AGENT_ERROR_BADJAR

AGENT_ERROR_BADJAR

Error message

Error opening zip file or JAR manifest missing: %s\n

What it means

Thrown on the attach path (Agent_OnAttach, error code AGENT_ERROR_BADJAR = 100): the native code could not open the given JAR as a zip or could not find/parse META-INF/MANIFEST.MF inside it, so readAttributes returned NULL. The attach fails and the attach API raises AgentInitializationException with return code 100.

Source

Thrown at src/java.instrument/share/native/libinstrument/InvocationAdapter.c:342

    if (parseArgumentTail(args, &jarfile, &options) != 0) {
        return JNI_ENOMEM;
    }

    jboolean print_warning = JVM_PrintWarningAtDynamicAgentLoad();
    initerror = createNewJPLISAgent(vm, &agent, jarfile, print_warning);
    if ( initerror == JPLIS_INIT_ERROR_NONE ) {
        int             oldLen, newLen;
        jarAttribute*   attributes;
        char *          agentClass;
        char *          bootClassPath;
        jboolean        success;

        /*
         * Open the JAR file and parse the manifest
         */
        attributes = readAttributes( jarfile );
        if (attributes == NULL) {
            fprintf(stderr, "Error opening zip file or JAR manifest missing: %s\n", jarfile);
            free(jarfile);
            if (options != NULL) free(options);
            return AGENT_ERROR_BADJAR;
        }

        agentClass = getAttribute(attributes, "Agent-Class");
        if (agentClass == NULL) {
            fprintf(stderr, "Failed to find Agent-Class manifest attribute from %s\n",
                jarfile);
            free(jarfile);
            if (options != NULL) free(options);
            freeAttributes(attributes);
            return AGENT_ERROR_BADJAR;
        }

        /*
         * Add the jarfile to the system class path
         */

View on GitHub (pinned to 88dfb74bbe)

Solutions

Verify the file is a valid zip: unzip -t agent.jar (or jar tf agent.jar)
Confirm META-INF/MANIFEST.MF exists in the jar root and is parseable
Check file permissions/reads on the target JVM's working user
Rebuild or re-download the agent jar and re-attach

Example fix

# before: corrupted jar silently fails to attach
vm.loadAgent("/tmp/agent.jar");
# after: validate before attaching
try (ZipFile z = new ZipFile("/tmp/agent.jar")) {
    if (z.getEntry("META-INF/MANIFEST.MF") == null) throw new IllegalStateException("manifest missing");
}
vm.loadAgent("/tmp/agent.jar");

Defensive patterns

Strategy: validation

Validate before calling

// before vm.loadAgent(path): confirm it is a readable zip with a manifest
Path p = Path.of(agentPath);
if (!Files.isRegularFile(p) || !Files.isReadable(p)) throw new IllegalArgumentException("agent jar missing/unreadable");
try (ZipFile z = new ZipFile(p.toFile())) {
    if (z.getEntry("META-INF/MANIFEST.MF") == null) throw new IllegalArgumentException("manifest missing");
}

Try / catch

try {
    vm.loadAgent(agentPath, options);
} catch (AgentInitializationException e) {
    if (e.returnValue() == 100) { /* BADJAR: re-fetch/rebuild jar, log and alert */ }
}

Prevention

Checksum-verify agent jars (sha256) after download before attaching
Store agents in a stable directory owned by the JVM user

When it happens

Trigger: VirtualMachine.loadAgent called with a path that is not a zip/jar (corrupt download, truncated file, plain directory), a jar built without a manifest, or a file unreadable due to permissions.

Common situations: APM/profiling tools (JMC, async-profiler wrappers, APM agents) attaching to a jar corrupted in transfer; agent jar generated by a pipeline step that skipped the manifest; typo'd or relative path resolved against the wrong working directory.

Related errors

AI-assisted analysis of openjdk/jdk@88dfb74bbe (2026-08-14). Data as JSON: /api/errors/edb3eee7dfb1996e. Report an issue: GitHub.