TilesTool

July 23, 2003

Here is the much anticipated TilesTool, to use with Velocity Tools and Struts 1.1

I personally use the nested tiles and tile-controllers features, but I haven't tried other features you might be interested in.

Any comments are welcome on the Velocity Developer's List <velocity-dev@jakarta.apache.org>.

Marinó A. Jónsson

{ { { 

package org.apache.velocity.tools.struts;

import java.util.Stack;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.ServletContext;

import java.io.StringWriter;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.Template;

import org.apache.struts.tiles.ComponentContext;
import org.apache.struts.tiles.ComponentDefinition;
import org.apache.struts.tiles.AttributeDefinition;
import org.apache.struts.tiles.DirectStringAttribute;
import org.apache.struts.tiles.DefinitionAttribute;
import org.apache.struts.tiles.DefinitionNameAttribute;
import org.apache.struts.tiles.PathAttribute;
import org.apache.struts.tiles.TilesUtil;
import org.apache.struts.tiles.DefinitionsFactoryException;
import org.apache.struts.tiles.Controller;

import org.apache.velocity.tools.view.context.ViewContext;
import org.apache.velocity.tools.view.tools.ViewTool;


/**
{{{ * <p>Title: TilesTool</p> 
 * <p>Description: A tool to use struts-tiles with Velocity</p> 
 * <p>Usage: 
 * 
 * Just call $tiles.name_of_tile_definition from the template to insert 
 * the tile. 
 * 
 * $tiles.getString("name_of_tile_attribute") fetches a named attribute-value 
 * from the current tiles-context. 
 * 
 * @author <a href="mailto:marinoj@centrum.is">Marino A. Jonsson</a> 
 * @version $Revision: 1.1 $ $Date: 2003/07/24 04:59:21 $ 
 */ 

public class TilesTool implements ViewTool {

{{{ protected ViewContext context;

• protected ServletContext application; protected HttpServletRequest request; protected HttpServletResponse response; /**

  • A stack to hold ComponentContexts while nested tile-definitions

  • are rendered.
  • /
  protected Stack contextStack; /******************************* Constructors ****************************/ /**
  • Default constructor. Tool must be initialized before use.
  • /

  public TilesTool() {} /**

  • Initializes this tool.

  • @param obj the current ViewContext

  • @throws IllegalArgumentException if the param is not a ViewContext

  • /
  public void init(Object obj) {

  • if (!(obj instanceof ViewContext)) {

    • throw new IllegalArgumentException("Tool can only be initialized with a ViewContext");

    }

    this.context = (ViewContext)obj; this.request = context.getRequest(); this.response = context.getResponse(); this.application = context.getServletContext();

  } /***************************** View Helpers ******************************/ /**
  • Fetches a named attribute value from the current tiles-context.

  • <p>This is functionally equivalent to

  • <code><tiles:getAsString name="title" /></code>.</p>

  • @param name the name of the tiles-attribute to fetch
  • @return the attribute value as String
  • /
  public String getString(String name) {

  • ComponentContext context = ComponentContext.getContext(request); Object attrValue = context.getAttribute(name); if (attrValue == null) {

    • return null;
    } return attrValue.toString();
  } /**

  • <p>A generic tiles insert function</p>

  • <p>This is functionally equivalent to

  • <code><tiles:insert attribute="menu" /></code>.</p>

  • @param attr - can be any of the following:

  • AttributeDefinition,

  • tile-definition name,
  • tile-attribute name,
  • regular uri.
  • (checked in that order)
  • @return the rendered template or value as a String
  • @throws Exception on failure
  • /
  public String get(Object attr) throws Exception {

  • ComponentContext currentContext = ComponentContext.getContext(request); Object attrValue = currentContext.getAttribute(attr.toString()); if (attrValue != null) {

    • return processObjectValue(attrValue);
    } return processAsDefinitionOrURL(attr.toString());
  } /************************** Protected Methods ****************************/ /**
  • Process an object retrieved as a bean or attribute.
  • @param value - Object can be a typed attribute, a String, or anything
  • else. If typed attribute, use associated type. Otherwise, apply
  • toString() on object, and use returned string as a name.
  • @throws Exception - Throws by underlying nested call to
  • processDefinitionName()
  • @return the fully processed value as String
  • /
  protected String processObjectValue(Object value) throws Exception {

  • First, check if value is one of the Typed Attribute if (value instanceof AttributeDefinition) {

    • We have a type => return appropriate IncludeType return processTypedAttribute((AttributeDefinition)value);

    }

    else if (value instanceof ComponentDefinition) {

    • return processDefinition((ComponentDefinition)value);

    }

    Value must denote a valid String return processAsDefinitionOrURL(value.toString());

