I have a problem with a throw execution in GWT. So I want to show a simple String list in Client side located on "Server Side". Ok, I have in my Main class this atributes:
private final GreetingServiceAsync greetingService = Util.getInstance(); // This is like > typing GWT.create( GreetingService.class );
public ArrayList songs = new ArrayList();
and in my onModuleLoad() method I have a call to another private method that make the Async call to the Server class:
songs.addAll(getSongsList());
So my getSongsList method is as follow:
public ArrayList<String> getSongsList() {
final int defaultSize = 4;
final ArrayList<String> temp = new ArrayList<String>();
GWT.log("Enter in getSongsLists");
greetingService.greetSongMostPopular(defaultSize,
new AsyncCallback<ArrayList<String>>() {
public void onSuccess(ArrayList<String> result) {
GWT.log("Result is:" + result);
temp.addAll(result);
GWT.log("Case 1 TEMP= " + temp);
}
public void onFailure(Throwable caught) {
// throw new
// UnsupportedOperationException("Not supported yet.");
Window.alert("Error greeting data");
}
});
GWT.log("CASE 2 TEMP = " + temp);
return temp;
}
My problem is that in Case 1 I get
[INFO] [MainModule] - Case 1 TEMP= [Song 1, Song 2, Song 3, Song 4]
but in CASE 2 I get the ArrayList empty!!!
[INFO] [MainModule] - Case 1 TEMP= []
What am I doing wrong?
Thanks in advance!
The call to greetSongsMostPopular is asynchronous. This means that the call begins and the code continues directly to the next line of code, in your case GWT.log("CASE 2 TEMP..."). When this line of code is executed, the results are not yet available and you end up with an empty list.
Later, in the background, onSuccess is called with the results. At this point you should call a function to process the results. You can use a pattern similar to the AsyncCallback class, with an onSuccess and onFailure so the caller of this code can handle both cases, or you can just have the caller pass in their own AsyncCallback instance which would make it a thin wrapper around your greetSongsMostPopular RPC function.
This is normal : the callback is called when your server send the answer but the greetSongMostPopular return imediatly.
The call is asynchronous.
All code must be done in the callback (call a function)
Here is the exact process :
greetingService.greetSongMostPopular is called
temp is empty
the second GWT.log is called : temp is always empty
the getSongsList method return : temp is always empty
the server send the answer to the callback : temp is filled
You are not doing anything wrong. This is expected since you are not dealing with synchronous calls. So the case 2 is only invoked after the asynchronous call returns from the server side.
Related
Is there a way to wait for a future to complete without blocking the event loop?
An example of a use case with querying Mongo:
Future<Result> dbFut = Future.future();
mongo.findOne("myusers", myQuery, new JsonObject(), res -> {
if(res.succeeded()) {
...
dbFut.complete(res.result());
}
else {
...
dbFut.fail(res.cause());
}
}
});
// Here I need the result of the DB query
if(dbFut.succeeded()) {
doSomethingWith(dbFut.result());
}
else {
error();
}
I know the doSomethingWith(dbFut.result()); can be moved to the handler, yet if it's long, the code will get unreadable (Callback hell ?) It that the right solution ? Is that the omny solution without additional libraries ?
I'm aware that rxJava simplifies the code, but as I don't know it, learning Vert.x and rxJava is just too much.
I also wanted to give a try to vertx-sync. I put the dependency in the pom.xml; everything got downloaded fine but when I started my app, I got the following error
maurice#mickey> java \
-javaagent:~/.m2/repository/co/paralleluniverse/quasar-core/0.7.5/quasar-core-0.7.5-jdk8.jar \
-jar target/app-dev-0.1-fat.jar \
-conf conf/config.json
Error opening zip file or JAR manifest missing : ~/.m2/repository/co/paralleluniverse/quasar-core/0.7.5/quasar-core-0.7.5-jdk8.jar
Error occurred during initialization of VM
agent library failed to init: instrument
I know what the error means in general, but I don't know in that context... I tried to google for it but didn't find any clear explanation about which manifest to put where. And as previously, unless mandatory, I prefer to learn one thing at a time.
So, back to the question : is there a way with "basic" Vert.x to wait for a future without perturbation on the event loop ?
