IntrospectionHelper has been modified such that overridden setter methods

that take in 'PreferredAttribute's as argument gain higher precedence.
New attribute types - SrcDir, SrcFile, DestDir and DestFile are introduced.  Each of these types is a PreferredAttribute.


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@270376 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/IntrospectionHelper.java

@@ -56,6 +56,8 @@ package org.apache.tools.ant;
 
 import org.apache.tools.ant.types.Path;
 import org.apache.tools.ant.types.EnumeratedAttribute;
+import org.apache.tools.ant.types.PreferredAttribute;
+import org.apache.tools.ant.types.ValidatedFileAttribute;
 
 import java.lang.reflect.Method;
 import java.lang.reflect.InvocationTargetException;
@@ -71,6 +73,7 @@ import java.util.Locale;
  * elements.
  *
  * @author <a href="mailto:stefan.bodewig@epost.de">Stefan Bodewig</a>
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
  */
 public class IntrospectionHelper implements BuildListener {
 
@@ -165,17 +168,25 @@ public class IntrospectionHelper implements BuildListener {
 
                 String propName = getPropertyName(name, "set");
                 if (attributeSetters.get(propName) != null) {
-                    if (java.lang.String.class.equals(args[0])) {
+                    if (java.lang.String.class.equals(args[0])
                         /*
                             Ignore method m, as there is an overloaded
                             form of this method that takes in a
                             non-string argument, which gains higher
                             priority.
-                        */
+                         */
+                        || PreferredAttribute.class.
+                            isAssignableFrom((Class)attributeTypes.get(propName))
+                        /*
+                            Ignore method m because there is an overloaded form of
+                            this method that takes in a PreferredAttribute argument,
+                            which gains higher priority.
+                         */
+                       ) {
                         continue;
                     }
                     /*
-                        If the argument is not a String, and if there
+                        If the above conditions are not true, and if there
                         is an overloaded form of this method already defined,
                         we just override that with the new one.
                         This mechanism does not guarantee any specific order
@@ -183,7 +194,7 @@ public class IntrospectionHelper implements BuildListener {
                         that depends on the order in which "set" methods have
                         been defined, is not guaranteed to be selected in any
                         particular order.
-                    */
+                     */
                 }
                 AttributeSetter as = createAttributeSetter(m, args[0]);
                 if (as != null) {
@@ -589,6 +600,23 @@ public class IntrospectionHelper implements BuildListener {
                     }
                 };
 
+        // ValidatedFileAttributes have their own helper class
+        } else if (ValidatedFileAttribute.class.isAssignableFrom(arg)) {
+            return new AttributeSetter() {
+                    public void set(Project p, Object parent, String value)
+                        throws InvocationTargetException, IllegalAccessException, BuildException {
+                        try {
+                            ValidatedFileAttribute[] vfa = {
+                                (ValidatedFileAttribute) arg.newInstance()
+                            };
+                            File f = p.resolveFile(value);
+                            vfa[0].setFile(f);
+                            m.invoke(parent, vfa);
+                        } catch (InstantiationException ie) {
+                            throw new BuildException(ie);
+                        }
+                    }
+                };
 
         // worst case. look for a public String constructor and use it
         } else {

src/main/org/apache/tools/ant/types/DestDir.java

@@ -0,0 +1,88 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 1999 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant.types;
+
+import java.io.File;
+
+/**
+ * This wrapper class is used to represent Destination Directories.
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public final class DestDir extends ValidatedFileAttribute {
+
+    private String message = null;
+
+    protected final String getMessage() {
+        return message;
+    }
+
+    /**
+     * @return false if DestDir is null or if DestDir exists, but
+     * is not a directory.  Return true, otherwise.
+     */
+    protected final boolean isValid() {
+        File f = getFile();
+        if (f == null) {
+            message = "DestDir must not be null";
+            return false;
+        }
+        if (f.exists() && !f.isDirectory()) {
+            message = "DestDir " + f + " is not a directory.";
+            return false;
+        }
+        return true;
+    }
+}

src/main/org/apache/tools/ant/types/DestFile.java

@@ -0,0 +1,88 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 1999 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant.types;
+
+import java.io.File;
+
+/**
+ * This wrapper class is used to represent Destination Files.
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public final class DestFile extends ValidatedFileAttribute {
+
+    private String message;
+
+    protected final String getMessage() {
+        return message;
+    }
+
+    /**
+     * @return false if DestFile is null or if DestFile exists, but
+     * is not a file.  Return true, otherwise.
+     */
+    protected final boolean isValid() {
+        File f = getFile();
+        if (f == null) {
+            message = "DestFile must not be null";
+            return false;
+        }
+        if (f.exists() && !f.isFile()) {
+            message = "DestFile " + f + " is not a file.";
+            return false;
+        }
+        return true;
+    }
+}

