来自可选 Object (Java 8) 的实体

Question

I am having some issue while trying to pull an entity out of an ArrayList that holds and Optional. When I do a breakpoint I get the return below the code. I know I am close but lack the knowledge on how to pull the GrandClientDataCore@9463 out of the data being returned to me.

Edited to add the previous line before the for loop.

Error occured: java.util.Optional cannot be cast to net.glmhc.dmhwebservices.entities.GrandClientDataCores. 

List<GrandClientDataCores> grandClientDataCoresList = getGrandClientDataCoreList(submitMode, grandClientDataCoreId);
for (GrandClientDataCores grandClientDataCores : grandClientDataCoresList) {
    CDCPAErrors request = new CDCPAErrors();
    request.setI(this.service.getRequestInfo(grandClientDataCores, submitMode, staff));
    logToFile(outDir, String.format("req_%s.xml", new Object[] {grandClientDataCores}), request);
    
    CDCPAErrorsResponse response = (CDCPAErrorsResponse) 
    getWebServiceTemplate().marshalSendAndReceive(getWebServiceUri(), request, 
    (WebServiceMessageCallback) new SoapActionCallback("http://tempuri.org/CDCPAErrors"));

    logToFile(outDir, String.format("res_%s.xml", new Object[] {grandClientDataCoreId}), response);
    DmhServicesCdcResponse responseObj = getResponse(submitMode, response);
    this.service.saveResponse(grandClientDataCores, submitMode, responseObj, staff);
    responses.add(responseObj);
}

This is the getGrandClientDataCoreList

 protected List<GrandClientDataCores> getGrandClientDataCoreList(SubmitMode submitMode, String grandClientDataCore) throws Exception {
        List<GrandClientDataCores> grandClientDataCoresList;
        try {
            grandClientDataCoresList = (List<GrandClientDataCores>) this.service.getGrandClientDataCoreList(submitMode, grandClientDataCore);
         } catch ( Exception ex) {
             throw new Exception(ex);
         }

         if (grandClientDataCore == null || grandClientDataCore.isEmpty()) {
             throw new NoDataException("No CDC record to validate.");

         }
        return grandClientDataCoresList;
    }

Answer 1

You have to invoke get() on the optional to retrieve its value. You cannot just cast Optional<T> to something else. According to the debug image, the declaration of grandClientDataCoresList looked like this:

List<Optional<GrandClientDataCores>> grandClientDataCoresList ...

Therefore you need something like this:

for (Optional<GrandClientDataCores> gcdcOpt: grandClientDataCoresList) {
    GrandClientDataCores gcdc = gcdcOpt.get();
    ....

values in grandClientDataCores are of type Optional<GrandClientDataCores> .

Your actual error is here:

   protected List<GrandClientDataCores> getGrandClientDataCoreList(SubmitMode submitMode, String grandClientDataCore) throws Exception {
        List<GrandClientDataCores> grandClientDataCoresList;
        try {
            grandClientDataCoresList = (List<GrandClientDataCores>) this.service.getGrandClientDataCoreList(submitMode, grandClientDataCore);
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                       This cast is invalid
                                       
         } catch ( Exception ex) {
             throw new Exception(ex);
         }

         if (grandClientDataCore == null || grandClientDataCore.isEmpty()) {
             throw new NoDataException("No CDC record to validate.");

         }
        return grandClientDataCoresList;
    }

You will find that the actual type returned by this.service.getGrandClientDataCoreList is List<Optional<GrandClientDataCores>> so you must update your code accordingly, in a number of places. For starters...

   protected List<Optional<GrandClientDataCores>> getGrandClientDataCoreList(SubmitMode submitMode, String grandClientDataCore) throws Exception {
        List<Optional<GrandClientDataCores>> grandClientDataCoresList;
        try {
            grandClientDataCoresList = this.service.getGrandClientDataCoreList(submitMode, grandClientDataCore);
         } catch ( Exception ex) {
             throw new Exception(ex);
         }

         if (grandClientDataCore == null || grandClientDataCore.isEmpty()) {
             throw new NoDataException("No CDC record to validate.");

         }
        return grandClientDataCoresList;
    }

and everywhere that you invoke this method.

Answer 2

use the " get() " function of Optional, which will retrieve the object itself. pay attention it will throw an exception if no object was populated into this Optional.

Answer 3

GrandClientDataCores values in List are wrapped with Optional, so you have to check if value present:

grandClientDataCores.isPresent()

and if it is then just get it:

grandClientDataCores.get();

Alternatively, you can do something like that:

grandClientDataCores.orElse(new GrandClientDataCores())

And I recommend to read this