How to read properties with no key giving

[Simpson Kumar]

I got a requirement which needs to read the config file (properties) and display the data accordingly. But that config file may change in future.
According to that changes we need to display.

We can read the file and display by passing the key to load the property, but here we can't guarantee what key and how many properties they are adding. Is there a way to load each property one by one sequentially?
I can read the properties by

Properties props = new Properties();
InputStream fileIn = null;
fileIn = getClass().getResourceAsStream("/" + "ConfigAttr.properties"); 
  			props.load(fileIn);
  			Set a = props.keySet();
  			Iterator i = a.iterator();
while(i.hasNext()){ ....
    

But I can't get the keys line by line (sequentially). I need that way. could someone give me suggestion on this

[Gregg Bolinger]

What do you mean you can't read the keys sequentially? You have Set a = props.keySet(); That gives you the list of keys. What else do you need?

[Simpson Kumar]

Hi Gregg,

Yes, I can't read properties sequentially, here I'm attaching the properties file and also result I got

Here is my properties file :

   
#cn=First Name
field1.ldapattribute=cn
field1.readOnly=false
field1.dispType=textbox
field1.dataType=text
field1.inputFormat=text

#sn=Last Name
field2.ldapattribute=sn
field2.readOnly=true
field2.dispType=textbox
field2.dataType=text
field2.inputFormat=text

#Given Name
field3.ldapattribute=givenname
field3.readOnly=true
field3.dispType=textbox
field3.dataType=text
field3.inputFormat=text

#employeetype Number
field4.ldapattribute=employeetype
field4.readOnly=false
field4.dispType=textbox
field4.dataType=number
field4.inputFormat=text
 

The java code to read properties sequentially

  
    	Properties props = new Properties();
  		InputStream fileIn = null;
 		BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
  		try {
  			fileIn = getClass().getResourceAsStream("/" + "ConfigAttr.properties"); 
  			props.load(fileIn);
  			Set a = props.keySet();
  			Iterator i = a.iterator();
  			List<UIConfigAttributes> propsList = new ArrayList<UIConfigAttributes>();
  			UIConfigAttributes ui = new UIConfigAttributes();
  			while(i.hasNext()){
  				String key = (String)i.next();
  			    int size = a.size()/5;
  				for(int j=0;j<size+1;j++){
  					if(key.indexOf(j+"")>0)
  						System.out.println(key+":"+props.getProperty(key));
  	  			 }
  			}
  		} 

  

Im expecting the results should be displayed like the properties listed in the properties file. but I got the following out of order. This is console output

   
field3.dataType:text
field3.readOnly:true
field3.inputFormat:text
field3.dispType:textbox
field1.dataType:text
field4.inputFormat:text
field1.readOnly:false
field1.dispType:textbox
field2.ldapattribute:sn
field4.dataType:number
field3.ldapattribute:givenname
field4.readOnly:false
field4.ldapattribute:employeetype
field4.dispType:textbox
field2.dataType:text
field2.readOnly:true
field1.inputFormat:text
field2.dispType:textbox
field1.ldapattribute:cn
field2.inputFormat:text

 

[Gregg Bolinger]

Yep, you are correct. No order is guaranteed. If you need to preserve order you are going to have to write a parser yourself. Which really isn't that hard.

try {
            final File file = new File("file.properties");
            final Scanner scanner = new Scanner(file);
            scanner.useDelimiter(System.getProperty("line.separator"));
            while (scanner.hasNext()) {
                String[] keyValue = scanner.next().split("=");
                // keyValue[0] is the key
                // keyValue[1] is the value
                // do something with them
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

If you aren't using Java5 then use the BufferedInputStream.readLine() instead of the Scanner class.

[Simpson Kumar]

Hi gregg,
Thanks for giving..

here I got a doubt.. what I'm supposed to put instead of System.getProperty("line.separator")

[Ulf Dittmer]

Gregg Bolinger wrote:If you need to preserve order you are going to have to write a parser yourself. Which really isn't that hard.

Especially if there's work one can draw on :-)

[Gregg Bolinger]

Sudhakar Kumar wrote:Hi gregg,
Thanks for giving..

here I got a doubt.. what I'm supposed to put instead of System.getProperty("line.separator")

Why would you put something instead of that? If using Scanner, that tells the scanner what to break elements on. You want it to break on a new line. If you aren't using Scanner, you don't need it at all.

[Simpson Kumar]

Gregg Bolinger wrote:

Why would you put something instead of that? If using Scanner, that tells the scanner what to break elements on. You want it to break on a new line. If you aren't using Scanner, you don't need it at all.

I got read properties sequentially with Scanner, now I will implement that into my real code. let me try..

Thanks for your suggestion

[Rob Spoor]

Are those really your field names? And will they always be "fieldX.readOnly" etc? If so, you can use the following technique:

int index = 1;
String property = "field" + index + ".readOnly";
String value = props.getProperty(property);
while (value != null)
{
    // get the rest of the field<index> properties
    index++;
    property = "field" + index + ".readOnly";
    value = props.getProperty(property);
}

This code will continue as long as the field for the index is there. You can't have any gaps, but the number of fields can be virtually unlimited.

[Simpson Kumar]

Rob Prime wrote:Are those really your field names? And will they always be "fieldX.readOnly" etc? If so, you can use the following technique:

int index = 1;
String property = "field" + index + ".readOnly";
String value = props.getProperty(property);
while (value != null)
{
    // get the rest of the field<index> properties
    index++;
    property = "field" + index + ".readOnly";
    value = props.getProperty(property);
}

This code will continue as long as the field for the index is there. You can't have any gaps, but the number of fields can be virtually unlimited.

Hey Rob, I tried your logic too, I feel this one is good and easy and it works. Thanks

Now I need another clue, how to read updated properties file without rebooting the server?
Generally if we update the properties file, we need to reboot the server in order to load updated properties. Is there any approach to avoid rebooting?

[Rob Spoor]

Create a method that reads the new properties file and propagates the fields to all code that needs them, then call that method.