar(255) DEFAULT NULL,
`cardId` int(11) NOT NULL,
PRIMARY KEY (`perId`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of person
-- ----------------------------
INSERT INTO `person` VALUES ('1', 'haha', '1');
INSERT INTO `person` VALUES ('2', '维尔瓦', '2');
INSERT INTO `person` VALUES ('3', '阿三', '3');
INSERT INTO `person` VALUES ('4', '32阿瑟东', '4');
INSERT INTO `person` VALUES ('5', '安抚', '5');
MYsql中的表，copy后导入数据库即可。
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.43</version>
</dependency>pom.xml
package com.hc.model;
public class Person {
private int perId;
private String perName;
private Card card;
public Person() {
}
public Person(String perName) {
this.perName = perName;
}
public int getPerId() {
return perId;
}
public void setPerId(int perId) {
this.perId = perId;
}
public String getPerName() {
return perName;
}
public void setPerName(String perName) {
this.perName = perName;
}
public Card getCard() {
return card;
}
public void setCard(Card card) {
this.card = card;
}
}
Person类
package com.hc.model;
public class Card {
private int cardId;
private String cardName;
private Person person;
public Card() {
}
public Card(String cardName) {
this.cardName = cardName;
}
public int getCardId() {
return cardId;
}
public void setCardId(int cardId) {
this.cardId = cardId;
}
public String getCardName() {
return cardName;
}
public void setCardName(String cardName) {
this.cardName = cardName;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
}
卡类
package com.hc.mapper;
import com.hc.model.Person;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import java.util.List;
public interface PersonMapper {
@Select("select * from Person")
@Results({
@Result(property = "card",column = "cardId",one = @One(select = "com.hc.mapper.CardMapper.selectCardByCid"))
})
public List<Person> allPerson();
@Select("select * from Person where cardId=#{cardId}")
public Person selectPersonByCid(int cardId);
}
person的MApper
person中有card的对象属性，
Results中的Result，property 为对象属性名，column 为关联的id，
因为person与card相关联的就是cardid
把cid传给关联对象Mapper中的方法，并获得需要的数据
one相对应的是一个对象，如果是多个，即为many
@one中的select固定，调用关联对象Mapper中的方法
package com.hc.mapper;
import com.hc.model.Card;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import java.util.List;
public interface CardMapper {
@Select("select * from Card where cardId=#{cardId}")
public Card selectCardByCid(int cardId);
@Select("select * from Card")
@Results({
@Result(id = true,property = "cardId",column = "cardId"),
// 关联 id 必须
@Result(property = "person",column = "cardId",one = @One(select = "com.hc.mapper.PersonMapper.selectPersonByCid"))
})
public List<Card> allCard();
}
卡的Mapper
selectCardByCid：看似只是一个条件查询，其实可以被Person mapper中的一对一方法@one调用
第二个方法，cardid是必须要拿到的，声明id=true
否则，最终的数据中拿不到这个cid
但是，不声明，又能拿到card对象，只是cid为0
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<typeAliases>
<package name="com.hc.model"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/cn?characterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper class="com.hc.mapper.UserMapper"/>
<mapper class="com.hc.mapper.PersonMapper"/>
<mapper class="com.hc.mapper.CardMapper"/>
<mapper class="com.hc.mapper.AuthorMapper"/>
<mapper class="com.hc.mapper.BookMapper"/>
<mapper class="com.hc.mapper.CourseMapper"/>
<mapper class="com.hc.mapper.StudentMapper"/>
</mappers>
</configuration>mybatis-config.xml
对象Mapper一定要加到mappers中
package com.hc.test;
import com.hc.mapper.CardMapper;
import com.hc.mapper.PersonMapper;
import com.hc.model.Card;
import com.hc.model.Person;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class TestPerson {
private SqlSession session;
@Before
public void before() {
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(getClass().getClassLoader().getResourceAsStream("myBatis-config.xml"));
session = factory.openSession();
}
@Test
public void testCard() {
CardMapper cardMapper = session.getMapper(CardMapper.class);
for (Card card : cardMapper.allCard()) {
System.out.println(card.getCardId() + "\t《" + card.getCardName() + "》");
Person person = card.getPerson();
System.out.println(person.getPerId() + "\t" + person.getPerName());
System.out.println("");
}
}
@Test
public void testPerson() {
PersonMapper personMapper;
personMapper = session.getMapper(PersonMapper.class);
for (Person person : personMapper.allPerson()) {
System.out.println(person.getPerId() + "\t" + person.getPerName());
Card card = person.getCard();
System.out.println(card.getCardId() + "\t《" + card.getCardName() + "》");
System.out.println("");
}
}
@After
public void after() {
session.commit();
session.close();
}
}
单元测试
第二个测试方法：拿到所有person，并通过person表的cid，去卡表拿到相对应的card对象。
第一个方法：
拿到所有的card，通过本身的cid，匹配person的cid，取得person对象。