Added TypeFactory.canCreate() method.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271310 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/myrmidon/components/type/MultiSourceTypeFactory.java

@@ -54,6 +54,14 @@ public class MultiSourceTypeFactory
         m_factorys.put( name, factory );
     }
 
+    /**
+     * Determines if this factory can create instances of a particular type.
+     */
+    public boolean canCreate( final String name )
+    {
+        return ( findFactory( name ) != null );
+    }
+
     /**
      * Create a type instance based on name.
      *
@@ -64,30 +72,37 @@ public class MultiSourceTypeFactory
     public Object create( final String name )
         throws TypeException
     {
-        TypeFactory factory = getTypeFactory( name );
-
-        if( null == factory && null != m_parent )
-        {
-            factory = m_parent.getTypeFactory( name );
-        }
-
+        // Locate the factory to use
+        TypeFactory factory = findFactory( name );
         if( null == factory )
         {
             final String message = REZ.getString( "no-factory.error", name );
             throw new TypeException( message );
         }
-        else
+
+        // Create the object
+        final Object object = factory.create( name );
+        if( !m_type.isInstance( object ) )
         {
-            final Object object = factory.create( name );
+            final String message = REZ.getString( "mismatched-type.error", name, object.getClass().getName() );
+            throw new TypeException( message );
+        }
 
-            if( !m_type.isInstance( object ) )
-            {
-                final String message = REZ.getString( "mismatched-type.error", name, object.getClass().getName() );
-                throw new TypeException( message );
-            }
+        return object;
+    }
 
-            return object;
+    /**
+     * Locates the type factory to use for a particular type.
+     */
+    private TypeFactory findFactory( final String name )
+    {
+        TypeFactory factory = getTypeFactory( name );
+        if( null == factory && null != m_parent )
+        {
+            factory = m_parent.getTypeFactory( name );
         }
+
+        return factory;
     }
 
     /**

proposal/myrmidon/src/java/org/apache/myrmidon/interfaces/type/DefaultTypeFactory.java

@@ -58,6 +58,14 @@ public class DefaultTypeFactory
         m_classNames.put( name, className );
     }
 
+    /**
+     * Determines if this factory can create instances of a particular type.
+     */
+    public boolean canCreate( String name )
+    {
+        return ( getClassName( name ) != null );
+    }
+
     /**
      * Create a type instance with appropriate name.
      *
@@ -68,7 +76,15 @@ public class DefaultTypeFactory
     public Object create( final String name )
         throws TypeException
     {
+        // Determine the name of the class to instantiate
         final String className = getClassName( name );
+        if( null == className )
+        {
+            final String message = REZ.getString( "no-mapping.error", name );
+            throw new TypeException( message );
+        }
+
+        // Instantiate the object
         try
         {
             final ClassLoader classLoader = getClassLoader();
@@ -83,16 +99,8 @@ public class DefaultTypeFactory
     }
 
     private String getClassName( final String name )
-        throws TypeException
     {
-        final String className = (String)m_classNames.get( name );
-        if( null == className )
-        {
-            final String message = REZ.getString( "no-mapping.error", name );
-            throw new TypeException( message );
-        }
-
-        return className;
+        return  (String)m_classNames.get( name );
     }
 
     protected ClassLoader getClassLoader()

proposal/myrmidon/src/java/org/apache/myrmidon/interfaces/type/TypeFactory.java

@@ -15,12 +15,19 @@ package org.apache.myrmidon.interfaces.type;
  */
 public interface TypeFactory
 {
+    /**
+     * Determines if this factory can create instances of a particular type.
+     *
+     * @param name the type name.
+     */
+    boolean canCreate( String name );
+
     /**
      * Create a type instance based on name.
      *
-     * @param name the name
+     * @param name the type name
      * @return the type instance
-     * @exception TypeException if an error occurs
+     * @exception TypeException if the type is unknown, or an error occurs.
      */
     Object create( String name )
         throws TypeException;