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MyBatis从入门到精通—MyBatis多表查询和注解开发

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Mybatis多表查询 一对一查询 一对一查询的模型MapperScannerConfigurer 用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户 一对一查询的需求：查询一个订单，与此同

Mybatis多表查询

一对一查询

一对一查询的模型MapperScannerConfigurer

用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

一对一查询的需求：查询一个订单，与此同时查询出该订单所属的用户

图片1.png

一对一查询的语句

对应的sql语句：

select * from orders o,user u where o.uid=u.id;

查询的结果如下：image.png

创建Order和User实体
public class Order { private int id; private Date ordertime; private double total; //代表当前订单从属于哪一个客户 private User user; } public class User { private int id; private String username; private String password; private Date birthday; }
创建OrderMapper接口
public interface OrderMapper { List<Order> findAll(); }
配置OrderMapper.xml
<mapper namespace="com.zjq.mapper.OrderMapper"> <resultMap id="orderMap" type="com.zjq.domain.Order"> <result column="uid" property="user.id"></result> <result column="username" property="user.username"></result> <result column="password" property="user.password"></result> <result column="birthday" property="user.birthday"></result> </resultMap> <select id="findAll" resultMap="orderMap"> select * from orders o,user u where o.uid=u.id </select> </mapper>

其中还可以配置如下：

<resultMap id="orderMap" type="com.zjq.domain.Order"> <result property="id" column="id"></result> <result property="ordertime" column="ordertime"></result> <result property="total" column="total"></result> <association property="user" javaType="com.zjq.domain.User"> <result column="uid" property="id"></result> <result column="username" property="username"></result> <result column="password" property="password"></result> <result column="birthday" property="birthday"></result> </association> </resultMap>
测试结果
OrderMapper mapper = sqlSession.getMapper(OrderMapper.class); List<Order> all = mapper.findAll(); for(Order order : all){ System.out.println(order); }

输出：

11:29:37,682 DEBUG JdbcTransaction:137 - Opening JDBC Connection 11:29:38,178 DEBUG PooledDataSource:406 - Created connection 1858609436. 11:29:38,179 DEBUG JdbcTransaction:101 - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c] 11:29:38,182 DEBUG findAll:159 - ==> Preparing: SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id 11:29:38,305 DEBUG findAll:159 - ==> Parameters: 11:29:38,351 DEBUG findAll:159 - <== Total: 3 11:29:38,357 DEBUG JdbcTransaction:123 - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c] Order{id=1, ordertime=Sun Dec 12 00:00:00 GMT+08:00 2021, total=3000.0, user=User{id=1, username='zjq', password='abc', birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=null}} Order{id=2, ordertime=Sun Dec 12 00:00:00 GMT+08:00 2021, total=4000.0, user=User{id=1, username='zjq', password='abc', birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=null}} Order{id=3, ordertime=Sun Dec 12 00:00:00 GMT+08:00 2021, total=5000.0, user=User{id=2, username='jack', password='123456', birthday=Fri Aug 20 00:00:00 GMT+08:00 2021, roleList=null}}

一对多查询

一对多查询的模型

用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

一对多查询的需求：查询一个用户，与此同时查询出该用户具有的订单

图片4.png

一对多查询的语句

对应的sql语句：

select *,o.id oid from user u left join orders o on u.id=o.uid;

查询的结果如下：image.png

修改User实体
public class Order { private int id; private Date ordertime; private double total; //代表当前订单从属于哪一个客户 private User user; } public class User { private int id; private String username; private String password; private Date birthday; //代表当前用户具备哪些订单 private List<Order> orderList; }
创建UserMapper接口
public interface UserMapper { List<User> findAll(); }
配置UserMapper.xml
<mapper namespace="com.zjq.mapper.UserMapper"> <resultMap id="userMap" type="com.zjq.domain.User"> <result column="id" property="id"></result> <result column="username" property="username"></result> <result column="password" property="password"></result> <result column="birthday" property="birthday"></result> <collection property="orderList" ofType="com.zjq.domain.Order"> <result column="oid" property="id"></result> <result column="ordertime" property="ordertime"></result> <result column="total" property="total"></result> </collection> </resultMap> <select id="findAll" resultMap="userMap"> select *,o.id oid from user u left join orders o on u.id=o.uid </select> </mapper>
测试结果
UserMapper mapper = sqlSession.getMapper(UserMapper.class); List<User> all = mapper.findAll(); for(User user : all){ System.out.println(user.getUsername()); List<Order> orderList = user.getOrderList(); for(Order order : orderList){ System.out.println(order); } System.out.println("----------------------------------"); }

