SystemEnvHelper.java

/*
 * Copyright (C) 2018-2019 Chatopera Inc, <https://www.chatopera.com>
 *
 * 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.chatopera.cc.util;

import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class SystemEnvHelper {
    private final static Logger logger = LoggerFactory.getLogger(SystemEnvHelper.class);
    private static Properties props;

    /**
     * 根据类的全名查找是否存在
     *
     * @param classFullName
     * @return
     */
    public static boolean isClassExistByFullName(final String classFullName) {
        try {
//             Class<?> uriClass =
            Class.forName(classFullName);
            return true;
        } catch (ClassNotFoundException ex) {
            return false;
        }
    }


    /**
     * 获得环境变量的值，如果不存在，返回默认值
     *
     * @param variable
     * @param defaultvalue
     * @return
     */
    public static String getenv(final String variable, final String defaultvalue) {
        final String val = System.getenv(variable);

        if (StringUtils.isBlank(val)) {
            return defaultvalue;
        }
        return val;
    }


    /**
     * 加载配置，先检查环境变量，再从application properties加载
     *
     * @param property
     * @return
     */
    public static String parseFromApplicationProps(final String property) {
        // 将 property 转化为环境变量
        String P = StringUtils.upperCase(property);

        P = StringUtils.replaceChars(P, "-", "_");
        P = StringUtils.replaceChars(P, ".", "_");
        String val = System.getenv(P);

        if (StringUtils.isBlank(val)) {
            val = getProps().getProperty(property);
        }
        return val;
    }

    /**
     * Get properties filename
     * @return
     */
    private static String getPropsFileName() {
        String profile = getenv("SPRING_PROFILES_ACTIVE", "");
        if (StringUtils.isNotBlank(profile)) {
            return "application-" + profile + ".properties";
        }
        return "application.properties";
    }

    /**
     * 加载 application.properties
     *
     * @return
     */
    private static Properties getProps() {
        if (props == null) {
            try (InputStream input = SystemEnvHelper.class.getClassLoader().getResourceAsStream(
                    getPropsFileName())) {
                // load a properties file
                props = new Properties();
                props.load(input);
            } catch (IOException ex) {
                logger.error("[getProps] error", ex);
            }
        }
        return props;
    }

}