今天主要學習的關聯關系是一對一關系與一對多關系。
一、一對一關系
還是通過例子來解釋說明。（一個妻子對應一個丈夫）。
1)數據庫信息
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）對應的JavaBean代碼
雖然在數據庫里只有一方配置的外鍵，但是這個一對一是雙向的關系。
HusbandBean.java
package com.cy.mybatis.beans;import java.io.Serializable;/*** one to one* @author acer**/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;}@Overridepublic String toString() {return "Husband [id=" + id + ", name=" + name + ", wife=" + wife + "]";}}WifeBean.java
package com.cy.mybatis.beans;import java.io.Serializable;/*** one to one* @author acer**/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;}@Overridepublic String toString() {return "Wife [id=" + id + ", name=" + name + ", husband=" + husband+ "]";}} 3）接下來建立兩個接口，HusbandMapper,WifeMapper.
HusbandMapper
package com.cy.mybatis.mapper;import com.cy.mybatis.beans.HusbandBean;public interface HusbandMapper {/*** 根據id查詢丈夫信息* @param id* @return* @throws Exception*/public HusbandBean selectHusbandById (int id) throws Exception;/*** 根據id查詢丈夫與妻子信息* @param id* @return* @throws Exception*/public HusbandBean selectHusbandAndWife(int id) throws Exception;} 4）定義HusbandMapper.xml文件
<?xml version="." encoding="UTF-"?><!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper ." "http://mybatis.org/dtd/mybatis--mapper.dtd"><mapper namespace="com.cy.mybatis.mapper.HusbandMapper"><resultMap type="HusbandBean" id="husbandAndWife"><id property="id" column="id" javaType="java.lang.Integer"/><result property="name" column="name" javaType="java.lang.String"/><!-- association 主站蜘蛛池模板： 黄平县| 沽源县| 白河县| 镇赉县| 英山县| 准格尔旗| 德格县| 仙游县| 郎溪县| 莱西市| 团风县| 京山县| 闵行区| 泰州市| 怀宁县| 新绛县| 西乌珠穆沁旗| 沈丘县| 略阳县| 平果县| 阿巴嘎旗| 青川县| 东乡县| 泽普县| 法库县| 瑞安市| 公安县| 城口县| 正宁县| 秀山| 柏乡县| 阳高县| 新源县| 延长县| 来凤县| 克拉玛依市| 五家渠市| 莱芜市| 云安县| 元阳县| 新晃|