[MDEP-435] Added xml outputType to dependency tree

src/main/java/org/apache/maven/plugins/dependency/tree/TreeMojo.java

@@ -107,8 +107,14 @@ public class TreeMojo
 
     /**
      * If specified, this parameter will cause the dependency tree to be written using the specified format. Currently
-     * supported format are: <code>text</code> (default), <code>dot</code>, <code>graphml</code> and <code>tgf</code>.
-     * These additional formats can be plotted to image files.
+     * supported format are:
+     * <ul>
+     *   <li>text (default)</li>
+     *   <li>dot</li>
+     *   <li>graphml</li>
+     *   <li>tgf</li>
+     *   <li>xml</li>
+     * </ul>
      *
      * @since 2.2
      */
@@ -384,6 +390,10 @@ else if ( "dot".equals( outputType ) )
         {
             return new DOTDependencyNodeVisitor( writer );
         }
+        else if ( "xml".equals( outputType ) )
+        {
+            return new XMLDependencyNodeVisitor( writer );
+        }
         else
         {
             return new SerializingDependencyNodeVisitor( writer, toGraphTokens( tokens ) );

src/main/java/org/apache/maven/plugins/dependency/tree/XMLDependencyNodeVisitor.java

@@ -0,0 +1,187 @@
+package org.apache.maven.plugins.dependency.tree;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+import javax.xml.transform.OutputKeys;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerException;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.dom.DOMSource;
+import javax.xml.transform.stream.StreamResult;
+
+import org.apache.maven.artifact.Artifact;
+import org.apache.maven.shared.dependency.graph.DependencyNode;
+import org.apache.maven.shared.dependency.graph.traversal.DependencyNodeVisitor;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import java.io.Writer;
+import java.util.List;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A dependency node visitor that serializes visited nodes to
+ * <a href="https://en.wikipedia.org/wiki/XML">XML format</a>
+ *
+ * @author <a href="mailto:[email protected]">Bogdan Sikora</a>
+ * @since 3.1.2
+ */
+public class XMLDependencyNodeVisitor
+    extends AbstractSerializingVisitor
+    implements DependencyNodeVisitor
+{
+    /**
+     * Constructor.
+     *
+     * @param writer the writer to write to.
+     */
+    public XMLDependencyNodeVisitor( Writer writer )
+    {
+        super( writer );
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean visit( DependencyNode node )
+    {
+        try
+        {
+            if ( node.getParent() == null || node.getParent() == node )
+            {
+                DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
+                DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
+                Document doc = dBuilder.newDocument();
+                Element rootElement = getNode( doc, node, true );
+                doc.appendChild( rootElement );
+
+                List<DependencyNode> children = node.getChildren();
+                for ( DependencyNode child : children )
+                {
+                    handleChild( doc, child, rootElement );
+                }
+
+                TransformerFactory transformerFactory = TransformerFactory.newInstance();
+                Transformer transformer = transformerFactory.newTransformer();
+                transformer.setOutputProperty( OutputKeys.INDENT, "yes" );
+                transformer.setOutputProperty( "{http://xml.apache.org/xslt}indent-amount", "2" );
+                DOMSource source = new DOMSource( doc );
+
+                StreamResult console = new StreamResult( writer );
+
+                transformer.transform( source, console );
+            }
+        }
+        catch ( ParserConfigurationException | TransformerException e )
+        {
+            LoggerFactory.getLogger(XMLDependencyNodeVisitor.class).error(e.getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean endVisit( DependencyNode node )
+    {
+        return true;
+    }
+
+    /**
+     * Render child with its children recursively
+     *
+     * @param doc Docuemnt to use
+     * @param node child node to handle
+     * @param depth depth of the child
+     */
+    private void handleChild( Document doc, DependencyNode node, Element parent )
+    {
+        Element element = getNode( doc, node, false );
+        Node dependencies = parent.getElementsByTagName( "dependencies" ).item( 0 );
+        dependencies.appendChild( element );
+
+        List<DependencyNode> children = node.getChildren();
+        for ( DependencyNode child : children )
+        {
+            handleChild( doc, child, element );
+        }
+    }
+
+    /**
+     * Get element from node
+     *
+     * @param doc Docuemnt to use
+     * @param node Node to get data from
+     */
+    private Element getNode( Document doc, DependencyNode node, boolean root )
+    {
+        Artifact artifact = node.getArtifact();
+        Element element = null;
+
+        if ( root )
+        {
+            element = doc.createElement( "project" );
+        }
+        else
+        {
+            element = doc.createElement( "dependency" );
+        }
+
+        Element groupId = doc.createElement( "groupId" );
+        groupId.setTextContent( artifact.getGroupId() );
+        element.appendChild( groupId );
+
+        Element artifactId = doc.createElement( "artifactId" );
+        artifactId.setTextContent( artifact.getArtifactId() );
+        element.appendChild( artifactId );
+
+        Element version = doc.createElement( "version" );
+        version.setTextContent( artifact.getVersion() );
+        element.appendChild( version );
+
+        if ( !root )
+        {
+            Element scope = doc.createElement( "scope" );
+            scope.setTextContent( artifact.getScope() );
+            element.appendChild( scope );
+
+            Element type = doc.createElement( "type" );
+            type.setTextContent( artifact.getType() );
+            element.appendChild( type );
+        }
+        else
+        {
+            Element packaging = doc.createElement( "packaging" );
+            packaging.setTextContent( artifact.getType() );
+            element.appendChild( packaging );
+        }
+
+        Element dependencies = doc.createElement( "dependencies" );
+        element.appendChild( dependencies );
+
+        return element;
+    }
+}