Hibernate（二）——一对多查询-白红宇

Hibernate（二）——一对多查询

阅读量：5238 次

发布时间：2019-06-14

本文共 14932 字，大约阅读时间需要 49 分钟。

1. 前言

本章节我们讨论Hibernate一对多查询的处理。

在上一章节中（），我们探讨了Hibernate执行最基本的增删改查操作。现在我们将情况复杂化：加入我们在查询用户信息的时候需要同时查询其登录日志，这样就涉及到一对多查询。那么一对多查询要怎么实现么？

2. jar包准备

在本节中，除了上一章节中用到的jar包，我还需要用log4j.jar来将Hibernate的查询语句输出到控制台。log4j.properties的配置如下：

1 log4j.rootLogger=info,console  2 log4j.appender.console=org.apache.log4j.ConsoleAppender  3 log4j.appender.console.layout=org.apache.log4j.PatternLayout  4 log4j.appender.console.layout.ConversionPattern=%d %p [%c] - %m%n

log4j的使用方法可查阅：中，log4j的学习和使用部分。

3. 数据库准备

我们需要新建立日志表tbLog，并产生部分的测试数据。代码如下：

1 CREATE TABLE tbLog (2     logID VARCHAR(50),3     userID VARCHAR(50),4     loginDate DATETIME5 )

1   tbUser  2   tbLog  3   4  @userID1 (50)  5  @userID2 (50)  6  @userID1 = NEWID();  7  @userID2 = NEWID();  8   9   tbUser(userID, loginName, userName, passWord) 10  @userID1,'luych','卢艳超','12333'   11  @userID2,'guest','游客','12333' 12  13   tbLog(logID, userID, loginDate) 14  NEWID(), @userID1, '2016-04-01'   15  NEWID(), @userID1, '2016-04-02'   16  NEWID(), @userID1, '2016-04-05'   17  NEWID(), @userID1, '2016-04-08'   18  19  NEWID(), @userID2, '2016-04-11'   20  NEWID(), @userID2, '2016-04-22' 21  22  *  tbUser; 23  *  tbLog;

4. 准备JAVA对象

（1）建立与数据表tbLog相对应的JAVA对象，代码如下：

1 package com.luych.hibernate.study.entity;  2   3 import java.util.Date;  4   5 import javax.persistence.Entity;  6 import javax.persistence.Id;  7 import javax.persistence.Table;  8   9  10 @Entity 11 @Table(name="tbLog") 12 public class LogEntity { 13  14     @Id 15     private String logID; 16     private String userID; 17     private Date loginDate; 18  19     public String getLogID() { 20         return logID; 21     } 22     public void setLogID(String logID) { 23         this.logID = logID; 24     } 25     public String getUserID() { 26         return userID; 27     } 28     public void setUserID(String userID) { 29         this.userID = userID; 30     } 31     public Date getLoginDate() { 32         return loginDate; 33     } 34     public void setLoginDate(Date loginDate) { 35         this.loginDate = loginDate; 36     } 37  38  39  40 }

当然，我们同时也要在Hibernate的xml中增加相应的配置

（2）调整UserEntity对象，建立其与LogEntity的一对多关系。

1 package com.luych.hibernate.study.entity;  2   3 import java.text.SimpleDateFormat;  4 import java.util.Set;  5   6 import javax.persistence.CascadeType;  7 import javax.persistence.Entity;  8 import javax.persistence.Id;  9 import javax.persistence.JoinColumn; 10 import javax.persistence.OneToMany; 11 import javax.persistence.Table; 12  13 @Entity 14 @Table(name="tbUser") 15 public class UserEntity { 16  17     @Id 18     private String userID; 19     private String loginName; 20     private String userName; 21     private String passWord; 22     @OneToMany(cascade=CascadeType.ALL) 23     @JoinColumn(name="userID") 24     private Set
     
       logs; 25  26     public String getUserID() { 27         return userID; 28     } 29     public void setUserID(String userID) { 30         this.userID = userID; 31     } 32     public String getLoginName() { 33         return loginName; 34     } 35     public void setLoginName(String loginName) { 36         this.loginName = loginName; 37     } 38     public String getUserName() { 39         return userName; 40     } 41     public void setUserName(String userName) { 42         this.userName = userName; 43     } 44     public String getPassWord() { 45         return passWord; 46     } 47     public void setPassWord(String passWord) { 48         this.passWord = passWord; 49     } 50     public Set
      
        getLogs() { 51         return logs; 52     } 53     public void setLogs(Set
       
         logs) { 54         this.logs = logs; 55     } 56     @Override 57     public String toString() { 58         String str = loginName+", "+userName+", "+passWord+", "+userID+" 登录日志：\n"; 59         for (LogEntity log: logs) { 60             str = str+new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(log.getLoginDate())+"\n"; 61         } 62         return str; 63     } 64 } 65

