MyBatis学习笔记(二)之关联关系

今天主要学习的关联关系是一对一关系与一对多关系。

一、一对一关系

还是通过例子来解释说明。（一个妻子对应一个丈夫）。

1)数据库信息

create table t_wife(
id int primary key auto_increment,
wife_name varchar(),
fk_husband_id int
);
create table t_husband(
id int primary key auto_increment,
husband_name varchar()
);
insert into t_husband values (null,'hello');
insert into t_wife values(null,'kitty',)

2）对应的JavaBean代码

虽然在数据库里只有一方配置的外键，但是这个一对一是双向的关系。

HusbandBean.java

package com.cy.mybatis.beans;
import java.io.Serializable;

public class HusbandBean implements Serializable{
private static final long serialVersionUID = L;
private Integer id;
private String name;
private WifeBean wife;
public HusbandBean() {
super();
}
public HusbandBean(Integer id, String name, WifeBean wife) {
super();
this.id = id;
this.name = name;
this.wife = wife;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public WifeBean getWife() {
return wife;
}
public void setWife(WifeBean wife) {
this.wife = wife;
}
@Override
public String toString() {
return "Husband [id=" + id + ", name=" + name + ", wife=" + wife + "]";
}
}

WifeBean.java

package com.cy.mybatis.beans;
import java.io.Serializable;

public class WifeBean implements Serializable{
private static final long serialVersionUID = L;
private Integer id;
private String name;
private HusbandBean husband;
public WifeBean() {
super();
}
public WifeBean(Integer id, String name, HusbandBean husband) {
super();
this.id = id;
this.name = name;
this.husband = husband;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public HusbandBean getHusband() {
return husband;
}
public void setHusband(HusbandBean husband) {
this.husband = husband;
}
@Override
public String toString() {
return "Wife [id=" + id + ", name=" + name + ", husband=" + husband
+ "]";
}
}

3）接下来建立两个接口，HusbandMapper,WifeMapper.

HusbandMapper

package com.cy.mybatis.mapper;
import com.cy.mybatis.beans.HusbandBean;
public interface HusbandMapper {

public HusbandBean selectHusbandById (int id) throws Exception;

public HusbandBean selectHusbandAndWife(int id) throws Exception;
}

4）定义HusbandMapper.xml文件












select * from t_husband where id=#{id}

在WifeMapper.xml里有个方法





select * from t_key where fk_lock_id = #{id}

 


LockMapper.xml
















insert into t_lock values (null,#{lock.lock}) 


select * from t_lock where id= #{id}

2.5 ）实现

package com.cy.mybatis.service;
import java.util.ArrayList;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import com.cy.mybatis.beans.KeyBean;
import com.cy.mybatis.beans.LockBean;
import com.cy.mybatis.mapper.KeyMapper;
import com.cy.mybatis.mapper.LockMapper;
import com.cy.mybatis.tools.DBTools;
public class oneToManyService {
public static void main(String[] args) {
// saveLock();
// batchSaveKeys();
findLockAndKeys();
}
private static void findLockAndKeys() {
SqlSession session = DBTools.getSession();
LockMapper lm = session.getMapper(LockMapper.class);
LockBean lock = lm.findLockAndKeys();
System.out.println(lock);
}
private static void batchSaveKeys() {
SqlSession session = DBTools.getSession();
LockMapper lm = session.getMapper(LockMapper.class);
KeyMapper km = session.getMapper(KeyMapper.class);
LockBean lock = lm.findLockById();
List keys = new ArrayList();
for(int i = ; i < ; i++){
KeyBean key = new KeyBean(null, "钥匙"+i, lock);
keys.add(key);
}
km.batchSaveKeys(keys);
session.commit();
}
private static void saveLock() {
SqlSession session = DBTools.getSession();
LockMapper lm = session.getMapper(LockMapper.class);
LockBean lock = new LockBean(null, "锁", null);
lm.saveLock(lock);
session.commit();
}
}

结果显示：

三、批量操作与分页

这里就使用前一章的User.就写出主要的代码。

首先定义分页对象。

package com.cy.mybatis.beans;
import java.util.List;

public class Pager {
private int pageNo;// 当前页码
private int pageTotal;// 总页码
private int rowsTotal;// 总条数
private int pageSize;// 每页显示条数
private List

MyBatis学习笔记(二)之关联关系

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