Configuring an `exception-output-type` in the logging\json-formatter breaks logging exceptions

Edgar Vonk

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Mar 31, 2026, 8:29:58 AMMar 31

to WildFly

We have configured our WildFly (bootable JAR) application to use JSON structured logging. We notice however that when setting the `exception-output-type` attribute (to any value), that no exceptions are logged at all anymore. Normal log messages are still logged fine.
Without setting the `exception-output-type` attribute both exceptions and normal messages are logged just fine (and in JSON).

Could this be a bug, or is this intended behavior, or a some misconfiguration on our side maybe?

Excerpt from our WildFly configuration CLI script:

```
# Configure JSON log output format for structured logging.
# This enables log aggregation tools to parse and index log messages including any added log context.
# Note: `exception-output-type` is intentionally not set.
# Setting it to any value (`formatted`, `detailed`, or `detailed-and-formatted`) results in WildFly silently dropping all log records containing exceptions.
# The default behaviour already includes exception details in the JSON output.
/subsystem=logging/json-formatter=JSON:add( \
pretty-print=false, \
meta-data={ \
"service"=>"zac" \
} \
)
/subsystem=logging/console-handler=CONSOLE:write-attribute(name=named-formatter, value=JSON)
```

Edgar Vonk

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Mar 31, 2026, 8:34:33 AMMar 31

to WildFly

Forgot to mention: we are using WildFly 39.0.0 Final.

James Perkins

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Apr 10, 2026, 1:03:30 PMApr 10

to WildFly

Sorry for the late reply, I thought I had already sent it :)

The default should be detailed so you should get the stack trace in a key of "exception". I used pretty printing for my example so it's easier to read:

