Hello everyone! I'm having a pretty hard time in a not-so-usual (I guess?) scenario, that I'd like to ask your expertise for your enlightment. This one is kind of tricky, and I have looked up in, pretty much, all related questions in SO and forums, but I couldn't find an definitive answer. Let me get you the context: The scenario is the following: Table: Product Table: ProductCategory Table: Category----------------| ----------------| |---------------| | partner_Id | | product_Id | | partner_Id | | product_Id | | category_Id | | category_Id | |---------------| | partner_Id | |---------------|| name | |---------------| | name || description | | extra_fields | | description || extra_fields | | | | extra_fields ||---------------| |---------------| |---------------| And here are the classes: Product.java @Entity@Table(name = "EC_PRODUCT")public class Product implements Serializable { private ProductPK productPK; private List<ProductCategory> productCategories; // Other Atributes @Embeddable public static class ProductPK implements Serializable { private String partnerId; private String productId; public String getPartnerId() { return this.partnerId; } public void setPartnerId(String partnerId) { this.partnerId = partnerId; } public String getProductId() { return this.productId; } public void setProductId(String productId) { this.productId = productId; } } public Product() { this.productPK = new ProductPK(); this.productCategories = new ArrayList<ProductCategory>(); } @Id @AttributeOverrides({ @AttributeOverride(name = "partnerId", column = @Column(name = "partner_Id")), @AttributeOverride(name = "productId", column = @Column(name = "product_Id")) }) public ProductPK getProductPK() { return this.productPK; } public void setProductPK(ProductPK productPK) { this.productPK = productPK; } /* ** Other Getters and Setters */} Category.java @Entity@Table(name = "EC_CATEGORY")public class Category implements Serializable { private CategoryPK categoryPK = new CategoryPK(); private List<ProductCategory> productCategories; // Other Attributes @Embeddable public static class CategoryPK implements Serializable { private String partnerId; private String categoryId; public String getPartnerId() { return this.partnerId; } public void setPartnerId(String partnerId) { this.partnerId = partnerId; } public String getCategoryId() { return this.categoryId; } public void setCategoryId(String categoryId) { this.categoryId = categoryId; } } @Id @AttributeOverrides({ @AttributeOverride(name = "partner_Id", column = @Column(name = "partner_id")), @AttributeOverride(name = "category_Id", column = @Column(name = "category_cod")) }) public CategoryPK getCategoryPK() { return this.categoryPK; } public void setCategoryPK(CategoryPK productPK) { this.categoryPK = productPK; } @OneToMany(mappedBy = "category", cascade = CascadeType.ALL) public List<ProductCategory> getProductCategories() { return this.productCategories; } public void setProductCategories(List<ProductCategory> productCategories) { this.productCategories = productCategories; } /* ** Other Getters and Setters */ } ProductCategory.java @Entity@Table(name = "EC_PRODUCT_CATEGORY")public class ProductCategory implements Serializable { private Product product = new Product(); private Category category = new Category(); public ProductCategory() { } public ProductCategory(Product product, Category category) { this.setProduct(product); this.setCategory(category); } @Id @ManyToOne @JoinColumns({@JoinColumn(name = "product_Id"), @JoinColumn(name = "partner_Id") }) public Product getProduct() { return product; } public void setProduct(Product product) { this.product = product; } @Id @ManyToOne @JoinColumns({@JoinColumn(name = "category_Id"), @JoinColumn(name = "partner_Id")}) public Category getCategory() { return category; } public void setCategory(Category category) { this.category = category; } } And here's a Snippet of what my Main class does: public class App { public static void main(String[] args) { // Sets up the Product Product product = new Product(); product.getProductPK().setPartnerId("1"); product.getProductPK().setProductId("99"); // Sets up the Category Category category = new Category(); category.getCategoryPK().setPartnerId("1"); category.getCategoryPK().setCategoryId("10"); // Sets up the ProductCategory product.getProductCategories().add(new ProductCategory(product, category)); // Data persistence w/ Hibernate Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); session.save(product) session.getTransaction().commit(); session.flush(); session.close(); } } And that's the stacktrace (I formated a bit to make it more legible): (...)Hibernate: select productcat_.product_id, productcat_.partner_id, productcat_.category_id, productcat_.partner_id from ECOM_STAGE_REL_CATEG_PROD productcat_ where productcat_.product_id=? and productcat_.partner_id=? and productcat_.category_id=? and productcat_.partner_id=? Aug 26, 2015 9:53:25 PM org.hibernate.engine.jdbc.batch.internal.AbstractBatchImpl release INFO: HHH000010: On release of batch it still contained JDBC statements Aug 26, 2015 9:53:25 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions WARN: SQL Error: 0, SQLState: S1009 Aug 26, 2015 9:53:25 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions ERROR: Parameter index out of range (4 > number of parameters, which is 3). org.hibernate.exception.GenericJDBCException: could not insert: [obscured_package_name.model.ProductCategory] Hibernate: insert into EC_PRODUCT_CATEGORY (product_id, partner_id, category_id) values (?, ?, ?) at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)(...) *Please notice that the 2nd and 4th line of the WHERE clause (in the SELECT statement) are the same* It's trying to get the partner_id for the Product (since its ProductPK is: productId, partnerId) AND the partner_id for the Category (since its CategoryPK is: categoryId, partnerId) It doesn't fail for the SELECT statement, because SQL-wise, it doesn't matter (but it does when it's doing an INSERT). And notice this at the end of the stack trace: ERROR: Parameter index out of range (4 > number of parameters, which is 3). org.hibernate.exception.GenericJDBCException: could not insert: [obscured_package_name.model.ProductCategory] Hibernate: insert into EC_PRODUCT_CATEGORY(product_id, partner_id, category_id) values (?, ?, ?) at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54) It says It's trying to insert 4 FIELDs in a table that expects 3. (The only reason the INSERT statement has 3 fields -- which is supposedly correct -- is because "partner_id" is a common name between the Product and Category). IF, and ONLY IF, in ProductCategory.java, I were to rewrite the @JoinColumns in the getters, like this: @Id @ManyToOne @JoinColumns({@JoinColumn(name = "product_Id"), @JoinColumn(name = "PRODUCT_partner_Id") }) public Product getProduct() { return product; } @Id @ManyToOne @JoinColumns({@JoinColumn(name = "category_Id"), @JoinColumn(name = "CATEGORY_partner_Id")}) public Category getCategory() { return category; } The error would be like this: Hibernate: insert into EC_PRODUCT_CATEGORY(product_id, PRODUCT_partner_id, category_id, CATEGORY_partner_id) values (?, ?, ?, ?) at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54) Did I make it clear ? I tried to provide as much detail as possible, since it's tricky to understand. But I truly have searched everything I could and didn't come up with a solution. Please, may I have your advice/expertise on how to solve this ? Thank you very much in advance!