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Micro Distribution of the Payara Project
There is a newer version: 7.2024.1.Alpha1
/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 *    Copyright (c) [2018-2023] Payara Foundation and/or its affiliates. All rights reserved.
 *
 *     The contents of this file are subject to the terms of either the GNU
 *     General Public License Version 2 only ("GPL") or the Common Development
 *     and Distribution License("CDDL") (collectively, the "License").  You
 *     may not use this file except in compliance with the License.  You can
 *     obtain a copy of the License at
 *     https://github.com/payara/Payara/blob/master/LICENSE.txt
 *     See the License for the specific
 *     language governing permissions and limitations under the License.
 *
 *     When distributing the software, include this License Header Notice in each
 *     file and include the License file at glassfish/legal/LICENSE.txt.
 *
 *     GPL Classpath Exception:
 *     The Payara Foundation designates this particular file as subject to the "Classpath"
 *     exception as provided by the Payara Foundation in the GPL Version 2 section of the License
 *     file that accompanied this code.
 *
 *     Modifications:
 *     If applicable, add the following below the License Header, with the fields
 *     enclosed by brackets [] replaced by your own identifying information:
 *     "Portions Copyright [year] [name of copyright owner]"
 *
 *     Contributor(s):
 *     If you wish your version of this file to be governed by only the CDDL or
 *     only the GPL Version 2, indicate your decision by adding "[Contributor]
 *     elects to include this software in this distribution under the [CDDL or GPL
 *     Version 2] license."  If you don't indicate a single choice of license, a
 *     recipient has the option to distribute your version of this file under
 *     either the CDDL, the GPL Version 2 or to extend the choice of license to
 *     its licensees as provided above.  However, if you add GPL Version 2 code
 *     and therefore, elected the GPL Version 2 license, then the option applies
 *     only if the new code is made subject to such option by the copyright
 *     holder.
 */
package fish.payara.microprofile.metrics.impl;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.function.Supplier;

import jakarta.enterprise.inject.Vetoed;
import org.eclipse.microprofile.metrics.Gauge;

@Vetoed
public class GaugeImpl implements Gauge, Supplier {

    private final Method method;
    private final Object target;

    public GaugeImpl() {
        method = null;
        target = null;
    }

    public GaugeImpl(Method method, Object target) {
        this.method = method;
        this.target = target;
        method.setAccessible(true);
    }

    @Override
    public T get() {
        return getValue();
    }

    @Override
    public T getValue() {
        return invokeMethod(method, target);
    }

    @SuppressWarnings("unchecked")
    private T invokeMethod(Method method, Object target) {
        try {
            return (T) method.invoke(target);
        } catch (IllegalAccessException | InvocationTargetException cause) {
            throw new IllegalStateException("Error while invoking method [" + method + "]", cause);
        }
    }

    @Override
    public String toString() {
        return "Gauge[" + getValue() + "]";
    }
}