  } /**
  • Process typed attribute according to its type.
  • @param value Typed attribute to process.
  • @return the fully processed attribute value as String.
  • @throws Exception - Throws by underlying nested call to processDefinitionName()
  • /

  protected String processTypedAttribute(AttributeDefinition value) throws Exception {

  • if (value instanceof DirectStringAttribute) {

    • return (String)value.getValue();
    }

    else if (value instanceof DefinitionAttribute) {

    • return processDefinition((ComponentDefinition)value.getValue());

    }

    else if (value instanceof DefinitionNameAttribute) {

    • return processAsDefinitionOrURL((String)value.getValue());
    }

    else if( value instanceof PathAttribute ) return doInsert((String)value.getValue(), null, null);

  } /**
  • Try to process name as a definition, or as an URL if not found.
  • @param name Name to process.
  • @return the fully processed definition or URL
  • @throws Exception
  • /
  protected String processAsDefinitionOrURL(String name) throws Exception {
  • try {

    • ComponentDefinition definition =

      • TilesUtil.getDefinition(name, request, application);

      if (definition != null) {
      • return processDefinition(definition);
      }
    }

    catch (DefinitionsFactoryException ex) {

    • silently failed, because we can choose to not define a factory.

    }

    no definition found, try as url return processUrl(name);

  } /**
  • End of Process for definition.
  • @param definition Definition to process.
  • @return the fully processed definition.

  • @throws Exception from InstantiationException Can't create requested controller

  • /

  protected String processDefinition(ComponentDefinition definition) throws Exception {

  • Controller controller = null; try {
    • controller = definition.getOrCreateController(); String role = definition.getRole(); String page = definition.getTemplate(); return doInsert(definition.getAttributes(),
      • page, role, controller);
    }

    catch (InstantiationException ex) {

    • throw new Exception(ex.getMessage());
    }
  } /**
  • Processes an url
  • @param url the URI to process.
  • @return the rendered template as String.
  • @throws Exception
  • /
  protected String processUrl(String url) throws Exception {
  • return doInsert(url, null, null);
  } /**
  • Use this if there is no nested tile.
  • @param page the page to process.
  • @param role possible user-role
  • @param controller possible tiles-controller
  • @return the rendered template as String.
  • @throws Exception
  • /
  protected String doInsert(String page, String role, Controller controller) throws Exception {

  • if (role != null && !request.isUserInRole(role)) {

    • return null;
    }

    ComponentContext subCompContext = new ComponentContext(); return doInsert(subCompContext, page, role, controller);

  } /**
  • Use this if there is a nested tile.
  • @param attributes attributes for the sub-context
  • @param page the page to process.
  • @param role possible user-role
  • @param controller possible tiles-controller
  • @return the rendered template as String.
  • @throws Exception
  • /
  protected String doInsert(Map attributes,
  • String page, String role, Controller controller) throws Exception
  {

  • if (role != null && !request.isUserInRole(role)) {

    • return null;
    }

    ComponentContext subCompContext = new ComponentContext(attributes); return doInsert(subCompContext, page, role, controller);

  } /**
  • An extension of the other two doInsert functions
  • @param subCompContext the sub-context to set in scope when the
  • template is rendered.
  • @param page the page to process.
  • @param role possible user-role
  • @param controller possible tiles-controller
  • @return the rendered template as String.
  • @throws Exception
  • /

  protected String doInsert(ComponentContext subCompContext,

  • String page, String role, Controller controller) throws Exception
  {
  • pushTilesContext(); try {

    • ComponentContext.setContext(subCompContext, request);

      Call controller if any if (controller != null) {

      • controller.perform(subCompContext,
        • request, response, application);
      } return parse(page);
    } finally {
    • popTilesContext();
    }
  } /**

  • <p>pushes the current tiles context onto the context-stack.

  • preserving the context is necessary so that a sub-context can be

  • put into request scope and lower level tiles can be rendered</p>

  • /
  protected void pushTilesContext() {
  • if (contextStack == null) {
    • contextStack = new Stack();
    }

    contextStack.push(ComponentContext.getContext(request));

  } /**

  • <p>pops the tiles sub-context off the context-stack after the lower level

  • tiles have been rendered</p>

  • /
  protected void popTilesContext() {

  • ComponentContext.setContext((ComponentContext)contextStack.pop(), request);

  } /**

  • <p>Renders a template</p>

  • @param templateName - name of template to be rendered
  • @throws Exception if it fails
  • @return the rendered template as a String
  • /
  protected String parse(String templateName) throws Exception {

  • StringWriter sw = new StringWriter(); Template template = Velocity.getTemplate(templateName); template.merge(context.getVelocityContext(), sw); return sw.toString();

  } }}}

}

{{{ } } }

• }}}