Add a fail task similar to ant1.xs except that it also has a condition.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@270246 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/antlib/core/Fail.java

@@ -0,0 +1,99 @@
+/*
+ * 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.antlib.core;
+
+import org.apache.avalon.framework.context.ContextException;
+import org.apache.myrmidon.api.AbstractTask;
+import org.apache.myrmidon.api.TaskException;
+import org.apache.myrmidon.framework.Condition;
+
+/**
+ * This is a task used to throw a TaskException.
+ * Useful for forcing a build to fail on a certain condition.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ */
+public class Fail
+    extends AbstractTask
+{
+    private String m_message;
+    private Condition m_condition;
+
+    public void setMessage( final String message )
+    {
+        checkNullMessage();
+        m_message = message;
+    }
+
+    public void addContent( final String message )
+    {
+        checkNullMessage();
+        m_message = message;
+    }
+
+    public void setIf( final String ifCondition )
+    {
+        checkNullCondition();
+        m_condition = new Condition( true, ifCondition );
+    }
+
+    public void setUnless( final String unlessCondition )
+    {
+        checkNullCondition();
+        m_condition = new Condition( false, unlessCondition );
+    }
+
+    public void execute()
+        throws TaskException
+    {
+        if( null == m_condition )
+        {
+            throw new TaskException( "Use did not specify a condition" );
+        }
+
+        try
+        {
+            final boolean failed =
+                m_condition.evaluate( getContext() );
+
+            if( failed )
+            {
+                if( null != m_message )
+                {
+                    throw new TaskException( m_message );
+                }
+                else
+                {
+                    throw new TaskException();
+                }
+            }
+        }
+        catch( final ContextException ce )
+        {
+            throw new TaskException( ce.toString(), ce );
+        }
+    }
+
+    private void checkNullMessage()
+    {
+        if( null != m_message )
+        {
+            final String message = "Message can only be set once by " +
+                "either nested content or the message attribute";
+            throw new IllegalStateException( message );
+        }
+    }
+
+    private void checkNullCondition()
+    {
+        if( null != m_condition )
+        {
+            throw new IllegalStateException( "Condition already set!" );
+        }
+    }
+}