maven-plugin-tools/maven-plugin-tools-generators/src/main/resources/help-class-source.vm

#if ($helpPackageName.length()>0)
package ${helpPackageName};
#end

import org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.MojoExecutionException;
#if ( $useAnnotations )
import org.apache.maven.plugins.annotations.Mojo;
import org.apache.maven.plugins.annotations.Parameter;
#end

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * Display help information on ${artifactId}.<br>
 * Call <code>mvn ${goalPrefix}:help -Ddetail=true -Dgoal=&lt;goal-name&gt;</code> to display parameter details.
 * @author
 * @version
#if ( !$useAnnotations )     
 * @goal help
 * @requiresProject false
 * @threadSafe
#end
 */
#if ( $useAnnotations )
@Mojo( name = "help", requiresProject = false, threadSafe = true )
#end
public class HelpMojo
    extends AbstractMojo
{
    /**
     * If <code>true</code>, display all settable properties for each goal.
     *
#if ( !$useAnnotations )     
     * @parameter property="detail" default-value="false"
#end
     */
#if ( $useAnnotations )     
    @Parameter( property = "detail", defaultValue = "false" )
#end
    private boolean detail;

    /**
     * The name of the goal for which to show help. If unspecified, all goals will be displayed.
     *
#if ( !$useAnnotations )     
     * @parameter property="goal"
#end
     */
#if ( $useAnnotations )     
    @Parameter( property = "goal" )
#end    
    private java.lang.String goal;

    /**
     * The maximum length of a display line, should be positive.
     *
#if ( !$useAnnotations )     
     * @parameter property="lineLength" default-value="80"
#end
     */
#if ( $useAnnotations )     
    @Parameter( property = "lineLength", defaultValue = "80" )
#end
    private int lineLength;

    /**
     * The number of spaces per indentation level, should be positive.
     *
#if ( !$useAnnotations )     
     * @parameter property="indentSize" default-value="2"
#end
     */
#if ( $useAnnotations )     
    @Parameter( property = "indentSize", defaultValue = "2" )
#end
    private int indentSize;

    // groupId/artifactId/plugin-help.xml
    private static final String PLUGIN_HELP_PATH = "/${pluginHelpPath}";

    private Document build()
        throws MojoExecutionException
    {
        getLog().debug( "load plugin-help.xml: " + PLUGIN_HELP_PATH );
        InputStream is = getClass().getResourceAsStream( PLUGIN_HELP_PATH );
        try
        {
            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 );
        }
    }

    /**
     * {@inheritDoc}
     */
    public void execute()
        throws MojoExecutionException
    {
        if ( lineLength <= 0 )
        {
            getLog().warn( "The parameter 'lineLength' should be positive, using '80' as default." );
            lineLength = 80;
        }
        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 );

        //<goalPrefix>plugin</goalPrefix>
        String goalPrefix = getValue( plugin, "goalPrefix" );

        Node mojos1 = getSingleChild( plugin, "mojos" );

        List<Node> mojos = findNamedChild( mojos1, "mojo" );

        if ( goal == null || goal.length() <= 0 )
        {
            append( sb, "This plugin has " + mojos.size() + ( mojos.size() > 1 ? " goals:" : " goal:" ), 0 );
            append( sb, "", 0 );
        }

        for ( Node mojo : mojos )
        {
            writeGoal( sb, goalPrefix, (Element) mojo );
        }

        if ( getLog().isInfoEnabled() )
        {
            getLog().info( sb.toString() );
        }
    }


    private static boolean isNotEmpty( String string )
    {
        return string != null && string.length() > 0;
    }

    private String getValue( Node node, String elementName )
        throws MojoExecutionException
    {
        return getSingleChild( node, elementName ).getTextContent();
    }

    private Node getSingleChild( Node node, String elementName )
        throws MojoExecutionException
    {
        List<Node> namedChild = findNamedChild( node, elementName );
        if ( namedChild.isEmpty() )
        {
            throw new MojoExecutionException( "Could not find " + elementName + " in plugin-help.xml" );
        }
        if ( namedChild.size() > 1 )
        {
            throw new MojoExecutionException( "Multiple " + elementName + " in plugin-help.xml" );
        }
        return namedChild.get( 0 );
    }

    private List<Node> findNamedChild( Node node, String elementName )
    {
        List<Node> result = new ArrayList<Node>();
        NodeList childNodes = node.getChildNodes();
        for ( int i = 0; i < childNodes.getLength(); i++ )
        {
            Node item = childNodes.item( i );
            if ( elementName.equals( item.getNodeName() ) )
            {
                result.add( item );
            }
        }
        return result;
    }

    private Node findSingleChild( Node node, String elementName )
        throws MojoExecutionException
    {
        List<Node> elementsByTagName = findNamedChild( node, elementName );
        if ( elementsByTagName.isEmpty() )
        {
            return null;
        }
        if ( elementsByTagName.size() > 1 )
        {
            throw new MojoExecutionException( "Multiple " + elementName + "in plugin-help.xml" );
        }
        return elementsByTagName.get( 0 );
    }

