franzone.com

I use and love the WordPress platform for this and several other blogs that I maintain. One of the many cool features of WordPress is that it supports XML-RPC. What does that mean? Well XML is… XML. It’s the extensible markup language and is basically just a way of formatting data in some meaningful way. RPC stands for remote procedure call. That is making calls to methods/procedures on a remote system. Put them together and you get the idea… making method/procedure calls on remote systems using XML to bundle up the method calls and returns.

Great, now I have to write some sort of custom program to build an XML formatted message and submit it to WordPress. Then I have to have the same program be able to parse and decipher the return XML format. Well, no you don’t! There are already libraries that will do this for you. WordPress supports the Blogger API, the metaWeblog API and the MoveableType API. These are blog specific APIs that use XML-RPC to communicate. You could very easily download one of these, read the documentation and become productive with Java in no time at all. That was actually my first step. But wait… the APIs don’t support all of the same methods. Which one should I use?

I actually decided not to use any of the APIs mentioned above. Instead I went with the Redstone XML-RPC library. This API provides a layer of abstraction from all of the XML-RPC details that is nice and it also gives me the flexibility to implement any methods that I want. This will come in handy as you will see in a later post. For now though, how might I make a post using this API? Simple really. We’ll start out with the Blogger API method call. The method signature looks like this:

blogger.newPost(blog_ID, user_login, user_pass, content, publish)

The blog_ID is used for systems that maintain multiple blogs. There is actually a method we could call to get that piece of information called blogger.getUsersBlogs. Here’s a little secret though… WordPress doesn’t currently support this feature and is just hard-coded to be “1″. So for brevity sake I’ll just use that for now.

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import redstone.xmlrpc.XmlRpcClient;
 
public class XmlRpcPoster
{
 
  public static void main( String[] args )
  {
    // Check command-line arguments
    if( args.length < 3 )
    {
      System.out.println( "Usage: java XmlRpcPoster <xml-rpc> <username> <password>" );
    }
    else
    {
      // Get command-line arguments into variables
      String sXmlRpcURL = args[0];
      String sUsername = args[1];
      String sPassword = args[2];
 
      // Hard-coded blog_ID
      int blog_ID = 1;
 
      // XML-RPC method
      String sXmlRpcMethod = "blogger.newPost";
 
      // We'll hard-code our blog content for now as well
      String sContent = "Hello XML-RPC World!";
 
      // You can specify whether or not you want the blog published immediately
      bool bPublish = true;
 
      // Try block
      try
      {
        // Create the XML-RPC client
        XmlRpcClient client = new XmlRpcClient( sXmlRpcURL );
 
        // Make our method call
        Object token = client.invoke( sXmlRpcMethod, new Object[] { new Integer( blog_ID ), sUsername, sPassword, sContent, new Boolean( bPublish ) } );
 
        // The return is a String containing the postID
        System.out.println( "Posted : " + (String)token );
      }
 
      // Catch exceptions
      catch( Exception e )
      {
        e.printStackTracke( System.err );
      }
 
    }
 
  }
 
}

Wait a minute… there is no XML code anywhere in your example. Exactly! The Redstone API uses serializers to take the Object[] you provide and create the appropriate XML. Spiffy, eh? Not only that, but if the return type of the method call happens to be a struct, then the token will contain a Map that you can iterate over and retrieve values from.

I hope you enjoyed this little excursion into XML-RPC and Java. Stay tuned for my next post where I’ll be kicking this example up a notch to get more functionality and meta-data into our WordPress posting.