You can set a handler for the future to be executed upon completion or failure:
Future<Result> dbFut = Future.future();
mongo.findOne("myusers", myQuery, new JsonObject(), res -> {
if(res.succeeded()) {
...
dbFut.complete(res.result());
}
else {
...
dbFut.fail(res.cause());
}
}
});
dbFut.setHandler(asyncResult -> {
if(asyncResult.succeeded()) {
// your logic here
}
});
This is a pure Vert.x way that doesn't block the event loop
I agree that you should not block in the Vertx processing pipeline, but I make one exception to that rule: Start-up. By design, I want to block while my HTTP server is initialising.
This code might help you:
/**
* #return null when waiting on {#code Future<Void>}
*/
#Nullable
public static <T>
T awaitComplete(Future<T> f)
throws Throwable
{
final Object lock = new Object();
final AtomicReference<AsyncResult<T>> resultRef = new AtomicReference<>(null);
synchronized (lock)
{
// We *must* be locked before registering a callback.
// If result is ready, the callback is called immediately!
f.onComplete(
(AsyncResult<T> result) ->
{
resultRef.set(result);
synchronized (lock) {
lock.notify();
}
});
do {
// Nested sync on lock is fine. If we get a spurious wake-up before resultRef is set, we need to
// reacquire the lock, then wait again.
// Ref: https://stackoverflow.com/a/249907/257299
synchronized (lock)
{
// #Blocking
lock.wait();
}
}
while (null == resultRef.get());
}
final AsyncResult<T> result = resultRef.get();
#Nullable
final Throwable t = result.cause();
if (null != t) {
throw t;
}
#Nullable
final T x = result.result();
return x;
}
Input PCollection is http requests, which is a bounded dataset. I want to make async http call (Java) in a ParDo , parse response and put results into output PCollection. My code is below. Getting exception as following.
I cound't figure out the reason. need a guide....
java.util.concurrent.CompletionException: java.lang.IllegalStateException: Can't add element ValueInGlobalWindow{value=streaming.mapserver.backfill.EnrichedPoint#2c59e, pane=PaneInfo.NO_FIRING} to committed bundle in PCollection Call Map Server With Rate Throttle/ParMultiDo(ProcessRequests).output [PCollection]
Code:
public class ProcessRequestsFn extends DoFn<PreparedRequest,EnrichedPoint> {
private static AsyncHttpClient _HttpClientAsync;
private static ExecutorService _ExecutorService;
static{
AsyncHttpClientConfig cg = config()
.setKeepAlive(true)
.setDisableHttpsEndpointIdentificationAlgorithm(true)
.setUseInsecureTrustManager(true)
.addRequestFilter(new RateLimitedThrottleRequestFilter(100,1000))
.build();
_HttpClientAsync = asyncHttpClient(cg);
_ExecutorService = Executors.newCachedThreadPool();
}
#DoFn.ProcessElement
public void processElement(ProcessContext c) {
PreparedRequest request = c.element();
if(request == null)
return;
_HttpClientAsync.prepareGet((request.getRequest()))
.execute()
.toCompletableFuture()
.thenApply(response -> { if(response.getStatusCode() == HttpStatusCodes.STATUS_CODE_OK){
return response.getResponseBody();
} return null; } )
.thenApply(responseBody->
{
List<EnrichedPoint> resList = new ArrayList<>();
/*some process logic here*/
System.out.printf("%d enriched points back\n", result.length());
}
return resList;
})
.thenAccept(resList -> {
for (EnrichedPoint enrichedPoint : resList) {
c.output(enrichedPoint);
}
})
.exceptionally(ex->{
System.out.println(ex);
return null;
});
}
}
The Scio library implements a DoFn which deals with asynchronous operations. The BaseAsyncDoFn might provide you the handling you need. Since you're dealing with CompletableFuture also take a look at the JavaAsyncDoFn.
Please note that you necessarily don't need to use the Scio library, but you can take the main idea of the BaseAsyncDoFn since it's independent of the rest of the Scio library.
The issue that your hitting is that your outputting outside the context of a processElement or finishBundle call.
You'll want to gather all your outputs in memory and output them eagerly during future processElement calls and at the end within finishBundle by blocking till all your calls finish.
