Basic Annotations in Java Persistence API(JPA)

Hi,

Today we will discuss some of the basic JPA annotations.

Annotations :-

• @Table
• @Column
• @Temporal
• @Transient

Lets consider below table -Company

SNO	NAME	MAIL
1	Google	google@gmail.com
2	Yahoo	yahoo@yahoo.com
3	Microsoft	microsoft@live.com

1.@Table :-is used to map your entity java bean with the table

In general your table name and entity bean will have same name at that time there is no need to use @Table

If the Entity bean is different from the table name we map it by using @Table annotation

Example :-

Lets take the above table-Company ,but my entity bean name is named as Organization  then we can use @Table to map them

@Entity

@Table(name="Company")

Public class Organization{.......}

2.@Column :- is used to map an instance variable with a column in a table

If the variable name and database column name is same ,then there is no need to use column

This is similar to @Table

Example :-

Lets take the data base column -Name in the above table

In Entity bean we have companyName.so how to map them?

@Column(name="Name")

Private String companyName;

3.@Temporal :-

• In Java we have java.util.Date and java.util.Calendar classes,if we wnat to persist them into data base we should use @Temporal
• Temporal are set of time based types

Example :-

@Temporal(TemporalType.DATE)

Date currentDate;

In Entity                                                                   Mapped to data base

TemporalType.DATE	Mapped to java.sql.Date
TemporalType.TIME	Mapped to java.sql.Time
TemporalType.TIMESTAMP	Mapped to java.sql.Timestamp

4.@Transient :-

• Attributes that are part of Entity but should not be persisted should be marked as @Transient
• Suppose we have a attribute lastName and should not be persisted to data base,we use@Transient

Example :-

@Transient

private String lastName;

There are many annotations in JPA,each one of them has special functionality which i will discuss in my later posts

Happy Learning

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