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CeWolf in Spring

At 7:45 AM on Dec 18, 2006, Alex Baranov wrote:

As SourceForge.com claims, Cewolf is a “tag library for charts of all kinds. It enables every JSP to easily embed chart images. It can be used by any web applications running in a servlet container.”

Indeed, it is very simple to use and very powerful in any kind of web application. Integrating Cewolf with Spring won’t take a lot of time as well.

To start working with Cewolf you should read a quite short tutorial on project’s site http://cewolf.sourceforge.net . It describes the basics: how to configure web.xml file, what libraries must be included into project.

Now, as you followed all those steps you have working diagram on your web page. But this diagram shows static random values. Now you probably want to fill it with real values that are retrieved for example from database.

Let’s say that you use standard model of building your web-application:

Controller -------> Service1 ---------> Object1DAO

| … \---> Object2DAO

\----> Service2 …

\---------------> Object3DAO

Services and DAO objects are beans that configured in your context configuration file. You retrieve them in your controller (whether you use Struts or Spring MVC or smth. else).

In order to use services in your DatasetProducer (to fill diagram with real data) you should define it as a bean in your Spring context configuration file:

<bean id="yourDatasetProducer" class="your.package.YourDatasetProducer">

<property name="service1">

<ref bean="service1"/>

</property>

</bean>

Then you can retrieve it in your controller (the same procedure as you use while retrieving services or other beans from Spring context). All Spring beans by default are singletons. We do not need to change that option for yourDatasetProducer bean.

Change example from the tutorial of http://cewolf.sourceforge.net so that our DatasetProducer will be retrieved from session and not created on-the-fly:

1)       change .jsp:

<jsp:useBean id="pageViews" scope=”session” class=" your.package.YourDatasetProducer "/>
<cewolf:chart
id="line"
title="Page View Statistics"
type="line"
xaxislabel="Page"
yaxislabel="Views">
<cewolf:data>
<cewolf:producer id="pageViews"/>
</cewolf:data>
</cewolf:chart>
<p>
<cewolf:img chartid="line" renderer="cewolf" width="400" height="300"/>
<P>

2)       in your controller put yourDatasetProducer bean (retrieved from Spring application contex) into the session:

request.getSession().setAttribute("pageViews", yourDatasetProducer);

And that’s it.

Alex Baranov , Software Developer, Itransition Software, Belhard Group JSC