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From: <one...@us...> - 2002-11-07 16:24:43
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Update of /cvsroot/hibernate/Hibernate/doc
In directory usw-pr-cvs1:/tmp/cvs-serv26764
Modified Files:
faq.aft faq.aft-TOC faq.html
Log Message:
new faqs
Index: faq.aft
===================================================================
RCS file: /cvsroot/hibernate/Hibernate/doc/faq.aft,v
retrieving revision 1.26
retrieving revision 1.27
diff -C2 -d -r1.26 -r1.27
*** faq.aft 30 Oct 2002 15:28:04 -0000 1.26
--- faq.aft 7 Nov 2002 16:24:07 -0000 1.27
***************
*** 55,58 ****
--- 55,96 ----
It doesn't.
+ *** I'm using a composite identifier and Hibernate causes a stack overfow!
+
+ You _must_ override |equals()| and |hashCode()| correctly on your composite identifier class. This is quite critical.
+
+ *** I'm seeing some strange behaviour with an embedded composite identifier or <key-many-to-one> when using proxies.
+
+ It is actually surprisingly hard to get your implementation of |equals()| right when proxies are enabled. You must be prepared for the possibility that that a class instance is really a proxy for that class, so you can't access instance variables directly (use the accessors).
+
+ And if you are using |<key-many-to-one>| you should compare entity equality by comparing identifiers instead of using |==|.
+
+ *** My class has two one-to-many associations to different subclasses of the same root class, but Hibernate ignores the actual concrete class when loading the associations.
+
+ This kind of mapping is unsupported:
+
+ <class name="BalanceSheet">
+ ....
+ <set role="purchases">
+ <key ....>
+ <one-to-many class="Purchase" column="bsid"/>
+ </set>
+ <set role="sales">
+ <key ....>
+ <one-to-many class="Sale" column="bsid"/>
+ </set>
+ </class>
+
+ <class name="Transaction">
+ ....
+ <subclass name="Purchase".../>
+ <subclass name="Sale".../>
+ </class>
+
+ You must either
+
+ 1. map each association to a different column of the |Transaction| table
+ 2. map a single association and use a collection filter to retrieve instances of a particular subclass
+ 3. use a table-per-concrete-class mapping strategy for the |Transaction| hierarchy
+
*** How can I count the number of query results without actually returning them?
***************
*** 85,92 ****
you will find it quite well documented.
-
- *** How can I use quoted SQL identifiers?
-
- You can't. Sorry. We will fix this at some stage....
*** What column should I map the index tag of an array or List to?
--- 123,126 ----
Index: faq.aft-TOC
===================================================================
RCS file: /cvsroot/hibernate/Hibernate/doc/faq.aft-TOC,v
retrieving revision 1.17
retrieving revision 1.18
diff -C2 -d -r1.17 -r1.18
*** faq.aft-TOC 30 Oct 2002 15:28:05 -0000 1.17
--- faq.aft-TOC 7 Nov 2002 16:24:07 -0000 1.18
***************
*** 9,12 ****
--- 9,15 ----
* {-Hibernate keeps deleting and recreating my collection!@Hibernate keeps deleting and recreating my collection!-}
* {-How does readonly="true" affect the semantics of cascade="all"@How does readonly="true" affect the semantics of cascade="all"-}
+ * {-I'm using a composite identifier and Hibernate causes a stack overfow!@I'm using a composite identifier and Hibernate causes a stack overfow!-}
+ * {-I'm seeing some strange behaviour with an embedded composite identifier or <key-many-to-one> when using proxies.@I'm seeing some strange behaviour with an embedded composite identifier or <key-many-to-one> when using proxies.-}
+ * {-My class has two one-to-many associations to different subclasses of the same root class, but Hibernate ignores the actual concrete class when loading the associations.@My class has two one-to-many associations to different subclasses of the same root class, but Hibernate ignores the actual concrete class when loading the associations.-}
* {-How can I count the number of query results without actually returning them?@How can I count the number of query results without actually returning them?-}
* {-How can I find the size of a collection without initializing it?@How can I find the size of a collection without initializing it?-}
***************
*** 14,18 ****
* {-Are collections pageable?@Are collections pageable?-}
* {-How do I specify the length of a column for the SchemExport tool? A unique column? A not-null column?@How do I specify the length of a column for the SchemExport tool? A unique column? A not-null column?-}
- * {-How can I use quoted SQL identifiers?@How can I use quoted SQL identifiers?-}
* {-What column should I map the index tag of an array or List to?@What column should I map the index tag of an array or List to?-}
* {-What are bags for?@What are bags for?-}
--- 17,20 ----
Index: faq.html
===================================================================
RCS file: /cvsroot/hibernate/Hibernate/doc/faq.html,v
retrieving revision 1.39
retrieving revision 1.40
diff -C2 -d -r1.39 -r1.40
*** faq.html 5 Nov 2002 08:04:00 -0000 1.39
--- faq.html 7 Nov 2002 16:24:08 -0000 1.40
