MyBatis多表操作查询功能
这篇文章主要介绍了MyBatis多表操作,包括一对一查询,一对多查询的模型,多对多查询的需求,本文通过实例代码给大家介绍的非常详细,需要的朋友可以参考下
一对一查询
用户表和订单表的关系为,一个用户多个订单,一个订单只从属一个用户
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
在只查询order表的时候,也要查询user表,所以需要将所有数据全部查出进行封装SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id
创建Order和User实体
order
1 2 3 4 5 6 | public class Order { private int id; private Date ordertime; private double total; //表示当前订单属于哪一个用户 private User user; |
user
1 2 3 4 5 | public class User { private int id; private String username; private String password; private Date birthday; |
创建OrderMapper接口
1 2 3 4 | public interface UserMapper { //查询全部的方法 public List<Order> findAll(); } |
配置OrderMapper.xml
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | <?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.zg.mapper.OrderMapper" > <resultMap id= "orderMap" type= "order" > <!--手动指定字段与实体的映射关系--> <!--comlumn:数据表的字段名称 property:实体的属性名称--> <id column= "oid" property= "id" ></id> <result column= "ordertime" property= "ordertime" ></result> <result column= "total" property= "total" ></result> <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> <!--这里不能使用resultType=“order”,因为order中没有user中的字段,只有一个user对象--> <select id= "findAll" resultMap= "orderMap" > SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id </select> </mapper> |
sqlMapConfig.xml
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | <?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" > <!--主要配置mybatis的核心配置--> <configuration> <!--通过properties标签加载外部properties文件--> <properties resource= "jdbc.properties" ></properties> <!--自定义别名--> <typeAliases> <typeAlias type= "com.zg.domain.User" alias= "user" ></typeAlias> <typeAlias type= "com.zg.domain.Order" alias= "order" ></typeAlias> </typeAliases> <!--配置当前数据源的环境--> <environments default = "developement" > <environment id= "developement" > <transactionManager type= "JDBC" ></transactionManager> <dataSource type= "POOLED" > <property name= "driver" value= "${jdbc.driver}" /> <property name= "url" value= "${jdbc.url}" /> <property name= "username" value= "${jdbc.username}" /> <property name= "password" value= "${jdbc.password}" /> </dataSource> </environment> </environments> <!--加载映射文件--> <mappers> <mapper resource= "com.zg.mapper/UserMapper.xml" ></mapper> <mapper resource= "com.zg.mapper/OrderMapper.xml" ></mapper> </mappers> </configuration> |
在一对一配置的时候,在order实体中创建了一个user,所以property属性都使用user.**
的方式进行编写,但是这里还可以使用association
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | <?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.zg.mapper.OrderMapper" > <resultMap id= "orderMap" type= "order" > <!--手动指定字段与实体的映射关系--> <!--comlumn:数据表的字段名称 property:实体的属性名称--> <id column= "oid" property= "id" ></id> <result column= "ordertime" property= "ordertime" ></result> <result column= "total" property= "total" ></result> <!--<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>--> <!--以上被封装到user内的还可以使用association进行配置--> <!--association匹配的意思,在order中有个属性叫user--> <!-- property= "user" 当前order实体中的属性名称,javaType= "user" 当前实体order中的属性类型user--> <association property= "user" javaType= "user" > <id column= "uid" property= "id" ></id> <result column= "username" property= "username" ></result> <result column= "password" property= "password" ></result> <result column= "birthday" property= "birthday" ></result> </association> </resultMap> <!--这里不能使用resultType=“order”,因为order中没有user中的字段,只有一个user对象--> <select id= "findAll" resultMap= "orderMap" > SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id </select> </mapper> |
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,一个当但只从属一个用户
一对多查询需求:查询一个用户,与此同时查询出该用户具有的订单
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | package com.zg.domain; import java.util.Date; import java.util.List; public class User { private int id; private String username; private String password; private Date birthday; //描述当前用户存在哪些订单 private List<Order> orderList; public List<Order> getOrderList() { return orderList; } public void setOrderList(List<Order> orderList) { this .orderList = orderList; } @Override public String toString() { return "User{" + "id=" + id + ", username='" + username + '\ '' + ", password='" + password + '\ '' + ", birthday=" + birthday + ", orderList=" + orderList + '}' ; } public int getId() { return id; } public void setId( int id) { this .id = id; } public String getUsername() { return username; } public void setUsername(String username) { this .username = username; } public String getPassword() { return password; } public void setPassword(String password) { this .password = password; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this .birthday = birthday; } } |
