Fixed javadoc generation  on JDK11 (#187)

diff --git a/api/pom.xml b/api/pom.xml
index 957542e..fe927b2 100644
--- a/api/pom.xml
+++ b/api/pom.xml
@@ -49,7 +49,6 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
                 <configuration>
-                    <docfilessubdirs>true</docfilessubdirs>
                     <groups>
                         <group>
                             <title>JSON Processing Packages</title>
@@ -57,7 +56,7 @@
                         </group>
                     </groups>
                     <bottom>
-<![CDATA[Copyright &#169; 2012-2018,
+<![CDATA[Copyright &#169; 2012-2019,
     <a href="http://www.oracle.com">Oracle</a>
     and/or its affiliates. All Rights Reserved.
     Use is subject to
@@ -65,11 +64,7 @@
     <br>Comments to : jsonp-dev@eclipse.org
 ]]>
                     </bottom>
-                    <links>
-                        <link>http://docs.oracle.com/javase/8/docs/api/</link>
-                    </links>
                 </configuration>
-
                 <executions>
                     <execution>
                         <id>attach-javadocs</id>
diff --git a/pom.xml b/pom.xml
index f6c448a..a146adf 100644
--- a/pom.xml
+++ b/pom.xml
@@ -185,7 +185,23 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-javadoc-plugin</artifactId>
-                    <version>3.0.1</version>
+                    <version>3.1.0</version>
+                    <configuration>
+                        <source>8</source>
+                        <additionalJOptions combine.children="append">
+                            <JOption>-J-Dhttp.agent=maven-javadoc-plugin</JOption>
+                        </additionalJOptions>
+                        <sourceFileExcludes>
+                            <sourceFileExclude>**/module-info.java</sourceFileExclude>
+                            <sourceFileExclude>target/**/*.java</sourceFileExclude>
+                        </sourceFileExcludes>
+                        <docfilessubdirs>true</docfilessubdirs>
+                        <links>
+                            <link>http://docs.oracle.com/javase/8/docs/api/</link>
+                        </links>
+                        <detectJavaApiLink>false</detectJavaApiLink>
+                        <detectOfflineLinks>false</detectOfflineLinks>
+                    </configuration>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>