Duplicate collection role mapping

[Ashish Yannam]

Hi,

I am trying to map two tables having one-many relationship.

<hibernate-mapping>
    <class name="com.example.hibernate.Customer" table="customer" schema="public">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="sequence">
            <param name="sequence">book_id_seq</param>
            </generator>
        </id>
        <set name="cooks" inverse="false" >
<key>
<column name="customer_fk"></column>
</key>
<one-to-many class="Book" />
</set>
        <property name="firstname" type="java.lang.String">
            <column name="firstname" />
        </property>
        <property name="lastname" type="java.lang.String">
            <column name="lastname" />
        </property>
        <property name="age" type="java.lang.Integer">
            <column name="age" />
        </property>
    </class>
</hibernate-mapping>

This is my mapping file for the "one side";

I am getting the following exception

 Caused by: org.hibernate.DuplicateMappingException: Duplicate collection role mapping com.example.hibernate.Customer.cooks
at org.hibernate.cfg.Mappings.addCollection(Mappings.java:124)
at org.hibernate.cfg.HbmBinder.createClassProperties(HbmBinder.java:2030)
at org.hibernate.cfg.HbmBinder.createClassProperties(HbmBinder.java:2005)
at org.hibernate.cfg.HbmBinder.bindRootPersistentClassCommonValues(HbmBinder.java:368)
at org.hibernate.cfg.HbmBinder.bindRootClass(HbmBinder.java:282)
at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:153)
at org.hibernate.cfg.Configuration.add(Configuration.java:386)
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:427)
at org.hibernate.cfg.Configuration.addResource(Configuration.java:482)
... 9 more
Exception in thread "main" java.lang.NullPointerException
at com.example.hibernate.test.LibraryTest.main(LibraryTest.java:34)
   

can anyone please help

[Jaikiran Pai]

This might be one possible reason.

[Ashish Yannam]

I am building a standalone application using eclipse.

can you help me with that.

[Cameron Wallace McKenzie]

My guess is that you have used the Cooks class twice somewhere, or even more likely, you have two mapping files for the Cooks class. Check for duplicate entries in your hibernate configuration file.

Show us your mappings element of the configuration file if you're still having problems.

-Cameron McKenzie

[Ashish Yannam]

I am putting up the mapping files here for Customer and the Book
I want a one to many relationship between the Customer and Book.

 <hibernate-mapping>
    <class name="com.example.hibernate.Customer" table="customer" schema="public">
       <id name="id" column="id" type="java.lang.Integer">
<generator class="sequence">
<param name="sequence">customer_id_seq</param>
</generator>
</id>
        <property name="firstname" type="java.lang.String">
            <column name="firstname" />
        </property>
        <property name="lastname" type="java.lang.String">
            <column name="lastname" />
        </property>
        <property name="age" type="java.lang.Integer">
            <column name="age" />
        </property>
         // getting the error if I include this set tag
        <set name="books" inverse="false" >
<key column="id" />
<column name="customer_fk"></column>
</key> 
<one-to-many class="Book" /> 
</set> 
        
    </class>
</hibernate-mapping>   
 
<hibernate-mapping>
    <class name="com.example.hibernate.Book" table="book" schema="public">
        <id name="id" column="id" type="java.lang.Integer">
<generator class="sequence">
<param name="sequence">book_id_seq</param>
</generator>
</id>
        <property name="title" type="java.lang.String">
            <column name="title" />
        </property>
        <property name="author" type="java.lang.String">
            <column name="author" />
        </property>
        <property name="borrowallowed" type="java.lang.Boolean">
            <column name="borrowallowed" not-null="true" />
        </property>
        <property name="customerFk" type="java.lang.Integer">
            <column name="customer_fk" not-null="false" />
        </property>
       
    </class>
</hibernate-mapping>

[Cameron Wallace McKenzie]

Are we talking about cooks or books?

-Cameron McKenzie

[Ashish Yannam]

It was an typing mistake there.
The name of the set is books, and am having getter and setter methods in the Customer class as

 getBooks()and setBooks().