Java Properties

Properties class表示一个属性的持久化集合，Properties能够被保存到stream中，也能从stream中读出Properties， 每个key和与其相应的value都是一个字符串，properties文件是一种配置文件，主要用于表达配置信息，文件类型为*.properties，格式为文本文件，文件的内容是格式是"键=值"的格式，在properties文件中，可以用"#"来作注释，properties文件在Java编程中用到的地方很多，操作很方便
1.获取jvm系统属性

package com.cn.tibco;

import java.util.Properties;

public class Properties1 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Properties pp = System.getProperties();
		pp.list(System.out);
	}

}

执行结果如下

引用

-- listing properties --
java.runtime.name=Java(TM) SE Runtime Environment
sun.boot.library.path=D:\Java6\jdk1.6.0_25\jre\bin
java.vm.version=20.0-b08
java.vm.vendor=Sun Microsystems Inc.
java.vendor.url=http://java.sun.com/
path.separator=;
java.vm.name=Java HotSpot(TM) Client VM
file.encoding.pkg=sun.io
user.country=US
sun.java.launcher=SUN_STANDARD
sun.os.patch.level=Service Pack 3
java.vm.specification.name=Java Virtual Machine Specification
user.dir=D:\dev-workspace\JavaPractices
java.runtime.version=1.6.0_25-ea-b01
java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment
java.endorsed.dirs=D:\Java6\jdk1.6.0_25\jre\lib\endorsed
os.arch=x86
java.io.tmpdir=C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\
line.separator=

java.vm.specification.vendor=Sun Microsystems Inc.
user.variant=
os.name=Windows XP
sun.jnu.encoding=GBK
java.library.path=D:\Java6\jdk1.6.0_25\bin;.;C:\WINDOWS...
java.specification.name=Java Platform API Specification
java.class.version=50.0
sun.management.compiler=HotSpot Client Compiler
os.version=5.1
user.home=C:\Documents and Settings\Administrator
user.timezone=
java.awt.printerjob=sun.awt.windows.WPrinterJob
file.encoding=Cp1252
java.specification.version=1.6
user.name=Administrator
java.class.path=D:\dev-workspace\JavaPractices\bin
java.vm.specification.version=1.0
sun.arch.data.model=32
java.home=D:\Java6\jdk1.6.0_25\jre
sun.java.command=com.cn.tibco.Properties1
java.specification.vendor=Sun Microsystems Inc.
user.language=en
awt.toolkit=sun.awt.windows.WToolkit
java.vm.info=mixed mode, sharing
java.version=1.6.0_25-ea
java.ext.dirs=D:\Java6\jdk1.6.0_25\jre\lib\ext;C:\W...
sun.boot.class.path=D:\Java6\jdk1.6.0_25\jre\lib\resource...
java.vendor=Sun Microsystems Inc.
file.separator=\
java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport...
sun.cpu.endian=little
sun.io.unicode.encoding=UnicodeLittle
sun.desktop=windows
sun.cpu.isalist=pentium_pro+mmx pentium_pro pentium+m...

2.如何读取配置文件
新建一个配置文件file1.properties，文件内容如下

name=leng
company=tibco
age=22

将class Properties1 修改为如下：

package com.cn.tibco;

import java.io.FileInputStream;
import java.util.Enumeration;
import java.util.Properties;

public class Properties1 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Properties pps = new Properties();
	    try {   
			        pps.load(new FileInputStream("D:\\dev-workspace\\JavaPractices\\src\\file.properties"));   
			        Enumeration enum1 = pps.propertyNames();   
			       while (enum1.hasMoreElements()) {   
			       String strKey = (String) enum1.nextElement();   
			      String strValue = pps.getProperty(strKey);   
			       System.out.println(strKey + "=" + strValue);   
			       }   
			    } catch (Exception e) {   
			        e.printStackTrace();   
			   } 

	}

}

运行结果如下:

引用

name=leng
company=tibco
age=22

3.一个完整的实例

package com.cn.tibco;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.Properties;

public class TestAll {
	//根据key读取value   
	 public static String readValue(String filePath,String key) {   
	  Properties props = new Properties();   
	        try {   
	         InputStream in = new BufferedInputStream (new FileInputStream(filePath));   
	         props.load(in);   
	         String value = props.getProperty (key);   
	            System.out.println(key+value);   
	            return value;   
	        } catch (Exception e) {   
	         e.printStackTrace();   
	         return null;   
	        }   
	 }   
	    
	 //读取properties的全部信息   
	    public static void readProperties(String filePath) {   
	     Properties props = new Properties();   
	        try {   
	         InputStream in = new BufferedInputStream (new FileInputStream(filePath));   
	         props.load(in);   
	            Enumeration en = props.propertyNames();   
	             while (en.hasMoreElements()) {   
	              String key = (String) en.nextElement();   
	                    String Property = props.getProperty (key);   
	                    System.out.println(key+Property);   
	                }   
	        } catch (Exception e) {   
	         e.printStackTrace();   
	        }   
	    }   
	  
	    //写入properties信息   
	    public static void writeProperties(String filePath,String parameterName,String parameterValue) {   
	     Properties prop = new Properties();   
	     try {   
	      InputStream fis = new FileInputStream(filePath);   
	            //从输入流中读取属性列表（键值对）   
	            prop.load(fis);   
	            //调用 Hashtable 的方法 put。使用 getProperty 方法提供并行性。   
	            //强制要求为属性的键和值使用字符串。返回值是 Hashtable 调用 put 的结果。   
	            OutputStream fos = new FileOutputStream(filePath);   
	            prop.setProperty(parameterName, parameterValue);   
	            //以适合使用 load 方法加载到 Properties 表中的格式，   
	            //将此 Properties 表中的属性列表（键和元素对）写入输出流   
	            prop.store(fos, "Update '" + parameterName + "' value");   
	        } catch (IOException e) {   
	         System.err.println("Visit "+filePath+" for updating "+parameterName+" value error");   
	        }   
	    }   
	  
	    public static void main(String[] args) {   
	     readValue("E:\\file.properties","name");   
	        writeProperties("E:\\file.properties","age","21");   
	        readProperties("E:\\file.properties" );   
	        System.out.println("OK");   
	    }   


}