Tapestry4Spring

Combining Tapestry 4 and Spring

How can you reference Spring beans from Tapestry 4? In earlier versions of Tapestry, the most common method was to extend the BaseEngine class. However, in Tapestry 4 the BaseEngine class is deprecated, and we now need to extend SpringBeanFactoryHolder.

(Basic knowledge of Java, Tapestry, and Spring assumed.)

Step 1: Hivemind Configuration

Note: You can skip this step by downloading tapestry-spring.jar from http://sourceforge.net/projects/diaphragma and placing it on your classpath.

Continue reading, if you're interested in how it works...

Tapestry uses Hivemind, behind the scenes, for dependency-injection. Hivemind's XML configuration is similar to Spring. The easiest way to contribute to the whole Hivemind registry is by creating hivemodule.xml in your WEB-INF directory.

Here is what you need in this project to provide a new implementation of the DefaultSpringBeanFactoryHolder:

<?xml version="1.0"?><module id="diaphragma.tapspr" version="1.0.0">    <implementation        service-id="hivemind.lib.DefaultSpringBeanFactoryHolder">        <invoke-factory>            <construct autowire-services="false"                class="diaphragma.tapspr.XSpringBeanFactoryHolderImpl">                <event-listener                    service-id="hivemind.ShutdownCoordinator" />                <set-object property="context"                    value="service:tapestry.globals.WebContext" />            </construct>        </invoke-factory>    </implementation></module>

Next job is to create XSpringBeanFactoryHolderImpl.java. It look like this:

package diaphragma.tapspr;import java.io.PrintStream;import org.apache.hivemind.events.RegistryShutdownListener;import org.apache.hivemind.lib.impl.SpringBeanFactoryHolderImpl;import org.apache.tapestry.web.WebContext;import org.springframework.beans.factory.BeanFactory;import org.springframework.context.ConfigurableApplicationContext;public class XSpringBeanFactoryHolderImpl extends SpringBeanFactoryHolderImpl    implements RegistryShutdownListener{    private WebContext context;    public XSpringBeanFactoryHolderImpl()    {    }    public void setContext(WebContext webcontext)    {        context = webcontext;    }    public WebContext getContext()    {        return context;    }    public BeanFactory getBeanFactory()    {        if(super.getBeanFactory() == null)            super.setBeanFactory(XWebApplicationContextUtils.getWebApplicationContext(getContext()));        return super.getBeanFactory();    }    public void registryDidShutdown()    {        ((ConfigurableApplicationContext)super.getBeanFactory()).close();    }}

As we can see, this class extends the default SpringBeanFactoryHolder. The important thing is what you see in getBeanFactory() method, there you define where our BeanFactory located. In this example, I use WebApplicationContextUtils.getRequiredWebApplicationContext() method. There is another method which doesn't throw exception WebApplicationContextUtils.getWebApplicationContext().

Next, we implement XWebApplicationContextUtils.java

package diaphragma.tapspr;import org.apache.tapestry.web.WebContext;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;public class XWebApplicationContextUtils extends WebApplicationContextUtils{    public XWebApplicationContextUtils()    {    }    public static WebApplicationContext getWebApplicationContext(WebContext webcontext)    {        Object obj = webcontext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);        if(obj == null)            return null;        if(obj instanceof RuntimeException)            throw (RuntimeException)obj;        if(obj instanceof Error)            throw (Error)obj;        if(!(obj instanceof WebApplicationContext))            throw new IllegalStateException((new StringBuilder()).append("Root context attribute is not of type WebApplicationContext: ").append(obj).toString());        else            return (WebApplicationContext)obj;    }    public static WebApplicationContext getRequiredWebApplicationContext(WebContext webcontext)        throws IllegalStateException    {        WebApplicationContext webapplicationcontext = getWebApplicationContext(webcontext);        if(webapplicationcontext == null)            throw new IllegalStateException("No WebApplicationContext found: no ContextLoaderListener registered?");        else            return webapplicationcontext;    }}

Step 2: Spring Configuration

Spring in servlet mode need two things, it needs the XML file for bean configuration and also a filter in web.xml. In web.xml, you will have to add this:

<context-param>        <param-name>contextConfigLocation</param-name>        <param-value>/WEB-INF/applicationContext.xml</param-value></context-param><listener>        <listener-class>                org.springframework.web.context.ContextLoaderListener        </listener-class></listener>

And now let us try a simple XML file (place it under WEB-INF/ as applicationContext.xml).

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"         "http://www.springframework.org/dtd/spring-beans.dtd"><beans>        <bean id="person" class="com.example.model.Person">        <property name="name">                <value>Nanda Firdausi</value>        </property>        </bean></beans>

It defines one object with one property.

Step 3: Access Spring property from Tapestry page specification

Now time to see whether our bean can be accessed from a Tapestry page. First, let us create the page specification (Home.page).

<?xml version="1.0" encoding="UTF-8"?>        <!DOCTYPE page-specification PUBLIC        "-//Apache Software Foundation//Tapestry Specification 4.0//EN"        "http://jakarta.apache.org/tapestry/dtd/Tapestry_4_0.dtd">        <page-specification class="org.apache.tapestry.html.BasePage">        <inject property="person" object="spring:person" /></page-specification>

The page template is trivial, one super-simple-example is like this (Home.html).

<span jwcid="@Insert" value="ognl:person.name" /> 

Please make comments, suggestions, and any other things related to this tutorial.

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This information was originally written in an email to the Tapestry User's List on March 7, 2005 by Nanda Firdausi

last edited 2005-10-28 20:39:17 by NandaFirdausi