MuleSoft

MuleSoft Java 17 Migration: Common Errors and How to Fix Them

DeviDevs Team
••4 min read
#mulesoft#java-17#migration#troubleshooting#jvm-errors

Migrating MuleSoft applications from Java 8/11 to Java 17 introduces several breaking changes. This troubleshooting guide covers the most common errors and their solutions.

Quick Diagnosis Checklist

Before diving into specific errors, verify your environment:

# Check Java version
java -version
 
# Verify JAVA_HOME
echo $JAVA_HOME
 
# Check MuleSoft runtime version (must be 4.4.0+ for Java 17)
mule -version

Error: InaccessibleObjectException - Module Access Denied

Symptom:

java.lang.reflect.InaccessibleObjectException: Unable to make field private final
java.lang.String java.lang.String.value accessible: module java.base does not
"opens java.lang" to unnamed module

Cause: Java 17 enforces strong encapsulation. Internal JDK APIs are no longer accessible by default.

Solution 1 - Add JVM Arguments:

<!-- In your mule-artifact.json or wrapper.conf -->
{
  "minMuleVersion": "4.4.0",
  "javaSpecificationVersions": ["17"],
  "additionalPluginDependencies": [],
  "secureProperties": [],
  "configs": {
    "wrapper.java.additional.20": "--add-opens=java.base/java.lang=ALL-UNNAMED",
    "wrapper.java.additional.21": "--add-opens=java.base/java.util=ALL-UNNAMED",
    "wrapper.java.additional.22": "--add-opens=java.base/java.lang.reflect=ALL-UNNAMED"
  }
}

Solution 2 - CloudHub 2.0 Configuration:

# In your deployment configuration
spec:
  muleAgent:
    jvmArgs: >-
      --add-opens=java.base/java.lang=ALL-UNNAMED
      --add-opens=java.base/java.util=ALL-UNNAMED
      --add-opens=java.base/java.lang.reflect=ALL-UNNAMED
      --add-opens=java.base/java.io=ALL-UNNAMED

Error: NoSuchMethodError with JAX-B/JAX-WS

Symptom:

java.lang.NoSuchMethodError: javax.xml.bind.DatatypeConverter.parseBase64Binary

Cause: JAX-B and JAX-WS were removed from JDK in Java 11+.

Solution - Add Dependencies:

<!-- In your pom.xml -->
<dependencies>
    <!-- JAX-B API -->
    <dependency>
        <groupId>jakarta.xml.bind</groupId>
        <artifactId>jakarta.xml.bind-api</artifactId>
        <version>4.0.0</version>
    </dependency>
 
    <!-- JAX-B Implementation -->
    <dependency>
        <groupId>org.glassfish.jaxb</groupId>
        <artifactId>jaxb-runtime</artifactId>
        <version>4.0.2</version>
    </dependency>
 
    <!-- JAX-WS if needed -->
    <dependency>
        <groupId>jakarta.xml.ws</groupId>
        <artifactId>jakarta.xml.ws-api</artifactId>
        <version>4.0.0</version>
    </dependency>
</dependencies>

Error: Illegal Reflective Access - Nashorn Script Engine

Symptom:

java.lang.IllegalAccessError: class org.mule.weave.v2.module.native.NativeRuntime
cannot access class jdk.nashorn.api.scripting.NashornScriptEngine

Cause: Nashorn JavaScript engine was removed in Java 15+.

Solution - Use GraalJS:

<!-- Replace Nashorn with GraalJS -->
<dependency>
    <groupId>org.graalvm.js</groupId>
    <artifactId>js</artifactId>
    <version>23.0.2</version>
</dependency>
<dependency>
    <groupId>org.graalvm.js</groupId>
    <artifactId>js-scriptengine</artifactId>
    <version>23.0.2</version>
</dependency>

Update your script references:

// Old (Nashorn)
ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
 
// New (GraalJS)
ScriptEngine engine = new ScriptEngineManager().getEngineByName("graal.js");

Error: ClassNotFoundException for sun.misc.Unsafe

Symptom:

java.lang.ClassNotFoundException: sun.misc.Unsafe

Cause: Direct usage of sun.misc.Unsafe is restricted in Java 17.

Solution:

<!-- Add JVM argument -->
--add-opens=java.base/sun.misc=ALL-UNNAMED
--add-opens=java.base/jdk.internal.misc=ALL-UNNAMED

Better Long-term Fix - Use VarHandle:

// Old (sun.misc.Unsafe)
Unsafe unsafe = Unsafe.getUnsafe();
unsafe.putLong(object, offset, value);
 
// New (VarHandle - Java 9+)
VarHandle handle = MethodHandles.lookup()
    .findVarHandle(MyClass.class, "myField", long.class);
handle.set(object, value);

Error: SSL/TLS Handshake Failures

Symptom:

javax.net.ssl.SSLHandshakeException: Received fatal alert: handshake_failure

Cause: Java 17 disabled weak TLS algorithms by default.

