Adding support for user interface extensions.

Change-Id: I1e41d16efc11be31ad4c2fb0c09e86e3dfd26706
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/AbstractInjectionResource.java b/web/gui/src/main/java/org/onosproject/ui/impl/AbstractInjectionResource.java
new file mode 100644
index 0000000..2ed4ecd
--- /dev/null
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/AbstractInjectionResource.java
@@ -0,0 +1,78 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed 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.onosproject.ui.impl;
+
+import org.onlab.rest.BaseResource;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.util.Enumeration;
+import java.util.Iterator;
+import java.util.List;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Resource for serving semi-static resources.
+ */
+public class AbstractInjectionResource extends BaseResource {
+
+    /**
+     * Returns the index into the supplied string where the end of the
+     * specified pattern is located.
+     *
+     * @param string      string to split
+     * @param start       index where to start looking for pattern
+     * @param stopPattern optional pattern where to stop
+     */
+    protected int split(String string, int start, String stopPattern) {
+        int i = stopPattern != null ? string.indexOf(stopPattern, start) : string.length();
+        checkArgument(i > 0, "Unable to locate stop pattern %s", stopPattern);
+        return i + (stopPattern != null ? stopPattern.length() : 0);
+    }
+
+    /**
+     * Produces an input stream from the bytes of the specified sub-string.
+     *
+     * @param string source string
+     * @param start  index where to start stream
+     * @param end    index where to end stream
+     */
+    protected InputStream stream(String string, int start, int end) {
+        return new ByteArrayInputStream(string.substring(start, end).getBytes());
+    }
+
+    /**
+     * Auxiliary enumeration to sequence input streams.
+     */
+    protected class StreamEnumeration implements Enumeration<InputStream> {
+        private final Iterator<InputStream> iterator;
+
+        StreamEnumeration(List<InputStream> streams) {
+            this.iterator = streams.iterator();
+        }
+
+        @Override
+        public boolean hasMoreElements() {
+            return iterator.hasNext();
+        }
+
+        @Override
+        public InputStream nextElement() {
+            return iterator.next();
+        }
+    }
+}