    private void writeGoal( StringBuilder sb, String goalPrefix, Element mojo )
        throws MojoExecutionException
    {
        String mojoGoal = getValue( mojo, "goal" );
        Node configurationElement = findSingleChild( mojo, "configuration" );
		Node description = findSingleChild( mojo, "description" );
        if ( goal == null || goal.length() <= 0 || mojoGoal.equals( goal ) )
        {
            append( sb, goalPrefix + ":" + mojoGoal, 0 );
            Node deprecated = findSingleChild( mojo, "deprecated" );
            if ( ( deprecated != null ) && isNotEmpty( deprecated.getNodeValue() ) )
            {
                append( sb, "Deprecated. " + deprecated, 1 );
                if ( detail && description != null )
                {
                    append( sb, "", 0 );
                    append( sb, description.getTextContent(), 1 );
                }
            }
            else if (description != null )
            {
                append( sb, description.getTextContent(), 1 );
            }
            append( sb, "", 0 );

            if ( detail )
            {
                Node parametersNode = getSingleChild( mojo, "parameters" );
                List<Node> parameters = findNamedChild( parametersNode, "parameter" );
                append( sb, "Available parameters:", 1 );
                append( sb, "", 0 );

                for ( Node parameter : parameters )
                {
                    writeParameter( sb, parameter, configurationElement );
                }
            }
        }
    }

    private void writeParameter( StringBuilder sb, Node parameter, Node configurationElement )
        throws MojoExecutionException
    {
        String parameterName = getValue( parameter, "name" );
        String parameterDescription = getValue( parameter, "description" );

        Node fieldConfigurationElement = findSingleChild( configurationElement, parameterName );

        String parameterDefaultValue = "";
        if ( fieldConfigurationElement != null && fieldConfigurationElement.getNodeValue() != null )
        {
            parameterDefaultValue = " (Default: " + ((Element)fieldConfigurationElement).getAttribute( "default-value" ) + ")";
        }
        append( sb, parameterName + parameterDefaultValue, 2 );
        Node deprecated = findSingleChild( parameter, "deprecated" );
        if ( ( deprecated != null ) && isNotEmpty( deprecated.getNodeValue() ) )
        {
            append( sb, "Deprecated. " + deprecated.getNodeValue(), 3 );
            append( sb, "", 0 );
        }
        append( sb, parameterDescription, 3 );
        if ( "true".equals( getValue( parameter, "required" ) ) )
        {
            append( sb, "Required: Yes", 3 );
        }
        Node expression = findSingleChild( parameter, "expression" );
        if ( ( expression != null ) && isNotEmpty( expression.getNodeValue() ) )
        {
        	String property = getPropertyFromExpression( expression.getNodeValue() );
            append( sb, "User property: " + property, 3 );
        }

        append( sb, "", 0 );
    }

    /**
     * <p>Repeat a String <code>n</code> times to form a new string.</p>
     *
     * @param str    String to repeat
     * @param repeat number of times to repeat str
     * @return String with repeated String
     * @throws NegativeArraySizeException if <code>repeat < 0</code>
     * @throws NullPointerException       if str is <code>null</code>
     */
    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.
     * <b>Note</b>: The last character is always a new line.
     *
     * @param sb          The buffer to append the description, not <code>null</code>.
     * @param description The description, not <code>null</code>.
     * @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 <code>null</code>.
     * @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 <code>null</code>.
     * @throws NegativeArraySizeException if <code>indent < 0</code>
     */
    private static List<String> toLines( String text, int indent, int indentSize, int lineLength )
    {
        List<String> lines = new ArrayList<String>();

        String ind = repeat( "\t", indent );

        String[] plainLines = text.split( "(\r\n)|(\r)|(\n)" );

        for ( String plainLine : plainLines )
        {
            toLines( lines, ind + plainLine, indentSize, lineLength );
        }

        return lines;
    }

    /**
     * Adds the specified line to the output sequence, performing line wrapping if necessary.
     *
     * @param lines      The sequence of display lines, must not be <code>null</code>.
     * @param line       The line to add, must not be <code>null</code>.
     * @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( List<String> lines, String line, int indentSize, int lineLength )
    {
        int lineIndent = getIndentLevel( line );
        StringBuilder buf = new StringBuilder( 256 );

        String[] tokens = line.split( " +" );

        for ( String token : tokens )
        {
            if ( buf.length() > 0 )
            {
                if ( buf.length() + token.length() >= lineLength )
                {
                    lines.add( buf.toString() );
                    buf.setLength( 0 );
                    buf.append( repeat( " ", lineIndent * indentSize ) );
                }
                else
                {
                    buf.append( ' ' );
                }
            }

            for ( int j = 0; j < token.length(); j++ )
            {
                char c = token.charAt( j );
                if ( c == '\t' )
                {
                    buf.append( repeat( " ", indentSize - buf.length() % indentSize ) );
                }
                else if ( c == '\u00A0' )
                {
                    buf.append( ' ' );
                }
                else
                {
                    buf.append( c );
                }
            }
        }
        lines.add( buf.toString() );
    }

    /**
     * Gets the indentation level of the specified line.
     *
     * @param line The line whose indentation level should be retrieved, must not be <code>null</code>.
     * @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;
    }
}