{
"timestamp": "2026-04-10T10:01:57.117-07:00",
"sequence": 110,
"loggerClassName": "org.jboss.logging.Logger",
"loggerName": "dev.resteasy.examples.resources.ErrorResource",
"level": "ERROR",
"message": "Logged error with stack trace",
"threadName": "default task-2",
"threadId": 380,
"mdc": {
},
"ndc": "",
"hostName": "stalefish",
"processName": "/usr/lib/jvm/java-25-openjdk/bin/java",
"processId": 2904098,
"exception": {
"refId": 1,
"exceptionType": "java.lang.RuntimeException",
"message": "Created for testing",
"frames": [
{
"class": "dev.resteasy.examples.resources.ErrorResource",
"method": "produceStackTrace",
"line": 37
},
{
"class": "dev.resteasy.examples.resources.ErrorResource$Proxy$_$$_WeldClientProxy",
"method": "produceStackTrace"
},
{
"class": "jdk.internal.reflect.DirectMethodHandleAccessor",
"method": "invoke",
"line": 104
},
{
"class": "java.lang.reflect.Method",
"method": "invoke",
"line": 565
},
{
"class": "org.jboss.resteasy.core.MethodInjectorImpl",
"method": "invoke",
"line": 154
},
{
"class": "org.jboss.resteasy.core.MethodInjectorImpl",
"method": "invoke",
"line": 118
},
{
"class": "org.jboss.resteasy.core.ResourceMethodInvoker",
"method": "internalInvokeOnTarget",
"line": 560
},
{
"class": "org.jboss.resteasy.core.ResourceMethodInvoker",
"method": "invokeOnTargetAfterFilter",
"line": 452
},
{
"class": "org.jboss.resteasy.core.ResourceMethodInvoker",
"method": "lambda$invokeOnTarget$2",
"line": 413
},
{
"class": "org.jboss.resteasy.core.interception.jaxrs.PreMatchContainerRequestContext",
"method": "filter",
"line": 321
},
{
"class": "org.jboss.resteasy.core.ResourceMethodInvoker",
"method": "invokeOnTarget",
"line": 415
},
{
"class": "org.jboss.resteasy.core.ResourceMethodInvoker",
"method": "invoke",
"line": 378
},
{
"class": "org.jboss.resteasy.core.ResourceMethodInvoker",
"method": "invoke",
"line": 356
},
{
"class": "org.jboss.resteasy.core.ResourceMethodInvoker",
"method": "invoke",
"line": 70
},
{
"class": "org.jboss.resteasy.core.SynchronousDispatcher",
"method": "invoke",
"line": 429
},
{
"class": "org.jboss.resteasy.core.SynchronousDispatcher",
"method": "lambda$invoke$4",
"line": 240
},
{
"class": "org.jboss.resteasy.core.SynchronousDispatcher",
"method": "lambda$preprocess$0",
"line": 154
},
{
"class": "org.jboss.resteasy.core.interception.jaxrs.PreMatchContainerRequestContext",
"method": "filter",
"line": 321
},
{
"class": "org.jboss.resteasy.core.SynchronousDispatcher",
"method": "preprocess",
"line": 157
},
{
"class": "org.jboss.resteasy.core.SynchronousDispatcher",
"method": "invoke",
"line": 229
},
{
"class": "org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher",
"method": "service",
"line": 222
},
{
"class": "org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher",
"method": "service",
"line": 55
},
{
"class": "org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher",
"method": "service",
"line": 51
},
{
"class": "jakarta.servlet.http.HttpServlet",
"method": "service",
"line": 614
},
{
"class": "io.undertow.servlet.handlers.ServletHandler",
"method": "handleRequest",
"line": 74
},
{
"class": "io.undertow.servlet.handlers.security.ServletSecurityRoleHandler",
"method": "handleRequest",
"line": 62
},
{
"class": "io.undertow.servlet.handlers.ServletChain$1",
"method": "handleRequest",
"line": 68
},
{
"class": "io.undertow.servlet.handlers.ServletDispatchingHandler",
"method": "handleRequest",
"line": 36
},
{
"class": "org.wildfly.elytron.web.undertow.server.ElytronRunAsHandler",
"method": "lambda$handleRequest$1",
"line": 68
},
{
"class": "org.wildfly.security.auth.server.FlexibleIdentityAssociation",
"method": "runAsFunctionEx",
"line": 103
},
{
"class": "org.wildfly.security.auth.server.Scoped",
"method": "runAsFunctionEx",
"line": 161
},
{
"class": "org.wildfly.security.auth.server.Scoped",
"method": "runAs",
"line": 73
},
{
"class": "org.wildfly.elytron.web.undertow.server.ElytronRunAsHandler",
"method": "handleRequest",
"line": 67
},
{
"class": "io.undertow.servlet.handlers.RedirectDirHandler",
"method": "handleRequest",
"line": 68
},
{
"class": "io.undertow.servlet.handlers.security.SSLInformationAssociationHandler",
"method": "handleRequest",
"line": 117
},
{
"class": "io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler",
"method": "handleRequest",
"line": 57
},
{
"class": "io.undertow.server.handlers.PredicateHandler",
"method": "handleRequest",
"line": 43
},
{
"class": "io.undertow.security.handlers.AbstractConfidentialityHandler",
"method": "handleRequest",
"line": 46
},
{
"class": "io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler",
"method": "handleRequest",
"line": 64
},
{
"class": "io.undertow.security.handlers.AbstractSecurityContextAssociationHandler",
"method": "handleRequest",
"line": 43
},
{
"class": "org.wildfly.elytron.web.undertow.server.servlet.CleanUpHandler",
"method": "handleRequest",
"line": 38
},
{
"class": "io.undertow.server.handlers.PredicateHandler",
"method": "handleRequest",
"line": 43
},
{
"class": "org.wildfly.extension.undertow.deployment.ControlPointDeploymentInfoConfigurator$ControlPointRequestAttributeHandler",
"method": "handleRequest",
"line": 175
},
{
"class": "org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler",
"method": "handleRequest",
"line": 44
},
{
"class": "io.undertow.server.handlers.PredicateHandler",
"method": "handleRequest",
"line": 43
},
{
"class": "io.undertow.servlet.handlers.SendErrorPageHandler",
"method": "handleRequest",
"line": 52
},
{
"class": "io.undertow.server.handlers.PredicateHandler",
"method": "handleRequest",
"line": 43
},
{
"class": "io.undertow.servlet.handlers.ServletInitialHandler",
"method": "handleFirstRequest",
"line": 271
},
{
"class": "io.undertow.servlet.handlers.ServletInitialHandler$1",
"method": "call",
"line": 130
},
{
"class": "io.undertow.servlet.handlers.ServletInitialHandler$1",
"method": "call",
"line": 127
},
{
"class": "io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1",
"method": "call",
"line": 48
},
{
"class": "io.undertow.servlet.core.ContextClassLoaderSetupAction$1",
"method": "call",
"line": 43
},
{
"class": "org.wildfly.extension.undertow.deployment.ControlPointDeploymentInfoConfigurator$1",
"method": "call",
"line": 100
},
{
"class": "org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction",
"method": "lambda$create$0",
"line": 1431
},
{
"class": "org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction",
"method": "lambda$create$0",
"line": 1431
},
{
"class": "org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction",
"method": "lambda$create$0",
"line": 1431
},
{
"class": "org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction",
"method": "lambda$create$0",
"line": 1431
},
{
"class": "io.undertow.servlet.handlers.ServletInitialHandler",
"method": "dispatchRequest",
"line": 251
},
{
"class": "io.undertow.servlet.handlers.ServletInitialHandler",
"method": "lambda$new$1",
"line": 99
},
{
"class": "io.undertow.server.Connectors",
"method": "executeRootHandler",
"line": 418
},
{
"class": "io.undertow.server.HttpServerExchange$1",
"method": "run",
"line": 938
},
{
"class": "org.jboss.threads.ContextHandler$1",
"method": "runWith",
"line": 18
},
{
"class": "org.jboss.threads.EnhancedQueueExecutor$Task",
"method": "doRunWith",
"line": 2651
},
{
"class": "org.jboss.threads.EnhancedQueueExecutor$Task",
"method": "run",
"line": 2630
},
{
"class": "org.jboss.threads.EnhancedQueueExecutor",
"method": "runThreadBody",
"line": 1622
},
{
"class": "org.jboss.threads.EnhancedQueueExecutor$ThreadBody",
"method": "run",
"line": 1589
},
{
"class": "org.xnio.XnioWorker$WorkerThreadFactory$1$1",
"method": "run",
"line": 1282
},
{
"class": "java.lang.Thread",
"method": "run",
"line": 1474
}
]
},
"service": "zac"
}

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