Sample datasheet: Team (Class), certificate (ID), Student (student)
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
-->
<class name= "Edu.dgut.ke.model.Team" table= "Team"
lazy = "true"><!--Multi-pair delay loading settings-->
<id name= "id" type= "java.lang.String" >
<column name= "ID" length= "/>"
<generator class= "Uuid.hex"/>
</id>
<property name= "Teamname" type= "java.lang.String" >
<column name= "Teamname" length= "not-null=" true "unique=" true "/>
</property>
<set name= "Students" inverse= "true" cascade= "all"
lazy= "true"> <!--one-to-many delay-Loading settings-->
<key>
<column name= "Teamid" length= "not-null=" "true"/>
</key>
<one-to-many class= "Edu.dgut.ke.model.Student"/>
</set>
</class>
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
-->
<class name= "edu.dgut.ke.model.Certificate" table= "certificate"
lazy= "true" ><!--a one-to-one delay-loading setting-->
<id name= "id" type= "java.lang.String" >
<column name= "ID" length= "/>"
<generator class= "UUID" >
</generator>
</id>
<property name= "describe" type= "java.lang.String" >
<column name= "' DESCRIBE '" length= "not-null=" true "/>
</property>
<one-to-one name= "Student"
Class= "Edu.dgut.ke.model.Student"
constrained= "true"><!--a one-to-one delay-loading setting-->
</one-to-one>
</class>
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
-->
<class name= "edu.dgut.ke.model.Student" table= "Student"Lazy= "true">
<id name= "id" type= "java.lang.String" >
<column name= "ID" length= "/>"
<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= "not-null=" "true"/>
</many-to-one>
<property name= "Studentname" type= "java.lang.String" >
<column name= "Studentname" length= "not-null=" true "unique=" true "/>
</property>
</class>
Note: Deferred loading of one-to-one relationships is slightly different than other relationships. Many-to-one Delay loading is the class tag in the configuration file
Set lazy= "True" on, One-to-many and Many-to-many delay loading is set lazy= "true" in the set label. and one-to-one not just in classs
The label setting is Lazy= "true" and you want to set constrained= "true" in the One-to-one tab.
If you do not set constrained= "true", the one-to-one query uses the default pre-crawl policy (fetch= "join"). 