其中，

@OneToMany的cascade可取值为：

CascadeType.PERSIST：级联新建，本例中即生成User的时候同时生成Log。

CascadeType.REMOVE : 级联删除，本例中即删除User的时候同时删除Log。

CascadeType.REFRESH：级联刷新，本例中即查询User的时候同时查询Log。

CascadeType.MERGE  ：级联更新，本例中即修改User的时候同时修改Log。

CascadeType.ALL    ：以上全部四项，即上面四个全都执行。

@JoinColumn的name取值为：LogEntity中的userID属性。

5. 调整Hibernate配置文件

1 
       2   5 
     
        6     
      
         7         
         8         
       
        com.microsoft.sqlserver.jdbc.SQLServerDriver
         9         
        10         
       
        jdbc:sqlserver://192.168.9.23:14433;databaseName=tempdb
        11         
        12         
       
        sa
        13         
        14         
       
        123@abcd
        15         
        16         
       
        true
        17         
       
        false
        18         
        19         
        20         
        21     
       22

我们增加了针对show_sql和format_sql的配置，加上这两个配置后，Hibernate会输出执行的SQL脚本。

- show_sql：true，输出SQL脚本。false，不输出。
- format_sql：true，格式化SQL脚本。false，不格式化。

本例中，并没有将format_sql设置为true，是因为格式化的SQL在控制台中显示很占篇幅，不利于我们后面看测试结果，所以关闭了。

6. 测试运行结果

1 package com.luych.hibernate.study.main;  2   3 import java.util.Date;  4 import java.util.HashSet;  5 import java.util.List;  6 import java.util.Set;  7 import java.util.UUID;  8   9 import org.hibernate.Query; 10 import org.hibernate.Session; 11 import org.hibernate.SessionFactory; 12 import org.hibernate.cfg.Configuration; 13 import org.junit.After; 14 import org.junit.Before; 15 import org.junit.Test; 16  17 import com.luych.hibernate.study.entity.LogEntity; 18 import com.luych.hibernate.study.entity.UserEntity; 19  20 @SuppressWarnings("unchecked") 21 public class TestMain { 22  23     private Session session; 24  25     @Before 26     public void getSession(){ 27         Configuration config = new Configuration().configure("hibernate-config.xml"); 28         SessionFactory sessionFactory = config.buildSessionFactory(); 29         session = sessionFactory.openSession(); 30     } 31  32     @After 33     public void freeSession(){ 34         session.close(); 35     } 36  37     public void sel() { 38         Query query = session.createQuery("FROM UserEntity WHERE 1=1"); 39         List
     
       userList = query.list(); 40         for (UserEntity userEntity : userList) { 41             System.out.println(userEntity.toString()); 42         } 43     } 44  45     public void add() { 46         session.beginTransaction(); 47         String userID = UUID.randomUUID().toString(); 48         UserEntity user  = new UserEntity(); 49         user.setLoginName("admin"); 50         user.setUserName("系统管理员"); 51         user.setPassWord("12333"); 52         user.setUserID(userID); 53         LogEntity log1 = new LogEntity(); 54         log1.setLogID(UUID.randomUUID().toString()); 55         log1.setUserID(userID); 56         log1.setLoginDate(new Date()); 57         LogEntity log2 = new LogEntity(); 58         log2.setLogID(UUID.randomUUID().toString()); 59         log2.setUserID(userID); 60         log2.setLoginDate(new Date()); 61         Set
      
        logs = new HashSet
       
        (); 62         logs.add(log1); 63         logs.add(log2); 64         user.setLogs(logs); 65         session.save(user); 66         session.getTransaction().commit(); 67     } 68  69     public void edt(){ 70         session.beginTransaction(); 71         Query query = session.createQuery("FROM UserEntity WHERE 1=1"); 72         List
        
          userList = query.list(); 73         for (UserEntity userEntity : userList) { 74             userEntity.setPassWord("45666"); 75             LogEntity log = new LogEntity(); 76             log.setLogID(UUID.randomUUID().toString()); 77             log.setUserID(userEntity.getUserID()); 78             log.setLoginDate(new Date()); 79             userEntity.getLogs().add(log); 80             session.update(userEntity); 81         } 82         session.getTransaction().commit(); 83     } 84  85     public void del(){ 86         session.beginTransaction(); 87         Query query = session.createQuery("FROM UserEntity WHERE 1=1"); 88         List
         
