How to use the spiderViewStatus Java API of OWASP ZAP to get the status/percentage of work done by the Spider?

I was following the API documentation of Using Spider. The Java based code block works great and I get an output.

• Code:

    import java.util.List;
  
    import org.zaproxy.clientapi.core.ApiResponse;
    import org.zaproxy.clientapi.core.ApiResponseElement;
    import org.zaproxy.clientapi.core.ApiResponseList;
    import org.zaproxy.clientapi.core.ClientApi;
  
    public class SpiderViewStatus {
  
        private static final String ZAP_ADDRESS = "localhost";
        private static final int ZAP_PORT = 8080;
        // Change to match the API key set in ZAP, or use NULL if the API key is disabled
        private static final String ZAP_API_KEY = "93tpvc1c5ek2b94arh0e7c8he";
        // The URL of the application to be tested
        private static final String TARGET = "https://public-firing-range.appspot.com";
        //private static final String TARGET = "http://localhost:3000"; //Juice Shop
  
        public static void main(String[] args) {
    	ClientApi api = new ClientApi(ZAP_ADDRESS, ZAP_PORT, ZAP_API_KEY);
  
    	try {
    	    // Start spidering the target
    	    System.out.println("Spidering target : " + TARGET);
    	    ApiResponse resp = api.spider.scan(TARGET, null, null, null, null);
    	    String scanID;
    	    int progress;
  
    	    // The scan returns a scan id to support concurrent scanning
    	    scanID = ((ApiResponseElement) resp).getValue();
    	    // Poll the status until it completes
    	    while (true) {
    		    Thread.sleep(1000);
    		    progress = Integer.parseInt(((ApiResponseElement) api.spider.status(scanID)).getValue());
    		    System.out.println("Spider progress : " + progress + "%");
    		    if (progress >= 100) {
    		        break;
    		    }
    	    }
    	    System.out.println("Spider completed");
    	    // If required post process the spider results
    			  List<ApiResponse> spiderResults = ((ApiResponseList)
    			  api.spider.results(scanID)).getItems(); for (ApiResponse
    			  spiderResult:spiderResults) System.out.println(spiderResult);
  
    	    // TODO: Explore the Application more with Ajax Spider or Start scanning the application for vulnerabilities
  
    	} catch (Exception e) {
    	    System.out.println("Exception : " + e.getMessage());
    	    e.printStackTrace();
    	}
        }
    }
  

• Output:

    Spidering target : https://public-firing-range.appspot.com
    Spider progress : 0%
    Spider progress : 66%
    Spider progress : 100%
    Spider completed
    https://public-firing-range.appspot.com/sitemap.xml
    https://public-firing-range.appspot.com/robots.txt
    https://public-firing-range.appspot.com
  

Within the View Status section it is also mentions to execute the status API to get the status/percentage of work done by the Spider. However when I append the code block of spiderViewStatus :

• Code Block:

    System.out.println("Spider completed");
    // If required post process the spider results
  
    //spiderViewStatus: https://www.zaproxy.org/docs/api/#spiderviewstatus
    URL obj = new URL("http://zap/JSON/spider/view/status/");
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();
    con.setRequestMethod("GET");
    int responseCode = con.getResponseCode();
    BufferedReader in = new BufferedReader(
    new InputStreamReader(con.getInputStream()));
    String inputLine;
    StringBuffer response = new StringBuffer();
    while ((inputLine = in.readLine()) != null) {
    response.append(inputLine);
    }
    in.close();
    System.out.println(response.toString());
  
    // TODO: Explore the Application more with Ajax Spider or Start scanning the application for vulnerabilities
  

I am facing java.net.UnknownHostException: zap as follows:

• Error stacktrace:

    Spidering target : https://public-firing-range.appspot.com
    Spider progress : 66%
    Spider progress : 100%
    Spider completed
    Exception : zap
    java.net.UnknownHostException: zap
    	at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    	at java.net.PlainSocketImpl.connect(Unknown Source)
    	at java.net.SocksSocketImpl.connect(Unknown Source)
    	at java.net.Socket.connect(Unknown Source)
    	at java.net.Socket.connect(Unknown Source)
    	at sun.net.NetworkClient.doConnect(Unknown Source)
    	at sun.net.www.http.HttpClient.openServer(Unknown Source)
    	at sun.net.www.http.HttpClient.openServer(Unknown Source)
    	at sun.net.www.http.HttpClient.<init>(Unknown Source)
    	at sun.net.www.http.HttpClient.New(Unknown Source)
    	at sun.net.www.http.HttpClient.New(Unknown Source)
    	at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
    	at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
    	at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
    	at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
    	at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
    	at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    	at java.net.HttpURLConnection.getResponseCode(Unknown Source)
    	at ZAP_tests.SpiderViewStatus.main(SpiderViewStatus.java:52)
  

I have tried to replace http://zap/JSON/spider/view/status/ with http://localhost:8080/JSON/spider/view/status/ still the same error.

Can anyone help me out please?

You are already calling that endpoint in your initial code using api.spider.status(scanID)

The http://zap/ host only works if you are proxying through ZAP, which you don't appear to be in your second section of code.