创建一个类来包装属性

Question

我想创建一个包装属性并专门隐藏文件I/O操作的类。我在下面提供了删节的代码。这是为了从类路径之外的固定位置的文件中读取属性。它还有一个将属性写入同一个文件的方法。

// 
/* Defines key properties of the iFlag application. 
    * Methods read and write properties. 
*/ 

public class ClientProperties { 
    private Properties props; 
    private static String xPanelSizeStg = "32"; 
    private static int xPanelSize = 32; 
    private static String configFilename = "/home/myname/config/client_config.properties"; 

    public ClientProperties() { 
     props = new Properties(); 
    } 


    /** 
    * Reads properties from file 
    * Reads the current properties object from file. 
    * The file is stored in /home/mimibox/config/flag_config.properties 
    */    

    public Properties readPropertiesFromFile(){ 
     // create and load default properties 
     InputStream input = null; 
     logger.trace("Read flag config properties."); 
     try { 
      input = new FileInputStream(configFilename); 
      //load a properties file from class path, inside static method  
      props.load(input); 
      //get the property values and save 
      xPanelSizeStg = props.getProperty("xPanelsize","32"); 
      yPanelSizeStg = props.getProperty("yPanelsize", "32"); 
     } 
     catch (IOException ex) { 
      logger.error("Could not open config file" + configFilename,ex); 
     } 
     finally{ 
      if(input!=null){ 
       try { 
        input.close(); 
       } 
       catch (IOException e) { 
       logger.error("Could not close config file" + configFilename,e); 
       } 
      } 
     } 
     return props; 
    } 
    /** 
    * Writes properties to file 
    * Writes the current properties object to file. 
    * The file is stored in /home/mimibox/config/flag_config.properties 
    */ 

    public void writePropertiesToFile() { 
    //saves the current properties to file. Overwrites the existing properties. 
    Properties props = new Properties(); //a list of properties 
    OutputStream outStrm = null; 
    logger.info("Writing default flag config properties."); 
       System.out.println("Panel size x = " + xPanelSizeStg); 
    try { 
     outStrm = new FileOutputStream(configFilename); 
     // set the properties values 
     props.setProperty("xPanelsize", xPanelSizeStg); 
     props.setProperty("yPanelsize", yPanelSizeStg); 
     // save properties to file, include a header comment 
     props.store(outStrm, "This is the Server configuration file"); 

     } catch (IOException io) { 
      logger.error("The file :{0} could not be opened", configFilename,io); 
     } finally { 
      if (outStrm!= null) { 
       try { 
        outStrm.close(); 
       } catch (IOException e) { 
        logger.error("The file :{0} could not be closed", configFilename, e); 
       } 
      } 
     } 
    } 
} 

读取和写入方法的工作。不起作用的是试图改变一个属性的值，然后保存它。下面的演示代码成功读取属性文件并显示XPanelsize的正确值。 然后我更改该值并尝试将属性写入文件。 xPanelsize的新值64不会写入文件。

public static void main(String[] args) { 
    Properties props; 
    ClientProperties p = new ClientProperties(); 
    props = p.readPropertiesFromFile(); 
    String txt = props.getProperty("xPanelsize"); 
     System.out.println("Panel size x = " + txt); 
    p.setProperty("xPanelsize","64"); //method not found error 
    p.writePropertiesToFile(); 

所以我想能够使用Property.setProperty（）方法来设置属性的值。当我这样做时，已更改的属性不会写入文件。我可以看到这是因为我有超过1个Property实例，另一个对另一个不可见。我想我需要扩展内置的Properties类来实现我想要做的事，但我不知道如何使它全部工作。

我发现了很多在互联网上使用属性的例子。我还没有找到任何隐藏类中的相关文件I/O的例子。我会怎么做？

Answer 1

您应该可能需要为您的'道具'物件创建一个吸气剂。

public Properties getProps() 
{ 
    return props; 
} 

而你，也就能够调用它像这样：

p.getProps().setProperty("key", "value"); 

或者，如果您打算让您的ClientProperties类属性类的孩子，那么你就需要使用“延伸'，你将能够使用

p.setProperty("key", "value"); 

