Say I have some middleware and an error is raised:
public class JWTHandler implements Handler<RoutingContext> {
public void handle(RoutingContext ctx) {
throw new Error("How can I capture this error and send a response.")
ctx.next();
}
}
How can I capture it using some error-handling middleware? Here is a global error handler but it can't reference any request/response pair.
vertx.createHttpServer()
.exceptionHandler(ctx -> {
// I cannot access the request that may have caused the error here
log.error("In the exception handler.");
log.error(ctx.getCause());
})
the only thing I can guess, is something like this:
public class ErrorHandler implements Handler<RoutingContext> {
public void handle(RoutingContext ctx) {
try{
ctx.next();
}
catch(Exception e){
ctx.response().end("We messed up.");
}
}
}
but I doubt that idea is right? What's the right way to do this?
perhaps one or both of these is sufficient?
router.route().failureHandler(ctx -> {
ctx.response().end("We failed here!");
});
router.route().last().handler(ctx -> {
ctx.response()
.setStatusCode(404)
.end("404 - route/resource could not be found.");
});
I think, the correct approach would be to use the ctx.fail(), when throwing an exception
public class JWTHandler implements Handler<RoutingContext> {
public void handle(RoutingContext ctx) {
ctx.fail(new Error("How can I capture this error and send a response.");
}
}
And then you can add a failerHandler and access to the Exception with ctx.failure()
router.route().failureHandler(ctx -> {
ctx.response().end(
ctx.failure().getMessage()
);
});
EDIT:
the failureHandler also catches exceptions that are thrown like you did:
public class JWTHandler implements Handler<RoutingContext> {
public void handle(RoutingContext ctx) {
throw new Error("How can I capture this error and send a response.")
ctx.next();
}
}
Related
I'm a little bit new to RxJava. I am trying to emit another item if onError() get called without losing the error(I still want onError() to be called on the observer). but when I'm implementing each of the error handling methods declared in the docs the error being swallowed and on error isn't being called. any solutions?
edit:
that's what I've tried to do yesterday -
#Override
public Observable<ArrayList<Address>> getAirports() {
return new Observable<ArrayList<AirportPOJO>>() {
#Override
protected void subscribeActual(Observer<? super ArrayList<AirportPOJO>> observer) {
try {
// get airports from api list and map it
ArrayList<AirportPOJO> airportsList = apiDb.getAirportsList(POJOHelper.toPOJO(AppCredentialManager.getCredentials()));
observer.onNext(airportsList);
} catch (Exception e) {
e.printStackTrace();
observer.onError(handleException(e));
}
}
}.map(AirportsMappers.getAirportsPojoToDomainAirportsMapper()).doOnNext(new Consumer<ArrayList<Address>>() {
#Override
public void accept(ArrayList<Address> airportsList) throws Exception {
// if airports loaded from api - save them to local db
if (airportsList != null) {
try {
localDb.saveAirportList(AirportsMappers.getAirportsToLocalDbAirportsMapper().apply(airportsList));
} catch (Exception e) {
e.printStackTrace();
}
}
}
}).onErrorResumeNext(new Function<Throwable, ObservableSource<? extends ArrayList<Address>>>() {
#Override
public ObservableSource<? extends ArrayList<Address>> apply(final Throwable throwable) throws Exception {
// load the local airports -
ArrayList<LocalDbAirportEntity> localAirportsEntities = localDb.getAirports();
// map
ArrayList<Address> airports = AirportsMappers.getLocalDbAirportsToAirportsMapper().apply(localAirportsEntities);
// return the concat observable with the error
return Observable.just(airports).concatWith(Observable.
<ArrayList<Address>>error(new Callable<Throwable>() {
#Override
public Throwable call() throws Exception {
return throwable;
}
}));
}
});
}
today I tought I might doing it wrong and tried -
#Override
public Observable<ArrayList<Address>> getAirports() {
ArrayList<Observable<ArrayList<Address>>> observables = new ArrayList<>();
observables.add(apiDb.getAirportsList(POJOHelper.toPOJO(AppCredentialManager.getCredentials())).map(AirportsMappers.getAirportsPojoToDomainAirportsMapper()));
observables.add(localDb.getAirports().map(AirportsMappers.getLocalDbAirportsToAirportsMapper()));
Observable<ArrayList<Address>> concatenatedObservable = Observable.concatDelayError(observables);
return concatenatedObservable;
}
but I've got the same result. the onNext() called with the data of the second observable and the onError() not being called afterwards.