I have a problem with RPC call in GWT.
Below is an example code snippet:
I have four columns in my UI with effdate and enddate as column header.
The values are not displaying in order. The first column value is displaying in 3rd column.
most of the time the order changes. Displaying randomly.
I guess the RPC call to the server side method for each count is delayed.
and I found out by debugging the server side method, the effdate and end date that i am passing for first loop is executing 2nd or 3rd sometimes. It is shuffling.
Can any one help me with this. what changes i need to do in my code to get correct values displayed in UI.
Any idea on this?
count=4;
List finalList = new arrayList();
for(i=0;i<count;count++)
{
effdate= list.get(countincr);
enddate= list.get(countincr+1);
//call to server side method to fetch values from DB by passing effdate and end date as parameter.
grp.ratecalc(startdate,enddate,new AsyncCallback<List<grVo>>()
{
public void onfailure(throwable caught)
{
sys.out.print("failure");
}
public void onsuccess(List<grVo> result)
{
List grpList= new GrpVO();
rate = result.get(0).getrate();
rate1 = result.get(0).getrate1();
grpList.setrate();
grpList.setrate1();
setting values in bean for the remaining values in the result.
finalList.add(grpList);
if(finalList.size()== count)
{
//calling a method to populate the values
methoddisplay(finalList);
}
}
}
);
countincr+=2;
} //end of for loop`
You can use a map instead of your finallist to keep track of the request and response.
I have made some changes to your code.(Its incomplete. plz make necessary changes).
int count=4;
Map<Integer,Object> map = new HashMap<Integer, Object>();
for(int i=0;i<count;count++)
{ final int index=i;
effdate= list.get(countincr);
enddate= list.get(countincr+1);
grp.ratecalc(startdate,enddate,new AsyncCallback<List<grVo>>()
{
public void onfailure(throwable caught) {
sys.out.print("failure");
}
public void onsuccess(List<grVo> result){
List grpList= new GrpVO();
rate = result.get(0).getrate();
rate1 = result.get(0).getrate1();
grpList.setrate();
grpList.setrate1();
map.put(index, grpList);
//check all items are put on the map and populate values.
}
}
);
countincr+=2;
}
Here index is used to identify the requset and response.
All the response GrpVO objects are put into the map along with its index.
Finally you have to generate your final list from the map.
Hope this works.
Ciao, I have tested in several ways, but I'm still unable to test and verify the Event expiration mechanism in Drools Fusion, so I'm looking for some little guidance, please?
I've read the manual and I'm interested in this feature:
In other words, one an event is inserted into the working memory, it is possible for the engine to find out when an event can no longer match other facts and automatically retract it, releasing its associated resources.
I'm using the Drools IDE in Eclipse, 5.4.0.Final and I modified the template code created by the "New Drools Project" wizard to test and verify for Event expiration.
The code below. The way I understood to make the "lifecycle" to work correctly is that:
You must setup the KBase in STREAM mode - check
You must Insert the Events in temporal order - check
You must define temporal constraints between Events - check in my case is last Message()
However, when I inspect the EventFactHandle at the end, none of the Event() has expired.
Thanks for your help.
