GUACAMOLE-1218: Refactor guacamole-auth-json's StringListProperty into guacamole-ext.

guacamole-ext/src/main/java/org/apache/guacamole/properties/StringListProperty.java

@@ -0,0 +1,61 @@
+/*
+ * 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.guacamole.properties;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.regex.Pattern;
+import org.apache.guacamole.GuacamoleException;
+
+/**
+ * A GuacamoleProperty whose value is a List of Strings. The string value
+ * parsed to produce this list is a comma-delimited list. Duplicate values are
+ * ignored, as is any whitespace following delimiters. To maintain
+ * compatibility with the behavior of Java properties in general, only
+ * whitespace at the beginning of each value is ignored; trailing whitespace
+ * becomes part of the value.
+ */
+public abstract class StringListProperty implements GuacamoleProperty<List<String>> {
+
+    /**
+     * A pattern which matches against the delimiters between values. This is
+     * currently simply a comma and any following whitespace. Parts of the
+     * input string which match this pattern will not be included in the parsed
+     * result.
+     */
+    private static final Pattern DELIMITER_PATTERN = Pattern.compile(",\\s*");
+
+    @Override
+    public List<String> parseValue(String values) throws GuacamoleException {
+
+        // If no property provided, return null.
+        if (values == null)
+            return null;
+
+        // Split string into a list of individual values
+        List<String> stringValues = Arrays.asList(DELIMITER_PATTERN.split(values));
+        if (stringValues.isEmpty())
+            return null;
+
+        return stringValues;
+
+    }
+
+}