How to build Rest Service with Spring Boot - A Step by Step Tutorial for Beginner - 1

Build a simple API service with Spring Boot. Feel the convenience, simplicity and efficiency of Spring Boot.

Development Environment

In tutorial, The software we use is free.

Java: JDK 8
IDE: IDEA 2019 Community

Build Project Skeleton

In Spring Boot Starter, fill in the basic configuration information of the project and the third-party components that need to be used in the project. According to the goal of the experiment, choose maven as the build tool and Java as the Programming language, the version of Spring Boot chooses the current stable version 2.5.2. Third-party package options: Lombok, Spring Web, Spring Data JPA, H2 Database.

Then click the “Generate the Project” button to download the generated project basic package. After downloading, you will get a file named: todo-api.zip, unzip it and enter the todo-api directory. Then use IDEA to open the project directory. Because there is a pom.xml file in the directory, IDEA can detect that this is a maven project and will automatically download the dependent third-party packages. (If you are building a Spring Boot project for the first time, the downloading process may be relatively long)

Create API class

In Spring Boot, building an API is very simple. First create a common Java class, and then define a common method that returns a string in the class. code show as below:

@RestController
@RequestMapping("/")
public class TodoApi {

    @GetMapping("/ok")
    public String ok() {
        return "ok";
    }

}

Now, run the program and visit the address localhost:8080/ok, you can see the “ok” is display in browser.

Build entity class Todo

Create a new model package in the project, and then create a simple Java class in it: Todo, add a few basic attributes to the class:

public class Todo {

    private Integer id;

    private String title;

    private String desc;

}

In the class, we have neither written get, set methods nor constructors. Because we will use Lombok to generate these.

If you need to generate get, set methods, add @Data annotations to the class definition
If you need to generate a constituent function, use the annotation of the corresponding constructor. In this example, we construct a constructor that includes all attributes, then add @AllArgsConstructor

The completed code is as follows:

@Data
@AllArgsConstructor
public class Todo {

    private Integer id;

    private String title;

    private String desc;

}

Retrofit API to return all Todos

Now return to the TodoApi class and add a method to return all Todo lists. The added code is as follows:

@GetMapping("/todo")
public List<Todo> getTodoList() {

    List<Todo> todos = new ArrayList<>();
    todos.add(new Todo(1, "Call Metting", ""));
    todos.add(new Todo(2, "Print File", ""));

    return todos;
}

Here, we map the method to the URL “/todo” and construct Todo data for two examples. If the error “Todo does not specify the composition method” appears after joining this program, you can refer to 让IDEA IDE识别Lombok的注解 to solve

Now, run the program and visit the address localhost:8080/todo, you can see that the Todo list is assembled into a json data format and returned.

1	[{"id":1,"title":"Call Metting","desc":""},{"id":2,"title":"Print File","desc":""}]

Next Step

In , we will add database functionality to the application.