JPA basic object ing Learning

An object class must follow the following requirements:

1. The class must be annotated with javax. Persistence. entity.

2. The class must have a public or protected non-parameter constructor. There can be other constructors.

3. The class cannot be declared as final.

4. The object class can inherit the object class or non-entity class. Non-entity classes can inherit entity classes.

 

Fields that can be persisted in JPA:

• Original Java type
• Java. Lang. String
• Serializable type
• Wrappersof Java primitive types
• Java. Math. biginteger
• Java. Math. bigdecimal
• Java. util. Date
• Java. util. Calendar
• Java. SQL. Date
• Java. SQL. Time
• Java. SQL. Timestamp
• User-definedserializable types
• Byte []
• Byte []
• Char []
• Character []
• Enumerated types
• Other entity or entity set
• Embedded class

 

Basic Object ing

@ Entity

@ Secondarytable (name = "salary ")

Public class employee implements serializable {

@ ID

@ Column (name = "emp_id ")

@ Generatedvalue (Strategy = generationtype.Sequence)

Private long ID;

 

@ Basic

@ Version

Private long version;

 

@ Basic

@ Column (name = "f_name ")

Private string firstname;

 

@ Basic

@ Column (name = "l_name ")

Private string lastname;

 

@ Basic

@ Column (name = "gender ")

@ Enumerated (enumtype.String)

Private gender Gender = gender.Male;

 

@ Column (Table = "salary ")

Private double salary;

......

}

 

 

 

Abstract entity Annotation

@ Entity

Public abstract class employee {

@ ID

Protectedinteger employeeid;

...

}

@ Entity

Public class fulltimeemployee extends employee {

Protectedinteger salary;

...

}

@ Entity

Public class parttimeemployee extends employee {

Protected floathourlywage;

}

 

 

Super class ing

 

 
@ Mappedsuperclass
 

Public class employee {
 

 
@ ID
 

 
Protected integer employeeid;
 

 
...
 

 
}
 

 
@ Entity
 

 
Public class fulltimeemployee extends employee {
 

 
Protected integer salary;
 

...
 

 
}
 

 
@ Entity
 

 
Public class parttimeemployee extends employee {
 

 
Protected float hourlywage;
 

 
...
 

 
}
 

 

Embedded entity class ing

@ Embeddable

// Embed the content into other entities and share the identity with them

Public class employmentperiod {

// @ Temporal must be a field of the Java. util. Date and Java. util. Calendar type,

// And it can only be for such type fields or attention encoding.

@ Temporal (temporaltype.Date)

Private calendar startdate;

@ Temporal (temporaltype.Date)

Private calendar enddate;

... ...

}

Public classemployee implements serializable {

... ...

@ Embedded

@ Attributeoverrides ({

@ Attributeoverride (name = "startdate", column = @ column (name = "start_date ")),

@ Attributeoverride (name = "enddate", column = @ column (name = "end_date "))})

Private employmentperiod period;

... ...

}