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Struts & Hibernate
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| | | Subject: Object Synchronization in DAO | Subject: Object Synchronization in DAO 2005-08-02 - By Chris Harrison
Back
Hi All,
If its local (if the DTO is not going to a remote client), why dont you use a
CMP bean to do it for you?
Chris.
-- --Original Message-- --
From: An interest list for Sun Java Center J2EE Pattern Catalog [mailto
:J2EEPATTERNS-INTEREST@(protected)]On Behalf Of Jerry Osme?a
Sent: Wednesday, 3 August 2005 9:12 AM
To: J2EEPATTERNS-INTEREST@(protected)
Subject: Re: Object Synchronization in DAO
I would assume that the User is a data transfer object(DTO), is that correct?
The way I will do this is I will modify the DTO to be sensitive to the changes
of any of its attributes. This can be done by adding a changes attribute of
type hashmap of Name/value pair to your dto. Then when an attribute of this
dto changes, add the name/value pair of this attribute in the hashmap. Then
during the implementation of your DAO, you pull this list of changes and use
the name and value to generate the sql accordingly.
for e.g.
Class User {
String name;
String userId;
HashMap changes;
Public User () {
changes = new HasMap();
}
setUserId(String userId)
{
this.userId = userId;
fireChanges("userId", userId); <-- you can also make a condition such that
if the value is Null or the same as the old value do not trigger the change.
}
fireChanges(String name, String value)
{
changes.put(name, value);
}
}
In your DAO implementation get the changes map and loop thru it. Based on its
name, generate the corresponding sql and bind the corresponding value.
Hope this helps.
Regards,
Jerry
Maciej Gawinecki <d299052@(protected)> wrote:
Imagine the situation from client side of DAO Design Pattern
class User {
String name;
int userID;
...
}
...
User user = UserDAO.findUser(UserID);
user.setName("Johny");
UserDAO.updateUser(user);
...
In what a way UserDAO could guess which record in DB should be updated, if
information contained in 'user' class are ambiguous, e.g. supposing there
doesn't exist any unique primary key like userID?
Any help would be appreciated,
Maciej
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<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=109551523-02082005>Hi
All,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=109551523-02082005></SPAN></FONT><FONT face=Arial color=#0000ff
size=2><SPAN class=109551523-02082005></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=109551523-02082005>If
its
local (if the DTO is not going to a remote client), w</SPAN></FONT><FONT
face=Arial color=#0000ff size=2><SPAN class=109551523-02082005>hy dont
you use a CMP bean to do it for you?</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2></FONT> </DIV>
<DIV><SPAN class=109551523-02082005><FONT face=Arial color=#0000ff
size=2>Chris.</FONT></SPAN></DIV>
<DIV><FONT face=Arial color=#0000ff size=2></FONT> </DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-- --Original Message-- --<BR><B>From:</B> An interest list for Sun
Java Center J2EE Pattern Catalog
[mailto:J2EEPATTERNS-INTEREST@(protected)]<B>On Behalf Of </B>Jerry
Osme?a<BR><B>Sent:</B> Wednesday, 3 August 2005 9:12 AM<BR><B>To:</B>
J2EEPATTERNS-INTEREST@(protected)<BR><B>Subject:</B> Re: Object
Synchronization in DAO<BR><BR></FONT></DIV>
<DIV>I would assume that the User is a data transfer object(DTO), is that
correct?</DIV>
<DIV> </DIV>
<DIV>The way I will do this is I will modify the DTO to be sensitive to the
changes of any of its attributes. This can be done by adding a changes
attribute of type hashmap of Name/value pair to your dto. Then when an
attribute of this dto changes, add the name/value pair of this attribute in
the hashmap. Then during the implementation of your DAO, you pull this list
of
changes and use the name and value to generate the sql accordingly.</DIV>
<DIV> </DIV>
<DIV>for e.g.</DIV>
<DIV> </DIV>
<DIV>Class User {</DIV>
<DIV>String name;</DIV>
<DIV>String userId;</DIV>
<DIV>HashMap changes;</DIV>
<DIV> </DIV>
<DIV>Public User () {</DIV>
<DIV> changes = new HasMap();</DIV>
<DIV>}</DIV>
<DIV> </DIV>
<DIV>setUserId(String userId)</DIV>
<DIV>{</DIV>
<DIV> this.userId = userId; </DIV>
<DIV> fireChanges("userId", userId); <-- you can also
make a condition such that if the value is Null or the same as the old value
do not trigger the change.</DIV>
<DIV>}</DIV>
<DIV> </DIV>
<DIV>fireChanges(String name, String value)</DIV>
<DIV>{</DIV>
<DIV> changes.put(name, value); </DIV>
<DIV>}</DIV>
<DIV> </DIV>
<DIV>}</DIV>
<DIV> </DIV>
<DIV>In your DAO implementation get the changes map and loop thru it. Based
on
its name, generate the corresponding sql and bind the corresponding
value.</DIV>
<DIV> </DIV>
<DIV>Hope this helps.</DIV>
<DIV> </DIV>
<DIV>Regards,</DIV>
<DIV> </DIV>
<DIV>Jerry<BR><B><I>Maciej Gawinecki <d299052@(protected)></I></B>
wrote:</DIV>
<BLOCKQUOTE class=replbq
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid"
>Imagine
the situation from client side of DAO Design Pattern<BR><BR>class User
{<BR>String name;<BR>int userID;<BR>...<BR>}<BR><BR><BR>...<BR>User user =
UserDAO.findUser(UserID);<BR>user.setName("Johny");<BR>UserDAO.updateUser
(user);<BR>...<BR><BR>In
what a way UserDAO could guess which record in DB should be updated,
if<BR>information contained in 'user' class are ambiguous, e.g. supposing
there<BR>doesn't exist any unique primary key like userID?<BR><BR>Any help
would be
appreciated,<BR><BR>Maciej<BR><BR>=========================================
===========================<BR>Companion
Site: http://www.corej2eepatterns.com<BR>J2EE BluePrints:
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>Unsubscribing:
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listserv@(protected)<BR></BLOCKQUOTE>
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