Support customized origin parser in legacy Dubbo 2.6.x adapter (alibaba#1555)

Author: cityiron

sentinel-adapter/sentinel-dubbo-adapter/README.md

@@ -69,4 +69,10 @@ flow control, degrade or system load protection. You can implement your own `Dub
 and then register to `DubboAdapterGlobalConfig`.
 If no fallback is configured, Sentinel will wrap the `BlockException` as the fallback result.
 
-Besides, we can also leverage [Dubbo mock mechanism](http://dubbo.apache.org/en-us/docs/user/demos/local-mock.html) to provide fallback implementation of degraded Dubbo services.
+Besides, we can also leverage [Dubbo mock mechanism](http://dubbo.apache.org/en-us/docs/user/demos/local-mock.html) to provide fallback implementation of degraded Dubbo services.
+
+## Global dubbo provider origin parse
+
+Sentinel Dubbo Adapter supports global origin parse for provider.
+You can implement your own `DubboOriginParser` interface
+and then register to `DubboOriginParserRegistry`. If no originParse is configured, Sentinel will user dubbo url property application.

sentinel-adapter/sentinel-dubbo-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/dubbo/origin/DubboOriginParserRegistry.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 1999-2020 Alibaba Group Holding Ltd.
+ *
+ * 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
+ *
+ *      https://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 com.alibaba.csp.sentinel.adapter.dubbo.origin;
+
+/**
+ * Global origin parser registry for Dubbo.
+ *
+ * @author tiecheng
+ */
+public final class DubboOriginParserRegistry {
+
+    private static volatile DubboOriginParser dubboOriginParser = new DefaultDubboOriginParser();
+
+    public static DubboOriginParser getDubboOriginParser() {
+        return dubboOriginParser;
+    }
+
+    public static void setDubboOriginParser(DubboOriginParser dubboOriginParser) {
+        DubboOriginParserRegistry.dubboOriginParser = dubboOriginParser;
+    }
+
+    private DubboOriginParserRegistry() {}
+
+}