IllegalArgumentException: argument type mismatch in Hibernate

Question

Out of the blue I started getting “IllegalArgumentException: argument type mismatch” in hibernate. The hibernate entity was working for quite some time and svn logs confirm the code to be intact. What might be the case? Here’s part of the exception ``` Jan 16, 2010 10:47:09 PM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet Faces Servlet threw exception java.lang.IllegalArgumentException: argument type mismatch at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:42) at org.hibernate.tuple.entity.AbstractEntityTuplizer.setPropertyValues(AbstractEntityTuplizer.java:337) at org.hibernate.tuple.entity.PojoEntityTuplizer.setPrope…

Accepted Answer

Translation: Hibernate provides an argument of wrong type when trying to invoke a setter method.

My first step would be to find out which setter that is (for instance by debugging the application in eclipse, setting an exception break point, and inspecting the stack variables once the breakpoint is reached).

Edit: What is the signature of the setter for the mapped property `qs`? It should take a `Set<Q>`.

IllegalArgumentException: argument type mismatch in Hibernate

Solution

Problem