java Hibernate延迟加载
2008-10-01 17:10
1286 查看
示例数据表:team(班级)、certificate(身份证)、student(学生)
Team.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="edu.dgut.ke.model.Team" table="TEAM" lazy ="true" ><!-- 多对一的延迟加载设置 -->
<id name="id" type="java.lang.String">
<column name="ID" length="32" />
<generator class="uuid.hex" />
</id>
<property name="teamname" type="java.lang.String">
<column name="TEAMNAME" length="32" not-null="true" unique="true" />
</property>
<set name="students" inverse="true" cascade="all" lazy="true" > <!-- 一对多的延迟加载设置 -->
<key>
<column name="TEAMID" length="32" not-null="true" />
</key>
<one-to-many class="edu.dgut.ke.model.Student" />
</set>
</class>
</hibernate-mapping>
Certificate.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="edu.dgut.ke.model.Certificate" table="CERTIFICATE" lazy="true" ><!-- 一对一的延迟加载设置 -->
<id name="id" type="java.lang.String">
<column name="ID" length="32" />
<generator class="uuid">
</generator>
</id>
<property name="describe" type="java.lang.String">
<column name="`DESCRIBE`" length="50" not-null="true" />
</property>
<one-to-one name="student"
class="edu.dgut.ke.model.Student"
constrained="true" ><!-- 一对一的延迟加载设置 -->
</one-to-one>
</class>
</hibernate-mapping>
Student.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="edu.dgut.ke.model.Student" table="STUDENT" lazy="true" >
<id name="id" type="java.lang.String">
<column name="ID" length="32" />
<generator class="uuid.hex" />
</id>
<many-to-one name="certificate"
class="edu.dgut.ke.model.Certificate"
unique="true"
column="cardId"
cascade="all"
>
</many-to-one>
<many-to-one name="team" class="edu.dgut.ke.model.Team">
<column name="TEAMID" length="32" not-null="true" />
</many-to-one>
<property name="studentname" type="java.lang.String">
<column name="STUDENTNAME" length="16" not-null="true" unique="true" />
</property>
</class>
</hibernate-mapping>
注意:对one-to-one 关系进行延迟加载和其他关系相比稍微有些不同。many-to-one 的延迟加载是在配置文件的class 标签
上设置 lazy="true" ,one-to-many 和 many-to-many 的延迟加载是在 set 标签中设置lazy="true"。而one-to-one 不只要在 classs
标签设置 lazy="true",而且要在one-to-one 标签中设置constrained="true" 。
如果不设置constrained="true",则一对一查询使用默认的预先抓取策略(fetch="join")。
Team.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="edu.dgut.ke.model.Team" table="TEAM" lazy ="true" ><!-- 多对一的延迟加载设置 -->
<id name="id" type="java.lang.String">
<column name="ID" length="32" />
<generator class="uuid.hex" />
</id>
<property name="teamname" type="java.lang.String">
<column name="TEAMNAME" length="32" not-null="true" unique="true" />
</property>
<set name="students" inverse="true" cascade="all" lazy="true" > <!-- 一对多的延迟加载设置 -->
<key>
<column name="TEAMID" length="32" not-null="true" />
</key>
<one-to-many class="edu.dgut.ke.model.Student" />
</set>
</class>
</hibernate-mapping>
Certificate.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="edu.dgut.ke.model.Certificate" table="CERTIFICATE" lazy="true" ><!-- 一对一的延迟加载设置 -->
<id name="id" type="java.lang.String">
<column name="ID" length="32" />
<generator class="uuid">
</generator>
</id>
<property name="describe" type="java.lang.String">
<column name="`DESCRIBE`" length="50" not-null="true" />
</property>
<one-to-one name="student"
class="edu.dgut.ke.model.Student"
constrained="true" ><!-- 一对一的延迟加载设置 -->
</one-to-one>
</class>
</hibernate-mapping>
Student.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="edu.dgut.ke.model.Student" table="STUDENT" lazy="true" >
<id name="id" type="java.lang.String">
<column name="ID" length="32" />
<generator class="uuid.hex" />
</id>
<many-to-one name="certificate"
class="edu.dgut.ke.model.Certificate"
unique="true"
column="cardId"
cascade="all"
>
</many-to-one>
<many-to-one name="team" class="edu.dgut.ke.model.Team">
<column name="TEAMID" length="32" not-null="true" />
</many-to-one>
<property name="studentname" type="java.lang.String">
<column name="STUDENTNAME" length="16" not-null="true" unique="true" />
</property>
</class>
</hibernate-mapping>
注意:对one-to-one 关系进行延迟加载和其他关系相比稍微有些不同。many-to-one 的延迟加载是在配置文件的class 标签
上设置 lazy="true" ,one-to-many 和 many-to-many 的延迟加载是在 set 标签中设置lazy="true"。而one-to-one 不只要在 classs
标签设置 lazy="true",而且要在one-to-one 标签中设置constrained="true" 。
如果不设置constrained="true",则一对一查询使用默认的预先抓取策略(fetch="join")。
您可能感兴趣的文章:
相关文章推荐
- 浅析Java的Hibernate框架中的缓存和延迟加载机制
- java Hibernate延迟加载
- java Hibernate延迟加载
- java-hibernate框架4(hibernate多表操作,级联操作与延迟加载,多对多关系操作,hibernate缓存技术)
- Java - 如何理解Hibernate的延迟加载机制?在实际应用中,延迟加载与Session关闭的矛盾是如何处理的?
- 【Java基础】Hibernate的缓存机制以及延迟加载
- Java Eclipse(mac)环境使用maven 加载spring,hibernate 及java的一些配置
- Hibernate延迟加载机制
- Hibernate延迟加载机制
- hibernate的延迟加载
- Hibernate延迟加载实现原理
- Hibernate各类概念-属性延迟加载lazyload
- Hibernate的延迟加载解决大全
- hibernate 延迟加载
- SpringMVC_v02中的总结(web项目、java项目中引入Config.properties,加载hibernate映射文件的配置的区别)
- spring+hibernate避免延迟加载异常
- Java程序中的延迟加载功能使用
- Hibernate延迟加载
- Hibernate性能优化之————延迟加载与抓取策略
- Hibernate延迟加载-by宋迪