Jackall Jackall - 17 days ago 9
Java Question

Issues while deserializing exception/throwable using Jackson in Java

I am facing issues while deserializing

Exception
and
Throwable
instances using Jackson (version 2.2.1). Consider the following snippet:

public static void main(String[] args) throws IOException
{
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true);
objectMapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
objectMapper.enableDefaultTyping(DefaultTyping.NON_FINAL, As.PROPERTY);

try {
Integer.parseInt("String");
}
catch (NumberFormatException e) {
RuntimeException runtimeException = new RuntimeException(e);
String serializedException = objectMapper.writeValueAsString(runtimeException);
System.out.println(serializedException);
Throwable throwable = objectMapper.readValue(serializedException, Throwable.class);
throwable.printStackTrace();
}
}


The output of
System.out.println
in the
catch
block is:

{
"@class" : "java.lang.RuntimeException",
"detailMessage" : "java.lang.NumberFormatException: For input string: \"String\"",
"cause" : {
"@class" : "java.lang.NumberFormatException",
"detailMessage" : "For input string: \"String\"",
"cause" : null,
"stackTrace" : [ {
"declaringClass" : "java.lang.NumberFormatException",
"methodName" : "forInputString",
"fileName" : "NumberFormatException.java",
"lineNumber" : 65
}, {
"declaringClass" : "java.lang.Integer",
"methodName" : "parseInt",
"fileName" : "Integer.java",
"lineNumber" : 492
}, {
"declaringClass" : "java.lang.Integer",
"methodName" : "parseInt",
"fileName" : "Integer.java",
"lineNumber" : 527
}, {
"declaringClass" : "test.jackson.JacksonTest",
"methodName" : "main",
"fileName" : "JacksonTest.java",
"lineNumber" : 26
} ],
"suppressedExceptions" : [ "java.util.ArrayList", [ ] ]
},
"stackTrace" : [ {
"declaringClass" : "test.jackson.JacksonTest",
"methodName" : "main",
"fileName" : "JacksonTest.java",
"lineNumber" : 29
} ],
"suppressedExceptions" : [ "java.util.ArrayList", [ ] ]
}


which seems fine. But when I attempt to deserialize this using
objectMapper.readValue()
, I get the following exception:

Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "declaringClass" (class java.lang.StackTraceElement), not marked as ignorable
at [Source: java.io.StringReader@3c5ebd39; line: 9, column: 27] (through reference chain: java.lang.StackTraceElement["declaringClass"])
at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:79)
at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty(DeserializationContext.java:555)
at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:708)
at com.fasterxml.jackson.databind.deser.std.JdkDeserializers$StackTraceElementDeserializer.deserialize(JdkDeserializers.java:414)
at com.fasterxml.jackson.databind.deser.std.JdkDeserializers$StackTraceElementDeserializer.deserialize(JdkDeserializers.java:380)
at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:151)
...


I then tried using mix-in annotations, to ignore
declaringClass
in
java.lang.StackTraceElement
, but now the deserialized
Exception
doesn't contain the declaring class in its stack trace:

java.lang.RuntimeException: java.lang.NumberFormatException: For input string: "String"
at .main(JacksonTest.java:33)
Caused by: java.lang.NumberFormatException: For input string: "String"
at .forInputString(NumberFormatException.java:65)
at .parseInt(Integer.java:492)
at .parseInt(Integer.java:527)
at .main(JacksonTest.java:30)


Am I missing anything? Any help is greatly appreciated.

Answer

There seems to be a Jackson JIRA entry for this here. Jackson doesn't seem to be able to handle the declaringClass in java.lang.StackTraceElement, since the getter corresponding to this field is called getClassName().

I fixed this issue by using a custom wrapper around StackTraceElement as suggested in the JIRA entry mentioned above. The custom wrapper (CustomStackTraceElement) will have the fields declaringClass, methodName, fileName, and lineNumber and the corresponding getters and setters in it. I modified the catch block (mentioned in the question) to be as follows:

catch (NumberFormatException e) {
    RuntimeException runtimeException = new RuntimeException(e);
    e.printStackTrace();
    String serializedException = objectMapper.writeValueAsString(runtimeException);
    System.out.println(serializedException);

    String serializedStackTrace = objectMapper.writeValueAsString(transformStackTrace(runtimeException));
    String serializedStackTraceForCause = objectMapper.writeValueAsString(transformStackTrace(runtimeException.getCause()));

    Throwable throwable = objectMapper.readValue(serializedException, Throwable.class);
    List<CustomStackTraceElement> customStackTraceElementList = objectMapper.readValue(serializedStackTrace, List.class);
    List<CustomStackTraceElement> customStackTraceElementListForCause = objectMapper.readValue(serializedStackTraceForCause, List.class);

    throwable.setStackTrace(reverseTransformStackTrace(customStackTraceElementList));
    throwable.getCause().setStackTrace(reverseTransformStackTrace(customStackTraceElementListForCause));
    throwable.printStackTrace();
}

The StackTraceElement[] will be converted into List<CustomStackTraceElement> by the following method during serialization:

private static List<CustomStackTraceElement> transformStackTrace(Throwable throwable)
{
    List<CustomStackTraceElement> list = new ArrayList<>();
    for (StackTraceElement stackTraceElement : throwable.getStackTrace()) {
        CustomStackTraceElement customStackTraceElement =
            new CustomStackTraceElement(stackTraceElement.getClassName(),
                                        stackTraceElement.getMethodName(),
                                        stackTraceElement.getFileName(),
                                        stackTraceElement.getLineNumber());

        list.add(customStackTraceElement);
    }

    return list;
}

... and the reverse transformation will be done during deserialization:

private static StackTraceElement[] reverseTransformStackTrace(List<CustomStackTraceElement> customStackTraceElementList)
{
    StackTraceElement[] stackTraceElementArray = new StackTraceElement[customStackTraceElementList.size()];
    for (int i = 0; i < customStackTraceElementList.size(); i++) {
        CustomStackTraceElement customStackTraceElement = customStackTraceElementList.get(i);
        StackTraceElement stackTraceElement =
            new StackTraceElement(customStackTraceElement.getDeclaringClass(),
                                  customStackTraceElement.getMethodName(),
                                  customStackTraceElement.getFileName(),
                                  customStackTraceElement.getLineNumber());

        stackTraceElementArray[i] = stackTraceElement;
    }

    return stackTraceElementArray;
}

Now, after deserialization, the Throwable object has the expected stack trace in it.