Send a simple POST request from Quarkus/Java

Question

I want to send a simple POST request to another application to trigger some action there.

I have a quarkus project and want to send the request from inside my CreateEntryHandler - is this possible in a simple way? Or do I need to add something like Apache Httpclient to my project? Does it make sense in combination with quarkus?

Answer 1

The other application, I assume has an API Endpoint?

Lets state that the API endpoint you are trying to call in the other app is:

POST /v1/helloworld

From your Quarkus Application, you will have to do the following:

• Register a RestClient *As a Service
• Specify the Service information in your configuration properties
• Inject and use this Service

--- In your current Application ---

Pay close attention to the package name. IT has to match exactly in your application.properties file.

HelloWorldService.java

package com.helloworld.services

@Path("/v1")
@RegisterRestClient
public interface HelloWorldService{

    @POST
    @Path("/helloworld")
    Response callHeloWorld(HelloWorldPojo payloadToSend);
}

//Notice that we are not including the /v1 in the mp-rest/url, why? Because it is included in the @RestClient path.

Update your application.properties to include the following:

com.helloworld.services.HelloWorldService/mp-rest/url=https://yourOtherApplication.com/API 

--- Your HelloWorldPojo which you will send as payload

HelloWorldProjo.java

@JsonPropertyOrder({"id", "name"})
public class HelloWorldProjo{

  private long id;
  private String name;

  //Setters
  //Getters

}

In another service where you actually want to use this:

ServiceWhichCallsYourOtherAPI.java

@RequestScoped
public class ServiceWhichCallsYourOtherAPI{


    @Inject
    @RestClient
    HelloWorldService helloWorldService;



    public void methodA(){

         HelloWorldPojo payloadToSend = new HelloWorldPojo();
         payloadToSend.setId(123);
         payloadToSend.setName("whee");

         helloWorldService.callHelloWorld(payloadToSend);

   } 

}

The POST request will then go to https://yourOtherApplication.com/API/v1/helloworld

The json will look like:

{
  "id":123,
  "name":"whee"
}

Really great read: https://quarkus.io/guides/rest-client