mvn plugin:help -Ddetail=true -Dgoal=<goal-name> to display parameter details.
+ * @author maven-plugin-tools
+ */
+@Mojo( name = "help", requiresProject = false, threadSafe = true )
+public class HelpMojo
+ extends AbstractMojo
+{
+ /**
+ * If true, display all settable properties for each goal.
+ *
+ */
+ @Parameter( property = "detail", defaultValue = "false" )
+ private boolean detail;
+
+ /**
+ * The name of the goal for which to show help. If unspecified, all goals will be displayed.
+ *
+ */
+ @Parameter( property = "goal" )
+ private java.lang.String goal;
+
+ /**
+ * The maximum length of a display line, should be positive.
+ *
+ */
+ @Parameter( property = "lineLength", defaultValue = "80" )
+ private int lineLength;
+
+ /**
+ * The number of spaces per indentation level, should be positive.
+ *
+ */
+ @Parameter( property = "indentSize", defaultValue = "2" )
+ private int indentSize;
+
+ // groupId/artifactId/plugin-help.xml
+ private static final String PLUGIN_HELP_PATH =
+ "/META-INF/maven/org.apache.maven.plugins/maven-plugin-plugin/plugin-help.xml";
+
+ private static final int DEFAULT_LINE_LENGTH = 80;
+
+ private Document build()
+ throws MojoExecutionException
+ {
+ getLog().debug( "load plugin-help.xml: " + PLUGIN_HELP_PATH );
+ InputStream is = null;
+ try
+ {
+ is = getClass().getResourceAsStream( PLUGIN_HELP_PATH );
+ DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
+ DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
+ return dBuilder.parse( is );
+ }
+ catch ( IOException e )
+ {
+ throw new MojoExecutionException( e.getMessage(), e );
+ }
+ catch ( ParserConfigurationException e )
+ {
+ throw new MojoExecutionException( e.getMessage(), e );
+ }
+ catch ( SAXException e )
+ {
+ throw new MojoExecutionException( e.getMessage(), e );
+ }
+ finally
+ {
+ if ( is != null )
+ {
+ try
+ {
+ is.close();
+ }
+ catch ( IOException e )
+ {
+ throw new MojoExecutionException( e.getMessage(), e );
+ }
+ }
+ }
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ public void execute()
+ throws MojoExecutionException
+ {
+ if ( lineLength <= 0 )
+ {
+ getLog().warn( "The parameter 'lineLength' should be positive, using '80' as default." );
+ lineLength = DEFAULT_LINE_LENGTH;
+ }
+ if ( indentSize <= 0 )
+ {
+ getLog().warn( "The parameter 'indentSize' should be positive, using '2' as default." );
+ indentSize = 2;
+ }
+
+ Document doc = build();
+
+ StringBuilder sb = new StringBuilder();
+ Node plugin = getSingleChild( doc, "plugin" );
+
+
+ String name = getValue( plugin, "name" );
+ String version = getValue( plugin, "version" );
+ String id = getValue( plugin, "groupId" ) + ":" + getValue( plugin, "artifactId" ) + ":" + version;
+ if ( isNotEmpty( name ) && !name.contains( id ) )
+ {
+ append( sb, name + " " + version, 0 );
+ }
+ else
+ {
+ if ( isNotEmpty( name ) )
+ {
+ append( sb, name, 0 );
+ }
+ else
+ {
+ append( sb, id, 0 );
+ }
+ }
+ append( sb, getValue( plugin, "description" ), 1 );
+ append( sb, "", 0 );
+
+ //Repeat a String n times to form a new string.
repeat < 0
+ * @throws NullPointerException if str is null
+ */
+ private static String repeat( String str, int repeat )
+ {
+ StringBuilder buffer = new StringBuilder( repeat * str.length() );
+
+ for ( int i = 0; i < repeat; i++ )
+ {
+ buffer.append( str );
+ }
+
+ return buffer.toString();
+ }
+
+ /**
+ * Append a description to the buffer by respecting the indentSize and lineLength parameters.
+ * Note: The last character is always a new line.
+ *
+ * @param sb The buffer to append the description, not null.
+ * @param description The description, not null.
+ * @param indent The base indentation level of each line, must not be negative.
+ */
+ private void append( StringBuilder sb, String description, int indent )
+ {
+ for ( String line : toLines( description, indent, indentSize, lineLength ) )
+ {
+ sb.append( line ).append( '\n' );
+ }
+ }
+
+ /**
+ * Splits the specified text into lines of convenient display length.
+ *
+ * @param text The text to split into lines, must not be null.
+ * @param indent The base indentation level of each line, must not be negative.
+ * @param indentSize The size of each indentation, must not be negative.
+ * @param lineLength The length of the line, must not be negative.
+ * @return The sequence of display lines, never null.
+ * @throws NegativeArraySizeException if indent < 0
+ */
+ private static Listnull.
+ * @param line The line to add, must not be null.
+ * @param indentSize The size of each indentation, must not be negative.
+ * @param lineLength The length of the line, must not be negative.
+ */
+ private static void toLines( Listnull.
+ * @return The indentation level of the line.
+ */
+ private static int getIndentLevel( String line )
+ {
+ int level = 0;
+ for ( int i = 0; i < line.length() && line.charAt( i ) == '\t'; i++ )
+ {
+ level++;
+ }
+ for ( int i = level + 1; i <= level + 4 && i < line.length(); i++ )
+ {
+ if ( line.charAt( i ) == '\t' )
+ {
+ level++;
+ break;
+ }
+ }
+ return level;
+ }
+
+ private String getPropertyFromExpression( String expression )
+ {
+ if ( expression != null && expression.startsWith( "${" ) && expression.endsWith( "}" )
+ && !expression.substring( 2 ).contains( "${" ) )
+ {
+ // expression="${xxx}" -> property="xxx"
+ return expression.substring( 2, expression.length() - 1 );
+ }
+ // no property can be extracted
+ return null;
+ }
+}