Java配置项

   背景：项目中有许多可选参数，这时如果采取硬编码的方式将非常不利于扩展，因此想到将参数写进配置文件，需要参数时再从配置文件中进行加载。

public class TestConfig {
    
    protected final static String enc = "utf-8";
    private final static String LINE_SEPARATOR = System.getProperty("line.separator");
    
    protected static Properties init(String configPath) {
        Properties p = new Properties();
        InputStream in = null;
        try {
            URL confFile = TestConfig.class.getClassLoader().getResource(configPath);
            in = confFile.openStream();
            p.load(in);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return p;
    }
    
    protected static String getProperty(Properties p, String key) {
        return p.getProperty(key.trim());
    }

    protected static boolean writeProperty(Properties p, String configPath, String key, String value) throws IOException {
        FileOutputStream out = new FileOutputStream(URLDecoder.decode(TestConfig.class.getClassLoader().getResource(configPath).getPath(), enc));
        BufferedOutputStream bos = new BufferedOutputStream(out);
        boolean isExistPropertyName = false;
        try {
            for (String tmpKey : p.stringPropertyNames()) {
                String line;
                if(key.equals(tmpKey)) {
                    isExistPropertyName = true;
                    p.setProperty(key, value);
                    line = tmpKey + "=" + value + LINE_SEPARATOR;
                } else {
                    line = tmpKey + "=" + p.getProperty(tmpKey) + LINE_SEPARATOR;
                }
                byte[] linebytes = line.getBytes(enc);
                bos.write(linebytes);
            }
            if(!isExistPropertyName) {
                p.put(key, value);
                String newLine = key + "=" + value + LINE_SEPARATOR;
                bos.write(newLine.getBytes(enc));
            }
            return true;
        } finally {
            bos.flush();
            bos.close();
        }
    }
}

调用方式：

public class MyConfigUtil extends TesttConfig {

    private static Properties p = new Properties();

    private final static int DEFAULT_SECURITY_POLICY_PORT = 5907;
    private final static String DEFAULT_GOOGLE_MAP_KEY = "ABQIAAAAWA_efwiQDHrv6MYDa3HE3hTwM0brOpm-All5BF6PoaKBxRWWERSSjUV6DjLhSErRl9rovZBNtOhfds";
    private final static String DEFAULT_GOOGLE_MAP_SERVER_URL="http://ditu.google.cn/maps";
    
    static {
        p = init(CONFIG_PATH);
    }
    
    //google map key
    public static String getGoogleMapKey() {
        String googleMapKey = getProperty(p, GOOGLE_MAP_KEY);
        if(googleMapKey == null || "".equals(googleMapKey)) {
            return DEFAULT_GOOGLE_MAP_KEY;
        }
        return googleMapKey;
    }
    public static boolean saveGoogleMapKey(String value) throws IOException {
        return writeProperty(p, CONFIG_PATH, GOOGLE_MAP_KEY, value);
    }
    
    //securityPort
    public static int getSecurityPolicyPort() throws Exception {
        File appFile = getFlexAppConfig();
        int port = -1;
        XMLBuilder builder = XMLBuilder.createBuilder(appFile);
        NodeList policyList = builder.findNodeList(APPLICATION_SECURITY_POLICY_PORT);
        if(policyList != null && policyList.getLength() > 0) {
            Node node = policyList.item(0);
            port = Integer.parseInt(node.getTextContent());
        }
        if(port == -1) {
            return DEFAULT_SECURITY_POLICY_PORT;
        }
        return port;
    }
    
    private static File getFlexAppConfig() throws UnsupportedEncodingException {
    	String filePath = URLDecoder.decode(AbstractConfig.class.getClassLoader().getResource(APP_CONFIG).getPath(), enc);
        return new File(filePath);
    }
}

解析之读属性：
a、URL confFile = TestConfig.class.getClassLoader().getResource(configPath);//查找指定名称的资源，资源是可以通过类代码以与代码基无关的方式访问的某些数据（图像、声音、文本等）。
    资源名称是以 '/' 分隔的标识资源的路径名称。

b、 in = confFile.openStream();//打开到此 URL 的连接并返回一个用于从该连接读入的 InputStream。此方法是下面方法的缩写：
     openConnection().getInputStream()

c、 p.load(in);//从输入流中读取属性列表（键和元素对）

d、String googleMapKey = getProperty(p, GOOGLE_MAP_KEY);//通过键搜索属性

  疑问：为什么使用到了ClassLoader机制，直接读不行吗?

解析之写属性：研究对象为writeProperty方法
a、 URLDecoder.decode(TestConfig.class.getClassLoader().getResource(configPath).getPath(), enc);//对路径进行解码
     URLDecoder:HTML 格式解码的实用工具类。该类包含了将 String 从application/x-www-form-urlencoded MIME 格式解码的静态方法

b、  p.stringPropertyNames()返回此属性列表中的键集