Start to play with a converter architecture decoupled from ant completely

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271327 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/aut/converter/AbstractConverter.java

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+/*
+ * 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.txt file.
+ */
+package org.apache.aut.converter;
+
+import java.util.Map;
+import org.apache.avalon.excalibur.i18n.ResourceManager;
+import org.apache.avalon.excalibur.i18n.Resources;
+
+/**
+ * Instances of this interface are used to convert between different types.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @version $Revision$ $Date$
+ */
+public abstract class AbstractConverter
+    implements Converter
+{
+    private final static Resources REZ =
+        ResourceManager.getPackageResources( AbstractConverter.class );
+
+    private final Class m_source;
+    private final Class m_destination;
+
+    /**
+     * Constructor for a converter between types source and destination
+     *
+     * @param source the source type
+     * @param destination the destination type
+     */
+    public AbstractConverter( final Class source, final Class destination )
+    {
+        m_source = source;
+        m_destination = destination;
+    }
+
+    /**
+     * Convert an object from original to destination types
+     *
+     * @param destination the destination type
+     * @param original the original Object
+     * @param context the context in which to convert
+     * @return the converted object
+     * @exception ConverterException if an error occurs
+     */
+    public Object convert( final Class destination,
+                           final Object original,
+                           final Map context )
+        throws ConverterException
+    {
+        if( m_destination != destination )
+        {
+            final String message =
+                REZ.getString( "bad-destination.error", destination.getName(), m_destination );
+            throw new IllegalArgumentException( message );
+        }
+
+        if( !m_source.isInstance( original ) )
+        {
+            final String message =
+                REZ.getString( "bad-instance.error", original, m_source.getName() );
+            throw new IllegalArgumentException( message );
+        }
+
+        return convert( original, context );
+    }
+
+    /**
+     * Overide this in a particular converter to do the conversion.
+     *
+     * @param original the original Object
+     * @param context the context in which to convert
+     * @return the converted object
+     * @exception ConverterException if an error occurs
+     */
+    protected abstract Object convert( Object original, Map context )
+        throws ConverterException;
+}
+

proposal/myrmidon/src/java/org/apache/aut/converter/Converter.java

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+/*
+ * 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.txt file.
+ */
+package org.apache.aut.converter;
+
+import org.apache.avalon.framework.context.Context;
+import java.util.Map;
+
+/**
+ * Instances of this interface are used to convert between different types.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @version $Revision$ $Date$
+ * @ant:role shorthand="converter"
+ */
+public interface Converter
+{
+    String ROLE = Converter.class.getName();
+
+    /**
+     * Convert original to destination type.
+     * Destination is passed so that one converter can potentiall
+     * convert to multiple different types.
+     *
+     * @param destination the destinaiton type
+     * @param original the original type
+     * @param context the context in which to convert
+     * @return the converted object
+     * @exception ConverterException if an error occurs
+     */
+    Object convert( Class destination, Object original, Map context )
+        throws ConverterException;
+}

proposal/myrmidon/src/java/org/apache/aut/converter/ConverterException.java

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+/*
+ * 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.txt file.
+ */
+package org.apache.aut.converter;
+
+import org.apache.avalon.framework.CascadingException;
+
+/**
+ * ConverterException thrown when a problem occurs during convertion etc.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @version $Revision$ $Date$
+ */
+public class ConverterException
+    extends CascadingException
+{
+    /**
+     * Basic constructor with a message
+     *
+     * @param message the message
+     */
+    public ConverterException( final String message )
+    {
+        this( message, null );
+    }
+
+    /**
+     * Constructor that builds cascade so that other exception information can be retained.
+     *
+     * @param message the message
+     * @param throwable the throwable
+     */
+    public ConverterException( final String message, final Throwable throwable )
+    {
+        super( message, throwable );
+    }
+}
+

proposal/myrmidon/src/java/org/apache/aut/converter/Resources.properties

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+bad-destination.error=Destination type ({0}) is not equal to {1}.
+bad-instance.error=Object {0} is not an instance of {1}.