在运行时在属性文件中设置值(setting value inside property file at run time)

是否可以在运行时设置属性文件中的值。

我尝试了这个并且在读取属性时它会发生变化，但是当我在文件中检查到没有反映出更改时。

try { Properties props = new Properties(); props.setProperty("ServerAddress", "ee"); props.setProperty("ServerPort", "123"); props.setProperty("ThreadCount", "456"); File f = new File("myApp.properties"); OutputStream out = new FileOutputStream( f ); props.store(out, "This is an optional header comment string"); System.out.println(props.get("ServerPort")); out.close(); } catch (Exception e ) { e.printStackTrace(); }

输出：123。

我的需要是有一个属性文件应用程序，并通过GUI网页，配置可以更改。

is it possible to set the value inside property file at runtime.

I tried this and it changes while reading property back, but when I check in file that changes are not reflected.

output: 123.

my need is to have one property file application wide and through GUI web page that configuration can be change.

最满意答案

我认为问题的一部分是每次运行该代码时都要覆盖当前存在的文件。您需要做的是将当前存在的属性加载到Properties对象中，然后更改需要更改的属性的值，最后存储这些属性。像这样的东西：

OutputStream out = null; try { Properties props = new Properties(); File f = new File("myApp.properties"); if(f.exists()){ props.load(new FileReader(f)); //Change your values here props.setProperty("ServerAddress", "ThatNewCoolValue"); } else{ //Set default values? props.setProperty("ServerAddress", "DullDefault"); props.setProperty("ServerPort", "8080"); props.setProperty("ThreadCount", "456"); f.createNewFile(); } out = new FileOutputStream( f ); props.store(out, "This is an optional header comment string"); System.out.println(props.get("ServerPort")); } catch (Exception e ) { e.printStackTrace(); } finally{ if(out != null){ try { out.close(); } catch (IOException ex) { System.out.println("IOException: Could not close myApp.properties output stream; " + ex.getMessage()); ex.printStackTrace(); } } }

首次运行后的结果：

#This is an optional header comment string #Thu Feb 28 13:04:11 CST 2013 ServerPort=8080 ServerAddress=DullDefault ThreadCount=456

第二次运行（以及每次后续运行）后的结果：

#This is an optional header comment string #Thu Feb 28 13:04:49 CST 2013 ServerPort=8080 ServerAddress=ThatNewCoolValue ThreadCount=456

I think part of the problem is that you are overwriting the currently existing file every time you run that code. What you need to do is load the properties that currently exist into the Properties object, and then change the values of the properties that need changing, and finally store those properties. Something like this:

Results after first run:

#This is an optional header comment string #Thu Feb 28 13:04:11 CST 2013 ServerPort=8080 ServerAddress=DullDefault ThreadCount=456

Results after second run (and each subsequent run):

#This is an optional header comment string #Thu Feb 28 13:04:49 CST 2013 ServerPort=8080 ServerAddress=ThatNewCoolValue ThreadCount=456

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