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mybatis-07-单表一对多查询

2019-02-03 18:14:55【个人日记】709人已围观

简介一张表对应多个数据

单表一对多查询

文件结构

文件系统

配置User.java文件

  1. import java.util.List;
  2. public class User {
  3.     private Integer id;
  4.     private String userName;
  5.     private String userTelephone;
  6.     private String userSex;
  7.     //这里封装多个信息   *注意*
  8.     "private List<Orders> orders;"
  9.     @Override
  10.     public String toString() {
  11.         return "User{" +
  12.                 "id=" + id +
  13.                 ", userName='" + userName + '\'' +
  14.                 ", userTelephone='" + userTelephone + '\'' +
  15.                 ", userSex='" + userSex + '\'' +
  16.                 ", orders=" + orders +
  17.                 '}';
  18.     }
  19.     public List<Orders> getOrders() {
  20.         return orders;
  21.     }
  22.     public void setOrders(List<Orders> orders) {
  23.         this.orders = orders;
  24.     }
  25.     public Integer getId() {
  26.         return id;
  27.     }
  28.     public void setId(Integer id) {
  29.         this.id = id;
  30.     }
  31.     public String getUserName() {
  32.         return userName;
  33.     }
  34.     public void setUserName(String userName) {
  35.         this.userName = userName;
  36.     }
  37.     public String getUserTelephone() {
  38.         return userTelephone;
  39.     }
  40.     public void setUserTelephone(String userTelephone) {
  41.         this.userTelephone = userTelephone;
  42.     }
  43.     public String getUserSex() {
  44.         return userSex;
  45.     }
  46.     public void setUserSex(String userSex) {
  47.         this.userSex = userSex;
  48.     }
  49. }

另一个Orders.java信息

  1. import java.util.Date;
  2. public class Orders {
  3.     private Integer id;
  4.     private String userId;
  5.     private Date createTime;
  6.     @Override
  7.     public String toString() {
  8.         return "Orders{" +
  9.                 "id=" + id +
  10.                 ", userId='" + userId + '\'' +
  11.                 ", createTime=" + createTime +
  12.                 '}';
  13.     }
  14.     public Integer getId() {
  15.         return id;
  16.     }
  17.     public void setId(Integer id) {
  18.         this.id = id;
  19.     }
  20.     public String getUserId() {
  21.         return userId;
  22.     }
  23.     public void setUserId(String userId) {
  24.         this.userId = userId;
  25.     }
  26.     public Date getCreateTime() {
  27.         return createTime;
  28.     }
  29.     public void setCreateTime(Date createTime) {
  30.         this.createTime = createTime;
  31.     }
  32. }

Orders接口

注意

如果封装另一张表,需要使用List来放入信息 

  1. import java.util.List;
  2. public interface OrderMapper {
  3.     /**
  4.      * 通过id查询
  5.      *
  6.      * @param orderId
  7.      * @return
  8.      */
  9.     List<Orders> orders(Integer orderId);
  10. }

User接口

  1. package com.huangxin.order.mapper;
  2. import com.huangxin.order.model.User;
  3. public interface UserMapper {
  4.     /**
  5.      * 通过id查询
  6.      *
  7.      * @param id
  8.      * @return
  9.      */
  10.     User getById(Integer id);
  11. }

配置OrderMapper.xml文件

  1. <?xml version="1.0" encoding="UTF-8" ?>
  2. <!DOCTYPE mapper
  3.         PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  4.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
  5. <!--接口的全限定名-->
  6. <mapper namespace="com.huangxin.order.mapper.OrderMapper">
  7.     <resultMap id="order" type="com.huangxin.order.model.Orders">
  8.         <id column="oid" property="id"></id>
  9.         <result column="user_id" property="userId"></result>
  10.         <result column="create_time" property="createTime"></result>
  11.     </resultMap>
  12.     <select id="orders" parameterType="java.lang.Integer" resultMap="order">
  13.         SELECT * FROM orders WHERE user_id=#{orderId};
  14.     </select>
  15. </mapper>

注意命名

重点

配置UserMapper.xml文件

  1. <?xml version="1.0" encoding="UTF-8" ?>
  2. <!DOCTYPE mapper
  3.         PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  4.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
  5. <!--接口的全限定名-->
  6. <mapper namespace="com.huangxin.order.mapper.UserMapper">
  7.     <resultMap id="user" type="com.huangxin.order.model.User">
  8.         <id column="id" property="id"></id>
  9.         <result column="user_name" property="userName"></result>
  10.         <result column="user_telephone" property="userTelephone"></result>
  11.         <result column="user_sex" property="userSex"></result>
  12.         <collection property="orders" select="com.huangxin.order.mapper.OrderMapper.orders" column="id">
  13.         </collection>
  14.     </resultMap>
  15.     <select id="getById" parameterType="java.lang.Integer" resultMap="user">
  16.         SELECT * FROM user WHERE id=#{id};
  17.     </select>
  18. </mapper>

注意

1) 注意看collection便签中的column属性,这里需要与SQL语句中查询的列明相对应, 可以忽略大小写,但是必须要相同 ,像上面的column=" id "与SELECT * FROM user WHERE id =#{id},这两个必须相同,这样才会查询到与id相同的信息
2) select="com.huangxin.order.mapper.OrderMapper.orders"这句是另一张对应表的映射信息, com.huangxin.order.mapper.OrderMapper 为namespace, orders 则为id命名

