5分钟教你学会Java properties

以前年轻的时候，总喜欢在代码中把参数的值写死，改一遍跑一遍，可移植性太糟糕了。自从用了Properties类之后，省事了，代码也规范了一点了。
也就是将常用的，且经常需要修改的参数放置在xx.properties文件中，利用Java中提供的Properties类读取文件中的参数值，从而避免多次在代码中修改参数的值，一劳永逸。

Properties其实是继承自HashTable，所以用起来也很简单，提供的操作主要有:

load(inputStream) ： 加载配置文件
store(outputStream,comment)：将新生成的Properties对象写出到文件中去，comment是添加说明性的文字；
getProperty(name):获取某个属性的值；
setProperty(name,value)：设置某个属性的值；这个属性可以事先不存在
putProperty(name,value)：新增一个属性值

package PropertiesTest;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;

/**
 *
 * @author wangjj
 *
 *         Jan 7, 2015
 */
public class TestPropertiesClass {

     public static Properties properties;

     public TestPropertiesClass(String propertiesFile) throws Exception {

           properties = new Properties();

           // properties文件的格式是： #comment，argument=value
          FileInputStream input = new FileInputStream(new File(propertiesFile));

           // 从input stream中读取数据
           properties.load(input);
     }

     /**
      * 测试properties中提供的方法：get,set,store,put
      *
      * @throws IOException
      * @throws FileNotFoundException
      */
     public void run(String outputProperty) throws FileNotFoundException,
              IOException {

           // read properties
          String firstname = properties.getProperty("firstname" );
          String hobby = properties.getProperty("hobby" );
          System. out.println("firstName: " + firstname);
          System. out.println("hobby:" + hobby);

           // set existed property
           properties.setProperty("firstname" , "jing" );
          firstname = properties.getProperty("firstname" );
          System. out.println("changed firstName:" + firstname);

           // set non-existed property
           properties.setProperty("hello" , "world" );
          System. out.println("hello :" + properties.getProperty("hello" ));

           // put non-existed property
           properties.put("newProperty" , "newValue" );
          System. out.println("New property :"
                   + properties.getProperty("newProperty" ));

           properties.store(new FileOutputStream(new File(outputProperty)),
                    "outputProperty");
     }

     public static void main(String[] args) throws Exception {
          String properFile = "conf/test.properties";
          TestPropertiesClass testProperties = new TestPropertiesClass(properFile);
          String outputProperty = "conf/testNew.properties" ;
          testProperties.run(outputProperty);
     }
}