From 48785248ddcd0b174fe63aba5aa4f4b5473773d6 Mon Sep 17 00:00:00 2001
From: Mikael Bung <mikael@comoyo.com>
Date: Tue, 27 May 2014 09:45:46 +0200
Subject: [PATCH] JUL logging uncaught exception handler

The default uncaught exception handler logs to stderr which means that uncaught exceptions
can potentially be logged outside of the context of the rest of the logs. UncaughtExceptionHandler
is a default exception handler replacement which logs using jul instead of printing directly to stderr.
In case jul logging fails stderr is used as a fallback.
---
 README.md                                     |  1 +
 logging-utilities/pom.xml                     | 13 ++++
 .../utilities/UncaughtExceptionHandler.java   | 61 +++++++++++++++++++
 pom.xml                                       |  1 +
 4 files changed, 76 insertions(+)
 create mode 100644 logging-utilities/pom.xml
 create mode 100644 logging-utilities/src/main/java/com/comoyo/commons/logging/utilities/UncaughtExceptionHandler.java

diff --git a/README.md b/README.md
index 2b46d62..ac2964c 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,7 @@ The list of components currently reads as follows:
 * [logging-context](logging-context) Structured application state/context for logging
 * [logging-context-gelf](logging-context-gelf) Context-aware GELF log handler
 * [logging-context-json](logging-context-json) Context-aware JSON/logstash log formatter
+* [logging-utilities](logging-utilities) Helpers for logging. Sensible default exception handler which logs to jul.
 * [pb-json](pb-json) Hassle-free conversion from Protobuf to JSON and back
 * [emjar](emjar) Class loader and supporting cast for using jar-in-jar embedded archives as part of classpath
 * [emjar-maven-plugin](emjar-maven-plugin) Generate EmJar-enabled bundle archives from Maven
diff --git a/logging-utilities/pom.xml b/logging-utilities/pom.xml
new file mode 100644
index 0000000..0f10321
--- /dev/null
+++ b/logging-utilities/pom.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>commons</artifactId>
+        <groupId>com.comoyo</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>logging-utilities</artifactId>
+</project>
diff --git a/logging-utilities/src/main/java/com/comoyo/commons/logging/utilities/UncaughtExceptionHandler.java b/logging-utilities/src/main/java/com/comoyo/commons/logging/utilities/UncaughtExceptionHandler.java
new file mode 100644
index 0000000..a67b15c
--- /dev/null
+++ b/logging-utilities/src/main/java/com/comoyo/commons/logging/utilities/UncaughtExceptionHandler.java
@@ -0,0 +1,61 @@
+/**
+ * Copyright (C) 2014 Telenor Digital AS
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.comoyo.commons.logging.utilities;
+
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * Uncaught exception handler which logs exceptions using JUL.
+ */
+public final class UncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
+    private static final Logger logger = Logger.getLogger(UncaughtExceptionHandler.class.getName());
+
+    private UncaughtExceptionHandler() {}
+
+    public void uncaughtException(Thread thread, Throwable throwable) {
+        if (throwable instanceof ThreadDeath) {
+            return;
+        }
+        try {
+            logger.log(Level.WARNING, "Uncaught exception in thread \""
+                    + thread.getName() + "\" ", throwable);
+        } catch (Error e) {
+            // Desperation attempt to not lose log messages, in case of error
+            // try to log it on sdterr.
+            // This logging matches the default behaviour if no UncaughtExceptionHandler
+            // is registered.
+            if (!(e instanceof ThreadDeath)) {
+                System.err.print("Exception when logging uncaught exception");
+                e.printStackTrace(System.err);
+            }
+            System.err.print("Uncaught exception in thread \""
+                    + thread.getName() + "\" ");
+            throwable.printStackTrace(System.err);
+            if (e instanceof ThreadDeath) {
+                throw e;
+            }
+        }
+    }
+
+    /**
+     * Install UncaughtExceptionHandler as the default uncaught exception handler.
+     */
+    public static void install() {
+        Thread.setDefaultUncaughtExceptionHandler(new UncaughtExceptionHandler());
+    }
+}
diff --git a/pom.xml b/pom.xml
index 5e62766..7d0179c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -44,6 +44,7 @@
     <module>logging-context</module>
     <module>logging-context-gelf</module>
     <module>logging-context-json</module>
+    <module>logging-utilities</module>
     <module>emjar</module>
     <module>emjar-maven-plugin</module>
   </modules>