GET/POST Requst to REST API using Spring Boot

Question

I have a REST Service an external server like https://api.myrestservice.com and I have a Spring Boot Application running locally on http://localhost:8080. Now I want to make GET or POST request to the REST API address i.e https://api.myrestservice.com/users to get all users, using my locally running Spring Boot App i.e through http://localhost:8080/users. I am not getting how to redirect local app request to external server request.

Answer 1

This is very Simple By using Java Clients you can Use RestTemplate or UniRest That one running on Remote is simply Producer and the one which is in local is Consumer So you can exchange method of Resttemplate or get method of Unirest Example Code is here.

@RequestMapping(value = "/testclient")
    public String testclient()
    {
        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
        HttpEntity<String> entity = new HttpEntity<String>(headers);
        return restTemplate.exchange("https://www.mocky.io/v2/5185415ba171ea3a00704eed", HttpMethod.GET, entity, String.class).getBody();
}

For Unirest code is like this

HttpResponse<JsonNode> jsonResponse = null;
    try {
        jsonResponse = Unirest.get("https://www.mocky.io/v2/5185415ba171ea3a00704eed")
                .header("accept", "application/json").queryString("apiKey", "123").asJson();
    } catch (UnirestException e) { // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return jsonResponse.getBody().toString();

Answer 2

Making post Api call from your code to another server:

suppose you have a server https://searchEmployee... which returns you list of employees belonging to a particular city or belonging to a particular organization:

request body:

{ 
"city" : "Ranchi",
"organisation" : "Bank Of America" 
}

json response: [{"name": "Vikash"},{"name":"kumar" },{}...etc]

Then to make a post api call you can use RestTemplate in java like this:

public void makeApiCall(){ 
    final String uri = "https://searchEmployee...";

    RestTemplate restTemplate = new RestTemplate();

    String reqBody = "{"city": "Ranchi"}";
    String result = restTemplate.postForObject(uri, reqBody, String.class);

    // convert your result into json

    try {
                jsonResponse = new JSONObject(result);
        } catch (JSONException e) {
            e.printStackTrace();
        }
   //extract a value "name" from your json data:
   try{
    String value = jsonResponse.getString("name");  
    }catch(JSONException e) {
            e.printStackTrace();
        }
}

/********************************************************************/

if you have more than one request body parameters to set do it like this:

String reqBody = "{\"quantity\":100,\"name\":\"product1\",\"ifBoolean\":false}";

false is a boolean value here in your request body and 100 is an integer.

NOTE if you are having problem in setting request body copy it directly from postman request body and paste it inside double quote.

Answer 3

I hope I got your question right. You are trying get your local app to get data from app running on your server.

You can use the below sample code in your spring boot application.

private void getUsers() {

     final String uri = "https://api.myrestservice.com/users";
     RestTemplate restTemplate = new RestTemplate();
     Users result = restTemplate.getForObject(uri, Users.class);      
     System.out.println(result); 
}

Then your getUsers can be invoked by getUsers Controller in your spring boot app.

I am adding the reference if you want to look at more examples - https://howtodoinjava.com/spring-restful/spring-restful-client-resttemplate-example/

Answer 4

There are many ways to do it. Like Apache HTTP Components and other. Sample

String type = "application/x-www-form-urlencoded" Or Set your desire content type;
String encodedData = URLEncoder.encode( rawData, "UTF-8" ); 
URL u = new URL("your remote url");
HttpURLConnection conn = (HttpURLConnection) u.openConnection();
conn.setDoOutput(true);
conn.setRequestMethod("POST");
conn.setRequestProperty( "Content-Type", type );
conn.setRequestProperty( "Content-Length", 
String.valueOf(encodedData.length()));
OutputStream os = conn.getOutputStream();
os.write(encodedData.getBytes());

There are a couple of thing going on here, Like URLEncoding is really mattered when came to security. Note: Source of above code:here.