Build as multi release jar

- make jakarta and javax annotation modules optional at runtime
- update travis ci to jdk 9
multi-release-jar
- added module info in java9 source folder
- added executions for java 8 and 9
- removed automatic module - added multi release entry to manifest

Author: Til7701

.travis.yml

@@ -1,6 +1,6 @@
 language: java
 jdk:
-  - openjdk8
+  - openjdk9
 
 cache:
   directories:

pom.xml

@@ -85,18 +85,40 @@
             </plugin>
             <plugin>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
-                </configuration>
+                <executions>
+                    <execution>
+                        <id>compile-java-8</id>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                        <configuration>
+                            <source>1.8</source>
+                            <target>1.8</target>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>compile-java-9</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                        <configuration>
+                            <release>9</release>
+                            <compileSourceRoots>
+                                <compileSourceRoot>${project.basedir}/src/main/java9</compileSourceRoot>
+                            </compileSourceRoots>
+                            <multiReleaseOutput>true</multiReleaseOutput>
+                        </configuration>
+                    </execution>
+                </executions>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-jar-plugin</artifactId>
                 <configuration>
                     <archive>
                         <manifestEntries>
-                            <Automatic-Module-Name>org.openapitools.jackson.nullable</Automatic-Module-Name>
+                            <Multi-Release>true</Multi-Release>
                         </manifestEntries>
                     </archive>
                 </configuration>

src/main/java9/module-info.java

@@ -0,0 +1,7 @@
+module org.openapitools.jackson.nullable {
+    requires com.fasterxml.jackson.databind;
+    requires static jakarta.validation;
+    requires static java.validation;
+
+    exports org.openapitools.jackson.nullable;
+}