com.netflix.iep.config.Configuration.java Source code

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Here is the source code for com.netflix.iep.config.Configuration.java

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/*
 * Copyright 2015 Netflix, 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
 *
 *     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.
 */
package com.netflix.iep.config;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Proxy;
import java.util.concurrent.atomic.AtomicReference;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.netflix.config.ConfigurationManager;
import org.apache.commons.configuration.AbstractConfiguration;

public final class Configuration {
    private final static Logger LOGGER = LoggerFactory.getLogger(Configuration.class);

    private static final IConfiguration iConfiguration = new IConfiguration() {
        public String get(String key) {
            AbstractConfiguration cfg = ConfigurationManager.getConfigInstance();
            return cfg.getString(key);
        }
    };

    public static <T> T apply(Class<T> ctype) {
        String pkg = ctype.getPackage().getName();
        String prefix = (pkg.startsWith("com.")) ? pkg.substring("com.".length()) : pkg;
        return newProxy(ctype, prefix);
    }

    @SuppressWarnings("unchecked")
    public static <T> T newProxy(final Class<T> ctype, final String prefix) {
        InvocationHandler handler = new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                if (method.getName().equals("get")) {
                    return iConfiguration.get((args[0] == null) ? null : args[0].toString());
                } else {
                    Class rt = method.getReturnType();
                    String key = (prefix == null) ? method.getName() : prefix + "." + method.getName();
                    if (IConfiguration.class.isAssignableFrom(rt)) {
                        return newProxy(rt, key);
                    } else {
                        String value = iConfiguration.get(key);
                        if (value == null) {
                            DefaultValue anno = method.getAnnotation(DefaultValue.class);
                            value = (anno == null) ? null : anno.value();
                        }
                        if (value == null) {
                            if (rt.isPrimitive())
                                throw new IllegalStateException("no value for property " + method.getName());
                            return null;
                        }
                        return Strings.cast(rt, value);
                    }
                }
            }
        };
        return (T) Proxy.newProxyInstance(ctype.getClassLoader(), new Class[] { ctype }, handler);
    }
}