Let's create a resource that throws an exception and send a GET request to it in order to understand how the application reacts to runtime exceptions.

Let's create a dummy service that throws an exception. The following code snippet shows a simple service:

    @GetMapping(path = "/users/dummy-service")
    public Todo errorService() {

      throw new RuntimeException("Some Exception Occured");

    }

A couple of important things to note are as follows:

• We are creating a GET service with the following URI: /users/dummy-service.
• The service throws RuntimeException. We chose RuntimeException to be able to create the exception easily. We can easily replace it with a custom exception if needed.

Let's fire a GET request to the preceding service at http://localhost:8080/users/dummy-service using Postman. The response is shown in the following code:

    {
      "timestamp": 1484028119553,
      "status": 500,
      "error": "Internal Server Error",
      "exception": "java.lang.RuntimeException",
      "message": "Some Exception Occured",
      "path": "/users/dummy-service"
   }

A couple of important things to note are as follows:

• The response header has an HTTP status of 500 Internal server error.
• Spring Boot also returns the message with which the exception is thrown.

As we can see in the preceding two examples, Spring Boot provides good default exception handling.

In the next section, we will focus on understanding how the application reacts to custom exceptions.