The latest gossip on java.util.Properties

The ubiquity of the Properties class is testament to its utility. It is a rare application that does not use an instance. I notice from the J2SE 5 javadocs that the java.util.Properties now supports an XML file -based backing store, leading to the addition of new methods:

public void storeToXML(OutputStream os, String comment)

                throws IOException;



public void storeToXML(OutputStream os, String comment, String encoding)

                throws IOException;    



public void loadFromXML(InputStream in)

                throws IOException,

                        InvalidPropertiesFormatException; 

that work off of an XML file with the schema:

    <?xml version="1.0" encoding="UTF-8"?>

    <!-- DTD for properties -->

    <!ELEMENT properties ( comment?, entry* ) >

    <!ATTLIST properties version CDATA #FIXED "1.0">

    <!ELEMENT comment (#PCDATA) >

    <!ELEMENT entry (#PCDATA) >

    <!ATTLIST entry key CDATA #REQUIRED>

 

which in turn looks like this:

    <?xml version="1.0" encoding="UTF-8"?>

    <!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">

    <properties>

      <comment>some comment</comment>



      <entry key="key1">value1</entry>

      <entry key="key2">value2</entry>

      <entry key="key3">value3</entry>



    </properties>

Now this is interesting. Purists -- in this case I fall into that category -- would argue that the simplicity of the key=value properties structure is the source of its strength and popularity. I do not see too much value in the XML form. The Java Preferences API hasn't gained much acceptance and the use of a totally different XML schema in the Properties class doesn't help that cause any.

And when are these deprecated methods going to be removed from the core Java source anyway? You know how we've always been instructed against catching exceptions but doing nothing about it (i.e. an empty catch clause)? Well the save method in the Properties class does exactly that. Take a look:

    public synchronized void save(OutputStream out, 

                                    String header)  {

        try {

            store(out, header);

        } catch (IOException e) {

        }

    }

To Sun's credit, this method has been deprecated for a while, with developers advised to use the more proper store method. There're a number of deprecated methods in Java and we still have no idea when these will be dealt with (see Bug 5093875). Oh, well that one's for another day.

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