It is unclear to me why JdbcJobInstanceDao inserts 0L values into the JOB_PARAMS table instead of NULL. This results, in example of a String parameter type, to the value 01 Jan 1970 in the column JOB_PARAMS.DATE_VAL, while it should be NULL. In my opinion the absence of an object is something different then a value of 0L.
The same goes voor the columns STRING_VAL, LONG_VAL, DOUBLE_VAL.

Example:
Actual code, line 142-144 of JdbcJobInstanceDao:
if (type == ParameterType.STRING) {
args = new Object[] { jobId, key, type, value, new Timestamp(0L), new Long(0), new Double(0) };
}

Fix:
if (type == ParameterType.STRING) {
args = new Object[] { jobId, key, type, value, null, null, null };
}



Mind that the schema allows null values.