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| <h1>Providing Create Connection Functionality</h1> |
| <h2>Creating a Create Connection Feature</h2> |
| <p>Usually a new connection object is created graphically by using the corresponding |
| connection tool from the editor’s tool palette. When using Graphiti you only have |
| to provide a so called create connection feature. The integration into the platform’s |
| UI is done by the framework.</p> |
| <p>A create connection feature has to implement the interface |
| <a href="../../../javadoc/org/eclipse/graphiti/features/ICreateConnectionFeature.html"> |
| ICreateConnectionFeature</a>. Instead of implementing it directly it should extend |
| one of the available base classes. In this example we extend the base class |
| <a href="../../../javadoc/org/eclipse/graphiti/features/impl/AbstractCreateConnectionFeature.html"> |
| AbstractCreateConnectionFeature</a>.</p> |
| <p>We have to implement/overwrite 3 methods:</p> |
| <ul> |
| <li>The method |
| <a href="../../../javadoc/org/eclipse/graphiti/func/ICreateConnection.html#canCreate(org.eclipse.graphiti.features.context.ICreateConnectionContext)">canCreate</a> has to check whether the connection can be created for the given context. |
| It has to check the business objects which are behind the source and the target |
| anchors.</li> |
| <li>The method |
| <a href="../../../javadoc/org/eclipse/graphiti/func/ICreateConnection.html#canStartConnection(org.eclipse.graphiti.features.context.ICreateConnectionContext)">canStartConnection</a> has to check whether the connection can be started at the |
| given source anchor.</li> |
| <li>The method |
| <a href="../../../javadoc/org/eclipse/graphiti/func/ICreateConnection.html#create(org.eclipse.graphiti.features.context.ICreateConnectionContext)">create</a> has to create the business object for the connection and also has to |
| add the graphical representation of the newly created business object to the diagram. |
| The creation of the business object must be implemented here. To add the graphical |
| representation, an <a href="add-connection-feature.htm">add connection feature</a> |
| should be used.</li> |
| </ul> |
| <p>In this example we want create an EReference between EClasses via the connection |
| tool from the palette.</p> |
| <p> </p> |
| <p> |
| <img alt="" height="251" src="visio/connection-routing-direct.png" width="251"></p> |
| <p><strong>Figure: EReference between EClasses</strong></p> |
| <p> </p> |
| <p>You can see the complete implementation of the create connection 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> TutorialCreateEReferenceFeature |
| extends<br> AbstractCreateConnectionFeature |
| {<br> <br> <span class="keyword">public </span>TutorialCreateEReferenceFeature |
| (IFeatureProvider fp) {<br> |
| <span class="comment">// provide name and description for the UI, e.g. the |
| palette</span><br> |
| <span class="keyword">super</span>(fp, <span class="string">"EReference"</span>, |
| <span class="string">"Create EReference"</span>);<br> |
| }<br> <br> <span class="keyword"> public boolean</span> |
| canCreate(ICreateConnectionContext context) {<br> |
| <span class="comment">// return true if both anchors belong to an EClass<br> |
| // and those EClasses are not identical</span><br> |
| EClass source = getEClass(context.getSourceAnchor());<br> |
| EClass target = getEClass(context.getTargetAnchor());<br> |
| <span class="keyword">if</span> (source != <span class="keyword">null |
| </span>&& target != <span class="keyword">null </span>&& source != target) |
| {<br> |
| <span class="keyword">return true</span>;<br> |
| }<br> <span class="keyword">return |
| false</span>;<br> }<br> <br> |
| <span class="keyword">public boolean</span> canStartConnection(ICreateConnectionContext |
| context) {<br> |
| <span class="comment">// return true if start anchor belongs to a EClass</span><br> |
| <span class="keyword">if </span>(getEClass(context.getSourceAnchor()) != |
| <span class="keyword">null</span>) {<br> |
| <span class="keyword">return true</span>;<br> |
| }<br> <span class="keyword"> return |
| false</span>;<br> }<br> <br> |
| <span class="keyword">public </span>Connection create(ICreateConnectionContext |
| context) {<br> Connection newConnection |
| = <span class="keyword">null</span>;<br> <br> |
| <span class="comment">// get EClasses which should be connected</span><br> |
| EClass source = getEClass(context.getSourceAnchor());<br> |
