This is the java notifier library for integrating your app with the Yeller exception notifier.

When an uncaught exception occurs, this library will record the exception in Yeller, letting you diagnose bugs in your running app.

Adding to your project

yeller-java is distributed via maven. Assuming your build system is maven compatible, you can add the following xml snippets to your pom file to import it:

<dependency>
  <groupId>yeller-java-api</groupId>
  <artifactId>yeller-java-api</artifactId>
  <version>1.2.0</version>
</dependency>

<repositories>
  <repository>
    <id>clojars.org</id>
    <url>http://clojars.org/repo</url>
  </repository>
</repositories>

Integrating

Once you've got the jar installed, you'll need to get running with a Yeller client. This means you'll need the api key from your Yeller project (which you can find on your project's setting screen). Once you have the api key, you instantiate a client with it thusly:

YellerClient yellerClient = new YellerHTTPClient("YOUR_API_KEY_HERE");

To report an exception, simply pass it into java yellerClient.report. That's all there is to it, we report the exception to the server. You'll be fixing your bugs in no time.

Report your own exception

try {
  // Your code here
} catch (Throwable t) {
  yellerClient.report(t);
  throw t;
}

Reporting more data

Yeller's api lets you include more detail with your exception. Yeller's Java client exposes two additional arguments to yellerClient.report, one that takes a HashMap<String, Object> of custom data to include (e.g. params, session, cookies, user information etc), and one that adds some extra information (url, location, which environment the app is running in).

Custom Data

Simply pass a HashMap<String, Object> to report.

try {
  // Your code here
} catch (Throwable t) {
  HashMap<String, Object> custom = new HashMap<String, Object>();
  custom.put("user_email", "[email protected]");
  yellerClient.report(t, custom);
  throw t;
}

Extra Detail

Construct and pass a YellerExtraDetail (which has a builder like interface):

try {
  // Your code here
} catch (Throwable t) {
  YellerExtraDetail detail = new YellerExtraDetail()
    .withApplicationEnvironment("production")
    .withUrl("http://example.com/error")
    .withLocation("UserServlet");
  yellerClient.report(t, extraDetail);
  throw t;
}

All of the fields are optional, so just miss out any that you can't fill in.

If you really want, you can also customize the datetime reported, by setting withDate on YellerExtraDetail. This takes a java.util.Date, and will UTC format it before sending it over the wire. This is not reccommended for most use (usually the client fills it in for you), but it's there if you need it.

** Bolth **

Of course, you can add both custom data and extra detail:

try {
  // Your code here
} catch (Throwable t) {
  YellerExtraDetail detail = new YellerExtraDetail()
    .withApplicationEnvironment("production")
    .withUrl("http://example.com/error")
    .withLocation("UserServlet");
  HashMap<String, Object> custom = new HashMap<String, Object>();
  custom.put("user_email", "[email protected]");
  yellerClient.report(t, detail, custom);
  throw t;
}

Uncaught Exception Handler

YellerHTTPClient also implements java.lang.Thread.UncaughtExceptionHandler. To se it as the default exception handler across all your threads:

Thread.setDefaultUncaughtExceptionHandler(yeller);

(it isn't set by default. Global mutable state :(((( )

Configuration

YellerClient (at the moment) exposes a few single configuration options. The one you are most likely to look at is setErrorHandler. This lets you plug in how you handle exceptions out of Yeller's servers. You can implement a new error handler by implementing the interface YellerErrorHandler, maybe logging to a particular logging framework, or sending to syslog, etc.

The standard error handler doesn't report IO exceptions at all, and prints authorization errors to stderr (these will only happen if you get your api key wrong, or your project got deleted).

Customizing the error handler:

client.setErrorHandler(myErrorHandler);

Writing your own error handler:

Here's the source code of the STDERRErrorHandler, which prints authorization errors to STDERR. Writing your own error handler looks much like this, just implement YellerErrorHandler, then pass it into client.setErrorHandler. You might want to do this for e.g. integration with a logging library you use.

package com.yellerapp.client;

public class STDERRErrorHandler implements YellerErrorHandler {

    public void reportAuthError(String backend, Throwable e) {
        System.err.println(backend);
        e.printStackTrace(System.err);
    }

    public void reportIOError(String backend, Throwable e) {
        // purposefully do nothing
    }

}

The other configuration option, which is only really exposed for testing purposes is setUrls. This lets you set which yeller backends to talk to, but is not intended for production use at all.

Robustness

This client does some basic roundtripping/timeouts, so it can handle problems with individual yeller servers. After trying all the servers twice, it will stop reporting the current exception, then try each one again for the next one.