build: fail on warning (#770)

Author: BenoitPerrot

pom.xml

@@ -83,10 +83,12 @@
                     <plugin>
                         <groupId>org.apache.maven.plugins</groupId>
                         <artifactId>maven-compiler-plugin</artifactId>
-                        <version>3.5.1</version>
+                        <version>3.9.0</version>
                         <configuration>
                             <source>1.8</source>
                             <target>1.8</target>
+                            <showWarnings>true</showWarnings>
+                            <failOnWarning>true</failOnWarning>
                         </configuration>
                     </plugin>
                     <plugin>
@@ -198,6 +200,15 @@
                 </dependency>
             </dependencies>
         </profile>
+        <profile>
+            <id>jdk-9-and-above</id>
+            <activation>
+                <jdk>[9,)</jdk>
+            </activation>
+            <properties>
+                <maven.compiler.release>8</maven.compiler.release>
+            </properties>
+        </profile>
         <profile>
             <id>release</id>
             <build>