wftk-j: Java client library (Repository class)

[wftk-j ] [ xml source ] [ discussion ]

This set of classes effectively forms a client for a wftk server. The server itself can either be a remote server with which we use some protocol (e.g. SOAP) to communicate with, or it can be a local implementation of a repository. Either way, the objects we use to build workflow-savvy code are the same. The sane way to implement this in Java is by designing a parent class ("Repository") which is extended by one or more specific classes ("RemoteSOAPRepository" and "LocalJNIRepository"). The parent class may or may not be abstract; I'm going to start with it not being abstract, and see how far I can get. Certainly I want to have entries, lists, and such implemented at the level of the parent class and blithely unaware of the underlying implementation of the repository. I had originally thought to make those subclasses, but I think that's wrong. So I changed my mind.

So. Let's push some boilerplate.
  
// Copyright (c) 2003, Vivtek.
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
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//  
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//  
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
Next up, as always, our includes. Who knows what'll end up here?
  
package org.wftk;
import java.io.*;
import java.util.Vector;
import java.util.Map;
Now down to business. We define a single superclass, Repository. This class will be used by classes "list", "entry", and "task", at the very least, but where we go from there is of course unclear. For the moment, entries will be assumed to be simple mappings (name->value) and we'll ignore all refinements like subrecords, list values, attachments, and so forth. They're only partially implemented here and there anyway, so no great loss.

Here's how I envision this working. Each function in Repository first does some common work (such as creating an entry object) and then calls an implementation-specific function or functions in order to do the actual work. So for "get", we create the entry object and we prepopulate some of its fields, then we call _get to actually do the retrieval. At first I was thinking that this class would define some kind of simple local pure-Java functionality -- but then I reconciled myself to the fact that this is indeed the whole reason for having abstract classes. So Repository is an abstract class. Feast your eyes.
  
public abstract class Repository {
   public Entry get (String list, String key) throws WftkException {
      Entry result = new Entry (this);
      result.list_id = list;
      result.key = key;

      _get(result);

      return result;
   }
   abstract void _get (Entry e) throws WftkException;
   public Entry get_task (Entry e, String local_key) throws WftkException {
      Entry result = new Entry (this);
      result.list_id = "_tasks";

      _get_task(result, e.list_id, e.key, local_key);

      return result;
   }
   abstract void _get_task (Entry e, String list, String key, String local_key) throws WftkException;

   public String format (String list, String key, String mode) throws WftkException {
      return _format(list, key, mode);
   }
   abstract String _format (String list, String key, String mode) throws WftkException;

   public void add (String list, Entry obj) throws WftkException {
      obj.list_id = list;
      _add (list, obj);  // _add must set "key" attribute properly according to implementation (SOAP returns it, for instance)
   }
   abstract void _add (String list, Entry obj) throws WftkException;

   public void merge (String list, Entry obj, String key) throws WftkException {
      _merge (list, obj, key);
   }
   abstract void _merge (String list, Entry obj, String key) throws WftkException;

   public void mod (String list, Entry obj, String key) throws WftkException {
      _mod (list, obj, key);
   }
   abstract void _mod  (String list, Entry obj, String key) throws WftkException;

   public void del (String list, String key) throws WftkException {
      _del (list, key);
   }
   abstract void _del (String list, String key) throws WftkException;

   public List list (String list) throws WftkException {
      List l = new List (this);
      l.id = list;
      _list (l);
      return (l);
   }
   public void list (List l) throws WftkException {
      _list (l);
   }
   abstract void _list (List l) throws WftkException;
   public List lists () throws WftkException { return (list("_lists")); }

   public List tasks () throws WftkException {
      List t = new List(this);
      t.id = "_tasks";

      _tasks (t);

      return (t);
   }
   public List tasks (Entry e) throws WftkException {
      List t = new List(this);
      t.id = "_tasks";

      _tasks (t,e);

      return (t);
   }
   abstract void _tasks (List t) throws WftkException;
   abstract void _tasks (List t, Entry e) throws WftkException;

   public List todo () throws WftkException {
      List t = new List(this);
      t.id = "_todo";

      _todo (t);

      return (t);
   }
   abstract void _todo (List t) throws WftkException;

   String userid = null;
   String authtoken = null;
   public boolean auth (String userid, String passwd) throws WftkException {
      this.userid = userid;
      return _auth (userid, passwd);
   }
   abstract boolean _auth (String userid, String passwd) throws WftkException;

   private Log log = null;
   public void setlog (Log _log) { log = _log; }
   public void textlog (int level, String str) {
      if (log == null) return;
      if (level > loglevel) return;
      log.textLog (str);
   }
   public void linklog (int level, String linktext, String content) {
      if (log == null) return;
      if (level > loglevel) return;
      log.linkLog (linktext, content);
   }
   private int loglevel = 0;
   public void set_loglevel (int level) { loglevel = level; }
   public int  get_loglevel ()          { return loglevel;  }
}
This code and documentation are released under the terms of the GNU license. They are copyright (c) 2001-2003, Vivtek. All rights reserved except those explicitly granted under the terms of the GNU license. This presentation was prepared with LPML. Try literate programming. You'll like it.