Java Spring Boot (Part 3)

Neil Haddley • October 28, 2023

SpringdatajpaApplication.java

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Spring Data JPA provides a set of abstractions and high-level, repository-style interfaces that make it easier to work with Java Persistence API (JPA) for data access in Spring applications. It reduces boilerplate code.

I created a Spring Boot application using Spring Data JPA

I created a new GitHub repository haddley-spring-data-jpa

I created a new GitHub repository haddley-spring-data-jpa

I opened the repository using GitHub Desktop

I opened the repository using GitHub Desktop

I cloned the GitHib repository

I cloned the GitHib repository

GitHub repository folder

GitHub repository folder

I created a new spring boot application springdatajpa

I created a new spring boot application springdatajpa

I copied the generated files to the GitHub repository folder

I copied the generated files to the GitHub repository folder

I updated SpringdatajpaApplication.java so that it would respond to http://localhost/hello requests

I updated SpringdatajpaApplication.java so that it would respond to http://localhost/hello requests

I accessed http://localhost/hello using my web browser

I accessed http://localhost/hello using my web browser

I created a TodoItem Java class

I created a TodoItem Java class

I created a Spring Data JPA repository interface (based on the TodoItem class)

I created a Spring Data JPA repository interface (based on the TodoItem class)

I created a TodoItemDataLoader to ensure that if the repository was empty two new TodoItems would be added as the application started

I created a TodoItemDataLoader to ensure that if the repository was empty two new TodoItems would be added as the application started

I updated SpringdatajpaApplication.java to return all of the TodoItems in response to http://localhost/hello requests

I updated SpringdatajpaApplication.java to return all of the TodoItems in response to http://localhost/hello requests

I accessed http://localhost/todos using my web browser

I accessed http://localhost/todos using my web browser

I added text to applications.properties

I added text to applications.properties

I accessed the h2 console (using values jdbc:h2:mem:testdb, sa and password)

I accessed the h2 console (using values jdbc:h2:mem:testdb, sa and password)

I clicked on the TODO_ITEM table

I clicked on the TODO_ITEM table

I clicked Run to execute the select query

I clicked Run to execute the select query

The haddley-spring-data-jpa application hosted in Azure

The haddley-spring-data-jpa application hosted in Azure

Accessing the haddley-spring-data-jpa application hosted in Azure

Accessing the haddley-spring-data-jpa application hosted in Azure

TEXT
1package com.haddley.springdatajpa;
2
3import org.springframework.boot.SpringApplication;
4import org.springframework.boot.autoconfigure.SpringBootApplication;
5
6import org.springframework.web.bind.annotation.GetMapping;
7import org.springframework.web.bind.annotation.RequestParam;
8import org.springframework.web.bind.annotation.RestController;
9
10@SpringBootApplication
11@RestController
12public class SpringdatajpaApplication {
13    public static void main(String[] args) {
14        SpringApplication.run(SpringdatajpaApplication.class, args);
15    }
16
17    @GetMapping("/hello")
18    public String hello(@RequestParam(value = "name", defaultValue = "World") String name) {
19        return String.format("Hello %s!", name);
20    }
21}

TodoItem.java

TEXT
1package com.haddley.springdatajpa.models;
2
3import java.time.Instant;
4
5import jakarta.persistence.Entity;
6import jakarta.persistence.GeneratedValue;
7import jakarta.persistence.GenerationType;
8import jakarta.persistence.Id;
9import jakarta.persistence.Table;
10import jakarta.validation.constraints.NotBlank;
11
12import lombok.Getter;
13import lombok.Setter;
14
15@Entity
16@Table(name = "todo_item")
17public class TodoItem {
18
19    @Id
20    @GeneratedValue(strategy = GenerationType.AUTO)
21    @Getter
22    @Setter
23    private Long id;
24
25    @Getter
26    @Setter
27    @NotBlank(message = "Description is required")
28    private String description;
29
30    @Getter
31    @Setter
32    private boolean complete;
33
34    @Getter
35    @Setter
36    private Instant createdDate;
37
38    @Getter
39    @Setter
40    private Instant modifiedDate;
41
42    public TodoItem() {}
43
44    public TodoItem(String description) {
45        this.description = description;
46        this.complete = false;
47        this.createdDate = Instant.now();
48        this.modifiedDate = Instant.now();
49    }
50
51    @Override
52    public String toString() {
53        return String.format("TodoItem{id=%d, description='%s', complete='%s', createdDate='%s', modifiedDate='%s'}", id, description, complete, createdDate, modifiedDate);
54    }
55
56
57}