           userList = query.list(); 89         for (UserEntity userEntity : userList) { 90             session.delete(userEntity); 91         } 92         session.getTransaction().commit(); 93     } 94  95     @Test 96     public void test(){ 97         System.out.println("\n----------现有用户："); 98         sel(); 99         System.out.println("\n----------开始增加用户：");100         add();101         System.out.println("\n----------增加用户后：");102         sel();103         System.out.println("\n----------开始修改用户：");104         edt();105         System.out.println("\n----------修改用户后：");106         sel();107         System.out.println("\n----------开始删除用户：");108         del();109         System.out.println("\n----------删除用户后：");110         sel();111     }112 }

getSession和freeSession和上一章节中相同，不再赘述。

add方法，新建了一个用户并设定了两条登录日志，然后保存。edt方法，将所有用户的密码改为45666，并为所有的用户增加一条登录日志。del方法，删除所有的用户。sel方法，查询所有用户信息并输出到控制台。

右键，Run As JUnit Test后，控制台输出结果为：

1   2 ----------现有用户：  3 Hibernate: select userentity0_.userID as userID1_1_, userentity0_.loginName as loginNam2_1_,

userentity0_.passWord as passWord3_1_, userentity0_.userName as userName4_1_

from tbUser userentity0_ where 1=1  4 Hibernate: select logs0_.userID as userID3_0_0_, logs0_.logID as logID1_0_0_,

logs0_.logID as logID1_0_1_, logs0_.loginDate as loginDat2_0_1_, logs0_.userID as userID3_0_1_

from tbLog logs0_ where logs0_.userID=?  5   6 luych, 卢艳超, 12333, CB6172E3-8750-4718-BEF6-EE0917015FA9 登录日志：  7 2016-04-01 00:00:00  8 2016-04-08 00:00:00  9 2016-04-05 00:00:00 10 2016-04-02 00:00:00 11  12 Hibernate: select logs0_.userID as userID3_0_0_, logs0_.logID as logID1_0_0_,

logs0_.logID as logID1_0_1_, logs0_.loginDate as loginDat2_0_1_, logs0_.userID as userID3_0_1_

from tbLog logs0_ where logs0_.userID=? 13  14 guest, 游客, 12333, 21539577-A3D1-4A1F-8D10-6ED0540A46A0 登录日志： 15 2016-04-11 00:00:00 16 2016-04-22 00:00:00 17  18  19 ----------开始增加用户： 20 Hibernate: select logentity_.logID, logentity_.loginDate as loginDat2_0_, logentity_.userID as userID3_0_

from tbLog logentity_ where logentity_.logID=? 21 Hibernate: select logentity_.logID, logentity_.loginDate as loginDat2_0_, logentity_.userID as userID3_0_

from tbLog logentity_ where logentity_.logID=? 22 Hibernate: insert into tbUser (loginName, passWord, userName, userID) values (?, ?, ?, ?) 23 Hibernate: insert into tbLog (loginDate, userID, logID) values (?, ?, ?) 24 Hibernate: insert into tbLog (loginDate, userID, logID) values (?, ?, ?) 25 Hibernate: update tbLog set userID=? where logID=? 26 Hibernate: update tbLog set userID=? where logID=? 27  28 ----------增加用户后： 29 Hibernate: select userentity0_.userID as userID1_1_, userentity0_.loginName as loginNam2_1_,

userentity0_.passWord as passWord3_1_, userentity0_.userName as userName4_1_

from tbUser userentity0_ where 1=1 30  31 luych, 卢艳超, 12333, CB6172E3-8750-4718-BEF6-EE0917015FA9 登录日志： 32 2016-04-01 00:00:00 33 2016-04-08 00:00:00 34 2016-04-05 00:00:00 35 2016-04-02 00:00:00 36  37  38 guest, 游客, 12333, 21539577-A3D1-4A1F-8D10-6ED0540A46A0 登录日志： 39 2016-04-11 00:00:00 40 2016-04-22 00:00:00 41  42  43 admin, 系统管理员, 12333, 99d5d264-9d02-4e45-a8c5-f710cc14107e 登录日志： 44 2016-04-26 17:06:00 45 2016-04-26 17:06:00 46  47  48 ----------开始修改用户： 49 Hibernate: select userentity0_.userID as userID1_1_, userentity0_.loginName as loginNam2_1_,

