CaptureLogs.java

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 * The MIT License (MIT)
 *
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 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
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package org.eolang.maven.log;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.Enumeration;
import org.apache.log4j.Appender;
import org.apache.log4j.ConsoleAppender;
import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;
import org.apache.log4j.spi.LoggingEvent;
import org.junit.jupiter.api.extension.AfterEachCallback;
import org.junit.jupiter.api.extension.BeforeEachCallback;
import org.junit.jupiter.api.extension.ExtendWith;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.ParameterContext;
import org.junit.jupiter.api.extension.ParameterResolver;

/**
 * Captured logs annotation for tests.
 * @todo #2896:90min Make '@CaptureLogs' thread-safe.
 *  'Logs' should contain only messages related to the test.
 *  Currently, '@CaptureLogs' appends all messages that
 *  were logged via 'Logger' to 'Logs', so messages from
 *  other tests (run in parallel) are also included, which causes
 *  problems when tests are run in parallel.
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@ExtendWith(CaptureLogs.CaptureLogsExtension.class)
@SuppressWarnings("JTCOP.RuleAllTestsHaveProductionClass")
public @interface CaptureLogs {

    /**
     * JUnit extension to capture log messages.
     *
     * @since 0.30
     */
    final class CaptureLogsExtension implements
        ParameterResolver, BeforeEachCallback, AfterEachCallback {

        /**
         * Logs.
         */
        private final Logs logs;

        /**
         * Appender.
         */
        private final CaptureLogsAppender appender;

        /**
         * Ctor.
         */
        CaptureLogsExtension() {
            this(new Logs());
        }

        /**
         * Ctor.
         * @param logs Where to save logs from the appender.
         */
        private CaptureLogsExtension(final Logs logs) {
            this(logs, new CaptureLogsAppender(logs));
        }

        /**
         * Ctor.
         * @param logs Where to save logs from the appender.
         * @param appender Appender to use.
         */
        private CaptureLogsExtension(final Logs logs, final CaptureLogsAppender appender) {
            this.logs = logs;
            this.appender = appender;
        }

        @Override
        public void beforeEach(final ExtensionContext context) {
            this.appender.init();
        }

        @Override
        public void afterEach(final ExtensionContext context) {
            this.appender.destroy();
        }

        @Override
        public boolean supportsParameter(
            final ParameterContext param,
            final ExtensionContext extension
        ) {
            return param.getParameter().getType() == Logs.class;
        }

        @Override
        public Object resolveParameter(
            final ParameterContext param,
            final ExtensionContext extension
        ) {
            return this.logs;
        }
    }

    /**
     * Log4j logger appender.
     *
     * @since 0.30
     */
    final class CaptureLogsAppender extends ConsoleAppender {

        /**
         * Where to save logs from the appender.
         */
        private final Logs logs;

        /**
         * Ctor.
         * @param logs Where to save logs from the appender.
         */
        CaptureLogsAppender(final Logs logs) {
            this.logs = logs;
        }

        @Override
        public void append(final LoggingEvent event) {
            this.logs.append(this.getLayout().format(event));
        }

        /**
         * Initialize the appender.
         * Adds appender to the root logger.
         */
        void init() {
            final Logger logger = LogManager.getRootLogger();
            final Enumeration<?> appenders = logger.getAllAppenders();
            if (appenders.hasMoreElements()) {
                final Object next = appenders.nextElement();
                if (next instanceof ConsoleAppender) {
                    this.setLayout(((Appender) next).getLayout());
                }
            }
            logger.addAppender(this);
            this.logs.waitForInit();
        }

        /**
         * Destroy the appender.
         * Removes appender from the root logger.
         */
        void destroy() {
            LogManager.getRootLogger().removeAppender(this);
        }
    }
}