I am using hibernate for entity persistance in application along with spring mvc I have a multiple #Transient fields in an entity in a application is there a way to tell Json parser to automatically ignore all #Transient annotated fields in entity without the need to use #JsonIgnore or #JsonIgnoreProperties
#Transient is to indicate the field is not persistent. #JsonIgnore is to indicate the field is to be ignored by the serialization/deserialization processor, they have very different meanings.
One option is have Json processor base serial/deserialization from available fields (vs getter/setters), then mark your #Transient fields with additional transient keyword. If you have getters/setters, you'll also need to add appropriate visibility rules. For example, this will serialize all fields not marked with transient.
#JsonAutoDetect(fieldVisibility=Visibility.ANY, getterVisibility=Visibility.NONE, setterVisibility = Visibility.NONE)
I have found a better way instead of using #jsonignore to the fields in an entity
on child class use JsonBackreference and on parent use JsonManagedReference
For more information go through this blog post
Related
I have some boolean fields in my JPA entities which are annotated in the following way:
#Column(length = 1)
#Type(type = "yes_no")
private final boolean myField;
Is it possible to create a combo-annotation (e. g. MyAnnotation) which combines both of this annotations?
#MyAnnotation
private final boolean myField;
How?
Obviously you could create an annotation that provides the equivalent of multiple other annotations.
Equally obviously no JPA provider will support it, since they will check for the javax.persistence annotations only (not that #Type is javax.persistence).
What you want is similar to CDI stereotypes - unfortunately, JPA does not support such a concept, therefore you must copy recurring annotations all over.
If you can afford to wrap your field into an object, you may mark it as #Embeddable and put your field into it - the annotations on that field will be copied wherever you embed that object into an entity. You may extend the annotations using #AnnotationOverrides. Obviously, the drawback of such solution is additional complexity when accessing the field in your entity.
#JsonBackReference
ObjectProperty<MyObject> myObjectProperty = new SimpleObjectProperty();
When I use this code, Jackson still tries to recursively go through myObjectProperty. Jackson has support for Collections and some other types, but how can I add support for ObjectProperty?
I was considering subclassing SimpleObjectProperty and annotating value with #JsonBackReference, but I don't have access to value as it is private.
I just had to annotate the getter for myObectProperty with #JsonBackReference.
I saw this #javax.persistence.Access(javax.persistence.AccessType.FIELD) for a Entity.
What does this mean? Is it really required to declare #Access this for a entity.
No, it's not required, but can be useful. #Access is used to specify how JPA must access (get and set) mapped properties of the entity. If access type is set to FIELD, the values will directly be read/set on the field, bypassing getters and setters. If set to PROPERTY, the getters and setters are used to access the field value.
By default (at least with Hibernate), FIELD is used if the #Id annotation is on a field, and PROPERTY is used if the #Id annotation is on a getter.
why the jpa annotations are applied on field or on getter methods. if i try to apply the annotations on setter method then compiler generate the error. because compiler ignore the annotation on setter method. what is the reason behind them?
This is is how it's specified. Per JPA Specification:
When field-based access is used, the object/relational mapping annotations for the entity class annotate the instance variables, and the persistence provider runtime accesses instance variables directly. All non-transient instance variables that are not annotated with the Transient annotation are persistent.
When property-based access is used, the object/relational mapping annotations for the entity class annotate the getter property accessors[7], and the persistence provider runtime accesses persistent state via the property accessor methods. All properties not annotated with the Transient annotation are persistent.
Mapping annotations must not be applied to fields or properties that are transient or Transient.
You have two options. Either use field level annotation or property (getter method) annotation. There is no third option.
Because for an Object, there r only two ways to access the properties, fields directly or getter indirectly.
for entity bean, annotation specifys how to map properties to the columns, and JPA needs to access these status of entity, so I guess this is the most intuitional way to put annotations on fields directly or getter.
When we put annotations on getters, JPA access properties via getters.There is no need to put annotations on setters.
I am using hibernate annotations. How to add methods to POJO object? For example i have "getChildNodes" method, associated with database, but i want also add recursive method "getAllChildNodes". I get "org.hibernate.PropertyNotFoundException: Could not find a setter for property progress in class" exception when i do it.
If I interpret this as "how do I add a method that is NOT related to persistence" then you need to use the #Transient annotation on the getAllChildNodes() method
There are two ways of defining the structure of your entity.
using annotations on the instance variables of your entity or
using annotations on the getter methods of your entity
When using the annotations on getter methods, Hibernate assumes that every getXxx (and isXxx for boolean types) represents definition of a persistent property. And this holds even if that particular getter does not contain any annotations, as happens in your case.
Hibernate also expects to find a matching setter method for each persistent property. And in your case that is what's missing and causes the exception.
You can solve this problem by declaring your custom getter as #Transient that says this getter does not represent a persistent property. Another way would be to convert the entity to use annotations on the instance variables. The latter would be my personal choice.
Open up the .java file and write a method named getAllChildNodes().
Hibernate doesn't write code for you, it maps fields in your database to your code. That's all. If you want to have extra logic in your domain/model classes besides the normal getters and setters for your properties, you'll have to add them yourself.