Spring boot Adding JPA Capability

Adding JPA Capability


adding spring-boot-starter-data-jpa dependency

➤Adds Spring JDBC/Transaction Management

• Adds Spring ORM
• Adds Hibernate/entity manager
• Adds Spring Data JPA subproject

➤does not add driver of database
needed to add manually (HSQL db)

SPRING Data JPA

• this is typical web application architecture
• REST controller provides CRUD interface to client
• DAO provide CRUD interface to DB

              JSON/XML

                      ⬍

               Controller

                      ⬇

               Services

                     ⬇

                DAO

                    ⬍

                  DB

Spring Data - 

spring data provides dynamic repositories,it dynamically implements 

JPA,MongoDB etc

Spring Layer/Controllers have almost no logic

                    JSON/XML

                      ⬍

                     Controller

                      ⬇

                      Services

                     ⬇

                Spring Data Repositories

                     ⬍

                  DB

Main Projects for Spring data

Spring data jpa

spring data mongodb

spring data Neo4j

spring data solar

spring data REDIS

..............

https://spring.io/projects/spring-data

Demo-

Demonstration Adding Spring Data JPA

add dependecy in pom.xml

- spring-boot-starter-data-jpa

- org.hsqldb/hsqldb

- Annotate domain objects with JPA

- Extend CrudRepository

1. Add dependency in my POM

             <dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-data-jpa</artifactId>

</dependency>

<dependency>

<groupId>org.hsqldb</groupId>

<artifactId>hsqldb</artifactId>

</dependency>

2. Annotate your pojo with JPA annotation

Team.java

public class Team {

  String name;

  String location;

  @Id @GeneratedValue

  Long id;

  @OneToMany(cascade = CascadeType.ALL)

  @JoinColumn(name="teamId")

  Set<Player> players;

  public Team() {

  super();

  }

.................

}

Player.java

@Entity

public class Player {

@Id @GeneratedValue

Long id;

public Player() {

super();

}

        ........

}

3- Create Repository

package com.dao;

import java.util.List;

import org.springframework.data.repository.CrudRepository;

import com.domain.Team;

public interface TeamDao extends CrudRepository<Team, Long>{

List<Team> findAll();

Team findByName(String name);

}

4- Change Controller class

package com.demo;

import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.PathVariable;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.ResponseBody;

import org.springframework.web.bind.annotation.RestController;

import com.dao.TeamDao;

import com.domain.Team;

@RestController

public class InitialController {

    @Autowired

private TeamDao teamDao;

@RequestMapping("/teams/{name}")

public @ResponseBody Team helloWorld(@PathVariable String name) {

return teamDao.findByName(name);

}

 

}

5- DemoApplication

package com.demo;

import java.util.HashSet;
import java.util.Set;

import javax.annotation.PostConstruct;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;

import com.dao.TeamDao;
import com.domain.Player;
import com.domain.Team;

@SpringBootApplication
public class DemoApplication extends SpringBootServletInitializer{

public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}

@Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(DemoApplication.class);

}

@PostConstruct
public void init() {
Set<Player> players = new HashSet<>();
players.add(new Player("player1","A"));
players.add(new Player("player2","B"));
players.add(new Player("player3","C"));

Team team= new Team("xyz","India","p",players);
teamDao.save(team);
}

@Autowired
TeamDao teamDao;

}

Spring Data - REST

• plugins to dynamic repositories
• Generate restful interface  
•          -get,put,post,delete
• code needed only to override defaults

                           JSON/XML

                                                      ⬍

                          spring Data Rest

                                                       ⬍

                          Spring data Repository

                                                       ⬍

                                   DB 

add below dependecy in pom.xml

          <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-rest</artifactId>

</dependency>

go to my teamDAO and add RestResources

package com.dao;

import java.util.List;

import org.springframework.data.repository.CrudRepository;
import org.springframework.data.rest.core.annotation.RestResource;

import com.domain.Team;
//it is typed repository i can tell what data type it is going to serve

@RestResource(path = "teams",rel = "teams")
public interface TeamDao extends CrudRepository<Team, Long>{

List<Team> findAll();

Team findByName(String name);

}

3.Controller

package com.demo;

import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import com.dao.TeamDao;
import com.domain.Team;

@RestController
public class InitialController {

    @Autowired
TeamDao teamDao;


@RequestMapping("/hi/{name}")
public @ResponseBody Team helloWorld(@PathVariable String name) {

return teamDao.findByName(name);
}
 

}

4. Application

package com.demo;

import java.util.HashSet;

import java.util.Set;

import javax.annotation.PostConstruct;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.boot.builder.SpringApplicationBuilder;

import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;

import com.dao.TeamDao;

import com.domain.Player;

import com.domain.Team;

@SpringBootApplication

public class DemoApplication extends SpringBootServletInitializer{

public static void main(String[] args) {

SpringApplication.run(DemoApplication.class, args);

}

@Override

protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {

return application.sources(DemoApplication.class);

}

@PostConstruct

public void init() {

Set<Player> players = new HashSet<>();

players.add(new Player("player1","A"));

players.add(new Player("player2","B"));

players.add(new Player("player3","C"));

Team team= new Team("xyz","India",players);

teamDao.save(team);

}

@Autowired

TeamDao teamDao;

}

so here

Adding Spring Data Rest 

when application starts

• @RestResource annotation interpreated
• @Controllers bean created
• @Request mapping created

Adding HATEOAS

➤spring data rest simply returns RESful resources

conversion handled by Jackson or JAXB

➤ underline Data relationship used to build Links

- if matching repositories exists