Resume with the desired value concatenated with the original error:
source.onErrorResumeNext(error ->
Observable.just(item).concatWith(Observable.<ItemType>error(error))
);
I have a Spring Boot application that has the following approximate structure:
project
Api
ApiImpl
Application
Api is an interface that looks like this:
public interface Api {
public String methodOne(...) throws ExceptionOne, ExceptionTwo, ExceptionThree;
...
public int methodN(...) throws ExceptionOne, ExceptionThree, ExceptionFour;
}
ApiImpls is the request controller (in reality there is a second layer, but this should suffice for this example). There, I do something like the following right now:
#Controller
public class ApiImpl {
public String methodOne(...) {
try {
// do stuff that can yield an exception
}
catch(ExceptionOne e) {
// set proper response code and return values
}
catch(ExceptionTwo e) {
// set proper response code and return values
}
catch(ExceptionThree e) {
// set proper response code and return values
}
}
}
Basically, this behaviour yields a lot of repetition (might as well name my exceptions D, R, and Y...), but is otherwise very suited to handling the internal application logic.
My question is: How can I implement a custom Exception Dispatcher that would handle this in Java? Ideally, I would want something like this answer here, but unfortunately simply throwing the current exception like in that C++ code is not possible in Java, as far as I know. For brevity, what I would like to accomplish is something like the following:
#Controller
public class ApiImpl {
public String methodOne(...) {
try {
// do stuff that can yield an exception
}
catch(ExceptionOne e) {
handle()
}
}
private void handle() { // maybe Throwable or Exception subclass as parameter
// handle the correct exception type, set correct response code, etc.
}
}
Are there any good approaches to doing this so as to minimize code repetition?
Here is a preliminary attempt I tried to get this working:
public class Thrower {
public Thrower(int e) throws ExceptionOne, ExceptionTwo, ExceptionThree {
if(e == 0) {
throw new ExceptionOne();
}
if(e == 1) {
throw new ExceptionTwo();
}
if(e == 2) {
throw new ExceptionThree();
}
}
}
class ExceptionOne extends Exception {}
class ExceptionTwo extends Exception {}
class ExceptionThree extends Exception {}
public class ExceptionHandler {
private void handle(Exception ex) throws Exception {
try {
throw ex;
}
catch(ExceptionOne e) {
e.printStackTrace();
System.out.println("Exception one");
}
catch(ExceptionTwo e) {
e.printStackTrace();
System.out.println("Exception two");
}
catch(ExceptionThree e) {
e.printStackTrace();
System.out.println("Exception three");
}
}
public void causesException(int which) throws Throwable {
try {
Thrower t = new Thrower(which);
}
catch(Exception e) {
handle(e);
}
}
public static void main(String[] args) throws Throwable {
ExceptionHandler eh = new ExceptionHandler();
eh.causesException(0);
eh.causesException(1);
eh.causesException(2);
}
}
This works as expected, and I can handle the different exception types as needed (shown here using a constructor, but the principle would be the same). However, this feels extremely clunky.
If you are looking for globally handling all Controller Layer exceptions (in Spring MVC architecture), you can do that at one place for all controllers (option1 below) by using #ExceptionHandler methods which is a ControllerAdvice from Spring.