TodoItemRepository.java

TEXT
1package com.haddley.springdatajpa.models;
2
3import com.haddley.springdatajpa.models.TodoItem;
4import org.springframework.data.repository.CrudRepository;
5
6public interface TodoItemRepository extends CrudRepository {
7}

TodoItemDataLoader.java

TEXT
1package com.haddley.springdatajpa.config;
2
3import com.haddley.springdatajpa.models.TodoItem;
4import com.haddley.springdatajpa.repositories.TodoItemRepository;
5
6import org.slf4j.Logger;
7import org.slf4j.LoggerFactory;
8import org.springframework.beans.factory.annotation.Autowired;
9import org.springframework.boot.CommandLineRunner;
10import org.springframework.stereotype.Component;
11
12@Component
13public class TodoItemDataLoader implements CommandLineRunner {
14
15    private final Logger logger = LoggerFactory.getLogger(TodoItemDataLoader.class);
16
17    @Autowired
18    TodoItemRepository todoItemRepository;
19
20    @Override
21    public void run(String... args) throws Exception {
22        loadSeedData();
23    }
24
25    private void loadSeedData() {
26        if (todoItemRepository.count() == 0) {
27            TodoItem todoItem1 = new TodoItem("get the milk");
28            TodoItem todoItem2 = new TodoItem("rake the leaves");
29
30            todoItemRepository.save(todoItem1);
31            todoItemRepository.save(todoItem2); 
32        }
33
34        logger.info("Number of TodoItems: {}", todoItemRepository.count());
35    }
36
37}

SpringdatajpaApplication.java updated

TEXT
1package com.haddley.springdatajpa;
2
3import org.springframework.boot.SpringApplication;
4import org.springframework.boot.autoconfigure.SpringBootApplication;
5
6import org.springframework.web.bind.annotation.GetMapping;
7import org.springframework.web.bind.annotation.RequestParam;
8import org.springframework.web.bind.annotation.RestController;
9
10import com.haddley.springdatajpa.models.TodoItem;
11import com.haddley.springdatajpa.repositories.TodoItemRepository;
12import org.springframework.beans.factory.annotation.Autowired;
13
14import java.util.stream.StreamSupport;
15import java.util.stream.Collectors;
16
17@SpringBootApplication
18@RestController
19public class SpringdatajpaApplication {
20    public static void main(String[] args) {
21        SpringApplication.run(SpringdatajpaApplication.class, args);
22    }
23
24    @GetMapping("/hello")
25    public String hello(@RequestParam(value = "name", defaultValue = "World") String name) {
26        return String.format("Hello %s!", name);
27    }
28
29    @Autowired
30    private TodoItemRepository todoItemRepository;
31
32    @GetMapping("/todos")
33    public String index() {
34
35        Iterable todos = todoItemRepository.findAll();
36
37        return StreamSupport.stream(todos.spliterator(), false)
38            .map(TodoItem::toString) 
39            .collect(Collectors.joining(", ")); 
40
41    }
42
43}

application.properties

TEXT
1spring.datasource.url=jdbc:h2:mem:testdb
2spring.datasource.driverClassName=org.h2.Driver
3spring.datasource.username=sa
4spring.datasource.password=password
5spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

References

Spring Data JPA: What is it? And Why Should You Use It?

90 Minutes to a Complete Java Spring Boot TODO App