Alexander Zapletal created OWB-1234:
---------------------------------------
Summary: generic classes are not correctly proxied when bridge
methods are involved
Key: OWB-1234
URL: https://issues.apache.org/jira/browse/OWB-1234
Project: OpenWebBeans
Issue Type: Bug
Components: Interceptor and Decorators
Affects Versions: 2.0.4
Reporter: Alexander Zapletal
The proxy generated by _NormalScopeProxyFactory_ does not contain (overriding)
proxy methods for bridge methods, because brdige methods are generally ignored
by the proxy generation, see _AbstractProxyFactory.unproxyableMethod()_ and
_ClassUtil.addNonPrivateMethods()_ .
(See also OWP-923)
But this can lead to wrong proxies:
{code:java}
interface Contract {
void doIt(Integer param);
}
{code}
{code:java}
public class BaseBean<T extends Number> {
public void doIt(T param) {
}
}
{code}
{code:java}
@ApplicationScoped
public class MyBean extends BaseBean<Integer> implements Contract {
}
{code}
When compiling this code the compiler performs type erasure and needs to
generate a bridge method. The generated byte code corresponds (roughly) to the
following code:
{code:java}
public class BaseBean {
public void doIt(Number param) {
}
}
{code}
{code:java}
public class MyBean {
// bridge method!
public void doIt(Integer param) {
super.doIt(param);
}
}
{code}
_NormalScopeProxyFactory_ generates a proxy class that (roughly) corresponds to
the following code:
{code:java}
public class MyBean$$OwbNormalScopeProxy extends MyBean {
public void doIt(Number var1) {
((MyBean)this.owbContextualInstanceProvider.get()).doIt(var1);
}
}
{code}
But when we now call, for instance, _doIt(4711)_ on an injected instance of
_Contract_ , we actually call _MyBean.doIt(Integer)_ and thereby we bypass the
proxy!
{code:java}
@Inject Contract handler;
handler.doIt(4711)
{code}
Reason: When _NormalScopeProxyFactory_ generated the proxy for _MyBean,_ it
found the following two methods (amongst others):
{code:java}
void doIt(Number var1) // inherited from BaseBean
void doIt(Integer var1) // bridge method
{code}
Since _NormalScopeProxyFactory_ ignores bridge methods, it only generated a
proxy method for _doIt(Number)_ . This method *overloads*
_MyBean.doIt(Integer)_ , it does not *override* it. So, _handler.doIt(4711)_
actually calls _MyBean.doIt(Integer)_ .
*IMPORTANT NOTE:* There is a quite simple workaround for this problem: Just
implement the bridge method yourself. I.e. in the example above use the
following implementation
{code:java}
@ApplicationScoped
public class MyBean extends BaseBean<Integer> implements Contract {
@Override
public void doIt(Integer param) {
super.doIt(param);
}
}
{code}
Now, the method _doIt(Integer)_ is not a bridge method anymore and
_NormalScopeProxyFactory_ will generate a proxy method for it.
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