输出：

11:38:28,060 DEBUG findAll:159 - ==> Preparing: SELECT *,o.id oid FROM USER u,orders o WHERE u.id=o.uid 11:38:28,179 DEBUG findAll:159 - ==> Parameters: 11:38:28,254 DEBUG findAll:159 - <== Total: 3 User{id=1, username='zjq', password='abc', birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=null} User{id=2, username='jack', password='123456', birthday=Fri Aug 20 00:00:00 GMT+08:00 2021, roleList=null} 11:38:28,265 DEBUG JdbcTransaction:123 - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c] 11:38:28,265 DEBUG JdbcTransaction:91 - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c] 11:38:28,265 DEBUG PooledDataSource:363 - Returned connection 1858609436 to pool.

多对多查询

多对多查询的模型

用户表和角色表的关系为，一个用户有多个角色，一个角色被多个用户使用

多对多查询的需求：查询用户同时查询出该用户的所有角色

图片7.png

多对多查询的语句

对应的sql语句：

select u.*,r.*,r.id rid from user u left join sys_user_role ur on u.id=ur.userid inner join sys_role r on ur.roleid=r.id;

查询的结果如下：image.png

创建Role实体，修改User实体
public class User { private int id; private String username; private String password; private Date birthday; //代表当前用户具备哪些订单 private List<Order> orderList; //代表当前用户具备哪些角色 private List<Role> roleList; } public class Role { private int id; private String rolename; }
 添加UserMapper接口方法
List<User> findAllUserAndRole();
配置UserMapper.xml
<resultMap id="userRoleMap" type="com.zjq.domain.User"> <result column="id" property="id"></result> <result column="username" property="username"></result> <result column="password" property="password"></result> <result column="birthday" property="birthday"></result> <collection property="roleList" ofType="com.zjq.domain.Role"> <result column="rid" property="id"></result> <result column="rolename" property="rolename"></result> </collection> </resultMap> <select id="findAllUserAndRole" resultMap="userRoleMap"> select u.*,r.*,r.id rid from user u left join sys_user_role ur on u.id=ur.userid inner join sys_role r on ur.roleid=r.id; </select>
测试结果
UserMapper mapper = sqlSession.getMapper(UserMapper.class); List<User> all = mapper.findAllUserAndRole(); for(User user : all){ System.out.println(user.getUsername()); List<Role> roleList = user.getRoleList(); for(Role role : roleList){ System.out.println(role); } System.out.println("----------------------------------"); } 11:45:51,443 DEBUG findUserAndRoleAll:159 - ==> Preparing: SELECT * FROM USER u,sys_user_role ur,sys_role r WHERE u.id=ur.userId AND ur.roleId=r.id 11:45:51,572 DEBUG findUserAndRoleAll:159 - ==> Parameters: User{id=1, username='zjq', password='abc', birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=[Role{id=1, roleName='CTO', roleDesc='CTO'}, Role{id=2, roleName='COO', roleDesc='COO'}]} User{id=2, username='jack', password='123456', birthday=Fri Aug 20 00:00:00 GMT+08:00 2021, roleList=[Role{id=1, roleName='CTO', roleDesc='CTO'}, Role{id=2, roleName='COO', roleDesc='COO'}]} 11:45:51,610 DEBUG findUserAndRoleAll:159 - <== Total: 4 11:45:51,618 DEBUG JdbcTransaction:123 - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c] 11:45:51,619 DEBUG JdbcTransaction:91 - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c] 11:45:51,619 DEBUG PooledDataSource:363 - Returned connection 1858609436 to pool.

Mybatis的注解开发

MyBatis的常用注解

这几年来注解开发越来越流行，Mybatis也可以使用注解开发方式，这样我们就可以减少编写Mapper

映射文件了。我们先围绕一些基本的CRUD来学习，再学习复杂映射多表操作。

@Insert：实现新增

@Update：实现更新

@Delete：实现删除

@Select：实现查询

@Result：实现结果集封装

@Results：可以与@Result 一起使用，封装多个结果集

@One：实现一对一结果集封装

@Many：实现一对多结果集封装

MyBatis的增删改查

我们完成简单的user表的增删改查的操作

private UserMapper userMapper; @Before public void before() throws IOException { InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml"); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream); SqlSession sqlSession = sqlSessionFactory.openSession(true); userMapper = sqlSession.getMapper(UserMapper.class); } @Test public void testAdd() { User user = new User(); user.setUsername("测试数据"); user.setPassword("123"); user.setBirthday(new Date()); userMapper.add(user); } @Test public void testUpdate() throws IOException { User user = new User(); user.setId(16); user.setUsername("测试数据修改"); user.setPassword("abc"); user.setBirthday(new Date()); userMapper.update(user); } @Test public void testDelete() throws IOException { userMapper.delete(16); } @Test public void testFindById() throws IOException { User user = userMapper.findById(1); System.out.println(user); } @Test public void testFindAll() throws IOException { List<User> all = userMapper.findAll(); for(User user : all){ System.out.println(user); } }

