Hi guys,

We have an old database running in MySQL. I want to Am pulling my hair with this error:
net.sf.hibernate.MappingException: composite-id class must override equals(): ontvmall.com.tw.hibernate.HProducts

The DB looks like this (PRODUCT_IMAGES PK is a child):

CREATE TABLE PRODUCT_IMAGES(
Product_ID INT NOT NULL,
Icon BLOB NOT NULL,
Icon_Name VARCHAR(20) NOT NULL,
VOD_Background BLOB NOT NULL,
VOD_Background_Name VARCHAR(20),
VOD_Substitute BLOB,
VOD_Substitute_Name VARCHAR(20),
More_Info BLOB,
More_Info_Name VARCHAR(20),
PRIMARY KEY (Product_ID)
)TYPE=INNODB;


CREATE TABLE PRODUCTS(
Product_ID INT NOT NULL,
Product_Code VARCHAR(15) NOT NULL,
Long_Name VARCHAR(50),
Short_Name VARCHAR(10),
VOD_Parameter VARCHAR(50),
Product_Count INT,
Initial_Price DOUBLE NOT NULL,
Minimum_Bid DOUBLE,
End_Date DATETIME NOT NULL,
Sell_Price DOUBLE,
PRIMARY KEY (Product_ID)
)TYPE=INNODB;

and the classes as follows:

public class HProductImages{
private Integer id;
private Blob icon;
private Blob vodBackground;
private Blob vodSubstitute;
private Blob info;
private String iconName;
private String vodBackgroundName;
private String vodSubstituteName;
private String infoName;
private HProducts product;
}

public class HProducts implements Serializable{
private Integer id;
private String productCode;
private String longName;
private String shortName;
private String vodParameter;
private Integer productCount;
private Double initialPrice;
private Double minimumBid;
private Date endDate;
private Double sellPrice;
}

And HProductImages.hbm.xml has this:
<class name="HProductImages" table="PRODUCT_IMAGES">
<composite-id name="product" class="HProducts" >
<key-property name="id" column="Product_ID" type="java.lang.Integer"/>
</composite-id>
<!-- property goes here -->
...
</class>

Can anyone please shed light on what this error is?

Thank you.[/quote]

Why not just use the PK id for HProductImages, instead of that composite-id?

The error "composite-id class must override equals()" hints pretty strongly that you need to override equals for that class, if you use a composite-id. Did you try that?

Well here are the reasons:
1. the key for PRODUCT_IMAGE isnt auto-generated. Instead the key is a Foreign key from PRODUCTS table's Primary Key. In every entry of the PRODUCT table, there is an entry in the PRODUCT_IMAGE.
2. True I could create an ordinary mapping and have the PK defined by me, but that wont be a good design. I want to maintain relationship.

I just want to know if composite-id is the correct way to map this. If it is, then i would like to know what's wrong with it.

Thank you.

As the error states, you'll need to override equals() to take this into account if you do this.

I still don't think composite id is correct for this case. The id is not a method for maintaining a relationship, but for assigning tuple identity. Use a constraint to seal the relationship.
Sounds like a standard one-to-one property instead:
http://www.hibernate.org/hib_docs/reference/en/html/mapping.html#mapping-declaration-onetoone

Thanks man it works! May I post this for other people's reference

For Product Class:

public class Products implements Serializable{
private java.lang.Integer productId;
private ProductImages productImages;
private java.lang.Double sellPrice;
//etc
}


<class name="Products" table="PRODUCTS">
<id name="productId" column="Product_ID" type="java.lang.Integer">
<generator class="increment"/>
</id>
<one-to-one name="productImages" class="ProductImages" cascade="save-update"/>
...all property here
</class>

For ProductImages Class:

public class ProductImages {

private Products products;
private Integer productId;
private String iconName;

<class name="ProductImages" table="PRODUCT_IMAGES">
<id name="productId" column="Product_ID" type="java.lang.Integer">
<generator class="foreign">
<param name="property">products</param>
</generator>
</id>

<one-to-one name="products" class="Products" constrained="true"/>
...all property here
</class>