mybatis（二）
阿新 • • 發佈：2020-10-08
目錄：
1、資料模型分析
1）明確每張表儲存的資訊
2）明確每張表中關鍵欄位（主鍵、外來鍵、非空）
3）明確資料庫中表與表之間的外來鍵關係
4）明確業務中表與表的關係（建立在具體的業務）
2、一對一對映(結果型別使用resultType)
需求：查詢訂單資訊，關聯查詢使用者資訊（主資訊：訂單資訊，從資訊：使用者資訊）
主資訊：orders表 從資訊：user表
sql 指令碼
create database db_mybatis_01 default character set utf8; use db_mybatis_01; ------------ user ------------View CodeCREATE TABLE `user` ( `id` int(11) NOT NULL AUTO_INCREMENT, `username` varchar(32) NOT NULL COMMENT '使用者名稱稱', `birthday` date DEFAULT NULL COMMENT '生日', `sex` char(1) DEFAULT NULL COMMENT '性別', `address` varchar(256) DEFAULT NULL COMMENT '地址', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=27 DEFAULT CHARSET=utf8; insert into `user`(`id`,`username`,`birthday`,`sex`,`address`) values (1,'王五',NULL,'2',NULL), (2,'張三','2014-07-10','1','北京市'), (3,'張小明',NULL,'1','河南鄭州'), (4,'陳小明',NULL,'1','河南鄭州'), (5,'張三丰',NULL,'1','河南鄭州'), (6,'陳小明',NULL,'1','河南鄭州'), (7,'王五',NULL,NULL,NULL); ------------ orders ------------CREATE TABLE `orders` ( `id` int(11) NOT NULL AUTO_INCREMENT, `user_id` int(11) NOT NULL COMMENT '下單使用者id', `number` varchar(32) NOT NULL COMMENT '訂單號', `createtime` datetime NOT NULL COMMENT '建立訂單時間', `note` varchar(100) DEFAULT NULL COMMENT '備註', PRIMARY KEY (`id`), KEY `FK_orders_1` (`user_id`), CONSTRAINT `FK_orders_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; insert into `orders`(`id`,`user_id`,`number`,`createtime`,`note`) values (3,1,'1000010','2015-02-04 13:22:35',NULL), (4,1,'1000011','2015-02-03 13:22:41',NULL), (5,2,'1000012','2015-02-12 16:13:23',NULL);
實體類 User
public class User { private int id; private String username; // 使用者名稱 private Date birthday; // 生日 private String sex; // 性別 private String address; // 地址 // getXxx和setXxx }
實體類 Orders
public class Orders { private Integer id; private Integer userId; // 下單使用者id private String number; // 訂單號 private Date createtime; // 建立訂單時間 private String note; // 備註 // getXxx和setXxx }
訂單擴充套件類 OrdersExt
public class OrdersExt extends Orders { private String username; private String sex; // getter和setter方法 }
db.properties
db.driver=com.mysql.jdbc.Driver db.url=jdbc\:mysql\://localhost\:3306/db_mybatis_01?useUnicode\=true&characterEncoding\=utf8 db.username=root db.password=
log4j.properties
# Global logging configuration log4j.rootLogger=DEBUG, stdout # Console output... log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n
mybatis全域性配置檔案 SqlMapConfig.xml
<?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> <!-- 載入properties檔案或者宣告屬性資訊 <property name="db.username" value="123" /> --> <properties resource="db.properties"> </properties> <!-- <settings></settings> --> <!-- 自定義別名 --> <typeAliases> <!-- 單個別名定義 --> <!-- <typeAlias type="com.oy.mybatis.po.User" alias="user"/> --> <!-- 批量別名定義（推薦） --> <!-- package：指定包名稱來為該包下的po類宣告別名，預設的別名就是類名（首字母大小寫都可） --> <package name="com.oy.domain" /> </typeAliases> <!-- 配置mybatis的環境資訊，與spring整合後，該資訊由spring來管理 --> <environments default="development"> <environment id="development"> <!-- 配置JDBC事務控制，由mybatis進行管理 --> <transactionManager type="JDBC"></transactionManager> <!-- 配置資料來源，採用mybatis連線池 --> <dataSource type="POOLED"> <property name="driver" value="${db.driver}" /> <property name="url" value="${db.url}" /> <property name="username" value="${db.username}" /> <property name="password" value="${db.password}" /> </dataSource> </environment> </environments> <!-- 載入對映檔案 --> <mappers> <mapper resource="OrdersMapper.xml"/> <!-- 批量載入對映檔案 --> <!-- <package name="com.oy.mybatis.mapper" /> --> </mappers> </configuration>
OrdersMapper
public interface OrdersMapper { public List<OrdersExt> findOrdersAndUser(); }
OrdersMapper.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.oy.mapper.OrdersMapper"> <select id="findOrdersAndUser" resultType="com.oy.domain.OrdersExt"> SELECT orders.`id`,orders.`user_id` userId,orders.`number`, user.`username`,user.`sex` FROM orders,user WHERE orders.`user_id` = user.`id` </select> </mapper>
