Add a PropertyUtil class that doesn't need avalons Context

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271471 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/myrmidon/components/configurer/PropertyException.java

@@ -0,0 +1,37 @@
+/*
+ * 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.myrmidon.components.configurer;
+
+/**
+ * Exception thrown when evaluating a property.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @version $Revision$ $Date$
+ */
+public class PropertyException
+    extends Exception
+{
+    /**
+     * Basic constructor for exception that does not specify a message
+     */
+    public PropertyException()
+    {
+        this( "" );
+    }
+
+    /**
+     * Basic constructor with a message
+     *
+     * @param message the message
+     */
+    public PropertyException( final String message )
+    {
+        super( message );
+    }
+}
+

proposal/myrmidon/src/java/org/apache/myrmidon/components/configurer/PropertyUtil.java

@@ -0,0 +1,245 @@
+/*
+ * 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.myrmidon.components.configurer;
+
+import org.apache.avalon.excalibur.i18n.ResourceManager;
+import org.apache.avalon.excalibur.i18n.Resources;
+import org.apache.avalon.framework.context.Context;
+import org.apache.avalon.framework.context.ContextException;
+
+/**
+ * Utility class to evaluate propertys.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @version $Revision$ $Date$
+ */
+public final class PropertyUtil
+{
+    private final static Resources REZ =
+        ResourceManager.getPackageResources( PropertyUtil.class );
+
+    private PropertyUtil()
+    {
+    }
+
+    /**
+     * Resolve a string property. This evaluates all property
+     * substitutions based on specified context.
+     *
+     * @param property the property to resolve
+     * @param context the context in which to resolve property
+     * @param ignoreUndefined if false will throw an PropertyException if property is not found
+     * @return the reolved property
+     * @exception PropertyException if an error occurs
+     */
+    public static Object resolveProperty( final String property,
+                                          final Context context,
+                                          final boolean ignoreUndefined )
+        throws PropertyException
+    {
+        int start = findBeginning( property, 0 );
+        if( -1 == start )
+        {
+            return property;
+        }
+
+        int end = findEnding( property, start );
+
+        final int length = property.length();
+
+        if( 0 == start && end == ( length - 1 ) )
+        {
+            return resolveValue( property.substring( start + 2, end ),
+                                 context,
+                                 ignoreUndefined );
+        }
+
+        final StringBuffer sb = new StringBuffer( length * 2 );
+        int lastPlace = 0;
+
+        while( true )
+        {
+            final Object value =
+                resolveValue( property.substring( start + 2, end ),
+                              context,
+                              ignoreUndefined );
+
+            sb.append( property.substring( lastPlace, start ) );
+            sb.append( value );
+
+            lastPlace = end + 1;
+
+            start = findBeginning( property, lastPlace );
+            if( -1 == start )
+            {
+                break;
+            }
+
+            end = findEnding( property, start );
+        }
+
+        sb.append( property.substring( lastPlace, length ) );
+
+        return sb.toString();
+    }
+
+    /**
+     * Resolve a string property. This recursively evaluates all property
+     * substitutions based on specified context.
+     *
+     * @param property the property to resolve
+     * @param context the context in which to resolve property
+     * @param ignoreUndefined if false will throw an PropertyException if property is not found
+     * @return the reolved property
+     * @exception PropertyException if an error occurs
+     */
+    public static Object recursiveResolveProperty( final String property,
+                                                   final Context context,
+                                                   final boolean ignoreUndefined )
+        throws PropertyException
+    {
+        int start = findBeginning( property, 0 );
+        if( -1 == start )
+        {
+            return property;
+        }
+
+        int end = findNestedEnding( property, start );
+
+        final int length = property.length();
+
+        if( 0 == start && end == ( length - 1 ) )
+        {
+            final String propertyName = property.substring( start + 2, end );
+            final Object key = recursiveResolveProperty( propertyName, context, ignoreUndefined );
+            return resolveValue( key.toString(), context, ignoreUndefined );
+        }
+
+        final StringBuffer sb = new StringBuffer( length * 2 );
+
+        int lastPlace = 0;
+
+        while( true )
+        {
+            final String propertyName = property.substring( start + 2, end );
+            final Object key = recursiveResolveProperty( propertyName, context, ignoreUndefined );
+            final Object value = resolveValue( key.toString(), context, ignoreUndefined );
+
+            sb.append( property.substring( lastPlace, start ) );
+            sb.append( value );
+
+            lastPlace = end + 1;
+
+            start = findBeginning( property, lastPlace );
+            if( -1 == start )
+            {
+                break;
+            }
+
+            end = findNestedEnding( property, start );
+        }
+
+        sb.append( property.substring( lastPlace, length ) );
+
+        return sb.toString();
+    }
+
+    private static int findBeginning( final String property, final int currentPosition )
+    {
+        //TODO: Check if it is commented out
+        return property.indexOf( "${", currentPosition );
+    }
+
+    private static int findEnding( final String property, final int currentPosition )
+        throws PropertyException
+    {
+        //TODO: Check if it is commented out
+        final int index = property.indexOf( '}', currentPosition );
+        if( -1 == index )
+        {
+            final String message = REZ.getString( "prop.mismatched-braces.error" );
+            throw new PropertyException( message );
+        }
+
+        return index;
+    }
+
+    private static int findNestedEnding( final String property, final int currentPosition )
+        throws PropertyException
+    {
+        final int length = property.length();
+        final int start = currentPosition + 2;
+
+        int weight = 1;
+        for( int i = start; ( weight > 0 ) && ( i < length ); i++ )
+        {
+            final char ch = property.charAt( i );
+            switch( ch )
+            {
+                case '}':
+                    //TODO: Check if it is commented out
+                    weight--;
+                    if( weight == 0 )
+                    {
+                        return i;
+                    }
+                    break;
+
+                case '$':
+                    {
+                        //TODO: Check if it is commented out
+                        final int next = i + 1;
+                        if( next < length && '{' == property.charAt( next ) )
+                        {
+                            weight++;
+                        }
+                    }
+                    break;
+            }
+        }
+
+        final String message = REZ.getString( "prop.mismatched-braces.error" );
+        throw new PropertyException( message );
+    }
+
+    /**
+     * Retrieve a value from the specified context using the specified key.
+     * If there is no such value and ignoreUndefined is not false then a
+     * PropertyException is generated.
+     *
+     * @param key the key of value in context
+     * @param context the Context
+     * @param ignoreUndefined true if undefined variables are ignored
+     * @return the object retrieved from context
+     * @exception PropertyException if an error occurs
+     */
+    private static Object resolveValue( final String key,
+                                        final Context context,
+                                        final boolean ignoreUndefined )
+        throws PropertyException
+    {
+        try
+        {
+            return context.get( key );
+        }
+        catch( final ContextException ce )
+        {
+            if( ignoreUndefined )
+            {
+                return "";
+            }
+            else
+            {
+                final String message =
+                    REZ.getString( "prop.missing-value.error", key );
+                throw new PropertyException( message );
+            }
+        }
+    }
+}
+