Can we add annotations to the decelerations instead to the getter methods.
I'm used to this
#Column(name="Part_ID")
public Long getPartId() {
return partId;
}
Can we use it like this
#Column(name="Part_ID")
private Long partId;
Thanks all.
Ravi
Yes, you can. See section 2.2.2.2 of the Hibernate annotations documentation:
By default the access type of a class
hierarchy is defined by the position
of the #Id or #EmbeddedId
annotations. If these annotations are
on a field, then only fields are
considered for persistence and the
state is accessed via the field. If
there annotations are on a getter,
then only the getters are considered
for persistence and the state is
accessed via the getter/setter. That
works well in practice and is the
recommended approach.
So if you put your #Id on a field, then Hibernate will look at annotations on the fields for the other properties. If you put #Id on a getter, then Hibernate will look at annotations on the other getters.
Related
This question already has answers here:
Hibernate Annotations - Which is better, field or property access?
(25 answers)
Hibernate/JPA - annotating bean methods vs fields [duplicate]
(5 answers)
Closed 5 years ago.
I am new to Spring Boot and JPA in general. I've seen examples of adding JPA annotations on field declarations such as this:
#Entity
public class Fizz {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
// other fields
public Fizz(Long id) {
super();
setId(id);
}
// setter defined here
public Long getId() {
return this.id;
}
}
...as well as examples putting the same annotations on the getters like this:
#Entity
public class Fizz {
private Long id;
// other fields
public Fizz(Long id) {
super();
setId(id);
}
// setter defined here
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
return this.id;
}
}
I'm wondering if they are semantically equivalent or if there are different use cases where you'd choose one over the other. I ask because I'm actually writing my Spring Boot/JPA app in Groovy where you typically don't define getters:
#Canonical
#Entity
class Fizz {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
Long id
}
By default, JPA providers access the values of entity fields and map those fields to database columns
using the entity’s JavaBean property accessor (getter) and mutator (setter) methods. As such, the
names and types of the private fields in an entity do not matter to JPA. Instead, JPA looks at only
the names and return types of the JavaBean property accessors. You can alter this using the #javax.persistence.Access annotation, which enables you to explicitly specify the access methodology
that the JPA provider should employ.
#Entity
#Access(AccessType.FIELD)
public class SomeEntity implements Serializable
{
...
}
The available options for the AccessType enum are PROPERTY (the default) and FIELD. With
PROPERTY, the provider gets and sets field values using the JavaBean property methods. FIELD makes
the provider get and set field values using the instance fields. As a best practice, you should just stick
to the default and use JavaBean properties unless you have a compelling reason to do otherwise.
You
can put these property annotations on either the private fields or the public accessor methods. If
you use AccessType.PROPERTY (default) and annotate the private fields instead of the JavaBean
accessors, the field names must match the JavaBean property names. However, the names do not
have to match if you annotate the JavaBean accessors. Likewise, if you use AccessType.FIELD and
annotate the JavaBean accessors instead of the fields, the field names must also match the JavaBean
property names. In this case, they do not have to match if you annotate the fields. It’s best to just
be consistent and annotate the JavaBean accessors for AccessType.PROPERTY and the fields for
AccessType.FIELD.
You should never mix JPA property annotations and JPA field annotations
in the same entity. Doing so results in unspecified behavior and is very
likely to cause errors.
in JPA 2.0 which is the difference between annotating a field and annotating a method (typically a getter)?
Example with field annotation
#Entity
public class MainEntity {
#Id
private Long id
#OneToMany
private RelatedEntity relatedEntity
//getters and setters and possible other methods
...
}
Example with method annotation
#Entity
public class MainEntity {
#Id
private Long id;
private RelatedEntity relatedEntity
//getters and setters and possible other methods
#OneToMany
public RelatedEntity getRelatedEntity(){
return relatedEntity
}
//other methods etc
...
}
With JPA you can use both methods to map the columns of your table in your entity class; fields/methods access doesn't change anything from a schema generation point of view nor in terms of translated queries. Generally speaking field annotation is cleaner (frameworks like Spring encourages it), methods annotation can grant you more flexibility (like with inheriting from an abstract entity class).
Please notice that in your second example there is an error:
#Entity
public class MainEntity {
private Long id;
private RelatedEntity relatedEntity
//getters and setters and possible other methods
#Id
public Long getId() {
return id;
}
#OneToMany
public RelatedEntity getRelatedEntity(){
return relatedEntity
}
//other methods etc
...
}
From user point of view there is no difference until it is consistent, but using annotation in different places change behavior of JPA provider (hibernate, EclipseLink, etc.).
Place where annotation were set gives JPA provider information about which access type you what to use. If you mix that setting annotations in both places then provider picks one and ignores rest. In example in your second listing hibernate will ignore #Id because you have #OneToMany on method and that means you prefer to use AccessType.PROPERTY.
