Facing a issue on client calling REST API of server

Question

I am facing a issue on calling REST API in following scenarios

1. There are two web application webappA(client), webappB(server)
2. Client webappA calling API of webappB(server)
3. If client webappA calling API and if the server application webappB has no such API(in case of previous build/war, before implementing API), then spring redirecting it to login page and then client is receiving response of API as login page as string( eg str = < html>.....< /htm> )

Rest client code (webappA) :

RestTemplate restTemplate = new RestTemplate().getForObject(serverUrl, String.class);

Server code(webappB) : Note that this code will not existin in old build/war/version of webappB

@RequestMapping(value = "/xyz.htm")
public ResponseEntity<String> apiMethod(HttpServletRequest request, HttpServletResponse response) {

    return (new ResponseEntity<String>(responseBody, HttpStatus.OK));
}

How I can solve this issue, instead of getting response string as login page (eg str = "< html>.........< /htm>" ). I need something from spring where rest client webappA can identify.

Thanks in advance.

Answer 1

Follow below steps to get a JSON response from webappB if no handler found for a particular URL requested by webappA:

Edit your web.xml as follows:

<servlet>
    <servlet-name>appServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/location/of/servlet_context.xml</param-value>
    </init-param>
    <init-param>
        <param-name>throwExceptionIfNoHandlerFound</param-name>
        <param-value>true</param-value>
    </init-param>
</servlet>

Now write a ExceptionHanler in your Controller or GlobalExceptionHandler class

@ExceptionHandler
public ResponseEntity<JSONReturned> exception(NoHandlerFoundException exception){

    ResponseEntity<JSONReturned> responseEntity = null;
    JSONReturned jsonReturned = new JSONReturned();
    jsonReturned.setMsg("Sorry your request cannot be completed.");
    jsonReturned.setResponse("Requested URL is not present.");
    responseEntity = new ResponseEntity<JSONReturned>(jsonReturned, HttpStatus.BAD_REQUEST);
    return responseEntity;
}

JSONReturned is a simple POJO class for carrying the message:

    public class JSONReturned {

    private String msg;
    private String response;

    //getters and setters
}

Answer 2

You are getting a 404 from the REST API since the path is not existing yet. You can change your default 404 response in your server (webappB) to what ever you prefer. https://spring.io/guides/tutorials/bookmarks/