Bugs item #837092, was opened at 2003-11-06 12:06
Message generated for change (Comment added) made by loubyansky
You can respond by visiting:
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Category: JBossCMP
Group: v3.2
Status: Open
Resolution: None
Priority: 5
Submitted By: Adrian Price (adrianprice)
>Assigned to: Alexey Loubyansky (loubyansky)
Summary: CMP Field Update Optimization is Broken
Initial Comment:
The mechanism for optimizing updates to CMP fields is
broken, because it makes the erroneous assumption that
the value being stored is immutable.
o.j.e.p.c.j.b.JDBCFieldBridge.setInstanceValue() or
thereabouts ignores the update if
oldValue().equals(newValue). Whilst this works for
primitives (or rather their immutable java.lang.*
wrappers), it breaks completely for mutable
serializable objects in a BLOB, because if one
retrieves such an object from a CMP field, modifies it
then updates the CMP field with the same, modified
object, that change will never get flushed to the
database and the update will have been ignored.
class MyBean implements Serializable {
int x, y;
// getters & setters...
// The correct implementation of equals() for this
class.
public boolean equals(Object o) {
if (!(o instanceof MyBean))
return false;
MyBean that = (MyBean)o;
return this == that || this.x = that.x &&
this.y = that.y;
}
/*
// Horrid kludge necessary to force JBossCMP to
store me :(
public boolean equals(Object o) {
return false;
}
*/
}
MyEntityLocal entity =
MyEntityLocalHome.findByPrimaryKey(pk);
// Retrieve bean from CMP field and modify it.
MyBean bean entity.getBean(); // CMP field getter
bean.x = 666;
bean.y = 777;
// Store modified bean. Setting field to null first
forces JBossCMP
// to recognize the update in 3.0.4 and 3.2.1, but not
3.2.2.
entity.setBean(null); // (shouldn't be necessary anyway)
entity.setBean(bean);
// TXN commit...
// asserts fail, bean not persisted. Uncommenting
Horrid Kludge forces JBossCMP v. 3.2.2 to recognize &
persist the update.
bean entity.getBean();
assert(bean.x == 666 && bean.y == 777);
----------------------------------------------------------------------
>Comment By: Alexey Loubyansky (loubyansky)
Date: 2003-11-07 19:53
Message:
Logged In: YES
user_id=543482
That is not completely correct. Check this link, for example
https://sourceforge.net/tracker/?func=detail&aid=816762&group_id=22866&atid=381174.
Current implementation relies on equals() implementation.
So, that is not the CMP engine who assumes your object is
not dirty. But you implementing equals() that way.
I can expose the mechanism that is used for Map, List, Set,
array to application developer and offer you to provide an
implementation of the following interface for MyBean to
solve the problem.
public interface CMPFieldStateFactory
{
/**
* Calculates and returns an object that represents the
state of the field value.
* The states produced by this method will be used to
check whether the field
* is dirty at commit time.
*
* @param fieldValue field's value.
* @return an object representing the field's state.
*/
Object getFieldState(Object fieldValue);
/**
* Checks whether the field's state <code>state</code>
* is equal to the field value's state (possibly,
calculated with
* the <code>getFieldState()</code> method).
*
* @param state the state to compare with field value's
state.
* @param fieldValue field's value, the state of which
will be compared
* with <code>state</code>.
* @return true if <code>state</code> equals to
<code>fieldValue</code>'s state.
*/
boolean isStateValid(Object state, Object fieldValue);
}
----------------------------------------------------------------------
Comment By: Adrian Price (adrianprice)
Date: 2003-11-06 12:10
Message:
Logged In: YES
user_id=580837
penultimate line should read:
bean = entity.getBean();
----------------------------------------------------------------------
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