com.alibaba.fastjson.util.ServiceLoader Maven / Gradle / Ivy

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Adapter alibaba fastjson to other json libraries. the fastjson version: 1.2.58
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/*
 * Copyright 2019 the original author or authors.
 *
 * Licensed under the Apache, 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.gnu.org/licenses/lgpl-3.0.html
 *
 * 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 com.alibaba.fastjson.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;

public class ServiceLoader {

    private static final String PREFIX = "META-INF/services/";

    private static final Set loadedUrls = new HashSet();

    @SuppressWarnings("unchecked")
    public static  Set load(Class clazz, ClassLoader classLoader) {
        if (classLoader == null) {
            return Collections.emptySet();
        }

        Set services = new HashSet();

        String className = clazz.getName();
        String path = PREFIX + className;

        Set serviceNames = new HashSet();

        try {
            Enumeration urls = classLoader.getResources(path);
            while (urls.hasMoreElements()) {
                URL url = urls.nextElement();
                if (loadedUrls.contains(url.toString())) {
                    continue;
                }
                load(url, serviceNames);
                loadedUrls.add(url.toString());
            }
        } catch (Throwable ex) {
            // skip
        }

        for (String serviceName : serviceNames) {
            try {
                Class serviceClass = classLoader.loadClass(serviceName);
                T service = (T) serviceClass.newInstance();
                services.add(service);
            } catch (Exception e) {
                // skip
            }
        }

        return services;
    }

    public static void load(URL url, Set set) throws IOException {
        InputStream is = null;
        BufferedReader reader = null;
        try {
            is = url.openStream();
            reader = new BufferedReader(new InputStreamReader(is, "utf-8"));
            for (; ; ) {
                String line = reader.readLine();
                if (line == null) {
                    break;
                }

                int ci = line.indexOf('#');
                if (ci >= 0) {
                    line = line.substring(0, ci);
                }
                line = line.trim();
                if (line.length() == 0) {
                    continue;
                }
                set.add(line);
            }
        } finally {
            IOUtils.close(reader);
            IOUtils.close(is);
        }
    }
}