AWS SDK Error: A JNI error has occurred, ... java.lang.NoClassDefFoundError

Question

I am trying to do the tutorial here using the SDK specified here.

Specifically, I am trying to execute the following Amazon Web Services DynamoDB sample code with Maven:

https://github.com/JohnReedLOL/DynamoDBTutorial/blob/master/src/main/java/org/example/basicapp/MoviesCreateTable.java

Like so...

c4b301bb8ad9:myapp StackOverflowUser$ pwd
/Users/StackOverflowUser/Downloads/apache-maven-3.5.2/bin/myapp

c4b301bb8ad9:myapp StackOverflowUser$ ./../mvn package
[INFO] Scanning for projects...
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] Building myapp 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ myapp ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/StackOverflowUser/Downloads/apache-maven-3.5.2/bin/myapp/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ myapp ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ myapp ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/StackOverflowUser/Downloads/apache-maven-3.5.2/bin/myapp/src/test/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ myapp ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ myapp ---
[INFO] Surefire report directory: /Users/StackOverflowUser/Downloads/apache-maven-3.5.2/bin/myapp/target/surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running org.example.basicapp.AppTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.006 sec

Results :

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

[INFO] 
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ myapp ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.557 s
[INFO] Finished at: 2018-01-20T13:37:59-05:00
[INFO] Final Memory: 12M/225M
[INFO] ------------------------------------------------------------------------

But when I try to run it I get this error...

c4b301bb8ad9:myapp StackOverflowUser$ java -cp target/myapp-1.0-SNAPSHOT.jar org.example.basicapp.MoviesCreateTable
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: com/amazonaws/services/dynamodbv2/document/Table
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
    at java.lang.Class.getMethod0(Class.java:3018)
    at java.lang.Class.getMethod(Class.java:1784)
    at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
    at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
Caused by: java.lang.ClassNotFoundException: com.amazonaws.services.dynamodbv2.document.Table
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 7 more
c4b301bb8ad9:myapp StackOverflowUser$

The Java version I am running is...

StackOverflowUser$ java -version
java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)

And I am running this jar file with this Mac version...

I tried adding to pom.xml:

  <build>
    <plugins>
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <configuration>
          <archive>
            <manifest>
              <mainClass>org.example.basicapp.MoviesCreateTable</mainClass>
            </manifest>
          </archive>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
      </plugin>
    </plugins>
  </build>

And then:

$ ./../mvn clean compile assembly:single

But when I run it I get:

$ java -cp target/myapp-1.0-SNAPSHOT.jar org.example.basicapp.MoviesCreateTable
Error: Could not find or load main class org.example.basicapp.MoviesCreateTable

Do you use the same pom.xml as the one in github.com/JohnReedLOL/DynamoDBTutorial/blob/master/pom.xml ? Do you see aws-java-sdk jar file in your local .m2 repository ? — Shmulik Klein
– Shmulik Klein, Commented Jan 20, 2018 at 19:12
I can't seem to find a directory named .m2 in my project or in the unzipped jar file. — Michael Lafayette
– Michael Lafayette, Commented Jan 20, 2018 at 19:45
c4b301bb8ad9:myapp StackOverflowUser$ pwd /Users/StackOverflowUser/Downloads/apache-maven-3.5.2/bin/myapp c4b301bb8ad9:myapp StackOverflowUser$ find ./ -name ".m2" c4b301bb8ad9:myapp StackOverflowUser$ — Michael Lafayette
– Michael Lafayette, Commented Jan 20, 2018 at 19:45

Shmulik Klein · Accepted Answer · 2018-01-20 20:00:59Z

1

The classloader can't load a class you are importing (com/amazonaws/services/dynamodbv2/document/Table.

You can prove this by running unzip -l myapp-1.0-SNAPSHOT.jar

It is missing because your final jar artifact is packed without its dependency (aws-java-sdk).

Please check if this dependency is reachable from your remote repository (in this case, maven central) and is downloaded to your local .m2 repository.

You can include it explicitly by using maven-assembly-plugin:

<build>
  <plugins>
    <plugin>
      <artifactId>maven-assembly-plugin</artifactId>
      <configuration>
        <archive>
          <manifest>
            <mainClass>org.example.basicapp.MoviesCreateTable</mainClass>
          </manifest>
        </archive>
        <descriptorRefs>
          <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
      </configuration>
    </plugin>
  </plugins>
</build>

And then package it by running mvn clean compile assembly:single.

A new jar will be created - myapp-1.0-SNAPSHOT-jar-with-dependencies.jar (along side your original jar),and now you don't have to specifiy the main class (you already did in the plugin configuration and it set it up to you on the jar manifest), just run java -jar target/myapp-1.0-SNAPSHOT-jar-with-dependencies.jar

edited Jan 20, 2018 at 20:00

answered Jan 20, 2018 at 18:58

Shmulik Klein

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5 Comments

Michael Lafayette Over a year ago

I can't seem to find a directory named .m2 in my project or in the unzipped jar file. The command find ./ -name ".m2" yields no results.

Michael Lafayette Over a year ago

I followed your instructions and now I'm getting: $ java -cp target/myapp-1.0-SNAPSHOT.jar org.example.basicapp.MoviesCreateTable Error: Could not find or load main class org.example.basicapp.MoviesCreateTable

Shmulik Klein Over a year ago

.m2 is an hidden directory on your home root directory - ~/.m2

Shmulik Klein Over a year ago

The new jar with dependencies will be named differently, and now you don't have to specifiy the main class (you already did in the plugin configuration and it set it up to you on the jar manifest), just run java -jar target/myapp-1.0-SNAPSHOT-jar-with-dependencies.jar

Michael Lafayette Over a year ago

When I do find ./ -name "aws-java-sdk" from the ~/.m2 directory I get .//com/amazonaws/aws-java-sdk , so it's currently there. When I run java -jar target/myapp-1.0-SNAPSHOT-jar-with-dependencies.jar it works. Thanks.

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