/*
 * Copyright 2021 VMware, Inc.
 *
 * 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
 *
 * https://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 io.micrometer.core.util.internal.logging;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.Supplier;

/**
 * Simple {@link InternalLoggerFactory} implementation that always returns an instance of
 * {@link MockLogger} so components that fetch the logger this way:
 * <code>InternalLogger logger = InternalLoggerFactory.getInstance(MyClass.class);</code>,
 * get a {@link MockLogger} instance if they are created using
 * <code>factory.injectLogger(MyClass::new)</code> or if
 * <code>InternalLoggerFactory.setDefaultFactory(mockLoggerFactory);</code> was set
 * previously.
 *
 * @author Jonatan Ivanov
 */
public class MockLoggerFactory extends InternalLoggerFactory {

    private final ConcurrentMap<String, MockLogger> loggers = new ConcurrentHashMap<>();

    /**
     * A convenient way to create a logger. In contrast of {@link #getInstance(Class)},
     * this method returns a {@link MockLogger} instead of an
     * {@link InternalLoggerFactory} so that you don't need to cast.
     * @param clazz The class that you need the logger for.
     * @return An instance of {@link MockLogger} for the provided class.
     */
    public MockLogger getLogger(Class<?> clazz) {
        return getLogger(clazz.getName());
    }

    /**
     * A convenient way to create a logger. In contrast of {@link #getInstance(String)},
     * this method returns a {@link MockLogger} instead of an
     * {@link InternalLoggerFactory} so that you don't need to cast.
     * @param name The name of the logger.
     * @return An instance of {@link MockLogger} for the provided name.
     */
    public MockLogger getLogger(String name) {
        return loggers.computeIfAbsent(name, MockLogger::new);
    }

    /**
     * A factory method that returns the result of the given {@code Supplier} and it also
     * injects the default factory. So if the logger is created this way:
     * <code>InternalLogger logger = InternalLoggerFactory.getInstance(MyClass.class);</code>,
     * the resulted logger will be a {@link MockLogger}.
     * @param supplier The logic that creates the object you need to inject the logger
     * into.
     * @param <T> The type of an object that will be created by the {@code Supplier}.
     * @return The result of the {@code Supplier}.
     */
    public <T> T injectLogger(Supplier<T> supplier) {
        synchronized (this) {
            InternalLoggerFactory original = getDefaultFactory();
            setDefaultFactory(this);
            T object = supplier.get();
            setDefaultFactory(original);

            return object;
        }
    }

    @Override
    protected InternalLogger newInstance(String name) {
        return getLogger(name);
    }

}

@@ -2453,11 +2453,8 @@
 and 
-it 
 also
@@ -2676,24 +2676,228 @@
 ockLogger%7D.%0A
+     * %3Cp%3E%0A     * NOTE: This doesn't work when a target logger is a static field and has been%0A     * initialized already. Use a non-static field for a target logger to make this work%0A     * consistently.%0A
      * @para

Add a note for MockLoggerFactory.injectLogger() about its limitation (#3184)