Properly propagate exceptions type from server client. (#150)

***Problem***
Errors generated from the `Responder` are serialized according to the spec
https://github.com/ReactiveSocket/reactivesocket/blob/master/Protocol.md#error-codes
but the type is lost when deserializing by the `Requester`.

***Solution***
Instead of generating a RuntimeException containing the string of the error,
generate the right Exception type based on the error code.
This allow user code, or filter to make smart decision based on the Exception
type (Retryable, ...)

Author: stevegury

reactivesocket-core/src/main/java/io/reactivesocket/exceptions/TransportException.java

@@ -24,5 +24,4 @@ public TransportException(Throwable t) {
     public synchronized Throwable fillInStackTrace() {
         return this;
     }
-
 }

reactivesocket-core/src/main/java/io/reactivesocket/internal/Requester.java

@@ -15,7 +15,6 @@
  */
 package io.reactivesocket.internal;
 
-import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.Collection;
@@ -837,9 +836,8 @@ public void onNext(Frame frame) {
                 cancel();
             } else if (type == FrameType.ERROR) {
                 terminated.set(true);
-                final ByteBuffer byteBuffer = frame.getData();
-                String errorMessage = getByteBufferAsString(byteBuffer);
-                onError(new RuntimeException(errorMessage));
+                Throwable throwable = Exceptions.from(frame);
+                onError(throwable);
                 cancel();
             } else {
                 onError(new RuntimeException("Unexpected FrameType: " + frame.getType()));

reactivesocket-core/src/test/java/io/reactivesocket/LeaseTest.java

@@ -15,6 +15,7 @@
  */
 package io.reactivesocket;
 
+import io.reactivesocket.exceptions.RejectedException;
 import io.reactivesocket.internal.Publishers;
 import io.reactivesocket.internal.Responder;
 import org.junit.After;
@@ -182,7 +183,7 @@ public void testWriteWithoutLease() throws InterruptedException {
         TestSubscriber<Payload> ts2 = new TestSubscriber<>();
         response2.subscribe(ts2);
         ts2.awaitTerminalEvent(500, TimeUnit.MILLISECONDS);
-        ts2.assertError(RuntimeException.class);
+        ts2.assertError(RejectedException.class);
     }
 
     @Test(timeout=2000)

reactivesocket-core/src/test/java/io/reactivesocket/internal/RequesterTest.java

@@ -21,6 +21,7 @@
 import io.reactivesocket.LatchedCompletable;
 import io.reactivesocket.Payload;
 import io.reactivesocket.TestConnection;
+import io.reactivesocket.exceptions.InvalidRequestException;
 import io.reactivesocket.util.PayloadImpl;
 import io.reactivex.Observable;
 import io.reactivex.subjects.ReplaySubject;
@@ -165,7 +166,7 @@ public void testRequestResponseError() throws InterruptedException {
 
         conn.toInput.send(Frame.Error.from(2, new RuntimeException("Failed")));
         ts.awaitTerminalEvent(500, TimeUnit.MILLISECONDS);
-        ts.assertError(Exception.class);
+        ts.assertError(InvalidRequestException.class);
         assertEquals("Failed", ts.errors().get(0).getMessage());
     }
 
@@ -313,7 +314,7 @@ public void testRequestStreamError() throws InterruptedException {
         conn.toInput.send(utf8EncodedErrorFrame(2, "Failure"));
 
         ts.awaitTerminalEvent(500, TimeUnit.MILLISECONDS);
-        ts.assertError(Exception.class);
+        ts.assertError(InvalidRequestException.class);
         ts.assertValue(utf8EncodedPayload("hello", null));
         assertEquals("Failure", ts.errors().get(0).getMessage());
     }