修改MyBatis的核心配置文件，我们使用了注解替代的映射文件，所以我们只需要加载使用了注解的Mapper接口即可

<mappers> <!--扫描使用注解的类--> <mapper class="com.zjq.mapper.UserMapper"></mapper> </mappers>

或者指定扫描包含映射关系的接口所在的包也可以

<mappers> <!--扫描使用注解的类所在的包--> <package name="com.zjq.mapper"></package> </mappers>

MyBatis的注解实现复杂映射开发

实现复杂关系映射之前我们可以在映射文件中通过配置来实现，使用注解开发后，我们可以使用@Results注解，@Result注解，@One注解，@Many注解组合完成复杂关系的配置

图片10.png

图片11.png

一对一查询

一对一查询的模型

用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

一对一查询的需求：查询一个订单，与此同时查询出该订单所属的用户

图片12.png

一对一查询的语句

对应的sql语句：

select * from orders; select * from user where id=查询出订单的uid;
创建Order和User实体
public class Order { private int id; private Date ordertime; private double total; //代表当前订单从属于哪一个客户 private User user; } public class User { private int id; private String username; private String password; private Date birthday; }
创建OrderMapper接口
public interface OrderMapper { List<Order> findAll(); }
使用注解配置Mapper
public interface OrderMapper { @Select("select * from orders") @Results({ @Result(id=true,property = "id",column = "id"), @Result(property = "ordertime",column = "ordertime"), @Result(property = "total",column = "total"), @Result(property = "user",column = "uid", javaType = User.class, one = @One(select = "com.zjq.mapper.UserMapper.findById")) }) List<Order> findAll(); } public interface UserMapper { @Select("select * from user where id=#{id}") User findById(int id); }
测试结果
@Test public void testSelectOrderAndUser() { List<Order> all = orderMapper.findAll(); for(Order order : all){ System.out.println(order); } }

一对多查询

一对多查询的模型

用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

一对多查询的需求：查询一个用户，与此同时查询出该用户具有的订单

图片15.png

一对多查询的语句

对应的sql语句：

select * from user; select * from orders where uid=查询出用户的id;
修改User实体
public class Order { private int id; private Date ordertime; private double total; //代表当前订单从属于哪一个客户 private User user; } public class User { private int id; private String username; private String password; private Date birthday; //代表当前用户具备哪些订单 private List<Order> orderList; }
创建UserMapper接口
List<User> findAllUserAndOrder();
使用注解配置Mapper
public interface UserMapper { @Select("select * from user") @Results({ @Result(id = true,property = "id",column = "id"), @Result(property = "username",column = "username"), @Result(property = "password",column = "password"), @Result(property = "birthday",column = "birthday"), @Result(property = "orderList",column = "id", javaType = List.class, many = @Many(select = "com.zjq.mapper.OrderMapper.findByUid")) }) List<User> findAllUserAndOrder(); } public interface OrderMapper { @Select("select * from orders where uid=#{uid}") List<Order> findByUid(int uid); }
测试结果
List<User> all = userMapper.findAllUserAndOrder(); for(User user : all){ System.out.println(user.getUsername()); List<Order> orderList = user.getOrderList(); for(Order order : orderList){ System.out.println(order); } System.out.println("-----------------------------"); }

多对多查询

多对多查询的模型

用户表和角色表的关系为，一个用户有多个角色，一个角色被多个用户使用

多对多查询的需求：查询用户同时查询出该用户的所有角色

图片18.png

多对多查询的语句

对应的sql语句：

select * from user; select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=用户的id
创建Role实体，修改User实体
public class User { private int id; private String username; private String password; private Date birthday; //代表当前用户具备哪些订单 private List<Order> orderList; //代表当前用户具备哪些角色 private List<Role> roleList; } public class Role { private int id; private String rolename; }
添加UserMapper接口方法
List<User> findAllUserAndRole();
使用注解配置Mapper
public interface UserMapper { @Select("select * from user") @Results({ @Result(id = true,property = "id",column = "id"), @Result(property = "username",column = "username"), @Result(property = "password",column = "password"), @Result(property = "birthday",column = "birthday"), @Result(property = "roleList",column = "id", javaType = List.class, many = @Many(select = "com.zjq.mapper.RoleMapper.findByUid")) }) List<User> findAllUserAndRole();} public interface RoleMapper { @Select("select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=#{uid}") List<Role> findByUid(int uid); }
测试结果
UserMapper mapper = sqlSession.getMapper(UserMapper.class); List<User> all = mapper.findAllUserAndRole(); for(User user : all){ System.out.println(user.getUsername()); List<Role> roleList = user.getRoleList(); for(Role role : roleList){ System.out.println(role); } System.out.println("----------------------------------"); }