userentity0_.passWord as passWord3_1_, userentity0_.userName as userName4_1_

from tbUser userentity0_ where 1=1 50 Hibernate: select logentity_.logID, logentity_.loginDate as loginDat2_0_,

logentity_.userID as userID3_0_

from tbLog logentity_ where logentity_.logID=? 51 Hibernate: select logentity_.logID, logentity_.loginDate as loginDat2_0_,

logentity_.userID as userID3_0_

from tbLog logentity_ where logentity_.logID=? 52 Hibernate: select logentity_.logID, logentity_.loginDate as loginDat2_0_,

logentity_.userID as userID3_0_

from tbLog logentity_ where logentity_.logID=? 53 Hibernate: insert into tbLog (loginDate, userID, logID) values (?, ?, ?) 54 Hibernate: insert into tbLog (loginDate, userID, logID) values (?, ?, ?) 55 Hibernate: insert into tbLog (loginDate, userID, logID) values (?, ?, ?) 56 Hibernate: update tbUser set loginName=?, passWord=?, userName=? where userID=? 57 Hibernate: update tbUser set loginName=?, passWord=?, userName=? where userID=? 58 Hibernate: update tbUser set loginName=?, passWord=?, userName=? where userID=? 59 Hibernate: update tbLog set userID=? where logID=? 60 Hibernate: update tbLog set userID=? where logID=? 61 Hibernate: update tbLog set userID=? where logID=? 62  63 ----------修改用户后： 64 Hibernate: select userentity0_.userID as userID1_1_, userentity0_.loginName as loginNam2_1_,

userentity0_.passWord as passWord3_1_, userentity0_.userName as userName4_1_

from tbUser userentity0_ where 1=1 65  66 luych, 卢艳超, 45666, CB6172E3-8750-4718-BEF6-EE0917015FA9 登录日志： 67 2016-04-01 00:00:00 68 2016-04-08 00:00:00 69 2016-04-05 00:00:00 70 2016-04-02 00:00:00 71 2016-04-26 17:06:00 72  73  74 guest, 游客, 45666, 21539577-A3D1-4A1F-8D10-6ED0540A46A0 登录日志： 75 2016-04-11 00:00:00 76 2016-04-22 00:00:00 77 2016-04-26 17:06:00 78  79  80 admin, 系统管理员, 45666, 99d5d264-9d02-4e45-a8c5-f710cc14107e 登录日志： 81 2016-04-26 17:06:00 82 2016-04-26 17:06:00 83 2016-04-26 17:06:00 84  85  86 ----------开始删除用户： 87 Hibernate: select userentity0_.userID as userID1_1_, userentity0_.loginName as loginNam2_1_,

userentity0_.passWord as passWord3_1_, userentity0_.userName as userName4_1_

from tbUser userentity0_ where 1=1 88 Hibernate: update tbLog set userID=null where userID=? 89 Hibernate: update tbLog set userID=null where userID=? 90 Hibernate: update tbLog set userID=null where userID=? 91 Hibernate: delete from tbLog where logID=? 92 Hibernate: delete from tbLog where logID=? 93 Hibernate: delete from tbLog where logID=? 94 Hibernate: delete from tbLog where logID=? 95 Hibernate: delete from tbLog where logID=? 96 Hibernate: delete from tbUser where userID=? 97 Hibernate: delete from tbLog where logID=? 98 Hibernate: delete from tbLog where logID=? 99 Hibernate: delete from tbLog where logID=?100 Hibernate: delete from tbUser where userID=?101 Hibernate: delete from tbLog where logID=?102 Hibernate: delete from tbLog where logID=?103 Hibernate: delete from tbLog where logID=?104 Hibernate: delete from tbUser where userID=?105 106 ----------删除用户后：107 Hibernate: select userentity0_.userID as userID1_1_, userentity0_.loginName as loginNam2_1_,

userentity0_.passWord as passWord3_1_, userentity0_.userName as userName4_1_

from tbUser userentity0_ where 1=1108

从打印结果中，我们可以看到，新增、编辑、删除用户信息的时候，Hibernate都帮我们完成登录日志的新增、删除、操作。查询的时候也如此。

但是需要提点的是：在Hibernate第一次查询中，我们看到它先查询了tbUser表，然后针对tbUser表的每一个记录都又查询了下tbLog表，这就是经典的N+1查询问题，所以效率嘛…

以上就是Hibernate中一对多的查询关联，其他关联情况将在后续的博文中讲解。

转载于:https://www.cnblogs.com/LOVE0612/p/5435886.html

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