Good learning Java programmers to share mybatis route map

Good learning Java programmers to share mybatis route map

Good learning Java programmers to share mybatis route map, we want to help.

Mybatis 1-on-1 associated with implementation

1. By way resultType
2. By way of cascade attribute [way] resultType and resultMap
3. By way of association association
4. By fractional association of query
5. By association of the double wrapper class associatively
6. Association by way of nested definitions

 

Case: Query user information corresponding to the order

Sql statements to build the table

user table:

-- ---------------------------- -- Table structure for `user` -- ---------------------------- DROP TABLE IF EXISTS `user`; CREATE TABLE `user` (   `id` int(11) NOT NULL AUTO_INCREMENT,   `Username` varchar (32) NOT NULL COMMENT 'username'   `Birthday` date DEFAULT NULL COMMENT 'birthday'   `Sex` char (1) DEFAULT NULL COMMENT 'Sex',   `address` varchar(256) DEFAULT NULL COMMENT '地址',   PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=27 DEFAULT CHARSET=utf8;   -- ---------------------------- -- Records of user -- ---------------------------- INSERT INTO `user` VALUES ( '1', 'Wang Wu', '2019-08-30', '2', 'Hangzhou'); INSERT INTO `user` VALUES ( '10', 'John Doe', '2014-07-10', '1', 'Beijing'); INSERT INTO `user` VALUES ( '16', 'Xiaoming', '2019-08-15', '1', 'Zhengzhou'); INSERT INTO `user` VALUES ( '22', 'John Doe', '2019-08-08', '1', 'Zhengzhou'); INSERT INTO `user` VALUES ( '24', 'Chi Master', '2019-08-15', '1', 'Changsha'); INSERT INTO `user` VALUES ( '25', 'Wu Xiaoming', '2019-08-08', '1', 'Zhengzhou'); INSERT INTO `user` VALUES ( '26', 'Wang Wu', '2019-08-14', '2', 'Wuhan');

Orders table:

-- ---------------------------- -- Table structure for `orders` -- ---------------------------- DROP TABLE IF EXISTS `orders`; CREATE TABLE `orders` (   `id` int(11) NOT NULL AUTO_INCREMENT,   `User_id` int (11) NOT NULL COMMENT 'single user id',   `number` varchar(32) NOT NULL COMMENT '订单号',   `createtime` datetime NOT NULL COMMENT '创建订单时间',   `note` varchar(100) DEFAULT NULL COMMENT '备注',   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=8 DEFAULT CHARSET=utf8;   -- ---------------------------- -- Records of orders -- ---------------------------- INSERT INTO `orders` VALUES ('3', '1', '1000010', '2015-02-04 13:22:35', null); INSERT INTO `orders` VALUES ('4', '1', '1000011', '2015-02-03 13:22:41', null); INSERT INTO `orders` VALUES ('5', '10', '1000012', '2015-02-12 16:13:23', null); INSERT INTO `orders` VALUES ('6', '10', '1000013', '2015-08-30 10:11:56', null); INSERT INTO `orders` VALUES ('7', '16', '100014', '2019-08-16 10:12:54', null);

 

实体类：

用户：User

public class User {     private Integer id;     private String name;     private Date birthday;     private String sex;     private String address;     //getter.. setter.. toString.. }

 

订单：Orders

public class Orders {     private Integer id;     private Integer userId;     private String number;     private Date createtime;     private String note;     //getter.. setter.. toString.. }

 

方式一：resultType方式

一个订单 对应 一个用户

对订单实体类进行扩展： 【只增加 对应的字段 ；例如案例中的 用户名称】

新建OrdersExtByColumn 的扩展类，继承 Orders， 并增加相应的字段

public class OrdersExtByColumn extends Orders {     private String username;    //getter.. setter.. toString.. }

 

OrdersMapper映射文件中，写对应的sql语句

<select id="queryOrdersByType" parameterType="int" resultType="OrdersExtByColumn">    SELECT o.id,number,createtime,note,user_id userId,username    FROM orders o ,user u    WHERE o.id = u.id and o.id = #{id} </select>

 

编写测试程序：

public class TestAssociation {     private SqlSession sqlSession;     @Before     public void initSqlSession(){         //1.读取核心配置文件 SqlMapConfig.xml         InputStream resourceAsStream = TestMain.class.getClassLoader().getResourceAsStream("SqlMapConfig.xml");         //2. 产生 SqlSessionFactory         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);         //3. 产生 SqlSession         sqlSession = sqlSessionFactory.openSession();     }     @Test     public void testQryName(){         //找对应的sqlID         String sqlID = "orders.queryOrdersByType";         //sqlSession 执行对应的数据库操作         OrdersExtByColumn orderInfo = sqlSession.selectOne(sqlID, 3);         //对查询的结果进行处理         System.out.println(orderInfo);     }     @After     public void closeResource(){         sqlSession.close();     } }

 

方式二 : 级联属性的方式

 

在orders类中， 增加 级联属性User user;

ResultType方式：

ResultMap方式：

方式三：association关联的方式

方式四：association的分步查询方式

分步查询：即多个sql查询 算出结果

此种方式，可以结合mybatis核心配置文件mybatisCfg.xml的配置项，产生延迟缓存；

mybatisCfg.xml 延迟加载相关设置项

方式五：包装类的双association的关联方式

新建包装类：

OrdersAndUser

public class OrdersAndUser {     private Orders orders;     private User user ;    //getter.. setter.. }

方式六：内嵌association级联

这种内嵌association会关联三张表；

需求简单变更为： 从某订单详情中，查询订单及对应 用户信息

追加一张订单详情表

-- ---------------------------- -- Table structure for `orderdetail` -- ---------------------------- DROP TABLE IF EXISTS `orderdetail`; CREATE TABLE `orderdetail` (   `id` int(11) NOT NULL AUTO_INCREMENT,   `orders_id` int(11) NOT NULL COMMENT '订单id',   `items_id` int(11) NOT NULL COMMENT '商品id',   `items_num` int(11) DEFAULT NULL COMMENT '商品购买数量',   PRIMARY KEY (`id`),   KEY `FK_orderdetail_1` (`orders_id`),   KEY `FK_orderdetail_2` (`items_id`),   CONSTRAINT `FK_orderdetail_1` FOREIGN KEY (`orders_id`) REFERENCES `orders` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,   CONSTRAINT `FK_orderdetail_2` FOREIGN KEY (`items_id`) REFERENCES `items` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;   -- ---------------------------- -- Records of orderdetail -- ---------------------------- INSERT INTO `orderdetail` VALUES ('1', '3', '1', '1'); INSERT INTO `orderdetail` VALUES ('2', '3', '2', '3'); INSERT INTO `orderdetail` VALUES ('3', '4', '3', '4'); INSERT INTO `orderdetail` VALUES ('4', '4', '2', '3');

 

新增OrderDeatil类 【关联Orders属性】

public class OrderDetail {     private Integer id;     private Integer orderId;     private Integer itemsId;     private Integer itemsNum;     private Orders orders;     //setter.. getter.. }