Of course sometimes we don't want to use property access, because we have some extra methods that provides some logic and match to naming convention. Then we should use AccessType.FIELD.
In project you should use consistent style. Mixed style is valid, but you need to define #Access for almost all elements in your POJO.
I am using hibernate 4.1.9.
My code is
#Transient
private String ldapIdTemp;
package is
import javax.persistence.Transient;
Still in hibernate query, it is not working and putting the attribute in the query.
part of query snippet (assetasset0_.ldapIdTemp as ldapIdTemp16_0_, )
I am not sure what I am doing wrong.
Can you try creating setter and getter for the field and annotate the get method with #Transient, as follows:
private String ldapIdTemp;
#Transient
public String getLdapIdTemp() {
return ldapIdTemp;
}
public void setLdapIdTemp(String ldapIdTemp) {
this.ldapIdTemp = ldapIdTemp;
}
Much depends on how you "integrated" this field in your Entity or class hierarchy. Moreover, field vs. property-access could cause an issue for your setting. See this post for a detailed explanation.
In your case, I could imagine that you either:
mixed field and property-access in your entity inheritance strategy
use XML-based configuration for Hibernate in your application.
In both cases the JPA 2.0/2.1 specification clearly states in Section 2.3.1:
It is an error if a default access type cannot be determined and an access type is not explicitly specified
by means of annotations or the XML descriptor. The behavior of applications that mix the placement of
annotations on fields and properties within an entity hierarchy without explicitly specifying the
Access annotation is undefined.
Please check that your persistent Entity classes have either field OR property-based annotations.
Check the #Transient annotation fully qualified name.
It can be from either,
org.springframework.data.annotation.Transient or javax.persistence.Transient.
Try to use javax.persistence.Transient.
I have one Pojo class in which I create one field which is not mapped with DataBase Table.
So i have to declare the field Declaration and setter and getter method #Transient, otherwise it would have shown an error.
#Transient
private String docHistoryString="";
#Transient
public String getDocHistoryString() {
return docHistoryString;
}
#Transient
public void setDocHistoryString(String docHistoryString) {
this.docHistoryString = docHistoryString;
}
Now, my problem is in the controller. I have set some value in this transient field but when I try to access this variable using EL in view(JSP) it is not giving value. I think this is becouse I used the #transient annotation in get method.
All Hibernate annotations, including #Transient must be applied according to access type. By default it will be the same way as #Id applied. That is if you place #Id on a field you must apply #Transient to the field. And if you apply #Id to getter method, you must apply #Transient method. Setter methods are always ignored.
It can be customized, though (per documentation), so make sure that someone didn't do something strange with access types.
According to this, it should be enough to declare the field/property
http://download.oracle.com/javaee/5/api/javax/persistence/Transient.html
Have you tried with just annotating the field/property? For further Help you have to post some more code snippets.
I have a class to map a table for using hibernate. There are some variable I want to ignore for mapping to use as constant. And I want to load constant value from properties so I code it like this:
#Transient
#Value("${something.value}")
private int MY_VALUE;
But, the value of MY_VALUE is always set to 0. Can't I use #Transient annotation with #Value annotation? Or I missed something else?
Those two annotations belong in different domains.
#Transient belongs to an entity, while #Value belongs to Spring Beans. Entities are managed by JPA / Hibernate, Spring Beans are managed by Spring. It is not a good idea to mix the two.
You could achieve this by using the #Configurable annotation and AspectJ compilation or Load Time Weaving, but I would strongly advise against such a hack. Use a Spring Bean to hold a #Value, not an entity!
You use #Value to specify a property value to load when Spring creates the bean.
However, if you are using Hibernate to load data from a database, Spring is not instantiating these classes for you. So your #Value annotation has no effect.
I would suggest injecting the #Value into the DAO that loads these entities from Hibernate, something like
public class FooDao {
#Value("...")
private int yourConfiguredValue;
public getFoo() {
Foo foo = sessionFactory.getCurrentSession().get(...);
foo.setYourValue(yourConfiguredValue);
return foo;
}
}
In my scenario I have a class Employee which has relation with class Organization.
I don't want to serialize a whole dependent object(Organization), rather serialize a single parameter of organization(e.g. orgID).
I tried following:
#Transient
#value("#{target.orgId.id}")
private UUID org_Id;
but it didnt work. So i used a simple getter mehtod instead of a field variable as follows:
#JsonIgnore
#ManyToOne(fetch = FetchType.LAZY, optional = false)
#JoinColumn(name = "orgID")
private Organization orgId;
#JsonProperty("orgId")
public UUID getOrg_ID() {
return orgId.getId();
}
it worked and i got simple orgId field in response serialized by Jackson.
It seems Jackson work with getters without considering a field variable is declared or not corresponding to that getter method.