Getting a whole lot of "scanned from multiple locations" warnings in simple Jersey web app

Question

Getting back to Java after some time, and I'm trying to get a simple RESTful API going on with Java 8, Jersey 2.27 and Jetty 9.4.9 using the command line. The app does work, but I keep getting hundreds of warnings like:

2018-04-27 01:17:24.845:WARN:oeja.AnnotationParser:main: Unrecognized runtime asm version, assuming 393216
2018-04-27 01:17:24.945:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.ArrayELResolver scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/ArrayELResolver.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/ArrayELResolver.class
2018-04-27 01:17:24.949:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.BeanELResolver$BeanProperties scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/BeanELResolver$BeanProperties.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/BeanELResolver$BeanProperties.class
2018-04-27 01:17:24.952:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.BeanELResolver$BeanProperty scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/BeanELResolver$BeanProperty.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/BeanELResolver$BeanProperty.class
2018-04-27 01:17:24.954:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.BeanELResolver scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/BeanELResolver.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/BeanELResolver.class
2018-04-27 01:17:24.959:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.CompositeELResolver scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/CompositeELResolver.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/CompositeELResolver.class
2018-04-27 01:17:24.961:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.ELContext scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/ELContext.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/ELContext.class
2018-04-27 01:17:24.962:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.Generated scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/Generated.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/Generated.class
2018-04-27 01:17:24.962:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.ManagedBean scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/ManagedBean.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/ManagedBean.class
2018-04-27 01:17:24.962:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.PostConstruct scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/PostConstruct.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/PostConstruct.class
2018-04-27 01:17:24.963:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.PreDestroy scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/PreDestroy.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/PreDestroy.class
2018-04-27 01:17:24.963:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.Priority scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/Priority.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/Priority.class
2018-04-27 01:17:24.963:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.Resource$AuthenticationType scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/Resource$AuthenticationType.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/Resource$AuthenticationType.class
2018-04-27 01:17:24.963:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.Resource scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/Resource.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/Resource.class
2018-04-27 01:17:24.963:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.Resources scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/Resources.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/Resources.class
2018-04-27 01:17:24.963:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.security.DeclareRoles scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/security/DeclareRoles.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/security/DeclareRoles.class
2018-04-27 01:17:24.964:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.security.DenyAll scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/security/DenyAll.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/security/DenyAll.class
2018-04-27 01:17:24.964:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.security.PermitAll scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/security/PermitAll.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/security/PermitAll.class
2018-04-27 01:17:24.964:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.security.RolesAllowed scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/security/RolesAllowed.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/security/RolesAllowed.class
2018-04-27 01:17:24.964:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.security.RunAs scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/security/RunAs.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/security/RunAs.class
2018-04-27 01:17:24.964:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.sql.DataSourceDefinition scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/sql/DataSourceDefinition.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/sql/DataSourceDefinition.class
2018-04-27 01:17:24.965:WARN:oeja.AnnotationParser:qtp988458918-15: javax.annotation.sql.DataSourceDefinitions scanned from multiple locations: jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/annotation/sql/DataSourceDefinitions.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.annotation-api-1.2.jar!/javax/annotation/sql/DataSourceDefinitions.class
2018-04-27 01:17:24.962:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.ELContextEvent scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/ELContextEvent.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/ELContextEvent.class
2018-04-27 01:17:24.966:WARN:oeja.AnnotationParser:qtp988458918-12: javax.el.ELContextListener scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/el-api-2.2.jar!/javax/el/ELContextListener.class, jar:file:///paste4j/deployment/jetty-runner-9.4.9.v20180320.jar!/javax/el/ELContextListener.class
2018-04-27 01:17:24.966:WARN:oeja.AnnotationParser:qtp988458918-17: javax.inject.Inject scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.inject-1.jar!/javax/inject/Inject.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.inject-2.5.0-b42.jar!/javax/inject/Inject.class
2018-04-27 01:17:24.966:WARN:oeja.AnnotationParser:qtp988458918-17: javax.inject.Named scanned from multiple locations: jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.inject-1.jar!/javax/inject/Named.class, jar:file:///tmp/jetty-0.0.0.0-8081-paste4j.war-_-any-8355640322316327743.dir/webapp/WEB-INF/lib/javax.inject-2.5.0-b42.jar!/javax/inject/Named.class

I have extracted the contents of jaxrs-ri-2.27.zip from https://jersey.github.io/download.html into the project WEB-INF\lib\ directory, so that all JAR files from the ZIP are in the same directory.

Then I compile it with:

# In project root
javac -classpath "WEB-INF/lib/*" WEB-INF/classes/com/paste/ws/*.java
jar -cvf paste4j.war WEB-INF/*

And finally attempt to run it with:

java -jar deployment/jetty-runner-9.4.9.v20180320.jar --port 8081 paste4j.war

But at that point, those warnings start to appear. What am I doing wrong?

Here's the files I have:

WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID"
    version="3.1">
    <servlet>
        <servlet-name>rest</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>com.paste.ws.MyApplication</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>rest</servlet-name>
        <url-pattern>/rest/*</url-pattern>
    </servlet-mapping>
</web-app>

WEB-INF/classes/com/paste/ws/MyApplication.java

package com.paste.ws;

import org.glassfish.jersey.server.ResourceConfig;

public class MyApplication extends ResourceConfig {
    public MyApplication() {
        packages("com.paste.ws");
    }
}

WEB-INF/classes/com/paste/ws/PasteResource.java

package com.paste.ws;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/hello")
public class PasteResource {
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String getMessage() {
        return "Hello there";
    }
}

And the structure:

The java version (sudo apt install openjdk-8-jdk):

$ java -version
openjdk version "9-internal"
OpenJDK Runtime Environment (build 9-internal+0-2016-04-14-195246.buildd.src)
OpenJDK 64-Bit Server VM (build 9-internal+0-2016-04-14-195246.buildd.src, mixed mode)

The app does work when I call it - but not sure if those warnings are safe to ignore?:

$ curl localhost:8081/rest/hello
Hello there

Answer 1

There are duplicates in there. Jersey is known for repackaging classes in it's own jars because of OSGI. Which sucks if you don't use and understand OSGI like me. I don't know all of them but for example javax.inject-1 and javax.inject-2.5.0-b42 are the same. Most people use maven which is a better way to manage dependencies (but a steep learning curve to get into) and then would exclude the repackaged one from jersey like:

   <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet</artifactId>
        <exclusions>
            <exclusion><!-- Exclude this repackaged javax.inject. -->
                <groupId>org.glassfish.hk2.external</groupId>
                <artifactId>javax.inject</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.inject</groupId>
        <artifactId>jersey-hk2</artifactId>
        <exclusions>
            <exclusion><!-- Exclude this repackaged javax.inject. -->
                <groupId>org.glassfish.hk2.external</groupId>
                <artifactId>javax.inject</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

But in your case just try to remove javax.inject-2.5.0-b42 and see if you get no more warnings for these classes:

You'll have to figure out the duplicates for the other warnings too. For me it was a little easier because I used maven and the dependency graph in netbeans to find duplicates. Hope this didn't ruin your return to Java.