如何模拟在 Spring Boot 中返回 json 字符串的 api

Question

I am a beginner in trying to mock an external api in Spring Boot. Here is the api: https://jsonplaceholder.typicode.com/posts

It returns a json string like this:

[
  {
    "userId": 1,
    "id": 1,
    "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
    "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"
  },
...

I've tried the following code:

    @Service
    public class BlogPostService {
        @Autowired
        private RestTemplate restTemplate;
     
        public String getAllBlogPosts() {
            ResponseEntity resp = restTemplate.getForEntity("http://localhost:8080/posts", String.class);
            
            return resp.getStatusCode() == HttpStatus.OK ? resp.getBody() : null;
        }
    
    }

But there is an error in the IDE at resp.getBody() which says 

Type mismatch: cannot convert from Object to String

Here is my BlogPost code:

public class BlogPost {
    private int userId;
    private String title;
    private String body;
     
    public BlogPost() {
    }
     
    public BlogPost(int userId, String title, String body) {
        this.title = title;
        this.body = body;
    }
//...getters & setters

Could one of you experts give me some guidance? Hopefully without the use of yet another tool. This is just a simple proof-of-concept app so not wanting to use JUnit or Mockito for testing.

Answer 1

The API https://jsonplaceholder.typicode.com/posts returns an array of JSON objects. You will need to reflect this in your request's desired response type

public String getAllBlogPosts() {
    ResponseEntity resp = restTemplate.getForEntity("http://localhost:8080/posts", BlogPost[].class);
            
    return resp.getStatusCode() == HttpStatus.OK ? resp.getBody() : null;
}

Notice the [] in BlogPost[].class .

Then, you are getting a Type mismatch: cannot convert from Object to String since ResponseBody.getBody() returns a generic type T , which is BlogPost[] but your method signature returns a String .

If all you want is the JSON string, then you can just do this

public String getAllBlogPosts() {
    ResponseEntity resp = restTemplate.getForEntity("http://localhost:8080/posts", String.class);

    return resp.getStatusCode() == HttpStatus.OK ? resp.getBody() : null;
}

Otherwise, if you want the actual POJO array then do this

public BlogPost[] getAllBlogPosts() {
    ResponseEntity resp = restTemplate.getForEntity("http://localhost:8080/posts", BlogPost[].class);

    return resp.getStatusCode() == HttpStatus.OK ? resp.getBody() : null;
}