java

java读取properties文件

在Java项目中，有很多场景需要读取配置文件的配置信息，比如properties文件。但是在Java项目中我们通常采用通过加载编译运行环境（target/class）下文件下加载，但是当项目打成jar包运行在Linux中就读取不到配置文件。本文介绍的是三个方法来读取properties文件。详细代码如下：

PropertiesUtil.java

package com.lakala.exices.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.util.Properties;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
 * 属性 工具操作类
 * 
 */
public class PropertiesUtil {
    static Logger logger = LoggerFactory.getLogger(PropertiesUtil.class);
    /**
     * 这是从resources/conf下读取的文件，如果配置文件不在conf下而直接在resources下则去除conf/
     */
    static String CONFIG_FILE = "conf/xxx.properties";
    static Properties memProperties = null;
    /**
     * 设置配置文件
     * 
     * @param fileName
     */
    public static void setConfigFile(String fileName) {
        if (StringUtils.isNotBlank(fileName)) {
            PropertiesUtil.CONFIG_FILE = fileName;
        }
    }
    /**
     * 通过key获取配置值
     * 
     * @param key
     * @return
     * @throws Exception
     */
    public static String getProperty(String key) throws Exception {
        return getProperty(key, null);
    }
    public static String getProperty(String key, String defaultVl) throws Exception {
        if (null == memProperties) {
            logger.info("The memProperties is empty ,read properties from " + CONFIG_FILE);
            memProperties = loadPropertiesFromFile(null);
        }
        String value = memProperties.getProperty(key, defaultVl);
        if (null == value) {
            String info = "Cannot get valid value for the key:" + key + " from file " + CONFIG_FILE;
            throw new Exception(info);
        }
        return value;
    }
    /**
     * 读取配置文件
     * 
     * @param fileName:配置文件名称
     * @return
     */
    protected static Properties loadPropertiesFromFile(String fileName) throws Exception {
        if (fileName == null || fileName.isEmpty()) {
            fileName = CONFIG_FILE;
        }
        memProperties = new Properties();
        FileInputStream in = null;
        try {
            logger.info("propertyUtil.classLoader=" + PropertiesUtil.class.getClassLoader());
            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
            InputStream inputStream = classLoader.getResourceAsStream(fileName);// 以数据流的方式加载
            /**
             * Method1:
             */
            if (inputStream == null) {
                inputStream = PropertiesUtil.class.getResourceAsStream(fileName);
            }
            /**
             * Method2:
             */
            if (inputStream == null) {
                inputStream = PropertiesUtil.class.getClassLoader().getResourceAsStream(fileName);
            }
            /**
             * Method3:
             */
            if (inputStream == null) {
                String localPath = new PropertiesUtil().getClass().getClassLoader().getResource(".").getPath();
                int idx = localPath.indexOf(":") + 1;
                localPath = localPath.substring(idx);
                String filePathName = localPath + fileName;
                inputStream = new FileInputStream(filePathName);
            }
            memProperties.load(inputStream);
        } catch (Exception ex) {
            logger.error("Error occured when reading the properties file：" + fileName, ex);
            throw ex;
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (Exception ex) {
                    //
                }
                in = null;
            }
        }
        return memProperties;
    }
    public static void main(String[] args) throws Exception {
        PropertiesUtil.setConfigFile("conf/manager.properties");
        System.out.println(PropertiesUtil.getProperty("basePath"));
        System.out.println(PropertiesUtil.getProperty("outFilePath"));
    }
}