Andy's Blog

Not long ago, some ppl in the Tapestry mailing list were asking for a shorcut when
using the Insert component.
They prefered writing ${user.name} instead of <span jwcid="Insert" value="ognl:user.name"/>

This functionality can easily be added into Tapestry 4. It’s a matter of finding which class to extend and which configuration point to set. So, let’s begin with the java code.
In this case, we’re going to extend org.apache.tapestry.parse.TemplateParser, overriding the method public TemplateToken[] parse(char[] templateData,
ITemplateParserDelegate delegate,
Resource resourceLocation)
In that method, we’re going to convert templateData to a String and then replace
all occurances of ${something} into <span jwcid=”@Insert” value=”ognl:something”/> . As seen, we’ll be adding a default binding of ognl, unless there’s already a binding.
In this way, ${message:home} will simply become <span jwcid=”@Insert” value=”message:home”/>. After that, we’ll just delegate to the base class. So here’s some code:

EasyInsertTemplateParser.java

 package andyhot.tap4.parse;
 
 import org.apache.hivemind.Resource;
 import org.apache.tapestry.parse.ITemplateParserDelegate;
 import org.apache.tapestry.parse.TemplateParseException;
 import org.apache.tapestry.parse.TemplateParser;
 import org.apache.tapestry.parse.TemplateToken;
 
 /**
  * For replacing ${something} into
  * <span jwcid="@Insert" value="ognl:something"/>
  * @author andyhot
  */
 public class EasyInsertTemplateParser extends TemplateParser
 {
     public TemplateToken[] parse(char[] templateData,
                                  ITemplateParserDelegate delegate,
                                  Resource resourceLocation)
     throws TemplateParseException
     {
         String template = new String(templateData);
         int pos = 0;
         boolean changed = false;
         do
         {
             pos = template.indexOf("${", pos);
             if (pos >=0)
             {
                 int pos2=template.indexOf("}", pos);
                 if (pos2>=0)
                 {
                     changed = true;
                     String oldValue = template.substring(pos + 2, pos2);
                     String newValue = applyBinding(oldValue);
                     template = template.substring(0, pos)
                     	+ "<span jwcid=\"@Insert\" value=\"" + newValue + "\"/>"
                     	+ template.substring(pos2 + 1);
                 }
             }
         }
         while (pos>=0);
         if (changed == true)
         {
             System.out.println("Expanded: " + resourceLocation.getPath());
             //System.out.println(template);
         }
         return super.parse(template.toCharArray(), delegate, resourceLocation);
     }
 
     private String applyBinding(String value)
     {
         int pos = value.indexOf(":");
         if (pos<0)
         {
             return "ognl:" + value;
         }
         else
         {
             for (int i = 0; i < pos; i++)
             {
                 char c = value.charAt(i);
                 if ((c>='a' && c<='z') || (c>='A' && c<='Z'))
                     continue;
                 return "ognl:" + value;
             }
             return value;
         }
     }
 }

hivemodule.xml

 <?xml version="1.0"?>
 
 <module id="EastInsert" version="1.0.0" package="andyhot.tap4">
 
   <service-point id="EasyTemplateParser" interface="org.apache.tapestry.parse.ITemplateParser">
 
     Parses a template into a series of tokens that are used to construct a component's body.
 
     <invoke-factory model="threaded">
       <construct class="andyhot.tap4.parse.EasyInsertTemplateParser">
         <set-object property="factory" value="instance:org.apache.tapestry.parse.TemplateTokenFactory"/>
       </construct>
     </invoke-factory>
 
   </service-point>
 
   <service-point id="EasyTemplateSource" interface="org.apache.tapestry.services.TemplateSource">
 
     A smart cache for localized templates for pages and components.  Retrieves a template on
     first reference, and returns it on subsequent references.
 
 
     <invoke-factory>
       <construct class="org.apache.tapestry.services.impl.TemplateSourceImpl">
         <set-service property="parser" service-id="EasyTemplateParser"/>
         <set-service property="delegate" service-id="tapestry.parse.TemplateSourceDelegate"/>
         <set-object property="contextRoot" value="infrastructure:contextRoot"/>
         <set-service property="componentSpecificationResolver" service-id="tapestry.page.ComponentSpecificationResolver"/>
         <set-object property="componentPropertySource"  value="infrastructure:componentPropertySource"/>
         <event-listener service-id="tapestry.ResetEventCoordinator"/>
       </construct>
     </invoke-factory>
 
   </service-point>
 
   <contribution configuration-id="tapestry.InfrastructureOverrides">
 	 <property name="templateSource" object="service:EasyTemplateSource" />
   </contribution>
 
 </module>