What is the purpose of AccessType.FIELD, AccessType.PROPERTY and @Access
java, jpa-2.0, transient
Solution
By default the access type is defined by the place where you put your mapping annotations. If you put them on the field - it will be `AccessType.FIELD`, if you put them on the getters - it will be `AccessType.PROPERTY`.
Sometimes you might want to annotate not fields but properties (e.g. because you want to have some arbitrary logic in the getter or because you prefer it that way.) In such situation you must define a getter and annotate it as `AccessType.PROPERTY`.
As far as I remember, if you specify either `AccessType.FIELD` or `AccessType.PROPERTY` on any of the entity fields / methods you must specify the default behaviour for the whole class. And that's why you need to have `AccessType.FIELD` on the class level (despite that `AccessType.FIELD` is the default value.)
Now, if you wouldn't have `@Transient` on the `phnnumber` field, the JPA would provide you with a 3 columns table:
- id,
- phnnumber,
- getphnnumber.
That's because it would use `AccessType.FIELD` for all of the entity fields (`id` and `phnnumber`) and, at the same time, it'd use `AccessType.PROPERTY` for your getter (`getPhnnumber()`). You'll end with phone number mapped twice in the database.
Therefore, the `@Transient` annotation is required - it means that the entity won't store the value of the field in the underlying storage but the value returned by your getter.
Problem
I just want to know what is the difference between all these annotations. Why are we using these... means they have no effect especially field level and property level. And what is the purpose of using mixed level annotation like: ``` @Entity @Access(AccessType.FIELD) class Employee { // why their is a field level access private int id; // whats the purpose of transient here @Transient private String phnnumber; // why its a property level access @Access(AccessType.property) public String getPhnnumber() { return "1234556"; } } ``` what exactly this class says?