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changes.mady.by.user Bob Harner

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Excerpt
hiddentrue

Adding an Annotation and a Filter to customize Tapestry's page rendering

...

Code Block
languagejava
titleFnordSymbols.java
package com.fnord;

import org.apache.tapestry5.http.services.BaseURLSource;

import com.fnord.annotations.ForbidFraming;

public class FnordSymbols {

  /**
   * Meta-data key; when true, MarkupRendererFilter will inject some extra
   * content into the response to enforce that the content may not be framed
   * (i.e., "stolen").
   * 
   * @see ForbidFraming
   */
  public static final String FORBID_FRAMING = "forbid-framing";

}

...

Code Block
languagejava
titleForbidFramingModule.class
package com.fnord.services.forbidframing;

import org.apache.tapestry5.ioccommons.MappedConfiguration;
import org.apache.tapestry5.ioc.annotations.Contribute;
import org.apache.tapestry5.ioc.services.FactoryDefaults;
import org.apache.tapestry5.ioc.services.SymbolProvider;

import com.fnord.FnordSymbols;

public class ForbidFramingModule {

  @Contribute(SymbolProvider.class)
  @FactoryDefaults
  public static void setupForbidFramingDefault(
      MappedConfiguration<String, String> configuration) {
    configuration.add(FnordSymbols.FORBID_FRAMING, "false");
  }
}

...

The work we ultimately want to do occurs when rendering a page. Tapestry defines a pipeline for that overall process. The point of a pipeline is that we can add filters to it. We'll add a filter that checks for the meta-data key and adds the response header and JavaScript.

...

There's a bit going on in this short piece of code. The heart of the code is the MetaDataLocator service; given a meta-data key and a page name, it can not only extract the value, but then coerce it to a desired type, all in one go.

...