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Ron Pall
Ron Pall

Reputation: 41

Java: Append Value to Property Key

I am using java.util.Properties to store properties in a file. I am able to store key/value pair successfully using the following code:

public String setKeyValue(String dir, String key, String value) throws FileNotFoundException, IOException
{
    File file = new File(dir);


    FileInputStream in = new FileInputStream(file);
    Properties properties = new Properties();
    properties.load(in);
    in.close();

    FileOutputStream out = new FileOutputStream(file);
    properties.setProperty(key, value);
    properties.store(out, null);
    out.close();

    String myValue = (String) properties.getProperty(key);
    System.out.println (myValue);
    return myValue;
}

However, I am interested in updating (not replacing) a previous property so I can later retrieve them as an array.

For example my current property looks something like this: 

email=email1

I want to change it to 

email=email1, email2 //(this will be a continuous process of adding more emails)

This way I can later retrieve them as follows:

String[] emailList = properties.getProperty("email").split(",");

If you use the previous code it simply replaces the property. I need to append additional "value" to key..

Upvotes: 0

Views: 1990

Answers (1)

Florian Schaetz
Florian Schaetz

Reputation: 10652

Well, the most simple way would be do this...

String oldValue = properties.getProperty( key );
String newValue = "bla something";
String toStore = oldValue != null ? oldValue + "," + newValue : newValue;
properties.setProperty( key, value );

Of course, that's not very elegant, so I personally would probably extend my own AppenderProperties class from Properties and then add an append method. This would also be a good place to put all the array-related methods, so that you can remove specific values from your keys, etc.

Upvotes: 1

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