Peer: Allow peer listeners to handle exceptions thrown in the peer thread.

core/src/main/java/com/google/bitcoin/core/AbstractPeerEventListener.java

@@ -45,4 +45,8 @@ public class AbstractPeerEventListener implements PeerEventListener {
     public List<Message> getData(Peer peer, GetDataMessage m) {
         return null;
     }
+
+    @Override
+    public void onException(Throwable throwable) {
+    }
 }

core/src/main/java/com/google/bitcoin/core/Peer.java

@@ -243,6 +243,7 @@ public class Peer {
     }
 
     private void processMessage(MessageEvent e, Message m) throws IOException, VerificationException, ProtocolException {
+        try {
             // Allow event listeners to filter the message stream. Listeners are allowed to drop messages by
             // returning null.
             for (PeerEventListener listener : eventListeners) {
@@ -306,6 +307,17 @@ public class Peer {
             } else {
                 log.warn("Received unhandled message: {}", m);
             }
+        } catch (Throwable throwable) {
+            log.warn("Caught exception in peer thread: {}", throwable.getMessage());
+            throwable.printStackTrace();
+            for (PeerEventListener listener : eventListeners) {
+                try {
+                    listener.onException(throwable);
+                } catch (Exception e1) {
+                    e1.printStackTrace();
+                }
+            }
+        }
     }
 
     private void startFilteredBlock(FilteredBlock m) throws IOException {

core/src/main/java/com/google/bitcoin/core/PeerEventListener.java

@@ -78,4 +78,11 @@ public interface PeerEventListener {
      * items as possible which appear in the {@link GetDataMessage}, or null if you're not interested in responding.
      */
     public List<Message> getData(Peer peer, GetDataMessage m);
+
+    /**
+     * Called if there is an exception thrown in a Netty worker thread whilst processing an inbound message. You
+     * can use this to report crashes of the peer threads back to your apps website, for instance. After this callback
+     * runs the peer will be disconnected. Any exceptions thrown by this method will be logged and ignored.
+     */
+    public void onException(Throwable throwable);
 }

core/src/test/java/com/google/bitcoin/core/PeerTest.java

@@ -17,6 +17,7 @@
 package com.google.bitcoin.core;
 
 import com.google.bitcoin.core.Peer.PeerHandler;
+import com.google.common.collect.Lists;
 import com.google.common.util.concurrent.ListenableFuture;
 import org.easymock.Capture;
 import org.easymock.CaptureType;
@@ -766,6 +767,31 @@ public class PeerTest extends TestWithNetworkConnections {
         peer.setMinProtocolVersion(500);
     }
 
+    @Test
+    public void exceptionListener() throws Exception {
+        wallet.addEventListener(new AbstractWalletEventListener() {
+            @Override
+            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+                throw new NullPointerException("boo!");
+            }
+        });
+        final Throwable[] throwables = new Throwable[1];
+        peer.addEventListener(new AbstractPeerEventListener() {
+            @Override
+            public void onException(Throwable throwable) {
+                throwables[0] = throwable;
+            }
+        });
+        control.replay();
+        connect();
+        Transaction t1 = new Transaction(unitTestParams);
+        t1.addInput(new TransactionInput(unitTestParams, t1, new byte[]{}));
+        t1.addOutput(Utils.toNanoCoins(1, 0), wallet.getChangeAddress());
+        inbound(peer, t1);
+        inbound(peer, new NotFoundMessage(unitTestParams, Lists.newArrayList(new InventoryItem(InventoryItem.Type.Transaction, t1.getInput(0).getHash()))));
+        assertTrue(throwables[0] instanceof NullPointerException);
+    }
+
     // TODO: Use generics here to avoid unnecessary casting.
     private Message outbound() {
         List<DownstreamMessageEvent> messages = event.getValues();