在这种情况下，你就不需要在类中的任何属性的对象调用它的领域。

Answer 2

这是我对你的例子的建议。

首先，你不必是编辑再次在writePropertiesToFile方法的属性是这样的：

public void writePropertiesToFile() { 
    // saves the current properties to file. Overwrites the existing properties. 
    // Properties props = new Properties(); // a list of properties 
    OutputStream outStrm = null; 
    logger.info("Writing default flag config properties."); 
    logger.debug("Panel size x = " + xPanelSizeStg); 
    try { 
     outStrm = new FileOutputStream(configFilename); 
     // set the properties values 
     //props.setProperty("xPanelsize", xPanelSizeStg); 
     //props.setProperty("yPanelsize", yPanelSizeStg); 
     // save properties to file, include a header comment 
     props.store(outStrm, "This is the Server configuration file"); 

    } catch (IOException io) { 
     logger.error("The file :{0} could not be opened", configFilename, io); 
    } finally { 
     if (outStrm != null) { 
      try { 
       outStrm.close(); 
      } catch (IOException e) { 
       logger.error("The file :{0} could not be closed", configFilename, e); 
      } 
     } 
    } 
} 

然后你只需要创建一个使用类中的全局变量-props-一个setProperty方法。

private void setProperty(String key, String value) { 
    this.props.setProperty(key, value); 
} 

如果你的属性文件看起来像下面的图片：

xPanelsize的值应该运行的应用程序后更改。

public static void main(String[] args) { 
    Properties props = null; 
    ClientProperties p = new ClientProperties(); 
    props = p.readPropertiesFromFile(); 
    String xPanelsize = props.getProperty("xPanelsize"); 
    System.out.println("Panel size x = " + xPanelsize); 
    p.setProperty("xPanelsize", "64"); // method not found error 

    p.writePropertiesToFile(); 

    props = p.readPropertiesFromFile(); 
    xPanelsize = props.getProperty("xPanelsize"); 
    System.out.println("So, now the Panel size x = " + xPanelsize); 
} 

调试消息是，

属性文件内容将是：

这里充满来源：

package stackoverflow; 

import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.util.Properties; 
import java.util.logging.Level; 

import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 

/* Defines key properties of the iFlag application. 
* Methods read and write properties. 
*/ 

public class ClientProperties { 
    Logger logger = LoggerFactory.getLogger(ClientProperties.class.getSimpleName()); 
    private Properties props; 
    private String xPanelSizeStg; 
    private String yPanelSizeStg; 
    private int xPanelSize; 
    private int yPanelSize; 
    // private static String configFilename = 
    // "/home/myname/config/client_config.properties"; 
    private static String configFilename = "resource/client_config.properties"; 

    public ClientProperties() { 
     props = new Properties(); 

     xPanelSizeStg = "32"; 
     yPanelSizeStg = "32"; 
     xPanelSize = 32; 
     yPanelSize = 32; 
    } 

    /** 
    * Reads properties from file Reads the current properties object from file. The 
    * file is stored in /home/mimibox/config/flag_config.properties 
    */ 

    public Properties readPropertiesFromFile() { 
     // create and load default properties 
     InputStream input = null; 
     logger.trace("Read flag config properties."); 
     try { 
      input = new FileInputStream(configFilename); 
      // load a properties file from class path, inside static method 
      props.load(input); 
      // get the property values and save 
      xPanelSizeStg = props.getProperty("xPanelsize", "32"); 
      yPanelSizeStg = props.getProperty("yPanelsize", "32"); 
     } catch (IOException ex) { 
      logger.error("Could not open config file" + configFilename, ex); 
     } finally { 
      if (input != null) { 
       try { 
        input.close(); 
       } catch (IOException e) { 
        logger.error("Could not close config file" + configFilename, e); 
       } 
      } 
     } 
     return props; 
    } 

    /** 
    * Writes properties to file Writes the current properties object to file. The 
    * file is stored in /home/mimibox/config/flag_config.properties 
    */ 

    public void writePropertiesToFile() { 
     // saves the current properties to file. Overwrites the existing properties. 
     // Properties props = new Properties(); // a list of properties 
     OutputStream outStrm = null; 
     logger.info("Writing default flag config properties."); 
     logger.debug("Panel size x = " + xPanelSizeStg); 
     try { 
      outStrm = new FileOutputStream(configFilename); 
      // set the properties values 
      //props.setProperty("xPanelsize", xPanelSizeStg); 
      //props.setProperty("yPanelsize", yPanelSizeStg); 
      // save properties to file, include a header comment 
      props.store(outStrm, "This is the Server configuration file"); 

