Update .travis.yml and dependencies to support build with JDK 11

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

.travis.yml

@@ -3,8 +3,14 @@ language: java
 sudo: required
 dist: trusty
 
-jdk:
-  - oraclejdk8
+matrix:
+  include:
+  - jdk: oraclejdk8
+    env: BUILD_JDK=ORACLE_JDK_8
+  - jdk: oraclejdk11
+    env: BUILD_JDK=ORACLE_JDK_11
+  allow_failures:
+  - env: BUILD_JDK=ORACLE_JDK_11
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)

sentinel-adapter/sentinel-grpc-adapter/pom.xml

@@ -39,6 +39,13 @@
             <version>${grpc.version}</version>
             <scope>provided</scope>
         </dependency>
+        <!-- workaround for compile in JDK 11 -->
+        <dependency>
+            <groupId>javax.annotation</groupId>
+            <artifactId>javax.annotation-api</artifactId>
+            <version>1.2</version>
+        </dependency>
+
 
         <dependency>
             <groupId>junit</groupId>