Java:
public class DroolsTest {
public static final void main(String[] args) {
try {
KnowledgeBase kbase = readKnowledgeBase();
// I do want the pseudo clock
KnowledgeSessionConfiguration conf = KnowledgeBaseFactory.newKnowledgeSessionConfiguration();
conf.setOption(ClockTypeOption.get("pseudo"));
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(conf, null);
SessionPseudoClock clock = ksession.getSessionClock();
KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test");
// Insert of 2 Event:
Message message = new Message();
message.setMessage("Message 1");
message.setStatus(Message.HELLO);
ksession.insert(message);
ksession.fireAllRules();
clock.advanceTime(1, TimeUnit.DAYS);
Message message2 = new Message();
message2.setMessage("Message 2");
message2.setStatus(Message.HELLO);
ksession.insert(message2);
ksession.fireAllRules();
clock.advanceTime(1, TimeUnit.DAYS);
ksession.fireAllRules();
// Now I do check what I have in the working memory and if EventFactHandle if it's expired or not:
for (FactHandle f : ksession.getFactHandles()) {
if (f instanceof EventFactHandle) {
System.out.println(((EventFactHandle)f)+" "+((EventFactHandle)f).isExpired());
} else {
System.out.println("not an Event: "+f);
}
}
logger.close();
} catch (Throwable t) {
t.printStackTrace();
}
}
private static KnowledgeBase readKnowledgeBase() throws Exception {
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add(ResourceFactory.newClassPathResource("Sample.drl"), ResourceType.DRL);
KnowledgeBuilderErrors errors = kbuilder.getErrors();
if (errors.size() > 0) {
for (KnowledgeBuilderError error: errors) {
System.err.println(error);
}
throw new IllegalArgumentException("Could not parse knowledge.");
}
KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());
// following 2 lines is the template code modified for STREAM configuration
KnowledgeBaseConfiguration config = KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
config.setOption( EventProcessingOption.STREAM );
return kbase;
}
/*
* This is OK from template, as from the doc:
* By default, the timestamp for a given event is read from the Session Clock and assigned to the event at the time the event is inserted into the working memory.
*/
public static class Message {
public static final int HELLO = 0;
public static final int GOODBYE = 1;
private String message;
private int status;
public String getMessage() {
return this.message;
}
public void setMessage(String message) {
this.message = message;
}
public int getStatus() {
return this.status;
}
public void setStatus(int status) {
this.status = status;
}
}
}
Drools:
package com.sample
import com.sample.DroolsTest.Message;
declare Message
#role(event)
end
declare window LastMessageWindow
Message() over window:length(1)
end
rule "Hello World"
when
accumulate( $m : Message(status==Message.HELLO) from window LastMessageWindow,
$messages : collectList( $m ) )
then
System.out.println( ((Message)$messages.get(0)).getMessage() );
end
Please note: even if I add expiration of 1second to the Message event, by
#expires(1s)
I still don't get the expected result that the very first Message event inserted, I would have expected is now expired? Thanks for your help.
Found solution! Obviously it was me being stupid and not realizing I was using Drools 5.4.0.Final while still referring to old documentation of 5.2.0.Final. In the updated documentation for Drools Fusion 5.4.0.Final, this box is added for 2.6.2. Sliding Length Windows:
Please note that length based windows do not define temporal constraints for event expiration from the session, and the engine will not consider them. If events have no other rules defining temporal constraints and no explicit expiration policy, the engine will keep them in the session indefinitely.
Therefore the 3rd requirement I originally enlisted of "You must define temporal constraints between Events" is obviously NOT met because I now understand Sliding Length Window in Drools 5.4.0.Final:
Message() over window:length(1)
are indeed NOT a definition of a temporal constraints for event expiration from the session.
Updating this answer hopefully somebody will find it helpful. Also, just so for your know, me being stupid actually for relying on googling in order to reach the doc, and sometimes you don't get redirected to the current release documentation, so it seems...
What I'm doing is:
getSecroleByOrgNID(orgList[i-2],cu.currentUser.getProfileObj());
System.out.println("Value of sec role is "+ secondryRole);
where the getSecroleByOrgNID function is:
private String getSecroleByOrgNID(COrganization srOrg, CProfile srUser) {
analyticsSrvc.getSecroleByOrgNID(srOrg, srUser,
new AsyncCallback<String>() {
#Override
public void onFailure(Throwable caught) {
}
#Override
public void onSuccess(String result) {
secondryRole = result;
System.out.println("Assigned role is " + secondryRole);
}
});
return null;
}
where secondryRole is
String secondryRole = " ";
The output is:
Value of sec role is
Assigned role is Admin
Query is why the "value of sec role is " statement prints before "Assigned role is Admin" since the function is called before print statement of "value of sec role is ".
And why does the value of secondryRole remain " " even though its value is reassigned inside the function?
As GWT docs says, in GWT you have to "embrace asynchronous transactions" and forget about synchronous ones.
The problem is that getSecroleByOrgNID() invoke an asynchronous call to the server but this call doesn't stop execution, so it continues his work (server needs more time to return). You are asking for secondryRole when server doesn't response yet.
You should call a method always inside onSuccess() that work with server response.