Pass missing argument for string formatting in ObjectMapper

[buehner]

I just upgraded the jackson dependency in a project from version 2.8.8 to 2.9.1.

We have a line of code that catches a JsonMappingException. Since upgrading to version 2.9.1, this catch block is not reached anymore - instead we get a java.util.MissingFormatArgumentException.

It seems that the following call is responsible, because the msg string contains three placeholders (%s)...

jackson-databind/src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java

Lines 3930 to 3934 in 85dafb9

	if (!expSimpleName.equals(actualName)) {
	ctxt.reportInputMismatch(rootType,
	"Root name '%s' does not match expected ('%s') for type %s",
	actualName, expSimpleName);
	}

...but in the implementation of reportInputMismatch only two arguments ( actualName and expSimpleName from above) are passed to the _format method (which again calls String.format(...)):

jackson-databind/src/main/java/com/fasterxml/jackson/databind/DeserializationContext.java

Lines 1351 to 1356 in 85dafb9

	public <T> T reportInputMismatch(JavaType targetType,
	String msg, Object... msgArgs) throws JsonMappingException
	{
	msg = _format(msg, msgArgs);
	throw MismatchedInputException.from(getParser(), targetType, msg);
	}

This will always lead to the following exception:

java.util.MissingFormatArgumentException: Format specifier '%s'

and the expected MismatchedInputException from line 1355 above (which is the JsonMappingException we try to catch in our project) will never be thrown.

This pull request fixes this bug by passing the rootType as third argument for the string formatting, which is the same approach that is already implemented in the ObjectReader class:

jackson-databind/src/main/java/com/fasterxml/jackson/databind/ObjectReader.java

Lines 1410 to 1414 in 85dafb9

	if (!expSimpleName.equals(actualName)) {
	ctxt.reportInputMismatch(rootType,
	"Root name '%s' does not match expected ('%s') for type %s",
	actualName, expSimpleName, rootType);
	}

[cowtowncoder]

Thank you for reporting this. Formatting bugs are pretty tricky; obviously higher test coverage would help here.

[cowtowncoder]

Thank you for reporting the fix -- I integrated it manually for 2.9 branch as suggested.