修改User实体
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | package com.zg.domain; import java.util.Date; import java.util.List; public class User { private int id; private String username; private String password; private Date birthday; //描述当前用户存在哪些订单 private List<Order> orderList; public List<Order> getOrderList() { return orderList; } public void setOrderList(List<Order> orderList) { this .orderList = orderList; } @Override public String toString() { return "User{" + "id=" + id + ", username='" + username + '\ '' + ", password='" + password + '\ '' + ", birthday=" + birthday + ", orderList=" + orderList + '}' ; } public int getId() { return id; } public void setId( int id) { this .id = id; } public String getUsername() { return username; } public void setUsername(String username) { this .username = username; } public String getPassword() { return password; } public void setPassword(String password) { this .password = password; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this .birthday = birthday; } } |
创建UserMapper接口
1 2 3 4 5 6 7 8 9 10 | package com.zg.mapper; import com.zg.domain.User; import java.util.List; public interface UserMapper { public List<User> findAll(); } |
配置UserMapper.xml
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | <?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.zg.mapper.UserMapper" > <resultMap id= "userMap" type= "user" > <id column= "uid" property= "id" ></id> <result column= "username" property= "username" ></result> <result column= "password" property= "password" ></result> <result column= "birthday" property= "birthday" ></result> <!--配置集合信息--> <!--property:集合名称 ofType:当前集合中的数据类型--> <collection property= "orderList" ofType= "order" > <!--封装order的数据--> <id column= "oid" property= "id" ></id> <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,orders o where u.id=o.uid </select> </mapper> |
测试
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | @Test //测试一对多 public void test2() throws IOException { InputStream resourceAsStream = Resources.getResourceAsStream( "sqlMapConfig.xml" ); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream); SqlSession sqlSession = sqlSessionFactory.openSession(); UserMapper mapper = sqlSession.getMapper(UserMapper. class ); List<User> userList = mapper.findAll(); for (User user : userList) { System.out.println(user); } sqlSession.close(); } |
多对多查询
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:查询用户同时查询该用户的所有角色
1 | select * from user u,sys_user_role ur ,sys_role r where u.id=ur.userId and ur.roleId=r.id |
创建Role实体,修改User实体
添加UserMapper接口
1 2 3 4 5 6 7 8 9 10 11 12 | package com.zg.mapper; import com.zg.domain.User; import java.util.List; public interface UserMapper { public List<User> findAll(); public List<User> findUserAndRoleAll(); } |
配置UserMapper.xml
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | <resultMap id= "userRoleMap" type= "user" > <!--user信息的封装--> <id column= "userid" property= "id" ></id> <result column= "username" property= "username" ></result> <result column= "password" property= "password" ></result> <result column= "birthday" property= "birthday" ></result> <!--user内部的rolelist信息--> <collection property= "roleList" ofType= "role" > <id column= "roleid" property= "id" ></id> <result column= "roleName" property= "roleName" ></result> <result column= "roleDesc" property= "roleDesc" ></result> </collection> </resultMap> <select id= "findUserAndRoleAll" resultMap= "userRoleMap" > select * from user u,sys_user_role ur ,sys_role r where u.id=ur.userId and ur.roleId=r.id </select> |
测试代码
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | @Test //测试多对多 public void test3() throws IOException { InputStream resourceAsStream = Resources.getResourceAsStream( "sqlMapConfig.xml" ); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream); SqlSession sqlSession = sqlSessionFactory.openSession(); UserMapper mapper = sqlSession.getMapper(UserMapper. class ); List<User> userAndRoleAll = mapper.findUserAndRoleAll(); for (User user : userAndRoleAll) { System.out.println(user); } sqlSession.close(); } |
到此这篇关于MyBatis多表操作的文章就介绍到这了
原文链接:https://blog.csdn.net/weixin_43914631/article/details/121267577