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*** 30,33 ****
--- 30,36 ----
<li> <a href="#Hibernate keeps deleting and recreating my collection!">Hibernate keeps deleting and recreating my collection!</a></li>
<li> <a href="#How does readonly="true" affect the semantics of cascade="all"">How does readonly="true" affect the semantics of cascade="all"</a></li>
+ <li> <a href="#I'm using a composite identifier and Hibernate causes a stack overfow!">I'm using a composite identifier and Hibernate causes a stack overfow!</a></li>
+ <li> <a href="#I'm seeing some strange behaviour with an embedded composite identifier or <key-many-to-one> when using proxies.">I'm seeing some strange behaviour with an embedded composite identifier or <key-many-to-one> when using proxies.</a></li>
+ <li> <a href="#My class has two one-to-many associations to different subclasses of the same root class, but Hibernate ignores the actual concrete class when loading the associations.">My class has two one-to-many associations to different subclasses of the same root class, but Hibernate ignores the actual concrete class when loading the associations.</a></li>
<li> <a href="#How can I count the number of query results without actually returning them?">How can I count the number of query results without actually returning them?</a></li>
<li> <a href="#How can I find the size of a collection without initializing it?">How can I find the size of a collection without initializing it?</a></li>
***************
*** 35,39 ****
<li> <a href="#Are collections pageable?">Are collections pageable?</a></li>
<li> <a href="#How do I specify the length of a column for the SchemExport tool? A unique column? A not-null column?">How do I specify the length of a column for the SchemExport tool? A unique column? A not-null column?</a></li>
- <li> <a href="#How can I use quoted SQL identifiers?">How can I use quoted SQL identifiers?</a></li>
<li> <a href="#What column should I map the index tag of an array or List to?">What column should I map the index tag of an array or List to?</a></li>
<li> <a href="#What are bags for?">What are bags for?</a></li>
--- 38,41 ----
***************
*** 126,129 ****
--- 128,177 ----
</p>
<!--End Section 3-->
+ <h4><a name="I'm using a composite identifier and Hibernate causes a stack overfow!">I'm using a composite identifier and Hibernate causes a stack overfow!</a></h4>
+ <p class="Body">
+ You <strong>must</strong> override <tt>equals()</tt> and <tt>hashCode()</tt> correctly on your composite identifier class. This is quite critical.
+ </p>
+ <!--End Section 3-->
+ <h4><a name="I'm seeing some strange behaviour with an embedded composite identifier or <key-many-to-one> when using proxies.">I'm seeing some strange behaviour with an embedded composite identifier or <key-many-to-one> when using proxies.</a></h4>
+ <p class="Body">
+ It is actually surprisingly hard to get your implementation of <tt>equals()</tt> right when proxies are enabled. You must be prepared for the possibility that that a class instance is really a proxy for that class, so you can't access instance variables directly (use the accessors).
+ </p>
+ <p class="Body">
+ And if you are using <tt><key-many-to-one></tt> you should compare entity equality by comparing identifiers instead of using <tt>==</tt>.
+ </p>
+ <!--End Section 3-->
+ <h4><a name="My class has two one-to-many associations to different subclasses of the same root class, but Hibernate ignores the actual concrete class when loading the associations.">My class has two one-to-many associations to different subclasses of the same root class, but Hibernate ignores the actual concrete class when loading the associations.</a></h4>
+ <p class="Body">
+ This kind of mapping is unsupported:
+ </p>
+ <pre>
+ <class name="BalanceSheet">
+ ....
+ <set role="purchases">
+ <key ....>
+ <one-to-many class="Purchase" column="bsid"/>
+ </set>
+ <set role="sales">
+ <key ....>
+ <one-to-many class="Sale" column="bsid"/>
+ </set>
+ </class>
+ </pre>
+ <pre>
+ <class name="Transaction">
+ ....
+ <subclass name="Purchase".../>
+ <subclass name="Sale".../>
+ </class>
+ </pre>
+ <p class="Body">
+ You must either
+ </p>
+ <ol>
+ <li> map each association to a different column of the <tt>Transaction</tt> table</li>
+ <li> map a single association and use a collection filter to retrieve instances of a particular subclass</li>
+ <li> use a table-per-concrete-class mapping strategy for the <tt>Transaction</tt> hierarchy</li>
+ </ol>
+ <!--End Section 3-->
<h4><a name="How can I count the number of query results without actually returning them?">How can I count the number of query results without actually returning them?</a></h4>
<pre>
***************
*** 163,171 ****
<p class="Body">
you will find it quite well documented.
- </p>
- <!--End Section 3-->
- <h4><a name="How can I use quoted SQL identifiers?">How can I use quoted SQL identifiers?</a></h4>
- <p class="Body">
- You can't. Sorry. We will fix this at some stage....
</p>
<!--End Section 3-->
--- 211,214 ----
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