最后是测试

  1. package com.huangxin.order.mapper;
  3. import com.huangxin.order.model.Orders;
  4. import org.apache.ibatis.io.Resources;
  5. import org.apache.ibatis.session.SqlSession;
  6. import org.apache.ibatis.session.SqlSessionFactory;
  7. import org.apache.ibatis.session.SqlSessionFactoryBuilder;
  8. import org.junit.Before;
  9. import org.junit.Test;
  10. import java.io.IOException;
  11. import java.io.InputStream;
  12. public class OrderMapperTest {
  13.     private SqlSessionFactory factory;
  14.     /**
  15.      * 初始化SqlSession工厂
  16.      */
  17.     @Before
  18.     public void init() throws IOException {
  19.         //将全局配置文件读取
  20.         InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
  21.         factory = new SqlSessionFactoryBuilder().build(in);
  22.     }
  23.     @Test
  24.     public void getById() {
  25.         SqlSession sqlSession = factory.openSession();
  26.         UserMapper mapper = sqlSession.getMapper(UserMapper.class);
  27.         System.out.println(mapper.getById(1));
  28.         sqlSession.close();
  29.     }
  30. }

控制台输出为

  1. D:\Java\bin\java.exe -ea -Didea.test.cyclic.buffer.size=1048576 -javaagent:D:\IntelliJ\lib\idea_rt.jar=4751:D:\IntelliJ\bin -Dfile.encoding=UTF-8 -classpath D:\IntelliJ\lib\idea_rt.jar;D:\IntelliJ\plugins\junit\lib\junit-rt.jar;D:\IntelliJ\plugins\junit\lib\junit5-rt.jar;D:\mybatis05\target\test-classes;D:\mybatis05\target\classes;C:\Users\Administrator\.m2\repository\log4j\log4j\1.2.17\log4j-1.2.17.jar;C:\Users\Administrator\.m2\repository\mysql\mysql-connector-java\5.1.46\mysql-connector-java-5.1.46.jar;C:\Users\Administrator\.m2\repository\org\mybatis\mybatis\3.4.6\mybatis-3.4.6.jar;C:\Users\Administrator\.m2\repository\junit\junit\4.12\junit-4.12.jar;C:\Users\Administrator\.m2\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit4 com.huangxin.order.mapper.OrderMapperTest,getById
  2. 2019-01-02 21:57:10 [DEBUG] Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter. 
  3. WARNING: An illegal reflective access operation has occurred
  4. WARNING: Illegal reflective access by org.apache.ibatis.reflection.Reflector (file:/C:/Users/Administrator/.m2/repository/org/mybatis/mybatis/3.4.6/mybatis-3.4.6.jar) to method java.lang.Class.checkPackageAccess(java.lang.SecurityManager,java.lang.ClassLoader,boolean)
  5. WARNING: Please consider reporting this to the maintainers of org.apache.ibatis.reflection.Reflector
  6. WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
  7. WARNING: All illegal access operations will be denied in a future release
  8. 2019-01-02 21:57:10 [DEBUG] PooledDataSource forcefully closed/removed all connections. 
  9. 2019-01-02 21:57:10 [DEBUG] PooledDataSource forcefully closed/removed all connections. 
  10. 2019-01-02 21:57:10 [DEBUG] PooledDataSource forcefully closed/removed all connections. 
  11. 2019-01-02 21:57:10 [DEBUG] PooledDataSource forcefully closed/removed all connections. 
  12. 2019-01-02 21:57:10 [DEBUG] Opening JDBC Connection 
  13. 2019-01-02 21:57:11 [DEBUG] Created connection 37981645. 
  14. 2019-01-02 21:57:11 [DEBUG] Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@2438dcd] 
  15. 2019-01-02 21:57:11 [DEBUG]  >  Preparing: SELECT * FROM user WHERE user_sex=?;  
  16. 2019-01-02 21:57:11 [DEBUG]  > Parameters: 1(Integer) 
  17. 2019-01-02 21:57:11 [DEBUG]   >  Preparing: SELECT * FROM orders WHERE user_id=?;  
  18. 2019-01-02 21:57:11 [DEBUG]   > Parameters: 1(Integer) 
  19. 2019-01-02 21:57:11 [DEBUG] <        Total: 2 
  20. 2019-01-02 21:57:11 [DEBUG] <       Total: 1 
  22. User{id=7, userName='1', userTelephone='1', userSex='1', orders=[Orders{id=1, userId='1', createTime=Tue Jan 01 19:49:58 CST 2019}, Orders{id=2, userId='1', createTime=Tue Jan 01 19:50:46 CST 2019}]}
  24. 2019-01-02 21:57:11 [DEBUG] Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@2438dcd] 
  25. 2019-01-02 21:57:11 [DEBUG] Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@2438dcd] 
  26. 2019-01-02 21:57:11 [DEBUG] Returned connection 37981645 to pool. 
  28. Process finished with exit code 0

可以看出User对象中封装这Orders信息,反映出一对多的信息

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