SolrJs

About

SolrJs is a javascript client library that is topic of a 2008 google summer of code project. It is currently work in progress, this page is intended to show the project's status, some technical documentation and a collection of thoughts about future features. The current trunk is accessible at [http://solrstuff.org/svn/solrjs/trunk]

Architectural Overview

The library is written using the javascript toolkit jQuery [http://jquery.com/] (Version 1.2.5). SolrJS is included in one additional javascript file "solrjs.js" The idea is to create several (reusable and extensible) "widgets" that represent solr queries. A widget is a javascript object that is responsible for creating the according solr query as well as render the result from the server to html. One manager object acts as a container that holds these widgets, performs the actual query using jQueries getJSON [http://docs.jquery.com/Ajax/jQuery.getJSON#urldatacallback] method. This method creates a dynamic script tag, making cross-domain solr requests possible.

Examples for widgets

Implementation

Javascript matters

All SolrJS objects are created inside the jQuery.solrjs namspace. Given JQueries support for overriding the $() function, it is easily possible to use SolrJS alongside other javascript toolkits like prototype or custom javascript code.

Just include the following includes in the header section of your html:

<script src="jquery-1.2.5.js"/>
<script src="solrjs.js"/>
<script> var $sj = jQuery.noConflict(); </script> 

After that, all objects are accessible using $sj.solrjs.*

The manager object

The manager object acts as "Controller" for the user input. It holds a state of the current solr query. The current query is represented by QueryItems objetcs. A query item simply is a field:value pair. A user may select or deselect multiple items. In the current work in progress, all query itemsa are concatinated using "AND" operators. More complex query generation may be implemented in the future. The manager currently provides the following methods:

How a query request works

Every widget implements a "getSolrUrl" method and performs its own http request. It also has to provide a "handleResult" method that gets the json data response to render. So if a user changes the selection:

Widget Inheritance

A main goal of the implementation was to create clean easy to understand code that can be easily extended by other developers. So I introduced a small OO inheritance pattern inspired by this thread [http://groups.google.com/group/jquery-dev/msg/12d01b62c2f30671] and created the factory method:

jQuery.solrjs.createClass = function(subClassName, baseClassName, subClass)

An "AbstractWidget" class is provided that acts as base class for all further widget implementations. In the source code, all methods that should be implemented by the child class are documented and marked as "abstract methods". An example syntax for a simple widget may be:

/*
 * Simple faceted view for one field.
 * 
 * @param "id": the widgetId
 * @param "target": the target html element in jquery notation
 * @param "fieldName": The facet field name
 */
jQuery.solrjs.createClass ("SimpleFacetWidget", "AbstractWidget", { 
  
  getSolrUrl : function(start) { 
    return "&facet=true&facet.field=" + this.fieldName;
  },

  handleResult : function(data) { 
    var values = data.facet_counts.facet_fields[this.fieldName];         
    jQuery(this.target).html("");
                
    for (var i = 0; i < values.length; i = i + 2) {
      var items =  "[new jQuery.solrjs.QueryItem({field:'" + this.fieldName + "',value:'" +  values[i] + "'})]";
      var label = values[i] + "(" + values[i+1] + ")";          
      jQuery('<a/>').html(label).attr("href","javascript:solrjsManager.selectItems('" + this.id + "'," + items + ")").appendTo(this.target);
        jQuery('<br/>').appendTo(this.target);
      }
  },

  handleSelect : function(data) { 
    jQuery(this.target).html(this.selectedItems[0].value);
    jQuery('<a/>').html("(x)").attr("href","javascript:solrjsManager.deselectItems('" + this.id + "')").appendTo(this.target);
  },

  handleDeselect : function(data) { 
    // do nothing
  }        
});

To add this widget to your html page, just create this script tag:

<script>
  var solrjsManager; 
  $sj(document).ready(function(){ 
    solrjsManager = new $sj.solrjs.Manager({solrUrl:"http://localhost:8983/solr/select"});   
    solrjsManager.addWidget(new $sj.solrjs.SimpleResultWidget({id:"result", target:"#result", rows:20}));       
    solrjsManager.addWidget(new $sj.solrjs.SimpleFacetWidget({id:"cat", target:"#cat", fieldName:"cat"}));
    solrjsManager.doRequestAll(); 
  });
</script>