build on pull request supports to master

Signed-off-by: rotty3000@apache.org
diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index c44c26d..3c05da3 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -1,6 +1,12 @@
 name: Java CI
 
-on: [push]
+on: 
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   build:
@@ -14,4 +20,4 @@
       with:
         java-version: 1.8
     - name: Build with Maven - Java 8
-      run: mvn -U -e -B -ntp clean verify --file pom.xml
+      run: mvn -U -e -B -ntp clean verify