[MDEP-799] tree: add optional output type json

Author: kezhenxu94

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

@@ -0,0 +1,126 @@
+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 org.apache.commons.lang3.StringUtils;
+
+import org.apache.maven.artifact.Artifact;
+import org.apache.maven.shared.dependency.graph.DependencyNode;
+import org.apache.maven.shared.dependency.graph.traversal.DependencyNodeVisitor;
+
+import java.io.Writer;
+import java.util.List;
+import com.google.common.base.Joiner;
+
+/**
+ * A dependency node visitor that serializes visited nodes to a writer using the
+ * JSON format.
+ *
+ * @author <a href="mailto:kezhenxu94@apache.org">Zhenxu Ke</a>
+ * @since 3.3.1
+ */
+public class JSONDependencyNodeVisitor
+    extends AbstractSerializingVisitor
+    implements DependencyNodeVisitor
+{
+
+    /**
+     * Constructor.
+     *
+     * @param writer the writer to write to.
+     */
+    public JSONDependencyNodeVisitor( Writer writer )
+    {
+        super( writer );
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean endVisit( DependencyNode node )
+    {
+        return true;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean visit( DependencyNode node )
+    {
+        if ( node.getParent() == null || node.getParent() == node )
+        {
+            writeNode( 0, node, true );
+        }
+
+        return true;
+    }
+
+    private void writeNode( int indent, DependencyNode node, boolean root )
+    {
+        Artifact artifact = node.getArtifact();
+
+        writer.println( indentations( indent ) + "{" );
+        indent++;
+        String groupId = indentations( indent ) + "\"groupId\": \"" + artifact.getGroupId() + "\"";
+        String artifactId = indentations( indent ) + "\"artifactId\": \"" + artifact.getArtifactId() + "\"";
+        String version = indentations( indent ) + "\"version\": \"" + artifact.getVersion() + "\"";
+        String type = indentations( indent ) + "\"type\": \"" + artifact.getType() + "\"";
+        String scope = root ? null : indentations( indent ) + "\"scope\": \"" + artifact.getScope() + "\"";
+
+        writer.print( Joiner.on( "," + System.lineSeparator() )
+                            .skipNulls()
+                            .join( groupId, artifactId, version, type, scope ) );
+
+        List<DependencyNode> children = node.getChildren();
+        if ( children.size() > 0 )
+        {
+            writer.println( "," );
+            writer.println( indentations( indent ) + "\"dependencies\": [" );
+            indent++;
+            for ( int i = 0; i < children.size(); i++ )
+            {
+                writeNode( indent, children.get( i ), false );
+                if ( i < children.size() - 1 )
+                {
+                    writer.println( "," );
+                }
+                else
+                {
+                    writer.println();
+                }
+            }
+            indent--;
+            writer.println( indentations( indent ) + "]" );
+        }
+        else
+        {
+            writer.println();
+        }
+        indent--;
+        writer.print(  indentations( indent ) + "}" );
+    }
+
+    private static String indentations( int indent )
+    {
+        return StringUtils.repeat( "\t", indent );
+    }
+}

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

@@ -88,7 +88,7 @@ public class TreeMojo
 
     @Parameter( defaultValue = "${session}", readonly = true, required = true )
     private MavenSession session;
-    
+
     @Parameter( property = "outputEncoding", defaultValue = "${project.reporting.outputEncoding}" )
     private String outputEncoding;
 
@@ -179,18 +179,18 @@ public class TreeMojo
     /**
      * A comma-separated list of artifacts to filter the serialized dependency tree by, or <code>null</code> not to
      * filter the dependency tree. The filter syntax is:
-     * 
+     *
      * <pre>
      * [groupId]:[artifactId]:[type]:[version]
      * </pre>
-     * 
+     *
      * where each pattern segment is optional and supports full and partial <code>*</code> wildcards. An empty pattern
      * segment is treated as an implicit wildcard.
      * <p>
      * For example, <code>org.apache.*</code> will match all artifacts whose group id starts with
      * <code>org.apache.</code>, and <code>:::*-SNAPSHOT</code> will match all snapshot artifacts.
      * </p>
-     * 
+     *
      * @see StrictPatternIncludesArtifactFilter
      * @since 2.0-alpha-6
      */
@@ -200,11 +200,11 @@ public class TreeMojo
     /**
      * A comma-separated list of artifacts to filter from the serialized dependency tree, or <code>null</code> not to
      * filter any artifacts from the dependency tree. The filter syntax is:
-     * 
+     *
      * <pre>
      * [groupId]:[artifactId]:[type]:[version]
      * </pre>
-     * 
+     *
      * where each pattern segment is optional and supports full and partial <code>*</code> wildcards. An empty pattern
      * segment is treated as an implicit wildcard.
      * <p>
@@ -416,6 +416,10 @@ else if ( "dot".equals( outputType ) )
         {
             return new DOTDependencyNodeVisitor( writer );
         }
+        else if ( "json".equals( outputType ) )
+        {
+            return new JSONDependencyNodeVisitor( writer );
+        }
         else
         {
             return new SerializingDependencyNodeVisitor( writer, toGraphTokens( tokens ) );

src/test/java/org/apache/maven/plugins/dependency/tree/TestTreeMojo.java

@@ -110,7 +110,7 @@ public void _testTreeDotSerializing()
 
     /**
      * Test the GraphML format serialization
-     * 
+     *
      * @throws Exception in case of an error.
      */
     public void _testTreeGraphMLSerializing()
@@ -129,7 +129,7 @@ public void _testTreeGraphMLSerializing()
 
     /**
      * Test the TGF format serialization
-     * 
+     *
      * @throws Exception in case of an error.
      */
     public void _testTreeTGFSerializing()
@@ -141,9 +141,32 @@ public void _testTreeTGFSerializing()
         assertTrue( findString( contents, "testGroupId:release:jar:1.0:compile" ) );
     }
 
+    /**
+     * Test the JSON format serialization
+     *
+     * @throws Exception in case of an error.
+     */
+    public void _testTreeJSONSerializing()
+        throws Exception
+    {
+        List<String> contents = runTreeMojo( "tree1.json", "json" );
+        assertTrue( findString( contents, "\"testGroupId\": \"project\"" ) );
+        assertTrue( findString( contents, "\"type: \"jar\"" ) );
+        assertTrue( findString( contents, "\"version\": \"1.0\"" ) );
+        assertTrue( findString( contents, "\"scope\": \"compile\"" ) );
+        assertTrue( findString( contents, "\"testGroupId\": \"snapshot\"" ) );
+        assertTrue( findString( contents, "\"type: \"jar\"" ) );
+        assertTrue( findString( contents, "\"version\": \"2.0-SNAPSHOT\"" ) );
+        assertTrue( findString( contents, "\"scope\": \"compile\"" ) );
+        assertTrue( findString( contents, "\"testGroupId\": \"release\"" ) );
+        assertTrue( findString( contents, "\"type: \"jar\"" ) );
+        assertTrue( findString( contents, "\"version\": \"1.0\"" ) );
+        assertTrue( findString( contents, "\"scope\": \"compile\"" ) );
+    }
+
     /**
      * Help finding content in the given list of string
-     * 
+     *
      * @param outputFile the outputFile.
      * @param format The format.
      * @throws Exception in case of an error.
@@ -187,7 +210,7 @@ private List<String> runTreeMojo( String outputFile, String format )
 
     /**
      * Help finding content in the given list of string
-     * 
+     *
      * @param contents The contents.
      * @param str The content which should be checked for.
      */