src/main/org/apache/tools/ant/types/PreferredAttribute.java

@@ -0,0 +1,65 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 1999 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant.types;
+
+/**
+ * IntrospectionHelper attaches higer priority to PreferredAttribute
+ * objects when compared to other objects.  This prioritization
+ * is used when there are multiple overridden Setter Methods.
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public interface PreferredAttribute {
+}

src/main/org/apache/tools/ant/types/SrcDir.java

@@ -0,0 +1,92 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 1999 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant.types;
+
+import java.io.File;
+
+/**
+ * This wrapper class is used to represent Source(Origin) Directories.
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public final class SrcDir extends ValidatedFileAttribute {
+
+    private String message;
+
+    protected final String getMessage() {
+        return message;
+    }
+
+    /**
+     * @return false if SrcDir is null or if SrcDir does not exist
+     * or if SrcDir is not a directory. Return true, otherwise.
+     */
+    protected final boolean isValid() {
+        File f = getFile();
+        if (f == null) {
+            message = "SrcDir must not be null";
+            return false;
+        }
+        if (!f.exists()) {
+            message = "SrcDir " + f + " does not exist.";
+            return false;
+        }
+        if (!f.isDirectory()) {
+            message = "SrcDir " + f + " is not a directory.";
+            return false;
+        }
+        return true;
+    }
+}

src/main/org/apache/tools/ant/types/SrcFile.java

@@ -0,0 +1,92 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 1999 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant.types;
+
+import java.io.File;
+
+/**
+ * This wrapper class is used to represent Source(Origin) Files.
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public final class SrcFile extends ValidatedFileAttribute {
+
+    private String message;
+
+    protected final String getMessage() {
+        return message;
+    }
+
+    /**
+     * @return false if SrcFile is null or if SrcFile does not exist
+     * or if SrcFile is not a file. Return true, otherwise.
+     */
+    protected final boolean isValid() {
+        File f = getFile();
+        if (f == null) {
+            message = "SrcFile must not be null";
+            return false;
+        }
+        if (!f.exists()) {
+            message = "SrcFile " + f + " does not exist.";
+            return false;
+        }
+        if (!f.isFile()) {
+            message = "SrcFile " + f + " is not a file.";
+            return false;
+        }
+        return true;
+    }
+}

src/main/org/apache/tools/ant/types/ValidatedFileAttribute.java

@@ -0,0 +1,117 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 1999 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+package org.apache.tools.ant.types;
+
+import java.io.File;
+import org.apache.tools.ant.BuildException;
+
+/**
+ * Wrapper class that can be extended to perform file type
+ * validation.
+ *
+ * Possible implementations may be SrcFile, SrcDir, DestFile,
+ * DestDir, JavaSrcFile, ReadableSrcFile, etc.
+ *
+ * The idea is to validate the attribute right when it is being
+ * set instead of performing the check later on.  This will
+ * remove redundant code as well as minimize the headache
+ * of writing validation code for the BuildWriter.
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public abstract class ValidatedFileAttribute implements PreferredAttribute {
+
+    private File file = null;
+
+    /**
+     * The implementing class must provide the message that
+     * is to be displayed if the file is not valid.
+     *
+     * @return the String message that is to be displayed
+     * if the file is not valid.
+     */
+    protected abstract String getMessage();
+
+    /**
+     * Is the file a valid file based on the context?
+     * This decision must be made by the subclass's
+     * implementation of this method.
+     *
+     * @return true or false depending upon the
+     * validity of the file.
+     */
+    protected abstract boolean isValid();
+
+    public ValidatedFileAttribute() {
+    }
+
+    /**
+     * Retrieves the file.
+     */
+    public final File getFile() {
+        return file;
+    }
+
+    /**
+     * Invoked by {@link org.apache.tools.ant.IntrospectionHelper IntrospectionHelper}.
+     */
+    public final void setFile(File f) throws BuildException {
+        file = f;
+        if (!isValid()) {
+            file = null;
+            throw new BuildException(getMessage());
+        }
+    }
+}