     } catch (IOException io) { 
      logger.error("The file :{0} could not be opened", configFilename, io); 
     } finally { 
      if (outStrm != null) { 
       try { 
        outStrm.close(); 
       } catch (IOException e) { 
        logger.error("The file :{0} could not be closed", configFilename, e); 
       } 
      } 
     } 
    } 

    private void setProperty(String key, String value) { 
     this.props.setProperty(key, value); 
    } 

    public int getxPanelSize() { 
     return this.xPanelSize; 
    } 

    public void setxPanelSize(int xPanelSize) { 
     this.xPanelSize = xPanelSize; 
    } 

    public int getyPanelSize() { 
     return yPanelSize; 
    } 

    public void setyPanelSize(int yPanelSize) { 
     this.yPanelSize = yPanelSize; 
    } 

    public static void main(String[] args) { 
     Properties props = null; 
     ClientProperties p = new ClientProperties(); 
     props = p.readPropertiesFromFile(); 
     String xPanelsize = props.getProperty("xPanelsize"); 
     System.out.println("Panel size x = " + xPanelsize); 
     p.setProperty("xPanelsize", "64"); // method not found error 

     p.writePropertiesToFile(); 

     props = p.readPropertiesFromFile(); 
     xPanelsize = props.getProperty("xPanelsize"); 
     System.out.println("So, now the Panel size x = " + xPanelsize); 
    } 

} 

Answer 3

行，所以拜评论和答案a博夫，我做了一些改变。对于那些偶然发现这篇文章的人，我已经在这个答案中发布了工作代码。主要的变化是扩展属性。这使我可以直接使用Properties方法。

package com.test; 

import java.util.Properties; 
import java.io.FileOutputStream; 
import java.io.FileInputStream; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.io.IOException; 
import org.apache.logging.log4j.LogManager; 
import org.apache.logging.log4j.Logger; 
import java.io.File; 

public class ClientProperties extends Properties { 

    //initiate logger 

    private final static Logger logger = LogManager.getLogger(); 

    private static String xPanelSizeStg = "32"; 
    private static String yPanelSizeStg = "32"; 
    private final configFilename = "/home/myname/myConfig.properties"; 

    public ClientProperties() { 

    } 


    public Properties readPropertiesFromFile(){ 
     // create and load default properties 
     InputStream input = null; 
     logger.trace("Read flag config properties."); 
     try { 
      input = new FileInputStream(configFilename); 
      //load a properties file from class path, inside static method  
      this.load(input); 
      //get the property values and save 
      xPanelSizeStg = this.getProperty("xPanelsize","32"); 
      yPanelSizeStg = this.getProperty("yPanelsize", "32"); 
     } 
     catch (IOException ex) { 
      logger.error("Could not open config file" + configFilename,ex); 
     } 
     finally{ 
      if(input!=null){ 
       try { 
        input.close(); 
       } 
       catch (IOException e) { 
       logger.error("Could not close config file" + configFilename,e); 
       } 
      } 
     } 
     return this; 
    } 

    public void writePropertiesToFile() { 
    //saves the current properties to file. Overwrites the existing properties. 
    //Properties props = new Properties(); //a list of properties 
    OutputStream outStrm = null; 
    logger.info("Writing default flag config properties."); 
       System.out.println("Panel size x = " + xPanelSizeStg); 
    try { 
     outStrm = new FileOutputStream(configFilename); 
     // save properties to file, include a header comment 
     this.store(outStrm, "This is the Server configuration file"); 

     } catch (IOException io) { 
      logger.error("The file :{0} could not be opened", configFilename,io); 
     } finally { 
      if (outStrm!= null) { 
       try { 
        outStrm.close(); 
       } catch (IOException e) { 
        logger.error("The file :{0} could not be closed", configFilename, e); 
       } 
      } 
     } 
    } 
} 

我已经依靠属性父来启动我用“this”访问过的属性。所以现在主要的样子：

public static void main(String[] args) { 

    ClientProperties p = new ClientProperties(); 
    p.readPropertiesFromFile(); 
    String txt = p.getProperty("xPanelsize"); 
     System.out.println("Panel size x = " + txt); 
    p.setProperty("xPanelsize","64"); 
    p.writePropertiesToFile(); 


} 

该类现在隐藏周围的阅读，写作和文件中的所有管理员。至关重要的是，它避免了为每个属性编写一个setter/getter（并且我拥有比这里显示的两个更多的属性）。这是我的第一个版本。

感谢您的帮助。如果我自己弄清楚这一切，我将花费很长时间。