调整registry api，保证其开放性

skywalking-registry/src/main/java/com/a/eye/skywalking/registry/RegistryCenterFactory.java

@@ -1,4 +1,7 @@
-package com.a.eye.skywalking.registry.api;
+package com.a.eye.skywalking.registry;
+
+import com.a.eye.skywalking.registry.api.Center;
+import com.a.eye.skywalking.registry.api.RegistryCenter;
 
 import java.util.HashMap;
 import java.util.Iterator;
@@ -10,7 +13,7 @@ import java.util.ServiceLoader;
  */
 public class RegistryCenterFactory {
 
-    private Map<CenterType, RegistryCenter> registryCenter = new HashMap<CenterType, RegistryCenter>();
+    private Map<String, RegistryCenter> registryCenter = new HashMap<String, RegistryCenter>();
 
     private RegistryCenterFactory() {
         ServiceLoader<RegistryCenter> loaders = ServiceLoader.load(RegistryCenter.class);
@@ -27,7 +30,7 @@ public class RegistryCenterFactory {
         }
     }
 
-    public RegistryCenter getRegistryCenter(CenterType type) {
+    public RegistryCenter getRegistryCenter(String type) {
         return registryCenter.get(type);
     }
 }

skywalking-registry/src/main/java/com/a/eye/skywalking/registry/api/Center.java

@@ -5,5 +5,5 @@ import java.lang.annotation.*;
 @Retention(RetentionPolicy.RUNTIME)
 @Target({ElementType.TYPE})
 public @interface Center {
-    CenterType type() default CenterType.zookeeper;
+    String type() default CenterType.DEFAULT_CENTER_TYPE;
 }

skywalking-registry/src/main/java/com/a/eye/skywalking/registry/api/CenterType.java

@@ -1,27 +1,8 @@
 package com.a.eye.skywalking.registry.api;
 
 /**
- * Created by xin on 2016/11/10.
+ * Created by wusheng on 2016/11/10.
  */
-public enum CenterType {
-    zookeeper("zookeeper");
-
-    private String type;
-
-    CenterType(String typeStr) {
-        this.type = typeStr;
-    }
-
-
-    public String getType() {
-        return type;
-    }
-
-    public static CenterType convert(String type) {
-        if (zookeeper.type.equals(type)) {
-            return zookeeper;
-        }
-
-        throw new IllegalArgumentException("Failed to find center type[" + type + "]");
-    }
+public interface CenterType {
+    String DEFAULT_CENTER_TYPE = "zookeeper";
 }