Hibernate Version: 3.3.0

When I merge an object which contains a collection of objects which are immutable (mutable=false) I get an exception:

Caused by: java.lang.Throwable: Merged entity does not have status set to MANAGED; EntityEntry[ca.gc.csc_scc.model.bean.offender.purchase.Tax#10](READ_ONLY) status=READ_ONLY
at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:97)
at org.hibernate.impl.SessionImpl.fireMerge(SessionImpl.java:704)
at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:688)
at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:692)
at ca.gc.csc_scc.model.impl.dao.OffenderEffectDAO.savePurchaseOrder(OffenderEffectDAO.java:792)
at ca.gc.csc_scc.model.impl.service.OffenderEffectServiceImpl.savePurchaseOrder(OffenderEffectServiceImpl.java:445)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at ca.gc.csc_scc.model.util.ServiceFacadeInvocationHandler.invoke(ServiceFacadeInvocationHandler.java:118)
... 27 more


Here are the mapping files (I removed some <property> values to keep the size down).

Here is mapping for the object which is merged (bolded item matches second mapping file):

<?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">
<hibernate-mapping
package="ca.gc.csc_scc.model.bean.offender.purchase"
default-lazy="false">
<class name="POItem" table="opp_purchase_order_line_item" select-before-update="true" dynamic-update="true" optimistic-lock="version">
<id name = "id"
column = "line_item_id"
type = "ca.gc.csc_scc.model.impl.dao.hibernate.type.StringNumber" >
<generator class="native">
<param name="sequence">sq_opol</param>
</generator>
</id>
<version name="entityVersion" column="record_version" type="long"/>
<property name="modSigID" access="field" type="string" length="10" column="changed_by"/>
<component
name = "securitySignature"
class = "ca.gc.csc_scc.model.bean.UserSignature">
<property
name = "assignmentId"
column = "security_entered_by"
type = "string"
length = "10" />
<property
name = "date"
column = "security_entered_date"
type = "calendar" />
</component>
<idbag name="taxes" cascade="all" table="opp_item_sales_tax">
<collection-id type="long" column="item_sales_tax_id">
<generator class="sequence">
<param name="sequence">sq_oist</param>
</generator>
</collection-id>
<key column="line_item_id"/>
<many-to-many class="Tax" column="sales_tax_id"/>
</idbag>
</class>
</hibernate-mapping>


Here is the immutable object mapping:

<?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">
<hibernate-mapping
package="ca.gc.csc_scc.model.bean.offender.purchase"
default-lazy="false">
<class name="Tax" table="sales_tax" mutable="false">
<id name = "id"
column = "sales_tax_id"
type = "ca.gc.csc_scc.model.impl.dao.hibernate.type.StringNumber" >
<generator class="assigned"/>
</id>
<property
name = "taxRate"
column = "tax_rate"
type = "big_decimal" />
</class>
</hibernate-mapping>