Java.lang.noclassdeffounderror: Org/mozilla/javascript/evaluatorexception

7 min read Oct 15, 2024

The java.lang.NoClassDefFoundError: org/mozilla/javascript/EvaluatorException is a common error encountered in Java applications that use the Rhino JavaScript engine. This error occurs when the Java Virtual Machine (JVM) cannot locate the EvaluatorException class, which is part of the Rhino JavaScript library.

Let's explore the causes and solutions for this frustrating error.

Understanding the Root Cause

The NoClassDefFoundError indicates that the JVM is unable to find the required class definition at runtime. In the context of the org/mozilla/javascript/EvaluatorException, the JVM cannot locate the EvaluatorException class within the Rhino JavaScript library. This problem usually arises from one of the following scenarios:

Missing Rhino JAR: The most common reason is that the Rhino JavaScript library JAR file is not included in your project's classpath. The Rhino JAR file (usually named rhino.jar) contains the necessary classes, including EvaluatorException.
Incorrect Classpath: Even if you have the Rhino JAR file, if it's not correctly specified in your project's classpath, the JVM won't be able to find it.
Conflicting JARs: You might have multiple versions of the Rhino JAR in your project's classpath, potentially causing conflicts. This can happen if you have conflicting dependencies in your project's build setup.
Packaging Issue: If your application is packaged as an executable JAR or WAR, the Rhino JAR might not be included properly. This can happen if the JAR file is not explicitly added to the packaging process.

Troubleshooting and Solutions

Here's a step-by-step guide to troubleshoot and fix the java.lang.NoClassDefFoundError: org/mozilla/javascript/EvaluatorException:

1. Verify Rhino JAR Inclusion

Maven/Gradle: If you are using a build tool like Maven or Gradle, make sure you have the Rhino dependency properly declared in your project's pom.xml or build.gradle file. The dependency should look like this:
```
    org.mozilla
    rhino
    1.7.14 
```
Manual Inclusion: If you are not using a build tool, manually include the Rhino JAR file in your project's classpath. You can do this by adding the path to the JAR file in the CLASSPATH environment variable or by specifying it in your application's launch configuration.

2. Check Your Classpath

Maven/Gradle: Ensure that the Rhino JAR is being included in your project's classpath by examining the output of your build process.
Manual Configuration: If you are manually setting the classpath, carefully review your configuration to make sure that the Rhino JAR file is listed correctly.

3. Address Conflicting JARs

Dependency Management: If you are using a build tool, carefully examine your project's dependencies to ensure there are no conflicts regarding the Rhino library. You might need to specify a specific version of Rhino to avoid conflicts.
Manual Inspection: If you are manually managing your JAR files, carefully inspect your project to find any potential duplicates or conflicting versions of the Rhino JAR.

4. Ensure Proper Packaging

Executable JAR: When creating an executable JAR file, ensure that the Rhino JAR is included in the final package. You can use tools like jar or maven-jar-plugin to include dependencies.
WAR File: When creating a WAR file, the Rhino JAR should be placed in the WEB-INF/lib directory.

Examples:

Example 1: Maven Dependency


  org.mozilla
  rhino
  1.7.14

Example 2: Classpath Configuration

java -cp .:rhino.jar MyApplication

Example 3: Maven Packaging


  org.apache.maven.plugins
  maven-jar-plugin
  3.2.0
  
    
      
        true
      
    
    
      **/rhino.jar

Conclusion

The java.lang.NoClassDefFoundError: org/mozilla/javascript/EvaluatorException is a clear signal that the Rhino JavaScript library is not properly included in your Java project. By carefully checking the Rhino JAR inclusion, classpath configuration, addressing potential conflicts, and ensuring proper packaging, you can resolve this error and continue using the power of Rhino for JavaScript execution within your Java applications.