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| <title>Providing create connection functionality</title> |
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| <h1>Providing Reconnection Functionality</h1> |
| <h2>Creating a Reconnection Feature</h2> |
| <p>The so called <em>create connection feature</em> manages <strong>only the creation</strong> |
| of new connections. If you select an EReference with the selection tool you can |
| drag and drop the endpoint to any other EClass as shown in the figure below. But |
| this is accomplished with a <i>reconnection feature</i>, in our case the default |
| implementation |
| <a href="../../../javadoc/org/eclipse/graphiti/features/impl/DefaultReconnectionFeature.html"> |
| DefaultReconnectionFeature</a>, which realizes the anchor handling.</p> |
| <p> </p> |
| <p> |
| <img alt="" height="101" src="visio/reconnection-1.png" width="450"></p> |
| <p> |
| <strong>Figure: Reconnection is allowed</strong></p> |
| <p> </p> |
| <p>The integration into the platform’s UI is done by the framework.</p> |
| <p>A reconnection feature has to implement the interface |
| <a href="../../../javadoc/org/eclipse/graphiti/features/IReconnectionFeature.html"> |
| IReconnectionFeature</a>. Instead of implementing it directly it should extend the |
| standard implementation <a href="../../../javadoc/org/eclipse/graphiti/features/impl/DefaultReconnectionFeature.html">DefaultReconnectionFeature</a>.</p> |
| <p>The most important methods here are:</p> |
| <ul> |
| <li>The method |
| <a href="../../../javadoc/org/eclipse/graphiti/func/IReconnection.html#canReconnect(org.eclipse.graphiti.features.context.IReconnectionContext)"> |
| canReconnect</a> has to check whether the reconnection is allowed for the given |
| context.</li> |
| <li>The methods |
| <a href="../../../javadoc/org/eclipse/graphiti/func/ICreateConnection.html#preReconnect(org.eclipse.graphiti.features.context.IReconnectionContext)"> |
| preReconnect</a> and |
| <a href="../../../javadoc/org/eclipse/graphiti/func/ICreateConnection.html#postReconnect(org.eclipse.graphiti.features.context.IReconnectionContext)"> |
| postReconnect</a> can be used to modify business objects, manage bend points |
| etc.</li> |
| </ul> |
| <p>In this example we simply do not want allow reconnecting existing EReferences |
| at all.</p> |
| <p> </p> |
| <p> |
| <img alt="" height="98" src="visio/reconnection-2.png" width="453"></p> |
| <p> |
| <strong>Figure. Reconnection is not possible</strong></p> |
| <p> </p> |
| <p>You can see the complete implementation of the reconnection feature here:</p> |
| <!-- Begin code ------------------------------------------------------------------------------- --> |
| <p> </p> |
| <div class="literallayout"> |
| <div class="incode"> |
| <p class="code"><span class="keyword">package</span> org.eclipse.graphiti.examples.tutorial.features;<br> <br> |
| <span class="keyword">public class</span> TutorialReconnectionFeature |
| <span class="keyword">extends</span> |
| DefaultReconnectionFeature {<br> <br> |
| <span class="keyword">public</span> TutorialReconnectionFeature(IFeatureProvider |
| fp) {<br> |
| <span class="keyword">super</span>(fp);<br> |
| }<br> <br> @Override<br> |
| <span class="keyword"> public boolean</span> canReconnect(IReconnectionContext |
| context) {<br> |
| <span class="comment">//do not allow to reconnect</span><br> <span class="keyword">return false</span>;<br> |
| }<br> <br>} </p> |
| </div> |
| </div> |
| <p> </p> |
| <!-- End code ------------------------------------------------------------------------------- --> |
| <p>Additionally the feature provider has to deliver our newly created feature (overwrite |
| the method |
| <a href="../../../javadoc/org/eclipse/graphiti/features/IFeatureProvider.html#getReconnectionFeature()"> |
| getReconnectionFeature</a>).</p> |
| <p>This implementation can be seen here:</p> |
| <!-- Begin code ------------------------------------------------------------------------------- --> |
| <p> </p> |
| <div class="literallayout"> |
| <div class="incode"> |
| <p class="code">@Override<br><span class="keyword">public</span> IReconnectionFeature |
| getReconnectionFeature(IReconnectionContext context) {<br> |
| <span class="keyword">return new</span> TutorialReconnectionFeature(<span class="keyword">this</span>);<br> |
| } </p> |
| </div> |
| </div> |
| <p> </p> |
| <!-- End code ------------------------------------------------------------------------------- --> |
| <h2>Test: Try to reconnect an EReference</h2> |
| <p>Now start the editor and test the create connection feature:</p> |
| <ol> |
| <li>create or open a diagram</li> |
| <li>create two new EClasses (if you do not have them already) and create an |
| EReference between them with the connection tool in the palette</li> |
| <li>click on the “EReference” with the selection tool in the palette that it |
| becomes selected</li> |
| <li>drag the end point as it is shown in the figure above. You should notice |
| the tiny prohibition symbol then. When you drop the endpoint, it snaps back |
| to the original position.</li> |
| </ol> |
| <p> </p> |
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