co.elastic.apm.agent.sdk.DynamicTransformer Maven / Gradle / Ivy

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/*-
 * #%L
 * Elastic APM Java agent
 * %%
 * Copyright (C) 2018 - 2020 Elastic and contributors
 * %%
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you 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.
 * #L%
 */
package co.elastic.apm.agent.sdk;

import co.elastic.apm.agent.shaded.bytebuddy.description.type.TypeDescription;
import co.elastic.apm.agent.shaded.bytebuddy.matcher.ElementMatcher;

import java.util.Collection;
import java.util.ServiceLoader;

public interface DynamicTransformer {

    /**
     * Instruments a specific class at runtime with one or multiple instrumentation classes.
     * 
     * Note that {@link ElasticApmInstrumentation#getTypeMatcher()} will be
     * {@linkplain co.elastic.apm.agent.shaded.bytebuddy.matcher.ElementMatcher.Junction#and(ElementMatcher) conjoined} with a
     * computed {@link ElementMatcher}{@code <}{@link TypeDescription}{@code >}
     * that is specific to the provided class to instrument.
     * 
     *
     * @param classToInstrument      the class which should be instrumented.
     * @param instrumentationClasses the instrumentation which should be applied to the class to instrument.
     */
    void ensureInstrumented(Class classToInstrument, Collection> instrumentationClasses);

    class Accessor {
        private static final DynamicTransformer transformer;

        static {
            ClassLoader classLoader = Accessor.class.getClassLoader();
            if (classLoader == null) {
                classLoader = ClassLoader.getSystemClassLoader();
            }
            // loads the implementation provided by the core module without depending on the class or class name
            transformer = ServiceLoader.load(DynamicTransformer.class, classLoader).iterator().next();
        }

        public static DynamicTransformer get() {
            return transformer;
        }
    }

}