Solution 1 - Update Target Systems:

Upgrade servers to support TLS 1.2+ with modern cipher suites.

Solution 2 - Temporary Workaround (Not Recommended for Production):

# In java.security file or via system property
jdk.tls.disabledAlgorithms=SSLv3, RC4, DES, MD5withRSA, \
    DH keySize < 1024, EC keySize < 224, 3DES_EDE_CBC

Solution 3 - Configure Specific Ciphers:

<tls:context name="Legacy_TLS_Context">
    <tls:trust-store path="truststore.jks" password="${secure::truststore.pass}"/>
    <tls:key-store path="keystore.jks"
                   keyPassword="${secure::key.pass}"
                   password="${secure::keystore.pass}"/>
    <tls:protocols>
        <tls:protocol value="TLSv1.2"/>
        <tls:protocol value="TLSv1.3"/>
    </tls:protocols>
</tls:context>

Error: DataWeave Memory Issues

Symptom:

com.mulesoft.weave.core.WeaveException: Memory limit exceeded

Cause: Java 17's G1GC has different default heap behavior.

Solution - Tune GC Settings:

# wrapper.conf or JVM arguments
wrapper.java.additional.30=-XX:+UseG1GC
wrapper.java.additional.31=-XX:MaxGCPauseMillis=200
wrapper.java.additional.32=-XX:G1HeapRegionSize=16m
wrapper.java.additional.33=-XX:InitiatingHeapOccupancyPercent=45
wrapper.java.additional.34=-Xms2g
wrapper.java.additional.35=-Xmx4g

Error: MVEL Compilation Failures

Symptom:

org.mvel2.CompileException: could not access field

Cause: MVEL uses reflection that's restricted in Java 17.

Solution:

<!-- Add these JVM arguments -->
--add-opens=java.base/java.lang=ALL-UNNAMED
--add-opens=java.base/java.util=ALL-UNNAMED
--add-opens=java.base/java.lang.reflect=ALL-UNNAMED
--add-opens=java.base/java.text=ALL-UNNAMED
--add-opens=java.desktop/java.awt.font=ALL-UNNAMED

Complete JVM Arguments Template

Here's a comprehensive set of JVM arguments for Java 17 migration:

# wrapper.conf - Complete Java 17 compatibility settings
 
# Module access for common reflection scenarios
wrapper.java.additional.20=--add-opens=java.base/java.lang=ALL-UNNAMED
wrapper.java.additional.21=--add-opens=java.base/java.util=ALL-UNNAMED
wrapper.java.additional.22=--add-opens=java.base/java.lang.reflect=ALL-UNNAMED
wrapper.java.additional.23=--add-opens=java.base/java.io=ALL-UNNAMED
wrapper.java.additional.24=--add-opens=java.base/java.nio=ALL-UNNAMED
wrapper.java.additional.25=--add-opens=java.base/java.text=ALL-UNNAMED
wrapper.java.additional.26=--add-opens=java.base/java.time=ALL-UNNAMED
wrapper.java.additional.27=--add-opens=java.base/sun.nio.ch=ALL-UNNAMED
wrapper.java.additional.28=--add-opens=java.base/sun.security.ssl=ALL-UNNAMED
wrapper.java.additional.29=--add-opens=java.base/sun.security.util=ALL-UNNAMED
 
# For XML processing
wrapper.java.additional.30=--add-opens=java.xml/com.sun.org.apache.xerces.internal.parsers=ALL-UNNAMED
wrapper.java.additional.31=--add-opens=java.xml/com.sun.org.apache.xalan.internal.xsltc.trax=ALL-UNNAMED
 
# For management/monitoring
wrapper.java.additional.32=--add-opens=java.management/sun.management=ALL-UNNAMED
 
# GC optimization
wrapper.java.additional.40=-XX:+UseG1GC
wrapper.java.additional.41=-XX:MaxGCPauseMillis=200

Migration Checklist

Follow this checklist for smooth migration:

  1. Runtime Version: Ensure MuleSoft 4.4.0+ (4.5.0+ recommended)
  2. Anypoint Studio: Update to 7.15+ for Java 17 support
  3. Dependencies: Audit all custom Java dependencies for Java 17 compatibility
  4. Connectors: Update to latest connector versions
  5. Test Environment: Test thoroughly in non-production first
  6. JVM Arguments: Apply module access arguments as needed
  7. Monitoring: Monitor memory and GC after migration
  8. Rollback Plan: Keep Java 11 deployment ready for quick rollback

Need Expert Help?

MuleSoft Java 17 migration can be complex, especially for large enterprise applications. Our team specializes in:

  • Migration assessment and planning
  • Custom connector Java 17 compatibility fixes
  • Performance optimization post-migration
  • 24/7 production support during migration

Contact us for a free migration assessment

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