Add basic class to listen to trax errors and print em out

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271383 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/antlib/xml/TraxErrorListener.java

@@ -0,0 +1,86 @@
+/*
+ * 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.antlib.xml;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+import javax.xml.transform.ErrorListener;
+import javax.xml.transform.SourceLocator;
+import javax.xml.transform.TransformerException;
+import org.apache.avalon.framework.logger.AbstractLogEnabled;
+
+final class TraxErrorListener
+    extends AbstractLogEnabled
+    implements ErrorListener
+{
+    private final boolean m_warn;
+    private boolean m_failed;
+
+    protected TraxErrorListener( final boolean warn )
+    {
+        m_warn = warn;
+    }
+
+    public void error( final TransformerException te )
+    {
+        m_failed = true;
+        getLogger().error( getMessage( te ), te );
+    }
+
+    public void fatalError( final TransformerException te )
+    {
+        m_failed = true;
+        getLogger().error( getMessage( te ), te );
+    }
+
+    public void warning( final TransformerException te )
+    {
+        // depending on implementation, XMLReader can yield hips of warning,
+        // only output then if user explicitely asked for it
+        if( m_warn )
+        {
+            getLogger().warn( getMessage( te ), te );
+        }
+    }
+
+    protected void reset()
+    {
+        m_failed = false;
+    }
+
+    // did an error happen during last parsing ?
+    protected boolean getFailure()
+    {
+        return m_failed;
+    }
+
+    private String getMessage( final TransformerException te )
+    {
+        final SourceLocator locator = te.getLocator();
+        final String systemID = locator.getSystemId();
+        if( null != systemID )
+        {
+            final int line = locator.getLineNumber();
+            final int column = locator.getColumnNumber();
+
+            try
+            {
+                //Build a message using standard compiler
+                //error format
+                return new URL( systemID ).getFile() +
+                    ( line == -1 ? "" : ( ":" + line +
+                    ( column == -1 ? "" : ( ":" + column ) ) ) ) +
+                    ": " + te.getMessage();
+            }
+            catch( final MalformedURLException mue )
+            {
+            }
+        }
+        return te.getMessage();
+    }
+}