Jörg Schaible wrote:
Is it binary backward compatible?
I think it is, but I'm not 100% certain; it's confusing.
I ran clirr on dbutils-1.2 and my locally built 1.3-SNAPSHOT; it found one
clear compatibility error which I just fixed (DBUTILS-61). This is what
it says as of r832529:
INFO: 7011: org.apache.commons.dbutils.ProxyFactory: Method 'public
java.lang.Object newProxyInstance(java.lang.Class,
java.lang.reflect.InvocationHandler)' has been added
INFO: 7011: org.apache.commons.dbutils.ResultSetIterator: Method 'public
java.lang.Iterable iterable(java.sql.ResultSet)' has been added
ERROR: 7006: org.apache.commons.dbutils.ResultSetIterator: Return type of
method 'public java.lang.Object next()' has been changed to java.lang.Object[]
INFO: 7011: org.apache.commons.dbutils.ResultSetIterator: Method 'public
java.lang.Object next()' has been added
INFO: 8000: org.apache.commons.dbutils.handlers.AbstractKeyedHandler: Class
org.apache.commons.dbutils.handlers.AbstractKeyedHandler added
ERROR: 7006: org.apache.commons.dbutils.handlers.AbstractListHandler: Return
type of method 'public java.lang.Object handle(java.sql.ResultSet)' has been
changed to java.util.List
INFO: 7011: org.apache.commons.dbutils.handlers.AbstractListHandler: Method
'public java.lang.Object handle(java.sql.ResultSet)' has been added
ERROR: 7006: org.apache.commons.dbutils.handlers.ArrayHandler: Return type of
method 'public java.lang.Object handle(java.sql.ResultSet)' has been changed to
java.lang.Object[]
INFO: 7011: org.apache.commons.dbutils.handlers.ArrayHandler: Method 'public
java.lang.Object handle(java.sql.ResultSet)' has been added
ERROR: 7006: org.apache.commons.dbutils.handlers.ArrayListHandler: Return type
of method 'protected java.lang.Object handleRow(java.sql.ResultSet)' has been
changed to java.lang.Object[]
INFO: 7011: org.apache.commons.dbutils.handlers.ArrayListHandler: Method
'protected java.lang.Object handleRow(java.sql.ResultSet)' has been added
ERROR: 7006: org.apache.commons.dbutils.handlers.BeanListHandler: Return type
of method 'public java.lang.Object handle(java.sql.ResultSet)' has been changed
to java.util.List
INFO: 7011: org.apache.commons.dbutils.handlers.BeanListHandler: Method 'public
java.lang.Object handle(java.sql.ResultSet)' has been added
INFO: 5000: org.apache.commons.dbutils.handlers.KeyedHandler: Added
org.apache.commons.dbutils.handlers.AbstractKeyedHandler to the list of
superclasses
INFO: 7000: org.apache.commons.dbutils.handlers.KeyedHandler: Method 'protected
java.util.Map createMap()' is now implemented in superclass
org.apache.commons.dbutils.handlers.AbstractKeyedHandler
ERROR: 7006: org.apache.commons.dbutils.handlers.KeyedHandler: Return type of
method 'protected java.lang.Object createRow(java.sql.ResultSet)' has been
changed to java.util.Map
INFO: 7011: org.apache.commons.dbutils.handlers.KeyedHandler: Method 'protected
java.lang.Object createRow(java.sql.ResultSet)' has been added
INFO: 7003: org.apache.commons.dbutils.handlers.KeyedHandler: Method 'public
java.lang.Object handle(java.sql.ResultSet)' has been removed, but an inherited
definition exists.
ERROR: 7006: org.apache.commons.dbutils.handlers.MapHandler: Return type of
method 'public java.lang.Object handle(java.sql.ResultSet)' has been changed to
java.util.Map
INFO: 7011: org.apache.commons.dbutils.handlers.MapHandler: Method 'public
java.lang.Object handle(java.sql.ResultSet)' has been added
ERROR: 7006: org.apache.commons.dbutils.handlers.MapListHandler: Return type of
method 'protected java.lang.Object handleRow(java.sql.ResultSet)' has been
changed to java.util.Map
INFO: 7011: org.apache.commons.dbutils.handlers.MapListHandler: Method
'protected java.lang.Object handleRow(java.sql.ResultSet)' has been added
All of the errors are complaints about covariant return types. In each
case, something that used to return an Object now returns a more specific
type (e.g. List or Object[]).
But it's confusing, because Java handles covariant return types by
generating replacement methods in the bytecode. So there IS still a
method that returns Object in the bytecode.
For example, according to Jad, BeanListHandler.class decompiles like this:
public List handle(ResultSet rs) throws SQLException {
return convert.toBeanList(rs, type);
}
public volatile Object handle(ResultSet resultset) throws SQLException {
return handle(resultset);
}
Strangely, Clirr is reporting this as an ERROR that the method has
changed, followed by an INFO remark that a new method was added that just
happens to be exactly like the old method! (I guess the new signature
isn't exactly the same, since it is marked "volatile" ...?)
I believe none of these errors are really errors. I tested this by
creating a subclass of KeyedHandler like this:
public class MyKeyedHandler extends KeyedHandler {
public boolean hit = false;
@Override
protected Object createRow(ResultSet rs) throws SQLException {
hit = true;
return super.createRow(rs);
}
}
I used that to create a jar called "backcompat.jar"
I then copied KeyedHandlerTest from 1.2 and changed it to refer to
MyKeyedHandler. I also added assertions that "hit" turned to true when it
was invoked. I ran the test against 1.2 and backcompat.jar and it passed;
then I replaced the 1.2 jar with the 1.3 jar and it again passed, with no
changes to backcompat.jar.
So it seems to me that all of these errors aren't really errors, but
rather bugs in clirr.
-Dan
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