README.md

Spring DataJPA

Spring data JPA will do operations with the connected DB
and do the ORM operations.

1. ORM AND JPA

- ORM: Object Relation Mapping 
- IN ORM : Class is Table , and vars. will be column filed and var type str, int will be column type 
- By using the ORM Tool we map these thing  in the table ex : Hibernet 

- JPA : if library is changed from Hibernet to other library the specification like JPA (java Persistent API)
- will make easy to implements with other ORM library 

2. Creating Table and Inserting Data using the JPA

2.1 Connecting to DB using JPA repository

• Student Model
• Repo Class
• DB Connection Config.

// setting up the student Model 

@Component
@Scope("prototype")

@Entity
public class Student {

    @Id
    private int rollno;
    private String name;
    private int marks;
}
    
// getter setters     
    

2.2 Fetching all objects

  System.out.println(repo.findAll());

          System.out.println(repo.findAll());

// find By ID
          System.out.println(repo.findById(101));

  // Student sfind = repo.findById(104);  // give the error of null pointer
  // Optional<Student> sfind = repo.findById(104);
  Optional<Student> sfind = repo.findById(103);
        System.out.println(sfind.orElse(new Student())); // get the other new obj if no data

2.3 DSL Query

• DSL Query

        // new method by using the query annotation
      // using the class name and property nam in JPA
        @Query("select s from Student s where s.name= ?1")  // ? is for the 1st parameter
        List<Student> findByStudentName(String name);

        //   //DSL Query ,  By default the JPA will implement the query for below things like :
        List<Student> findByName(String name);
        List<Student> findByMarks(int marks);
        List<Student> findByMarksGreaterThan(int marks);
        List<Student> findByNameAndMarks(String name, int marks);
    }

//search By Name
        // using the @Query annotation
        System.out.println(repo.findByStudentName("John"));
        // using the DSL query
        System.out.println(repo.findByStudentName("Jane"));
        System.out.println(repo.findByMarksGreaterThan(30));
        System.out.println(repo.findByMarks(23));

2.3 Update and Delete

// Update and Delete

        s3.setRollno(103);
        s3.setName("JP");
        s3.setMarks(99);
        repo.save(s3);

        repo.delete(s3);

3. JPA in Web APP

JPA in job app

4. Search by Keyword