j2me 实现 j2se 的 Properties 功能

我们知道 j2me 中没有 j2se 里边的 Properties 类，要自己实现才能像 j2se 那样读取文件的，现在 j2mepolish 里边的 de.enough.polish.util.Properties 就实现了类似 j2se 的 Properties, 加上de.enough.polish.util.ResourceStreamUtil（旧版本polish 没有这个类，要自己实现相应功能）可以让我们容易读取属性文件。关于 ResourceStreamUtil 类和 Properties 类的介绍大家可以参考 j2mepolish 里边的 api doc。

只要在把你所新建的 .properties 文件放在 resources 文件夹下(相当于一个资源文件,也可以放其他地方，但一定要把它配置成资源),就可以用相应的方法读取, 看下边例子:

test.properties文件:

name=muscle-liu
sex=male
age=24

读取时的部分代码：

Properties prop = new Properties();
InputStream in = null;
try{
  byte[] sData = ResourceStreamUtil.getResourceAsByteArray("/test.properties");
  System.out.println("sData.length:  "+sData.length);
  in =  new ByteArrayInputStream(sData);
            
  prop.load(in);
}catch (IOException e){
  e.printStackTrace();
}

System.out.println("prop.getProperty(\"name\"): "+prop.getProperty("name"));
System.out.println("prop.getProperty(\"sex\"): "+prop.getProperty("sex"));
System.out.println("prop.getProperty(\"age\"): "+prop.getProperty("age"));

运行结果如下：

prop.getProperty("name"): muscle-liu
prop.getProperty("sex"): male
prop.getProperty("age"): 24

在运用中我发现这个 Properties 类有个 bug，就是不支持 # 的注释(也就是说，属性文件里边除了 key-value 的内容，不能有其他的非 k-v 内容)。下边是我修改 Properties 里边的 load 方法，令它支持 # 注释:
原来的 load 方法：

public void load(InputStream in, String encoding, boolean generateIntegerValues ) throws IOException
	{
		this.isIntegerValues = generateIntegerValues;
		int bufferLength = 2 * 1024;
		byte[] buffer = new byte[ bufferLength ];
		int read;
		int start = 0;
		int end = 0;
		boolean newLineFound;
		while ( (read = in.read(buffer, start, bufferLength - start )) != -1) {
			// search for next \r or \n
			String line;
			if (encoding != null) {
				line = new String( buffer, 0, read + start, encoding );
			} else {
				line = new String( buffer, 0, read + start );				
			}
			start = 0;
			newLineFound = true;
			while (newLineFound) {
				newLineFound = false;
				char c = '\n';
				for (int i = start; i < line.length(); i++) {
					c = line.charAt(i);
					if (c == '\r' || c == '\n') {
						end = i;
						newLineFound = true;
						break;
					}
				}
				if (newLineFound) {
					int splitPos = line.indexOf('=', start);
					if(splitPos == -1) {
						throw new IOException("no = separator: " + line.substring( start, end ));
					}
					String key = line.substring( start, splitPos );
					String value = line.substring( splitPos + 1, end );
					if (generateIntegerValues) {
						try {
							put( key, Integer.valueOf(value) );
						} catch(NumberFormatException ex) {
							throw new IOException( ex.toString() );
						}												
					} else {
						put( key, value );	
					}
					if (c == '\r') {
						start = end + 2;
					} else {
						start = end + 1;
					}
				}
			}
			// now all key-value pairs have been read, now move any remaining data to the beginning of the buffer:
			if (start < read) {
				System.arraycopy( buffer, start, buffer, 0, read - start );
				start = read - start;
			} else {
				start = 0;
			}
		}
	}	

修改后的 load 方法:

public void load(InputStream in, String encoding, boolean generateIntegerValues ) throws IOException
	{
		this.isIntegerValues = generateIntegerValues;
		int bufferLength = 2 * 1024;
		byte[] buffer = new byte[ bufferLength ];
		int read;
		int start = 0;
		int end = 0;
		boolean newLineFound;
		boolean isComment;
		while ( (read = in.read(buffer, start, bufferLength - start )) != -1) {
			// search for next \r or \n
			String line;
			if (encoding != null) {
				line = new String( buffer, 0, read + start, encoding );
			} else {
				line = new String( buffer, 0, read + start );				
			}
			start = 0;
			newLineFound = true;
			while (newLineFound) {
				newLineFound = false;
				isComment = false;
				char c = '\n';

				char firstChar = line.charAt(start);
				if(firstChar == '#'){
					isComment = true;
				}

				for (int i = start; i < line.length(); i++) {
					c = line.charAt(i);
					
					if (c == '\r' || c == '\n') {
						end = i;
						newLineFound = true;
						break;
					}
				}
				if (newLineFound && !isComment) {
					int splitPos = line.indexOf('=', start);
					if(splitPos == -1) {
						throw new IOException("no = separator: " + line.substring( start, end ));
					}
					String key = line.substring( start, splitPos );
					String value = line.substring( splitPos + 1, end );
					if (generateIntegerValues) {
						try {
							put( key, Integer.valueOf(value) );
						} catch(NumberFormatException ex) {
							throw new IOException( ex.toString() );
						}												
					} else {
						put( key, value );	
					}
				}

				if (c == '\r') {
					start = end + 2;
				} else {
					start = end + 1;
				}
			}
			// now all key-value pairs have been read, now move any remaining data to the beginning of the buffer:
			if (start < read) {
				System.arraycopy( buffer, start, buffer, 0, read - start );
				start = read - start;
			} else {
				start = 0;
			}
		}
	}

这样我们就可以像 j2se 那样写 properties 文件了..当然，如果你的项目中没有用 j2mepolish, 那你也可以借用这两个类到你的工程，照样可以实现 j2se 的 properties 功能

评论

3 楼 muscle-liu 2008-07-30  

我们可以继承j2me里边的Hashtable来实现的，而接口Externalizable 是继承Serializable的，所以完全可以改为自己的properties,在其他的j2me项目里都能用

2 楼 jandyguan 2008-07-15  

因为Properties类继承Hashmap，实现接口Externalizable,这些都是Polish的东西，所以在其它项目单用这两个类是不行的。

1 楼 mingkg21 2008-04-14  

复杂了一些，还可以简单一点。。。。。