8144967: javax.xml.transform.Source and org.xml.sax.InputSource can be empty

Reviewed-by: darcy, rriggs

jaxp/src/java.xml/share/classes/javax/xml/transform/Source.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -52,4 +52,17 @@ public interface Source {
      * if setSystemId was not called.
      */
     public String getSystemId();
+
+    /**
+     * Indicates whether the {@code Source} object is empty. Empty means
+     * that there is no input available from this Source.
+     *
+     * @implSpec The default implementation of this method throws
+     * {@link UnsupportedOperationException}.
+     *
+     * @return true if the {@code Source} object is empty, false otherwise
+     */
+    default boolean isEmpty() {
+        throw new UnsupportedOperationException("The isEmpty method is not supported.");
+    }
 }

jaxp/src/java.xml/share/classes/javax/xml/transform/dom/DOMSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -122,6 +122,7 @@ public class DOMSource implements Source {
      *
      * @param systemID Base URL for this DOM tree.
      */
+    @Override
     public void setSystemId(String systemID) {
         this.systemID = systemID;
     }
@@ -132,7 +133,25 @@ public class DOMSource implements Source {
      *
      * @return Base URL for this DOM tree.
      */
+    @Override
     public String getSystemId() {
         return this.systemID;
     }
+
+    /**
+     * Indicates whether the {@code DOMSource} object is empty. Empty is
+     * defined as follows:
+     * <ul>
+     * <li>if the system identifier and node are {@code null};
+     * </li>
+     * <li>if the system identifier is null, and the {@code node} has no child nodes.
+     * </li>
+     * </ul>
+     *
+     * @return true if the {@code DOMSource} object is empty, false otherwise
+     */
+    @Override
+    public boolean isEmpty() {
+        return systemID == null && (node == null || !node.hasChildNodes());
+    }
 }

jaxp/src/java.xml/share/classes/javax/xml/transform/sax/SAXSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2006, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -147,6 +147,7 @@ public class SAXSource implements Source {
      *
      * @param systemId The system identifier as a URI string.
      */
+    @Override
     public void setSystemId(String systemId) {
 
         if (null == inputSource) {
@@ -162,6 +163,7 @@ public class SAXSource implements Source {
      *
      * @return Base URL for the <code>Source</code>, or <code>null</code>.
      */
+    @Override
     public String getSystemId() {
 
         if (inputSource == null) {
@@ -207,4 +209,22 @@ public class SAXSource implements Source {
             return null;
         }
     }
+
+    /**
+     * Indicates whether the {@code SAXSource} object is empty. Empty is
+     * defined as follows:
+     * <ul>
+     * <li>if the system identifier and {@code InputSource} are {@code null};
+     * </li>
+     * <li>if the system identifier is {@code null}, and the {@code InputSource}
+     * is empty.
+     * </li>
+     * </ul>
+     *
+     * @return true if the {@code SAXSource} object is empty, false otherwise
+     */
+    @Override
+    public boolean isEmpty() {
+        return getSystemId() == null && (inputSource == null || inputSource.isEmpty());
+    }
 }

jaxp/src/java.xml/share/classes/javax/xml/transform/stax/StAXSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -209,6 +209,7 @@ public class StAXSource implements Source {
      * @throws UnsupportedOperationException Is <strong>always</strong>
      *   thrown by this method.
      */
+    @Override
     public void setSystemId(final String systemId) {
 
         throw new UnsupportedOperationException(
@@ -229,8 +230,21 @@ public class StAXSource implements Source {
      *
      * @return System identifier used by this <code>StAXSource</code>.
      */
+    @Override
     public String getSystemId() {
 
         return systemId;
     }
+
+    /**
+     * Indicates whether the {@code StAXSource} object is empty. Since a
+     * {@code StAXSource} object can never be empty, this method always returns
+     * false.
+     *
+     * @return unconditionally false
+     */
+    @Override
+    public boolean isEmpty() {
+        return false;
+    }
 }

jaxp/src/java.xml/share/classes/javax/xml/transform/stream/StreamSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,8 +26,10 @@
 package javax.xml.transform.stream;
 
 import java.io.File;
+import java.io.IOException;
 import java.io.InputStream;
 import java.io.Reader;
+import javax.xml.transform.Result;
 
 import javax.xml.transform.Source;
 
@@ -233,6 +235,7 @@ public class StreamSource implements Source {
      *
      * @param systemId The system identifier as a URL string.
      */
+    @Override
     public void setSystemId(String systemId) {
         this.systemId = systemId;
     }
@@ -243,6 +246,7 @@ public class StreamSource implements Source {
      * @return The system identifier that was set with setSystemId, or null
      * if setSystemId was not called.
      */
+    @Override
     public String getSystemId() {
         return systemId;
     }
@@ -259,6 +263,59 @@ public class StreamSource implements Source {
         this.systemId = f.toURI().toASCIIString();
     }
 
+    /**
+     * Indicates whether the {@code StreamSource} object is empty. Empty is
+     * defined as follows:
+     * <ul>
+     * <li>All of the input sources, including the public identifier, system
+     * identifier, byte stream, and character stream, are {@code null}.
+     * </li>
+     * <li>The public identifier and system identifier are {@code null}, and
+     * byte and character stream are either {@code null} or contain no byte or
+     * character.
+     * <p>
+     * Note that this method will reset the byte stream if it is provided, or
+     * the character stream if the byte stream is not provided.
+     * </li>
+     * </ul>
+     * <p>
+     * In case of error while checking the byte or character stream, the method
+     * will return false to allow the XML processor to handle the error.
+     *
+     * @return true if the {@code StreamSource} object is empty, false otherwise
+     */
+    @Override
+    public boolean isEmpty() {
+        return (publicId == null && systemId == null && isStreamEmpty());
+    }
+
+    private boolean isStreamEmpty() {
+        boolean empty = true;
+        try {
+            if (inputStream != null) {
+                inputStream.reset();
+                int bytesRead = inputStream.available();
+                if (bytesRead > 0) {
+                    return false;
+                }
+            }
+
+            if (reader != null) {
+                reader.reset();
+                int c = reader.read();
+                reader.reset();
+                if (c != -1) {
+                    return false;
+                }
+            }
+        } catch (IOException ex) {
+            //in case of error, return false
+            return false;
+        }
+
+        return empty;
+    }
+
     //////////////////////////////////////////////////////////////////////
     // Internal state.
     //////////////////////////////////////////////////////////////////////