Java中獲取包含變量的配置文件config.properties內容

應用場景

有些時候項目中會用到不少路徑，而且極可能多個路徑在同一個根目錄下，那爲了方便配置的修改，達到只修改根目錄便可達到一改全改的效果，此時就會想到要是有變量就行了；

另外有時候路徑中的文件名是不肯定的，要靠業務程序運行時去判斷文件名應該如何設置，而又但願此文件下的目錄名是肯定的，那此時用變量也是比較好的解決方式。

示例代碼

config.properties 以下

#根目錄
root_path = D:/myroot

#用戶目錄
users_path = ${root_path}/users

#用戶相冊目錄
pictures_path = ${users_path}/{username}/pictures/{year}/{month}/{date}

#用戶文件目錄
files_path = ${users_path}/{username}/files/{year}/{month}/{date}

#系統日誌文件
logs_path = ${root_path}/logs

說明：${root_path}形式的做爲配置文件中路徑變量；{year}形式的做爲運行時替換的字段。

PropertiesUtil 工具類以下，用於配置文件值和轉化變量

package com.tz.util;

import java.io.IOException;
import java.io.InputStream;
import java.util.Calendar;
import java.util.Map;
import java.util.Properties;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * 
 * @author tianzhen
 *
 */
public enum PropertiesUtil {
    
    ROOT_PATH("root_path"),
    USERS_PATH("users_path"),
    PICTURES_PATH("pictures_path"),
    FILES_PATH("files_path"),
    LOGS_PATH("logs_path");
    
    private String title;
    private static Properties props;
    private PropertiesUtil(String title){
        this.title = title;
    }

    private static final String PROPERTIES = "config.properties";
    
    private static final Pattern PATTERN = Pattern.compile("\\$\\{([^\\}]+)\\}");
    
    static{
        try {
            props = new Properties();
            InputStream ins = PropertiesUtil.class.getClassLoader().getResourceAsStream(PROPERTIES);
            props.load(ins);
            ins.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    private String getTitle() {
        return title;
    }

    public static String getTranslate(PropertiesUtil prop, Map<String, String> params){
        String path = get(prop);
        if(path==null||path.equals("")){
            return "";
        }
        if(params!=null && !params.keySet().isEmpty()){
            //須要替換的字段均放入map中，包括須要替換的日期
            for(String key : params.keySet()){
                path = path.replace("{"+key+"}", params.get(key));
            }
        }
        
        //如不指定日期，則替換爲當前日期
        Calendar cal = Calendar.getInstance();
        path = path.replace("{year}", cal.get(Calendar.YEAR)+"")
                .replace("{month}", cal.get(Calendar.MONTH)+1>9?cal.get(Calendar.MONTH)+1+"":"0"+(cal.get(Calendar.MONTH)+1))
                .replace("{date}", cal.get(Calendar.DATE)>9?cal.get(Calendar.DATE)+"":"0"+cal.get(Calendar.DATE));
        
        return path;
    }
    
    public static String get(PropertiesUtil prop){
        String value = props.getProperty(prop.getTitle());
        return value==null?null:loop(value);
    }
    
    @SuppressWarnings("static-access")
    private static String loop(String key){
        //定義matcher匹配其中的路徑變量
        Matcher matcher = PATTERN.matcher(key);
        StringBuffer buffer = new StringBuffer();
        boolean flag = false;
        while (matcher.find()) {
            String matcherKey = matcher.group(1);//依次替換匹配到的路徑變量
            String matchervalue = props.getProperty(matcherKey);
            if (matchervalue != null) {
                matcher.appendReplacement(buffer, matcher.quoteReplacement(matchervalue));//quoteReplacement方法對字符串中特殊字符進行轉化
                flag = true;
            }
        }
        matcher.appendTail(buffer);
        //flag爲false時說明已經匹配不到路徑變量，則不須要再遞歸查找
        return flag?loop(buffer.toString()):key;
    }

}

測試代碼以下

package com.tz.test;

import java.util.HashMap;
import java.util.Map;

import com.tz.util.PropertiesUtil;

public class Test {

    public static void main(String[]  args) {
        System.out.println("********無參取路徑***********");
        System.out.println("    [root_path] "+PropertiesUtil.get(PropertiesUtil.ROOT_PATH));
        System.out.println("   [users_path] "+PropertiesUtil.get(PropertiesUtil.USERS_PATH));
        System.out.println("[pictures_path] "+PropertiesUtil.get(PropertiesUtil.PICTURES_PATH));
        System.out.println("   [files_path] "+PropertiesUtil.get(PropertiesUtil.FILES_PATH));
        System.out.println("    [logs_path] "+PropertiesUtil.get(PropertiesUtil.LOGS_PATH));
        
        System.out.println("\n********無參轉化取路徑***********");
        System.out.println("    [root_path] "+PropertiesUtil.getTranslate(PropertiesUtil.ROOT_PATH , null));
        System.out.println("   [users_path] "+PropertiesUtil.getTranslate(PropertiesUtil.USERS_PATH, null));
        System.out.println("[pictures_path] "+PropertiesUtil.getTranslate(PropertiesUtil.PICTURES_PATH, null));
        System.out.println("   [files_path] "+PropertiesUtil.getTranslate(PropertiesUtil.FILES_PATH, null));
        System.out.println("    [logs_path] "+PropertiesUtil.getTranslate(PropertiesUtil.LOGS_PATH, null));
        
        System.out.println("\n********帶參轉化取路徑***********");
        Map<String, String> map = new HashMap<String, String>();
        map.put("username", "tianzhen");
        map.put("year", "2017");
        map.put("month", "01");
        map.put("date", "02");
        
        System.out.println("    [root_path] "+PropertiesUtil.getTranslate(PropertiesUtil.ROOT_PATH , map));
        System.out.println("   [users_path] "+PropertiesUtil.getTranslate(PropertiesUtil.USERS_PATH, map));
        System.out.println("[pictures_path] "+PropertiesUtil.getTranslate(PropertiesUtil.PICTURES_PATH, map));
        System.out.println("   [files_path] "+PropertiesUtil.getTranslate(PropertiesUtil.FILES_PATH, map));
        System.out.println("    [logs_path] "+PropertiesUtil.getTranslate(PropertiesUtil.LOGS_PATH, map));
    }

}

結果截圖：