Select max value of numeric CollectionOfElements with Hibernate

Tue, 23 Feb 2010 00:00:00 +0000

Consider a numeric CollectionOfElements held by a class Product such as:

@Entity(name="Product")public class Product {protected Set serialNumbers = new HashSet();@CollectionOfElements@JoinTable(name="product_serialnumbers")public Set getSerialNumbers() { return serialNumbers;}public void setSerialNumbers(Set serialNumbers) { this.serialNumbers = serialNumbers;}}

You can use a NamedQuery to determine the maximum SerialNumber held by any Product like this:

@Entity(name="Product")@NamedQueries ({ @NamedQuery( name = "maxSerialNumber", query = "select max(elements(p.serialNumbers)) as value from Product p" )})public class Product {protected Set serialNumbers = new HashSet();@CollectionOfElements@JoinTable(name="product_serialnumbers")public Set getSerialNumbers() { return serialNumbers;}public void setSerialNumbers(Set serialNumbers) { this.serialNumbers = serialNumbers;}}

Hibernate Annotations - IdentifierGenerationException: attempted to assign id from null one-to-one property

Wed, 18 Feb 2009 00:00:00 +0000

While using Hibernate annotations to implement a @OneToOne relationship where the entities are joined by primary key (@PrimaryKeyJoinColumn) I kept encountering a relatively infamous Exception:

IdentifierGenerationException: attempted to assign id from null one-to-one property

I discovered that my issue could easily be resolved by adding "optional=false" to the dependent side of the relation. Here's a brief summary of the relevant related code.

@Entitypublic class Profile implements Serializable { @OneToOne(mappedBy="profile", optional=false, fetch=FetchType.LAZY) public Hospital getHospital() { return hospital; } @Id @GeneratedValue(generator="foreign") @GenericGenerator(name="foreign", strategy = "foreign", parameters={ @Parameter(name="property", value="hospital") }) public Long getId() { return this.id; }}@Entitypublic class Hospital implements Serializable { @OneToOne(cascade = CascadeType.ALL,fetch=FetchType.LAZY) @PrimaryKeyJoinColumn public Profile getProfile() { return profile; } @Id @GeneratedValue(strategy=GenerationType.AUTO) public Long getId() { return id; }}

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Select max value of numeric CollectionOfElements with Hibernate

Hibernate Annotations - IdentifierGenerationException: attempted to assign id from null one-to-one property