SSM框架整合

1.1 原始方式整合

1.准备工作

7.png

2.创建Maven工程

image.png

3.导入Maven坐标

参考：素材/配置文件/pom.xml文件

4.编写实体类
public class Account { private int id; private String name; private double money; //省略getter和setter方法 }
5.编写Mapper接口
public interface AccountMapper { //保存账户数据 void save(Account account); //查询账户数据 List<Account> findAll(); }
6.编写Service接口
public interface AccountService { void save(Account account); //保存账户数据 List<Account> findAll(); //查询账户数据 }
7.编写Service接口实现
@Service("accountService") public class AccountServiceImpl implements AccountService { public void save(Account account) { SqlSession sqlSession = MyBatisUtils.openSession(); AccountMapper accountMapper = sqlSession.getMapper(AccountMapper.class); accountMapper.save(account); sqlSession.commit(); sqlSession.close(); } public List<Account> findAll() { SqlSession sqlSession = MyBatisUtils.openSession(); AccountMapper accountMapper = sqlSession.getMapper(AccountMapper.class); return accountMapper.findAll(); } }
8.编写Controller
@Controller public class AccountController { @Autowired private AccountService accountService; @RequestMapping("/save") @ResponseBody public String save(Account account){ accountService.save(account); return "save success"; } @RequestMapping("/findAll") public ModelAndView findAll(){ ModelAndView modelAndView = new ModelAndView(); modelAndView.setViewName("accountList"); modelAndView.addObject("accountList",accountService.findAll()); return modelAndView; } }
9.编写添加页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> 保存账户信息表单 <form action="${pageContext.request.contextPath}/save.action" method="post"> 用户名称<input type="text" name="name"><br/> 账户金额<input type="text" name="money"><br/> <input type="submit" value="保存"><br/> </form> </body> </html>
10.编写列表页面
<table border="1"> <tr> <th>账户id</th> <th>账户名称</th> <th>账户金额</th> </tr> <c:forEach items="${accountList}" var="account"> <tr> <td>${account.id}</td> <td>${account.name}</td> <td>${account.money}</td> </tr> </c:forEach> </table>
11.编写相应配置文件(文件参考目录：素材/配置文件)

•Spring配置文件：applicationContext.xml

•SprngMVC配置文件：spring-mvc.xml

•MyBatis映射文件：AccountMapper.xml

•MyBatis核心文件：sqlMapConfig.xml

•数据库连接信息文件：jdbc.properties

•Web.xml文件：web.xml

•日志文件：[log4j.xml](

12.测试添加账户

9.jpg

13.测试账户列表

image.png

1.2 Spring整合MyBatis

1.整合思路

11.png

2.将SqlSessionFactory配置到Spring容器中
<!--加载jdbc.properties--> <context:property-placeholder location="classpath:jdbc.properties"/> <!--配置数据源--> <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <property name="driverClass" value="${jdbc.driver}"/> <property name="jdbcUrl" value="${jdbc.url}"/> <property name="user" value="${jdbc.username}"/> <property name="password" value="${jdbc.password}"/> </bean> <!--配置MyBatis的SqlSessionFactory--> <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="dataSource" ref="dataSource"/> <property name="configLocation" value="classpath:sqlMapConfig.xml"/> </bean>
3.扫描Mapper，让Spring容器产生Mapper实现类
<!--配置Mapper扫描--> <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"> <property name="basePackage" value="com.zjq.mapper"/> </bean>
4.配置声明式事务控制
<!--配置声明式事务控制--> <bean id="transacionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="dataSource"/> </bean> <tx:advice id="txAdvice" transaction-manager="transacionManager"> <tx:attributes> <tx:method name="*"/> </tx:attributes> </tx:advice> <aop:config> <aop:pointcut id="txPointcut" expression="execution(* com.zjq.service.impl.*.*(..))"/> <aop:advisor advice-ref="txAdvice" pointcut-ref="txPointcut"/> </aop:config>
5.修改Service实现类代码
@Service("accountService") public class AccountServiceImpl implements AccountService { @Autowired private AccountMapper accountMapper; public void save(Account account) { accountMapper.save(account); } public List<Account> findAll() { return accountMapper.findAll(); } }

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