Hibernate annotation location in java file

Question

I am following hibernate tutorial from the "Beginning hibernate" book. And I see that the annotations like @Id, @Column are specified above the getXXX() methods.

such as:

@Id
@GeneratedValue
public long getId()
{
    return id;
}

@Column(unique=true)
public String getName()
{
    return name;
}

But not in the attribute definition it self like:

private long id;
private String name;

Is there a link/reference that specifies where the annotation should be placed? and the reasoning behind it. More specifically; how does Hibernate interpret the placement of different annotations and is there a guide to it?

I am talking about the javax.persistence.* annotations

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

I have looked at http://docs.jboss.org/hibernate/annotations/3.5/reference/en/html_single

I am using:

Hibernate 4.2.6.Final 
Windows 8, 32 bit.

score 1 · Accepted Answer · edited May 23 '17 at 12:12

Annotations can be placed on fields or on methods. The option you choose is really a matter of personal preference although I have seen it said to prefer fields over methods.

Personally I prefer field annotations as I find them much easier to work with:

all the persistence mappings are located at the top of your source file.
if you have any any other methods in your Entity not concerned with JPA mappings then these have to be annotated with @Transient which 'just seems wrong'.
when using property access you will have to include a getter even if you don't require one (although this can be be private (or at least protected).
if you want to encapsulte add/remove operations for assocations then it is often desirable to return a wrapped, Unmodifiable collection: you cannot do this if the persistance mappings are on the property.

When scanning your class Hibernate will firstly look for a field or method with the @Id annotation and will then look for other mappings accordingly, viz. if @Id is on a field only other fields will be scanned: any mappings defined on a method will, by default, be ignored and vice versa although this behaviour can be modified using:

@Access(AccessType.PROPERTY)
@Access(AccessType.FIELD)

What is the purpose of AccessType.FIELD, AccessType.PROPERTY and @Access

Hibernate annotation location in java file

1 Answers1