[JOHNZON-151] Serializing nulls within a list, within a type or map produces unexpected results

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.1.0, 1.1.1, 1.1.2, 1.1.3, 1.1.4, 1.1.5
• Fix Version/s: 1.1.7
• Component/s: Mapper
• Assignee: Mark Struberg
• Reporter: Steven Walters
• Created: 29/Dec/17 08:33
• Updated: 26/Feb/18 12:45
• Resolved: 26/Feb/18 12:45

Description

When a Collection (such as a List) contains a null entry and is serialized through a parent map or defined type, the serialization produces unexpected results.

With 1.1.0 through 1.1.4, the nulls are silently ignored.
With 1.1.5, a NullPointerException occurs instead.
I did not check 1.0.0

Local analysis indicates that in 1.1.5, code block

MappingGeneratorImpl.java

private void writeValue(final Class<?> type, ...
...
if (objectConverterToUse == null) {
    objectConverterToUse = config.findObjectConverterWriter(o.getClass());
}

is the culprit by trying to invoke getClass() on a null object.

Nulls are ignored in 1.1.4 and prior due to code blocks

MappingGeneratorImpl.java

private void writeItem(final Object o, final Collection<String> ignoredProperties, JsonPointerTracker jsonPointer) {
    if (!writePrimitives(o)) {
        if (Collection.class.isInstance(o)) {

MappingGeneratorImpl.java

private boolean writePrimitives(final Object value) {
    boolean handled = false;
    if (value == null) {
        return true; // fake a write
    }

That is, the writeItem invokes writePrimitives and writePrimitives says it handled the null, when it in fact did nothing.

Currently serializing null within a list only produces correct results when the list is the root object of serialization.
Test cases attached; run mvn test to see include tests against 1.1.5

I've had to include our own altered copy of MappingGeneratorImpl to the classpath (at a higher priority) to workaround the issue indicated here in our project.