bugfix for issue #11 (skip xml entities in filter method)

core/src/main/java/org/apache/struts/util/ResponseUtils.java

@@ -23,6 +23,8 @@
 import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;
 import java.nio.charset.Charset;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -35,6 +37,9 @@
  *          $
  */
 public class ResponseUtils {
+
+	protected static Pattern XML_ENTITY_PATTERN = Pattern.compile("&(?:[a-z\\d]+|#\\d+|#x[a-f\\d]+);");
+
     // ------------------------------------------------------- Static Variables
 
     /**
@@ -82,8 +87,11 @@ public static String filter(String value) {
                 break;
 
             case '&':
-                filtered = "&";
-
+            	if ( isStartOfXmlEntity(value,i) ) {
+            		filtered = "&"; // leave unchanged
+            	} else {
+            		filtered = "&";
+            	}
                 break;
 
             case '"':
@@ -120,6 +128,21 @@ public static String filter(String value) {
     }
 
     /**
+     * Checks, if a given string contains a XML entity starting at a specified position
+     * @param str the string value to check
+     * @param startpos the index where the entity is expected to start
+     * @return <code>true</code> if a XML entity was found, <code>false</code> otherwise
+     */
+    private static boolean isStartOfXmlEntity(String str, int startpos) {
+    	Matcher matcher = XML_ENTITY_PATTERN.matcher(str.substring(startpos));
+    	if ( matcher.find() && matcher.start() == 0 ) {
+    		return true;
+    	} else {
+    		return false;
+    	}
+	}
+
+	/**
      * URLencodes a string assuming the character encoding is UTF-8.
      *
      * @param url
@@ -162,4 +185,5 @@ public static String encodeURL(String url, String enc) {
         return str;
 
     }
+
 }

core/src/test/java/org/apache/struts/util/TestResponseUtils.java

@@ -0,0 +1,60 @@
+/*
+ * $Id$
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.struts.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.apache.struts.mock.TestMockBase;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for {@link ResponseUtils}.
+ *
+ * @version $Rev$ $Date$
+ */
+public class TestResponseUtils extends TestMockBase {
+    // ----------------------------------------------------- Instance Variables
+    // ----------------------------------------------------- Setup and Teardown
+    @BeforeEach
+    public void setUp() {
+        super.setUp();
+    }
+
+    @AfterEach
+    public void tearDown() {
+        super.tearDown();
+    }
+
+    // ------------------------------------------------------- Individual Tests
+    // ---------------------------------------------------------- filter()
+    @Test
+    public void testFilter() {
+        assertEquals("123&456", ResponseUtils.filter("123&456"));
+        assertEquals("123&456", ResponseUtils.filter("123&456"));
+        assertEquals("123{456", ResponseUtils.filter("123{456"));
+        assertEquals("123&#12a;456", ResponseUtils.filter("123&#12a;456"));
+        assertEquals("123Ī456", ResponseUtils.filter("123Ī456"));
+        assertEquals("123&#x12ah;456", ResponseUtils.filter("123&#x12ah;456"));
+        assertEquals("123&lt;&gt;&quot;&#39;456", ResponseUtils.filter("123<>\"'456"));
+   }
+}