Hibernate5-一对多双向关联-迫切左外连接-HQL
2017-03-31 14:11
323 查看
1.创建项目,项目名称hibernatedemo19,目录结构如图所示
![](https://s5.51cto.com/wyfs02/M01/8F/6B/wKioL1jd8N7Ak-HgAAAikE-tcMI024.png-wh_500x0-wm_3-wmp_4-s_2248312027.png)
2.在项目中创建lib目录存储jar文件,目录结构如图所示
![](https://s1.51cto.com/wyfs02/M01/8F/6E/wKiom1jd8QjSQbnLAABdd-lR0OE413.png-wh_500x0-wm_3-wmp_4-s_3759094861.png)
3.在src目录中创建实体Bean Forum,包名(com.mycompany.demo.bean),如图所示
![](https://s5.51cto.com/wyfs02/M02/8F/6C/wKioL1jd8XixOTRRAAA62crPwog588.png-wh_500x0-wm_3-wmp_4-s_459237390.png)
4.实体Bean Forum的内容如下
package com.mycompany.demo.bean; import java.util.Set; public class Forum { private int fid; private String name; private Set<ForumPost> forumPosts; public int getFid() { return fid; } public void setFid(int fid) { this.fid = fid; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set<ForumPost> getForumPosts() { return forumPosts; } public void setForumPosts(Set<ForumPost> forumPosts) { this.forumPosts = forumPosts; } }
5.在src目录中创建实体Bean Forum的映射文件Forum.hbm.xml,包名(com.mycompany.demo.bean),如图所示
![](https://s2.51cto.com/wyfs02/M01/8F/6E/wKiom1jd8bDzZfNbAAA9XNEnIHE626.png-wh_500x0-wm_3-wmp_4-s_2964243332.png)
6.映射文件Forum.hbm.xml的内容如下
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <!-- package:指定<class/>所在的包 --> <hibernate-mapping package="com.mycompany.demo.bean"> <!-- name:类名 table:表名 catalog:数据库名称,默认为hibernate.cfg.xml中配置的数据库名称 --> <class name="Forum" table="forum"> <meta attribute="class-description"> This class contains the forum detail. </meta> <!-- name:属性名 colum:列名 --> <id name="fid" type="int" column="fid"> <!-- increment:hibernate维护主键值 identity:数据库自增长 sequence:序列 native:根据不同的数据库选择生成策略 uuid:通过UUID算法生成,实际使用较多 assigned:手工设置 --> <generator class="native"/> </id> <!-- length:字节长度 type:字段类型,支持java和hibernate类型 not-null:非空约束 unique:唯一性约束 --> <property name="name" column="name" /> <set name="forumPosts" cascade="all"> <key column="fid"/> <one-to-many class="ForumPost"/> </set> </class> </hibernate-mapping>
7.在src目录中创建实体Bean ForumPost,包名(com.mycompany.demo.bean),如图所示
![](https://s1.51cto.com/wyfs02/M01/8F/6C/wKioL1jd8ezDzRlDAAA8xFFb7XM914.png-wh_500x0-wm_3-wmp_4-s_1615069622.png)
8.实体Bean ForumPost的内容如下
package com.mycompany.demo.bean; public class ForumPost { private int pid; private String subject; private Forum forum; public int getPid() { return pid; } public void setPid(int pid) { this.pid = pid; } public String getSubject() { return subject; } public void setSubject(String subject) { this.subject = subject; } public Forum getForum() { return forum; } public void setForum(Forum forum) { this.forum = forum; } }
9.在src目录中创建实体Bean ForumPost的映射文件ForumPost.hbm.xml,包名(com.mycompany.demo.bean),如图所示
![](https://s3.51cto.com/wyfs02/M01/8F/6C/wKioL1jd8iHSVEYmAAA8t0MPN3A312.png-wh_500x0-wm_3-wmp_4-s_2905968684.png)
10.映射文件ForumPost.hbm.xml的内容如下
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <!-- package:指定<class/>所在的包 --> <hibernate-mapping package="com.mycompany.demo.bean"> <!-- name:类名 table:表名 catalog:数据库名称,默认为hibernate.cfg.xml中配置的数据库名称 --> <class name="ForumPost" table="forumpost"> <meta attribute="class-description"> This class contains the forumpost detail. </meta> <!-- name:属性名 colum:列名 --> <id name="pid" type="int" column="pid"> <!-- increment:hibernate维护主键值 identity:数据库自增长 sequence:序列 native:根据不同的数据库选择生成策略 uuid:通过UUID算法生成,实际使用较多 assigned:手工设置 --> <generator class="native"/> </id> <!-- length:字节长度 type:字段类型,支持java和hibernate类型 not-null:非空约束 unique:唯一性约束 --> <property name="subject" column="subject" type="string" length="50" not-null="true" unique="false"/> <!-- name:关联属性 column:关联属性在数据库对应的字段 class:关联属性所对应的类型 --> <many-to-one name="forum" class="Forum" column="fid"/> </class> </hibernate-mapping>
11.在src目录中创建工具类 HbnUtil,包名(com.mycompany.demo.util),如图所示
![](https://s2.51cto.com/wyfs02/M01/8F/6C/wKioL1jd8laSpDrNAAAwQGoRfyo093.png-wh_500x0-wm_3-wmp_4-s_1884818975.png)
12.工具类 HbnUtil的内容如下
package com.mycompany.demo.util; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; public class HbnUtil { private static SessionFactory sessionFactory; public static Session getSession(){ if(sessionFactory == null || sessionFactory.isClosed()){ sessionFactory = new Configuration().configure().buildSessionFactory(); } return sessionFactory.getCurrentSession(); } }
