Daily Archives: September 21, 2011

Introducing FOORM – Form Oriented Object Relational Mapper

FOORM Presentation and Persistance

Note: This is extracted from one of my earlier blog posts. FOORM is still a work in progress and while I love using it and think it is the best presentation and persistence framework the world has ever seen – it is still early days and the framework maker must endure using it for a *long* time before accepting any new customers. So this is and will continue to be a work in progress for quite some time with the Sakai support for LTI as my test bed for FOORM.

In FOORM you build a model using an array of strings that look as follows;

  static String[] CONTENT_MODEL = { 
      "updated_at:autodate" };

This is kind of like a Rails model in colon-separated form. One thing that FOORM assumes is that you will be internationalizing your UI and so it even encodes the field labels..

You can build an input form with the following lines of code:

String formInput(Object previousData, String [] modelInfo, Object resourceLoader)

This returns a set of input tags, one for each field, repopulated from the previous data (can be Properties, Map<String,Object>, or ResultSet) and using the provided resource loader.

You embed the form tags in some Velocity as follows:

<form action="#toolForm("")" method="post" name="customizeForm" >
    <input type="hidden" name="sakai_csrf_token" value="$sakai_csrf_token" />  
   <input type="submit" accesskey ="s" class="active" name="$doAction" 
        value="$tlang.getString('gen.save')" />
   <input type="submit" accesskey ="x" name="$doCancel" 
        onclick="location = '$sakai_ActionURL.setPanel("Content")';return false;">

There are utilities to validate incoming data, and extract it into the right objects and type for inserting into a database. with a very few lines of code. Here is an extract from request properties into newMapping and insert into the database:

    HashMap<String, Object> newMapping = new HashMap<String, Object>();

    String errors = foorm.formExtract(requestProperties, formModel, 
        rb, true, newMapping, null);
    if (errors != null) return errors;

    String[] insertInfo = foorm.insertForm(newMapping);
    String makeSql = "INSERT INTO " + table + " ( " + insertInfo[0] + 
          " ) VALUES ( " + insertInfo[1] + " )";
    final Object[] fields = foorm.getInsertObjects(newMapping);
    m_sql.dbInsert(null, sql, fields);

It supports a very REST-style property bag approach to data models except that all the fields are properly and fully realized as database columns so they can be searched, selected, grouped, and ordered with as sophisticated query as you want to create.

FOORM is designed to be extended so you have the generic Foorm and you extend it to make a SakaiFoorm that captures all the Sakai-specific rules for generating fields, handling internationalization, etc.

I even dispensed with the “CREATE TABLE” scripts – since Foorm knows the entire model, it can make the tables and sequences automatically. It know about the various rules for fields in MySql, HSQL, and Oracle. The AutoDDL code looks as follows:

 String[] sqls = foorm.formSqlTable("lti_content", 
     LTIService.CONTENT_MODEL, m_sql.getVendor(), doReset);
        for (String sql : sqls)
          if (m_sql.dbWriteFailQuiet(null, sql, null)) M_log.info(sql);

I could make this more succinct with an overridable method in Foorm. Foorm still needs to learn about changes to data models and automatically generate “ALTER TABLE” commands. I will write that code when I need to do a conversion when I release a future version of DBLTIService is released and I need to expand the model.

I think that Foorm has a lot of potential. It is kind of a weird combination of a partial presentation layer and partial object relational mapper. It is focused on providing useful library utilities that let the developer get as tricky as they want, making sure that the nasty repetitive common tasks take as little effort as possible.

You can ask me “Why not Hibernate?” or “Why not Spring JDBC?” at a bar sometime. Be prepared to hear my voice raise a few notches as I rail about “Hibernate’s is an overbearing over-engineered steaming pile of…(oops did I say that out loud?)” or “Spring JDBC makes SQL portable in Java only to the level that they solve the trivial problems and punt on anything mildly interesting or complex…”. If I have had a few beers before the conversation starts, it will be more (or less) interesting.

Oh by the way, Foorm provides a nice, generic way to handle paged SQL queries. I still need to build advanced WHERE clauses, and support ORDER BY and GROUP BY operations.

This is why Foorm is still a prototype and I don’t want anyone else using it for a while. I feel that any library / framework should be used by its creator for a long time, solving lots of real-world problems before they claim to have anything truly reusable. But I figured I would show folks what I am thinking.

I have been experimenting with finding the right combination of power and convenience for both display layers and persistence. Before FOORM there was OMG-ORM (http://omg-software.com/) – it too was an exploration of the balance between powerful capabilities and intrusiveness as well as trying to make things intuitive. FOORM is much simpler than OMG and I find it more natural to use.