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<a class="edit-on-gh" href="https://github.com/apache/struts-site/edit/master/source/tag-developers/cewolf-charts-using-velocity-templates.md" title="Edit this page on GitHub">Edit on GitHub</a>
<h1 id="cewolf-charts-using-velocity-templates">CeWolf charts using Velocity templates</h1>
<h2 id="setup-cewolf">Setup CeWolf</h2>
<p><strong>This currently only works with the most recent CVS version of WebWork but should be available in the upcoming 2.0 beta2</strong></p>
<ol>
<li>
<p>Go to <a href="http://cewolf.sourceforge.net">http://cewolf.sourceforge.net</a> and grab a stable release of CeWolf (at the time of writing, the unstable builds do not work with WebWork).</p>
</li>
<li>
<p>Edit your webwork.properties file and add “de.laures.cewolf.taglib.tags” to the property “webwork.velocity.tag.path”</p>
</li>
</ol>
<p>Lastly add the CeWolf servlet to web.xml:</p>
<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code>
<span class="nt">&lt;servlet&gt;</span>
<span class="nt">&lt;servlet-name&gt;</span>CewolfServlet<span class="nt">&lt;/servlet-name&gt;</span>
<span class="nt">&lt;servlet-class&gt;</span>de.laures.cewolf.CewolfRenderer<span class="nt">&lt;/servlet-class&gt;</span>
<span class="nt">&lt;/servlet&gt;</span>
<span class="nt">&lt;servlet-mapping&gt;</span>
<span class="nt">&lt;servlet-name&gt;</span>CewolfServlet<span class="nt">&lt;/servlet-name&gt;</span>
<span class="nt">&lt;url-pattern&gt;</span>/cewolf/*<span class="nt">&lt;/url-pattern&gt;</span>
<span class="nt">&lt;/servlet-mapping&gt;</span>
</code></pre></div></div>
<h2 id="create-a-datasetproducer">Create a DatasetProducer</h2>
<p>This is the default DatasetProducer from the CeWolf tutorial.</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code>
<span class="kn">import</span> <span class="nn">java.io.Serializable</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">java.util.Date</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">java.util.Map</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jfree.data.DefaultCategoryDataset</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">de.laures.cewolf.DatasetProduceException</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">de.laures.cewolf.DatasetProducer</span><span class="o">;</span>
<span class="kd">public</span> <span class="kd">class</span> <span class="nc">PageViewCountData</span> <span class="kd">implements</span> <span class="n">DatasetProducer</span><span class="o">,</span> <span class="n">Serializable</span> <span class="o">{</span>
<span class="c1">// These values would normally not be hard coded but produced by</span>
<span class="c1">// some kind of data source like a database or a file</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">String</span><span class="o">[]</span> <span class="n">categories</span> <span class="o">=</span> <span class="o">{</span><span class="s">"mon"</span><span class="o">,</span> <span class="s">"tue"</span><span class="o">,</span> <span class="s">"wen"</span><span class="o">,</span> <span class="s">"thu"</span><span class="o">,</span> <span class="s">"fri"</span><span class="o">,</span> <span class="s">"sat"</span><span class="o">,</span> <span class="s">"sun"</span><span class="o">};</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">String</span><span class="o">[]</span> <span class="n">seriesNames</span> <span class="o">=</span> <span class="o">{</span><span class="s">"cewolfset.jsp"</span><span class="o">,</span> <span class="s">"tutorial.jsp"</span><span class="o">,</span> <span class="s">"testpage.jsp"</span><span class="o">,</span> <span class="s">"performancetest.jsp"</span><span class="o">};</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">Integer</span><span class="o">[]</span> <span class="o">[]</span> <span class="n">values</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Integer</span><span class="o">[</span><span class="nl">OS:</span><span class="n">seriesNames</span><span class="o">.</span><span class="na">length</span><span class="o">]</span> <span class="o">[</span><span class="nl">OS:</span><span class="n">categories</span><span class="o">.</span><span class="na">length</span><span class="o">];</span>
<span class="kd">public</span> <span class="n">Object</span> <span class="nf">produceDataset</span><span class="o">(</span><span class="n">Map</span> <span class="n">params</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">DatasetProduceException</span> <span class="o">{</span>
<span class="n">DefaultCategoryDataset</span> <span class="n">dataset</span> <span class="o">=</span> <span class="k">new</span> <span class="n">DefaultCategoryDataset</span><span class="o">();</span>