Option(1): Configure Exceptions in Separate Class
#ControllerAdvice
class MyProjectExceptionHandler {
#ExceptionHandler(value = ExceptionOne.class)
public R exceptionOne(ExceptionOne exe) {
//set proper response code and return values
}
#ExceptionHandler(value = ExceptionTwo.class)
public R exceptionTwo(ExceptionTwo exe) {
//set proper response code and return values
}
}
Option(2): Configure Exceptions in Controller Class itself
If you are looking for handling the exceptions within the Controller class itself, then you can do that as below:
#Controller
public class ApiImpl {
public String methodOne(...) {
}
#ExceptionHandler(ExceptionOne.class)
public R exceptionTwo(ExceptionOne exe) {
//set proper response code and return values
}
//other exceptions
}
You can look more on this at here
I did all the setup for error handling
#PostConstruct
public void addStateMachineInterceptor() {
stateMachine.getStateMachineAccessor().withRegion().addStateMachineInterceptor(interceptor);
stateMachine.getStateMachineAccessor().doWithRegion(errorinterceptor);
}
created interceptor to handle error:
#Service
public class OrderStateMachineFunction<T> implements StateMachineFunction<StateMachineAccess<String, String>> {
#Override
public void apply(StateMachineAccess<String, String> stringStringStateMachineAccess) {
stringStringStateMachineAccess.addStateMachineInterceptor(
new StateMachineInterceptorAdapter<String, String>() {
#Override
public Exception stateMachineError(StateMachine<String, String> stateMachine,
Exception exception) {
// return null indicating handled error
return exception;
}
});
}
}
But I can't see the call going into OrderStateMachineFunction, when we throw the exception from the action.
And after that state machine behave some wired way, like it stops calling preStateChange method after this.stateMachine.sendEvent(eventData);. It seems state machine breaks down after you throw the exception from the action.
#Service
public class OrderStateMachineInterceptor extends StateMachineInterceptorAdapter {
#Override
public void preStateChange(State newState, Message message, Transition transition, StateMachine stateMachine) {
System.out.println("Manish");
}
}
After trying few bit, I have seen that if I comment the resetStateMachine, it works as expected, but without that I am not able to inform the currentstate to state machine:
public boolean fireEvent(Object data, String previousState, String event) {
Message<String> eventData = MessageBuilder.withPayload(event)
.setHeader(DATA_KEY, data)
.build();
this.stateMachine.stop();
// this.stateMachine
// .getStateMachineAccessor()
// .withRegion()
// .resetStateMachine(new DefaultStateMachineContext(previousState, event, eventData.getHeaders(), null));
this.stateMachine.start();
return this.stateMachine.sendEvent(eventData);
}
Not sure if you still need this. But I bumped into similar issue. I wanted to propagate exception from state machine to the caller. I implemented StateMachineInterceptor. And inside the state machine transition functions I am setting:
try
{
..
}
catch (WhateverException e)
{
stateMachine.setStateMachineError(e);
throw e;
}
Then inside the interceptor's stateMachineError method, I have added the Exception in the extendedState map:
public Exception stateMachineError(StateMachine<States, Events> stateMachine, Exception exception)
{
stateMachine.getExtendedState().getVariables().put("ERROR", exception);
logger.error("StateMachineError", exception);
return exception;
}
Inside resetStateMachine I have added the interceptor to the statemachine.
a.addStateMachineInterceptor(new LoggingStateMachineInterceptor());
Then when I am calling the sendEvent method, I am doing this:
if (stateMachine.hasStateMachineError())
{
throw (Exception) svtStateMachine.getExtendedState().getVariables().get("ERROR");
}
This is returning the WhateverException right to the caller. Which in my case is a RestController.
The approach I'm taking here is combining the extended state to store errors with an error action.
If an expected exception happens in your action and any class inside of it, I include it in the extended state context
context.getExtendedState().getVariables().put("error", MyBussinessException);
then, on my error action (configured like this)
.withExternal()
.source(State.INIT)
.target(State.STARTED)
.action(action, errorAction)
.event(Events.INIT)
Outside machine context, I always check if that field is present or not, and translate it to proper response code.
If any exception is thrown from action, error action will be triggered. There you can check known errors (and let them bubble up), or include a new errors (if that was unexpected)
public class ErrorAction implements Action<States, Events> {
#Override
public void execute(StateContext<States, Events> context) {
if(!context.getExtendedState().getVariables().containsKey("error")
context.getExtendedState().getVariables().put("error", new GenericException());
}
}
I am using netty for developing my server.
I am also implementing the Idle state handling in netty.
I got it working but an issue I recently found out.
I can't access the channel context attributes inside the userEventTriggered method.
here is my code and can anybody tell me why it is not possible.
I am setting it like
public static final AttributeKey<Agent> CLIENT_MAPPING = AttributeKey.valueOf("clientMapping");
...
ctx.attr(CLIENT_MAPPING).set(agent);
and inside handler, I am getting the value like (this is working perfectly)
Agent agent = ctx.attr(CLIENT_MAPPING).get();
But inside userEventTriggered it is returning null. (I am sure that it is set before this function is being called.)
public class Server
{
...
public void run() throws Exception
{
...
