I’ve never done this with Log4j2, so I don’t know how convoluted the appender
is.
However, I wouldn’t make the appender actually write the data - I’d just
validate the payload is what I wanted.
I’d try and create the appender in the unit test, install the appender during
the initialization of the test, and then call a method on the appender to
validate the format inside a JUnit assert. Hopefully that makes sense - I
don’t have time to work up an example at the moment.
HTH
> On Nov 9, 2016, at 10:28 AM, idioma <corda.ila...@gmail.com> wrote:
>
> Hi, thanks for your reply. It is exactly what I am trying to do as my
> processor is calling a void method that if a certain condition is met prints
> out LOG.info("some text {}", arg1, arg2). The issue is that I can't really
> Unit test the format of the message because it is a void method. I have had
> a look around in terms of custom appenders and found out that with Log4j2
> (which I am currently using) requires a slightly more convoluted solution.
> Here an example:
>
> import java.io.Serializable;
> import java.util.concurrent.locks.*;
> import org.apache.logging.log4j.core.*;
> import org.apache.logging.log4j.core.appender.AbstractAppender;
> import org.apache.logging.log4j.core.appender.AppenderLoggingException;
> import org.apache.logging.log4j.core.config.plugins.*;
> import org.apache.logging.log4j.core.layout.PatternLayout;
>
> // note: class name need not match the @Plugin name.
> @Plugin(name="MyCustomAppender", category="Core", elementType="appender",
> printObject=true)
> public final class MyCustomAppenderImpl extends AbstractAppender {
>
> private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
> private final Lock readLock = rwLock.readLock();
>
> protected MyCustomAppenderImpl(String name, Filter filter,
> Layout<? extends Serializable> layout, final boolean
> ignoreExceptions) {
> super(name, filter, layout, ignoreExceptions);
> }
>
> // The append method is where the appender does the work.
> // Given a log event, you are free to do with it what you want.
> // This example demonstrates:
> // 1. Concurrency: this method may be called by multiple threads
> concurrently
> // 2. How to use layouts
> // 3. Error handling
> @Override
> public void append(LogEvent event) {
> readLock.lock();
> try {
> final byte[] bytes = getLayout().toByteArray(event);
> System.out.write(bytes);
> } catch (Exception ex) {
> if (!ignoreExceptions()) {
> throw new AppenderLoggingException(ex);
> }
> } finally {
> readLock.unlock();
> }
> }
>
> // Your custom appender needs to declare a factory method
> // annotated with `@PluginFactory`. Log4j will parse the configuration
> // and call this factory method to construct an appender instance with
> // the configured attributes.
> @PluginFactory
> public static MyCustomAppenderImpl createAppender(
> @PluginAttribute("name") String name,
> @PluginElement("Layout") Layout<? extends Serializable> layout,
> @PluginElement("Filter") final Filter filter,
> @PluginAttribute("otherAttribute") String otherAttribute) {
> if (name == null) {
> LOGGER.error("No name provided for MyCustomAppenderImpl");
> return null;
> }
> if (layout == null) {
> layout = PatternLayout.createDefaultLayout();
> }
> return new MyCustomAppenderImpl(name, filter, layout, true);
> }
> }
>
> I wonder whether I am going too far in order to test the log output. I have
> tried to have the log4j2 configurations for the file output working with the
> intent to read the content of the log file, but with no luck. I am not sure
> I can see how to use the above implementation in my test, any idea?
>
> Thank you,
>
> I.
>
>
>
> --
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