13.在src目录中创建Hibernate的配置文件hibernate.cfg.xml,如图所示
![](https://s3.51cto.com/wyfs02/M00/8F/6E/wKiom1jd8oazgYhyAAAsKhqqIlg431.png-wh_500x0-wm_3-wmp_4-s_107239864.png)
14.Hibernate的配置文件hibernate.cfg.xml的内容如下
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-configuration SYSTEM "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- 方言,可以从Hibernate核心jar(hibernate-core-x.x.x.Finall.jar) 文件中的or.hibernate.dialect包中找到相应的类,类的全名就是 --> <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> <!-- 驱动 --> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <!-- 数据库连接地址 --> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/test</property> <!-- 用户名 --> <property name="hibernate.connection.username"> root </property> <!-- 密码 --> <property name="hibernate.connection.password"></property> <!-- create:每次都新创建,如果存在就删除 create-drop:创建新表,sessionFactory关闭,表会删除 update :表字段增加,会同步,字段减少不同步,数据改变会同步修改 --> <property name="hibernate.hbm2ddl.auto">update</property> <!-- 输出sql --> <property name="hibernate.show_sql">true</property> <!-- 格式化sql --> <property name="hibernate.format_sql">true</property> <!-- 事务环境一个线程对一个事务 thread:本地事务环境 jta:分布式事务环境 SpringSessionContext:用于ssh整合 --> <property name="hibernate.current_session_context_class">thread</property> <!-- 使用c3p0数据源 --> <property name="hibernate.connection.provider_class"> org.hibernate.c3p0.internal.C3P0ConnectionProvider</property> <!-- List of XML mapping files --> <mapping resource="com/mycompany/demo/bean/Forum.hbm.xml"/> <mapping resource="com/mycompany/demo/bean/ForumPost.hbm.xml"/> </session-factory> </hibernate-configuration>
15.在项目中创建test目录存储测试文件,文件名称TestApp,包名(com.mycompany.demo.bean),目录结构如图所示
![](https://s4.51cto.com/wyfs02/M01/8F/6C/wKioL1jd8rzQQnOoAAAo8ScEZtI176.png-wh_500x0-wm_3-wmp_4-s_1749370225.png)
16.TestApp测试类的内容如下
package com.mycompany.demo.bean; import java.util.HashSet; import java.util.List; import java.util.Set; import org.hibernate.Session; import org.junit.Before; import org.junit.Test; import com.mycompany.demo.util.HbnUtil; public class TestApp { private Session session; @Before public void init(){ session = HbnUtil.getSession(); } /* * 一对多双向关联-添加 */ @Test public void testOneToManyAdd(){ try { session.beginTransaction(); ForumPost forumPost1 = new ForumPost(); forumPost1.setSubject("A"); ForumPost forumPost2 = new ForumPost(); forumPost2.setSubject("B"); Set<ForumPost> forumPosts = new HashSet<ForumPost>(); forumPosts.add(forumPost1); forumPosts.add(forumPost2); Forum forum = new Forum(); forum.setName("foruma"); forum.setForumPosts(forumPosts); session.save(forum); session.getTransaction().commit(); } catch (Exception e) { session.getTransaction().rollback(); e.printStackTrace(); } } /* * 一对多双向关联-迫切左外连接-HQL */ @Test public void testLeft(){ try { session.beginTransaction(); String hsql = "FROM Forum f LEFT OUTER JOIN FETCH f.forumPosts"; List<Forum> list = session.createQuery(hsql).list(); for (Forum forum : list) { System.out.println(forum.getName()); } session.getTransaction().commit(); } catch (Exception e) { session.getTransaction().rollback(); e.printStackTrace(); } } /* * 一对多双向关联-迫切左外连接-去重复-HQL */ @Test public void testLeftFetch(){ try { session.beginTransaction(); String hsql = "SELECT distinct f FROM Forum f LEFT OUTER JOIN FETCH f.forumPosts"; List<Forum> list = session.createQuery(hsql).list(); for (Forum forum : list) { System.out.println(forum.getName()); } session.getTransaction().commit(); } catch (Exception e) { session.getTransaction().rollback(); e.printStackTrace(); } } }
![](https://s2.51cto.com/wyfs02/M02/8F/6E/wKiom1jd8uWSnC31AABwCKMO5XE263.png-wh_500x0-wm_3-wmp_4-s_1801566037.png)
相关文章推荐
- Hibernate5-一对多双向关联-左外连接-HQL
- [原创]java WEB学习笔记91:Hibernate学习之路-- -HQL 迫切左外连接,左外连接,迫切内连接,内连接,关联级别运行时的检索策略 比较。理论,在于理解
- 无连接表的双向1-n关联,和单项关联
- hql关联和连接查询实例
- 6.4.3:HQL的关联和连接
- Hibernate04(无连接表的双向1-N关联)
- 【SSH进阶之路】【十一】hibernate5 注解映射【3】一对多多对一双向关联
- Hibernate HQL基础 HQL中的连接 迫切内连接
- hibernate5(11)注解映射[3]一对多多对一双向关联
- Hibernate HQL基础 HQL中的连接 迫切左外连接
- Hql 左连接 (left join 非表关联)
- Hibernate5-多对一双向关联-fetch="select",lazy="proxy"
- 有连接表的双向1-1关联
- hibernate_day04_13_HQL多表查询(内连接和迫切内连接)
- Hibernate5-双向关联-多对多(n:n)
- NHibernate实践总结(三)HQL的theta-style join对无关联实体的连接与应用
- Hibernate 学习笔记 之 HQL 内连接和迫切内连接
- 使用hql查询---6.4.3: 关联和连接
- HQL (迫切)左外连接
- hibernate_day04_14_HQL多表查询(左外连接和迫切左外连接)