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).
channel(NioServerSocketChannel.class).
childHandler(new SslServerInitializer());
...
}
}
class SslServerInitializer extends ChannelInitializer<SocketChannel>
{
#Override
public void initChannel(SocketChannel ch) throws Exception
{
ChannelPipeline pipeline = ch.pipeline();
....
pipeline.addLast("idleStateHandler", new IdleStateHandler(0, 0, Integer.parseInt(Main.configurations.get("netty.idleTimeKeepAlive.ms"))));
pipeline.addLast("idleTimeHandler", new ShelloidIdleTimeHandler());
}
}
class ShelloidIdleTimeHandler extends ChannelDuplexHandler
{
#Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception
{
if (evt instanceof IdleStateEvent)
{
try
{
// This I am getting null, but I confirmed that I set the attribute from my handler and is accessible inside handler.
Agent agt = ctx.attr(WebSocketSslServerHandler.CLIENT_MAPPING).get();
ctx.channel().writeAndFlush(new TextWebSocketFrame("{\"type\":\"PING\", \"userId\": \"" + agt.getUserId() + "\"}"));
}
catch (Exception ex)
{
ctx.disconnect();
ex.printStackTrace();
}
}
}
}
Are you sure you set and get it in the same ChannelHandler? If you want to set and get it in different ChannelHandler you need to use Channel.attr(...)
Following up with this comment of my previous question. I'm trying to throw an exception from the #Around advice, and catch it within the callee class and/or method. But I'm getting this error:
Stacktraces
java.lang.Exception: User not authorized
com.company.aspect.AuthorizeUserAspect.isAuthorized(AuthorizeUserAspect.java:77)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:616)
...
The Aspect code is:
#Aspect
public class AuthorizeUserAspect {
#AuthoWired
private UserService service;
#Pointcut("#annotation(module)")
public void authorizeBeforeExecution(AuthorizeUser module) {}
#Around(value = "authorizeBeforeExecution(module)", argNames="module")
public Object isAuthorized(ProceddingJoinPoint jp, AuthorizeUser module) throws Throwable {
// Check if the user has permission or not
service.checkUser();
if ( /* User has NOT permission */ ) {
throw new MyCustomException("User not authorized"); // => this is line 77
}
return jp.proceed();
}
}
and the Struts's based UI action code is:
#Component
public class DashboardAction extends ActionSupport {
#Override
#AuthorizeUser
public String execute() {
...
}
private void showAccessDenied() {
...
}
}
The question is How or Where I can catch that exception to execute showAccessDenied()?
To handle uncaught exceptions like MyCustomException you need to define a global exception handler in Struts 2. Please check this guide: http://struts.apache.org/2.3.4.1/docs/exception-handling.html
For user interface I'd recommend writing a short code for catching any uncaught exceptions.
class EventQueueProxy extends EventQueue {
#Override
protected void dispatchEvent(AWTEvent newEvent) {
try {
super.dispatchEvent(newEvent);
} catch (Throwable t) {
String message = t.getMessage();
if (message == null || message.length() == 0) {
message = "Fatal: " + t.getClass();
}
JOptionPane.showMessageDialog(null, message, "Unhandled Exception Caught!", JOptionPane.ERROR_MESSAGE);
}
}
}
And then in the ui class:
public static void main(String args[]) {
EventQueue queue = Toolkit.getDefaultToolkit().getSystemEventQueue();
queue.push(new EventQueueProxy());
//your code goes here...
}
Note, it will show the dialog window with an error information each time uncaught exception appears. This is just the suggestion for your ui, for the particular case of your ploblem, do use try for firing method(s) that authorizes a user and catch for firing method(s) that should be executed if the user is not authorized. in such case authorization method should throw an exception if an authorization fails. Then the error will not be printed but the particular method will be fired instead.
That's what I'd add to your code:
#Component
public class DashboardAction extends ActionSupport {
#Override
try {
#AuthorizeUser
public String execute() {
...
}
} catch (Exception e) {
private void showAccessDenied() {
...
}
}
}