JCR-4935 skip invalid xml characters in session.exportDocumentView()

jackrabbit-core/src/test/java/org/apache/jackrabbit/core/xml/DocumentViewTest.java

@@ -127,4 +127,41 @@ public void testMultiValue() throws Exception {
         }
     }
 
+    /**
+     * Test case for
+     * <a href="https://issues.apache.org/jira/browse/JCR-4935">JCR-4935</a>:
+     * session.exportDocumentView() generates unparsable XML if a JCR Property contains invalid XML character
+     */
+    public void testInvalidXmlCharacter() throws Exception {
+
+        Node root = superuser.getRootNode();
+
+        Node node = root.addNode("invalid-xml-character-test", "nt:unstructured");
+        node.setProperty("0x3", "\u0003");
+        node.setProperty("0xB", "\u000B");
+        node.setProperty("0xC", "\u000C");
+        node.setProperty("0x19", "\u0019");
+        node.setProperty("0xD800", "\uD800");
+        node.setProperty("0xFFFE", "\uFFFE");
+        node.setProperty("0xD800", "\uD800");
+
+        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        superuser.exportDocumentView("/invalid-xml-character-test", buffer, true, true);
+        superuser.refresh(false);
+
+        superuser.importXML(
+                "/", new ByteArrayInputStream(buffer.toByteArray()),
+                ImportUUIDBehavior.IMPORT_UUID_COLLISION_THROW);
+
+        node = root.getNode("invalid-xml-character-test");
+        assertEquals("\\u0003", node.getProperty("0x3").getString());
+        assertEquals("\\u000b", node.getProperty("0xB").getString());
+        assertEquals("\\u000c", node.getProperty("0xC").getString());
+        assertEquals("\\u0019", node.getProperty("0x19").getString());
+        assertEquals("\\ud800", node.getProperty("0xD800").getString());
+        assertEquals("\\ufffe", node.getProperty("0xFFFE").getString());
+        assertEquals("\\ud800", node.getProperty("0xD800").getString());
+    }
+
+
 }

jackrabbit-jcr-commons/src/main/java/org/apache/jackrabbit/commons/xml/ToXmlContentHandler.java

@@ -24,6 +24,8 @@
 import java.io.Writer;
 import java.nio.charset.StandardCharsets;
 
+import org.apache.jackrabbit.util.Text;
+import org.apache.jackrabbit.util.XMLChar;
 import org.xml.sax.Attributes;
 import org.xml.sax.ContentHandler;
 import org.xml.sax.SAXException;
@@ -140,7 +142,11 @@ private void write(char[] ch, int start, int length, boolean attribute)
                 } else if (attribute && ch[i] == '\'') {
                     writer.write("'");
                 } else {
-                    writer.write(ch[i]);
+                    if (XMLChar.isValid(ch[i])) {
+                        writer.write(ch[i]);
+                    } else {
+                        writer.append(escapeIllegalXmlChar(ch[i]));
+                    }
                 }
             } catch (IOException e) {
                 throw new SAXException(
@@ -149,6 +155,22 @@ private void write(char[] ch, int start, int length, boolean attribute)
         }
     }
 
+    /**
+     * Escape invalid xml characters to Unicode code points,
+     * similar to  FileVault .
+     *
+     * See https://jackrabbit.apache.org/filevault/docview.html#escaping
+     */
+    private String escapeIllegalXmlChar(char c){
+        StringBuilder buf = new StringBuilder();
+        buf.append("\\u");
+        buf.append(Text.hexTable[(c >> 12) & 15]);
+        buf.append(Text.hexTable[(c >> 8) & 15]);
+        buf.append(Text.hexTable[(c >> 4) & 15]);
+        buf.append(Text.hexTable[c & 15]);
+        return buf.toString();
+    }
+
     private void closeStartTagIfOpen() throws SAXException {
         if (startTagIsOpen) {
             try {
@@ -275,5 +297,4 @@ public void endElement(
     public String toString() {
         return writer.toString();
     }
-
 }