proposal/myrmidon/src/java/org/apache/myrmidon/api/DefaultTaskContext.java

/*
 * Copyright (C) The Apache Software Foundation. All rights reserved.
 *
 * This software is published under the terms of the Apache Software License
 * version 1.1, a copy of which has been included with this distribution in
 * the LICENSE file.
 */
package org.apache.myrmidon.api;

import java.io.File;
import java.util.Map;
import org.apache.avalon.excalibur.io.FileUtil;
import org.apache.avalon.excalibur.property.PropertyException;
import org.apache.avalon.excalibur.property.PropertyUtil;
import org.apache.avalon.framework.context.ContextException;
import org.apache.avalon.framework.context.DefaultContext;

/**
 * Default implementation of TaskContext.
 *
 * @author <a href="mailto:donaldp@apache.org">Peter Donald</a>
 */
public class DefaultTaskContext
    extends DefaultContext
    implements TaskContext
{
    /**
     * Constructor for Context with no parent contexts.
     */
    public DefaultTaskContext( final Map contextData )
    {
        super( contextData );
    }

    /**
     * Constructor for Context with no parent contexts.
     */
    public DefaultTaskContext()
    {
        this( (TaskContext)null );
    }

    /**
     * Constructor.
     */
    public DefaultTaskContext( final TaskContext parent )
    {
        super( parent );
    }

    /**
     * Retrieve JavaVersion running under.
     *
     * @return the version of JVM
     */
    public JavaVersion getJavaVersion()
    {
        try { return (JavaVersion)get( JAVA_VERSION ); }
        catch( final ContextException ce )
        {
            throw new IllegalStateException( "No JavaVersion in Context" );
        }
    }


    /**
     * Retrieve Name of tasklet.
     *
     * @return the name
     */
    public String getName()
    {
        try { return (String)get( NAME ); }
        catch( final ContextException ce )
        {
            throw new IllegalStateException( "No Name in Context" );
        }
    }

    /**
     * Retrieve base directory.
     *
     * @return the base directory
     */
    public File getBaseDirectory()
    {
        try { return (File)get( BASE_DIRECTORY ); }
        catch( final ContextException ce )
        {
            throw new IllegalStateException( "No Base Directory in Context" );
        }
    }

    /**
     * Resolve filename.
     * This involves resolving it against baseDirectory and
     * removing ../ and ./ references. It also means formatting
     * it appropriately for the particular OS (ie different OS have
     * different volumes, file conventions etc)
     *
     * @param filename the filename to resolve
     * @return the resolved filename
     */
    public File resolveFile( final String filename )
    {
        return FileUtil.resolveFile( getBaseDirectory(), filename );
    }

    /**
     * Retrieve property for name.
     *
     * @param name the name of property
     * @return the value of the property
     */
    public Object getProperty( final String name )
    {
        try { return get( name ); }
        catch( final ContextException ce )
        {
            return null;
        }
    }

    /**
     * Set property value in current context.
     *
     * @param name the name of property
     * @param value the value of property
     */
    public void setProperty( final String name, final Object value )
        throws TaskException
    {
        setProperty( name, value, CURRENT );
    }

    /**
     * Set property value.
     *
     * @param property the property
     */
    public void setProperty( final String name, final Object value, final ScopeEnum scope )
        throws TaskException
    {
        checkPropertyValid( name, value );

        if( CURRENT == scope ) put( name, value );
        else if( PARENT == scope )
        {
            if( null == getParent() )
            {
                throw new TaskException( "Can't set a property with parent scope when context " +
                                         " has no parent" );
            }
            else
            {
                ((TaskContext)getParent()).setProperty( name, value );
            }
        }
        else if( TOP_LEVEL == scope )
        {
            DefaultTaskContext context = this;

            while( null != context.getParent() )
            {
                context = (DefaultTaskContext)context.getParent();
            }

            context.put( name, value );
        }
        else
        {
            throw new IllegalStateException( "Unknown property scope! (" + scope + ")" );
        }
    }

    /**
     * Make sure property is valid if it is one of the "magic" properties.
     *
     * @param name the name of property
     * @param value the value of proeprty
     * @exception TaskException if an error occurs
     */
    protected void checkPropertyValid( final String name, final Object value )
        throws TaskException
    {
        if( BASE_DIRECTORY.equals( name ) && !( value instanceof File ) )
        {
            throw new TaskException( "Property " + BASE_DIRECTORY +
                                     " must have a value of type " +
                                     File.class.getName() );
        }
        else if( NAME.equals( name ) && !( value instanceof String ) )
        {
            throw new TaskException( "Property " + NAME +
                                     " must have a value of type " +
                                     String.class.getName() );
        }
        else if( JAVA_VERSION.equals( name ) && !( value instanceof JavaVersion ) )
        {
            throw new TaskException( "Property " + JAVA_VERSION +
                                     " must have a value of type " +
                                     JavaVersion.class.getName() );
        }
    }
}