| EClass target = getEClass(context.getTargetAnchor());<br> <br> |
| <span class="keyword">if</span> (source != <span class="keyword">null |
| </span>&& target != <span class="keyword">null</span>) {<br> |
| <span class="comment">// create new business object </span><br> |
| EReference eReference = createEReference(source, target);<br> |
| <span class="comment">// add connection for business object</span><br> |
| AddConnectionContext addContext =<br> |
| new AddConnectionContext(context.getSourceAnchor(), context<br> |
| .getTargetAnchor());<br> |
| addContext.setNewObject(eReference);<br> |
| newConnection =<br> |
| (Connection) getFeatureProvider().addIfPossible(addContext);<br> |
| }<br> <br> |
| <span class="keyword">return </span>newConnection;<br> |
| }<br> <br> <span class="string">/**<br> |
| * Returns the EClass belonging to the anchor, or null if not available.<br> |
| */</span><br> <span class="keyword">private </span>EClass |
| getEClass(Anchor anchor) {<br> |
| <span class="keyword">if </span>(anchor != <span class="keyword">null</span>) |
| {<br> |
| Object object =<br> |
| getBusinessObjectForPictogramElement(anchor.getParent());<br> |
| <span class="keyword">if</span> (object <span class="keyword">instanceof |
| </span>EClass) {<br> |
| <span class="keyword">return </span>(EClass) object;<br> |
| }<br> }<br> |
| <span class="keyword">return null</span>;<br> }<br> <br> |
| <span class="string">/**<br> * Creates a EReference between |
| two EClasses.<br> */</span><br> |
| <span class="keyword">private </span>EReference createEReference(EClass |
| source, EClass target) {<br> EReference |
| eReference = EcoreFactory.eINSTANCE.createEReference();<br> |
| eReference.setName(<span class="string">"new EReference"</span>);<br> |
| eReference.setEType(target);<br> |
| eReference.setLowerBound(0);<br> |
| eReference.setUpperBound(1);<br> |
| source.getEStructuralFeatures().add(eReference);<br> |
| <span class="keyword">return </span>eReference;<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#getCreateConnectionFeatures()"> |
| getCreateConnectionFeatures</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>ICreateConnectionFeature[] getCreateConnectionFeatures() {<br> |
| <span class="keyword">return new</span> ICreateConnectionFeature[] { <br> |
| <span class="keyword">new </span>TutorialCreateEReferenceFeature (<span class="keyword">this</span>) |
| };<br> } </p> |
| </div> |
| </div> |
| <p> </p> |
| <!-- End code ------------------------------------------------------------------------------- --> |
| <p>Before we can run the editor we have to add <a href="anchors.htm">anchors</a> |
| to the container shapes of the EClasses. Anchors are explained later in detail.</p> |
| <p>For now simply create an anchor at end of the add method of the |
| <span class="inlinecode">TutorialAddEClassFeature</span>, |
| as shown in the following code snippet:</p> |
| <!-- Begin code ------------------------------------------------------------------------------- --> |
| <p> </p> |
| <div class="literallayout"> |
| <div class="incode"> |
| <p class="code"> <span class="keyword">public </span>PictogramElement |
| add(IAddContext context) {<br> |
| <br> <span class="comment">// |
| ... EXISTING CODING ... <br> |
| <br> // add a chopbox anchor to |
| the shape </span><br> peCreateService.createChopboxAnchor(containerShape);<br> |
| <br> <span class="comment">// |
| call the layout feature</span><br> |
| layoutPictogramElement(containerShape);<br> <br> |
| <span class="keyword">return </span>containerShape;<br> |
| } <br> </p> |
| </div> |
| </div> |
| <p> </p> |
| <!-- End code ------------------------------------------------------------------------------- --> |
| <h2>Test: Create a Connection</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 (existing EClasses don’t work because they have |
| no anchor</li> |
| <li>click on "EReference" which should be now available as connection tool in |
| the palette</li> |
| <li>move the mouse over the EClasses; you can see that it is allowed to start |
| the connection</li> |
| <li>click on one EClass</li> |
| <li>move mouse over the start EClass; you can see that it is not allowed to |
| end the connection on the same EClass</li> |
| <li>move the mouse over the other EClass and click</li> |
| <li>the new connection should be created</li> |
| </ol> |
| <p> </p> |
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