Merge branch 'master' into bugfix

.github/workflows/ci.yml

+#
+#    Copyright 2009-2021 the original author or authors.
+#
+#    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.
+#
+
+name: Java CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK 8
+        uses: actions/setup-java@v2
+        with:
+          java-version: '8'
+          distribution: 'adopt'
+      - name: Cache Maven
+        uses: actions/cache@v2.1.6
+        with:
+          path: ~/.m2
+          key: m2
+          restore-keys: m2
+      - name: Chmod
+        run:  chmod +x mvnw
+      - name: Maven Build
+        run: ./mvnw install -B -V -Dmaven.test.skip=true
+      - name: Java Doc
+        run: ./mvnw javadoc:javadoc