#What is JPA?

#Does JPA performs the actual task like access, persist and manage data?

No, JPA is only a specification. The ORM tools like Hibernate, EcpliseLink, iBatis, and TopLink implements the JPA specification and perform these type of tasks.

#How to define composite key in jpa?

Two ways:

1. The IdClass Annotation

public class AccountId implements Serializable {
    private String accountNumber;
 
    private String accountType;
 
    // default constructor
 
    public AccountId(String accountNumber, String accountType) {
        this.accountNumber = accountNumber;
        this.accountType = accountType;
    }
 
    // equals() and hashCode()
}
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And Entity Class:

@Entity
@IdClass(AccountId.class)
public class Account {
    @Id
    private String accountNumber;
 
    @Id
    private String accountType;
 
    // other fields, getters and setters
}
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2. The EmbeddedId Annotation

   ```java
   @Embeddable
   public class BookId implements Serializable {
       private String title;
       private String language;
    
       // default constructor
    
       public BookId(String title, String language) {
           this.title = title;
           this.language = language;
       }
    
       // getters, equals() and hashCode() methods
   }
   ```
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   The Enitty Class:

@Entity
public class Book {
    @EmbeddedId
    private BookId bookId;
 
    // constructors, other fields, getters and setters
}
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#How to call a function in JPA?

• Using native query
• Using JPQL. using function
• Using criteria
  • if you want to use in where clause, CriteriaBuilder.function.

#How will you define ManyToMany relationship in JPA?