I am attempting to create a one-to-one relationship between a parent and a child object. The child object has a getter and setter in the parent object. The key for the child is the parent key. I'm new so a simple or complex answer that solves the problem would be great.

Mapping:

<class name="User" table="users">
<id name="id" column="user_id">
<generator class="native"/>
</id>
<property name="username"/>
<property name="password"/>
<one-to-one name="userInfo" class="UserPrimaryInfo" cascade="save-update"/>
</class>

<class name="UserPrimaryInfo" table="user_primary_info">
<id name="id" column="user_id">
<generator class="foreign">
<param name="property">id</param>
</generator>
</id>
<property name="name"/>

<one-to-one name="id" class="User" property-ref="id" constrained="true"/>
</class>

Class Code:

public class User {

private Long id;
private String username;
private String password;
private UserPrimaryInfo userInfo;

public User() {}

public Long getId() {
return id;
}

public void setId(Long id) {
this.id = id;
}

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

public UserPrimaryInfo getUserInfo() {
return userInfo;
}

public void setUserInfo(UserPrimaryInfo userInfo) {
this.userInfo = userInfo;
}

}

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import java.io.Serializable;

public class UserPrimaryInfo implements Serializable{
private static final long serialVersionUID = 1L;

private Long id;
private String name;

public Long getId() {
return id;
}

public void setId(Long id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}
}

Adding the line in red causes the following error:

org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property: id
org.hibernate.id.ForeignGenerator.generate(ForeignGenerator.java:68)
org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:122)
org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:117)
org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:535)
org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:527)
org.hibernate.engine.CascadingAction$5.cascade(CascadingAction.java:241)
org.hibernate.engine.Cascade.cascadeToOne(Cascade.java:292)
org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:240)
org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:193)
org.hibernate.engine.Cascade.cascade(Cascade.java:154)
org.hibernate.event.def.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:479)
org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:357)
org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:563)
org.hibernate.impl.SessionImpl.save(SessionImpl.java:551)
org.hibernate.impl.SessionImpl.save(SessionImpl.java:547)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:342)
$Proxy0.save(Unknown Source)
com.locklevels.servlet.utility.Register.doPost(Register.java:58)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.locklevels.filter.utility.Security.doFilter(Security.java:57)