測試類
package com.oy.test; import java.io.InputStream; import java.util.List; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.junit.Before; import org.junit.Test; import com.oy.domain.OrdersExt; import com.oy.mapper.OrdersMapper; public class Test1 { private SqlSessionFactory sqlSessionFactory; @Before public void setUp() throws Exception { String resource = "SqlMapConfig.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } @Test public void testFindOrdersAndUser() throws Exception { // 建立OrdersMapper物件 SqlSession sqlSession = sqlSessionFactory.openSession(); OrdersMapper mapper = sqlSession.getMapper(OrdersMapper.class); List<OrdersExt> orderExtList = mapper.findOrdersAndUser(); for (OrdersExt o : orderExtList) { System.out.println(o.getId() + "--" + o.getUserId() + "--" + o.getNumber() + "--" + o.getUsername() + "--" + o.getSex()); } sqlSession.close(); } }
注意：由於實體類Orders中屬性userId對應表列名為user_id，所以sql語句中使用了別名。
也可以通過定義resultMap來實現上面的問題：實體類Orders中屬性userId對應表列名為user_id。
<resultMap type="com.oy.domain.OrdersExt" id="RstMap"> <id column="id" property="id"/> <id column="user_id" property="userId"/> <id column="number" property="number"/> <id column="username" property="username"/> <id column="sex" property="sex"/> </resultMap> <select id="findOrdersAndUser" resultMap="RstMap"> SELECT orders.`id`,orders.`user_id`,orders.`number`, user.`username`,user.`sex` FROM orders,user WHERE orders.`user_id` = user.`id` </select>
3、一對一對映(使用resultMap)---對上個案例的補充
擴充套件類
public class OrdersExt extends orders{ private User user; //getter和setter方法 }
對映檔案OrdersMapper.xml
<resultMap type="com.oy.domain.OrdersExt" id="RstMap"> <id column="id" property="id"/> <result column="user_id" property="userId"/> <result column="number" property="number"/> <result column="username" property="user.username"/> <result column="sex" property="user.sex"/> </resultMap> <select id="findOrdersAndUser" resultMap="RstMap"> SELECT orders.`id`,orders.`user_id`,orders.`number`, user.`username`,user.`sex` FROM orders,user WHERE orders.`user_id` = user.`id` </select>
另外，也可以使用<association>來實現一對一對映
<resultMap type="com.oy.domain.OrdersExt" id="RstMap"> <id column="id" property="id"/> <result column="user_id" property="userId"/> <result column="number" property="number"/> <!--使用者資訊(一對一)--> <association property="user" javaType="com.oy.domain.User"> <id column="user_id" property="id"/> //不寫不會報錯，但是會影響效能 <result column="username" property="username"/> <result column="sex" property="sex"/> </association> </resultMap> <select id="findOrdersAndUser" resultMap="RstMap"> SELECT orders.`id`,orders.`user_id`,orders.`number`, user.`username`,user.`sex` FROM orders,user WHERE orders.`user_id` = user.`id` </select>
4、一對多對映
需求：查詢使用者資訊，關聯查詢訂單資訊（一個使用者有多個訂單，所以是一對多）
擴充套件類
public class UserExt extends User{ private List<Orders> orderList; //getter和setter方法 }
對映檔案
<!-- 查詢所有使用者 --> <resultMap type="com.oy.domain.UserExt" id="userExtRst"> <id column="id" property="id"/> <result column="username" property="username"/> <result column="birthday" property="birthday"/> <result column="sex" property="sex"/> <result column="address" property="address"/> <collection property="orderList" ofType="com.oy.domain.Orders"> <id column="ordersId" property="id"/> <result column="createtime" property="createtime"/> <result column="number" property="number"/> </collection> </resultMap> <select id="findAll" resultMap="userExtRst"> select user.id,user.username,user.birthday,user.sex,user.address, orders.id ordersId,orders.createtime,orders.number from user,orders where user.id=orders.user_id </select>
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