use jdk 13 everywhere to avoid resource encoding issues present in older jdks

.github/workflows/tests.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        java: [ '1.8', '1.13' ]
+        java: [ '1.13' ]
 
     steps:
     - uses: actions/checkout@v1

acrarium/Dockerfile

@@ -1,4 +1,4 @@
-FROM openjdk:8-jdk-alpine
+FROM openjdk:13-slim
 VOLUME /tmp
 ARG DEPENDENCY=target/dependency
 COPY ${DEPENDENCY}/WEB-INF/lib /acrarium/lib

acrarium/pom.xml

@@ -13,7 +13,7 @@
     <properties>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <java.version>1.8</java.version>
+        <java.version>13</java.version>
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <vaadin.version>14.0.14</vaadin.version>
@@ -233,14 +233,6 @@
             <id>central</id>
             <url>https://repo1.maven.org/maven2/</url>
         </pluginRepository>
-        <pluginRepository>
-            <snapshots>
-                <enabled>false</enabled>
-            </snapshots>
-            <id>bintray-f43nd1r-maven</id>
-            <name>bintray-plugins</name>
-            <url>https://dl.bintray.com/f43nd1r/maven</url>
-        </pluginRepository>
     </pluginRepositories>
     <build>
         <defaultGoal>spring-boot:run</defaultGoal>
@@ -327,6 +319,22 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>3.1.1</version>
+                <executions>
+                    <execution>
+                        <id>attach-javadocs</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                        <configuration>
+                            <doclint>none</doclint>
+                            <javadocExecutable>${java.home}/bin/javadoc</javadocExecutable>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
             <plugin>
                 <groupId>com.faendir.maven</groupId>
                 <artifactId>resource-class-generator</artifactId>

pom.xml

@@ -33,21 +33,6 @@
           <tagNameFormat>v@{project.version}</tagNameFormat>
         </configuration>
       </plugin>
-      <plugin>
-        <artifactId>maven-javadoc-plugin</artifactId>
-        <version>3.1.1</version>
-        <executions>
-          <execution>
-            <id>attach-javadocs</id>
-            <goals>
-              <goal>jar</goal>
-            </goals>
-            <configuration>
-              <doclint>none</doclint>
-            </configuration>
-          </execution>
-        </executions>
-      </plugin>
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>flatten-maven-plugin</artifactId>