<span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">series</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> <span class="n">series</span> <span class="o">&lt;</span> <span class="n">seriesNames</span><span class="o">.</span><span class="na">length</span><span class="o">;</span> <span class="n">series</span> <span class="o">++)</span> <span class="o">{</span>
<span class="kt">int</span> <span class="n">lastY</span> <span class="o">=</span> <span class="o">(</span><span class="kt">int</span><span class="o">)(</span><span class="n">Math</span><span class="o">.</span><span class="na">random</span><span class="o">()</span> <span class="o">*</span> <span class="mi">1000</span> <span class="o">+</span> <span class="mi">1000</span><span class="o">);</span>
<span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">categories</span><span class="o">.</span><span class="na">length</span><span class="o">;</span> <span class="n">i</span><span class="o">++)</span> <span class="o">{</span>
<span class="kd">final</span> <span class="kt">int</span> <span class="n">y</span> <span class="o">=</span> <span class="n">lastY</span> <span class="o">+</span> <span class="o">(</span><span class="kt">int</span><span class="o">)(</span><span class="n">Math</span><span class="o">.</span><span class="na">random</span><span class="o">()</span> <span class="o">*</span> <span class="mi">200</span> <span class="o">-</span> <span class="mi">100</span><span class="o">);</span>
<span class="n">lastY</span> <span class="o">=</span> <span class="n">y</span><span class="o">;</span>
<span class="n">dataset</span><span class="o">.</span><span class="na">addValue</span><span class="o">((</span><span class="kt">double</span><span class="o">)</span><span class="n">y</span><span class="o">,</span> <span class="n">seriesNames</span><span class="o">[</span><span class="nl">OS:</span><span class="n">series</span><span class="o">],</span> <span class="n">categories</span><span class="o">[</span><span class="n">i</span><span class="o">]);</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="k">return</span> <span class="n">dataset</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="kt">boolean</span> <span class="nf">hasExpired</span><span class="o">(</span><span class="n">Map</span> <span class="n">params</span><span class="o">,</span> <span class="n">Date</span> <span class="n">since</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="o">(</span><span class="n">System</span><span class="o">.</span><span class="na">currentTimeMillis</span><span class="o">()</span> <span class="o">-</span> <span class="n">since</span><span class="o">.</span><span class="na">getTime</span><span class="o">())</span> <span class="o">&gt;</span> <span class="mi">5000</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="n">String</span> <span class="nf">getProducerId</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="s">"PageViewCountData DatasetProducer"</span><span class="o">;</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div></div>
<h2 id="create-the-velocity-template">Create the Velocity template</h2>
<p>With the new WebWork refactorings, nested JSP tags with arbitrary parameters can be used, so we convert the CeWolf tutorial JSP script to Velocity.</p>
<pre><code class="language-jsp">
&lt;jsp:useBean id="pageViews" class="de.laures.cewolf.example.PageViewCountData"/&gt;
&lt;cewolf:chart
id="line"
title="Page View Statistics"
type="line"
xaxislabel="Page"
yaxislabel="Views"&gt;
&lt;cewolf:data&gt;
&lt;cewolf:producer id="pageViews"/&gt;
&lt;/cewolf:data&gt;
&lt;/cewolf:chart&gt;
&lt;cewolf:img chartid="line" renderer="cewolf" width="400" height="300"/&gt;
</code></pre>
<p>In Velocity it looks like this:</p>
<div class="highlighter-rouge"><div class="highlight"><pre class="highlight"><code>
#set( $pageViews = $stack.findValue("new com.PageViewCountData()") )
$req.session.setAttribute("pageViews", $pageViews )
#bodytag( SimpleChart "id=line" "title=Page View Statistics" "type=line" "xaxislabel=Page" "yaxslabel=Views" )
#bodytag( Data )
#tag( Producer "id=pageViews" )
#end
#end
#tag( ChartImg "chartid=line" "renderer=cewolf" "width=400" "height=300" )
</code></pre></div></div>
<p>As you may notice, CeWolf looks up it’s DatasetProducer in the request attributes - it has no knowledge of the Velocity context. That’s why we call $req.session.setAttribute(). The other attributes (such as the chartid) will be set by CeWolf, so we don’t need to care about them.</p>
<h2 id="setup-an-action-to-disply-the-template">Setup an action to disply the template</h2>
<p>Now you should be able to fire up an action in the usual way with this template as the result and a nice chart should appear.</p>
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