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ReplicationMode.LATEST_VERSION Overwrites the row in the target database if its version is earlier than the version of the object, or ignores the object otherwise. Requires enabled Hibernate optimistic concurrency control.

in the .NET framework SDK, they only work on a Windows PC with the SDK installed. You do not need the commercial Visual Studio.Net, just the downloadable SDK. The jEdit editor has a C# mode for editing, and we will build with Ant. The Ant .NET tasks have not been tested with either the Rotor public source version of .NET for FreeBSD or with the Ximian team s Mono implementation. Building a .NET client for our service is nearly identical to building a Java version: we run a program to generate the stub classes, add an entry point class, build them, and then run the program with our chosen arguments. See figure 15.5.

You may need replication when you reconcile data entered into different databases, when you re upgrading system configuration information during product upgrades (which often involves a migration to a new database instance), or when you need to roll back changes made during non-ACID transactions. You now know the persistence lifecycle and the basic operations of the persistence manager. Using these together with the persistent class mappings we discussed in earlier chapters, you may now create your own small Hibernate application. Map some simple entity classes and components, and then store and load objects in a stand-alone application. You don t need a web container or application server: Write a main() method, and call the Session as we discussed in the previous section. In the next sections, we cover the detached object state and the methods to reattach and merge detached objects between persistence contexts. This is the foundation knowledge you need to implement long units of work conversations. We assume that you re familiar with the scope of object identity as explained earlier in this chapter.

Figure 15.5 The stages of building and running a C# client match that of the Java client, except that we cannot generate unit tests automatically. We still implement the web service in Java.

Modifying the item after the Session is closed has no effect on its persistent representation in the database. As soon as the persistence context is closed, item becomes a detached instance. If you want to save modifications you made to a detached object, you have to either reattach or merge it.

Probing for the classes Because we are only supporting the Windows implementation of .NET, we can only build the .NET client on Windows, and then only those versions with the .NET SDK installed and on the PATH. How do we restrict this With a few moderately complex conditions:

Reattaching a modified detached instance A detached instance may be reattached to a new Session (and managed by this new persistence context) by calling update() on the detached object. In our experience, it may be easier for you to understand the following code if you rename the update() method in your mind to reattach() however, there is a good reason it s called updating. The update() method forces an update to the persistent state of the object in the database, always scheduling an SQL UPDATE. See listing 9.6 for an example of detached object handling.

item.setDescription(...); // Loaded in previous Session Session sessionTwo = sessionFactory.openSession(); Transaction tx = sessionTwo.beginTransaction(); sessionTwo.update(item); item.setEndDate(...); tx.commit(); sessionTwo.close();

<target name="probe_for_dotnet_apps" > <condition property="wsdl.found"> <or> <available file="wsdl" filepath="${env.PATH}" /> <available file="wsdl.exe" filepath="${env.PATH}" /> <available file="wsdl.exe" filepath="${env.Path}" /> </or> </condition> <echo> wsdl.found=${wsdl.found}</echo> <condition property="csc.found"> <or>

It doesn t matter if the item object is modified before or after it s passed to update(). The important thing here is that the call to update() is reattaching the detached instance to the new Session (and persistence context). Hibernate always treats the object as dirty and schedules an SQL UPDATE., which will be executed during flush. You can see the same unit of work in figure 9.8. You may be surprised and probably hoped that Hibernate could know that you modified the detached item s description (or that Hibernate should know you did not modify anything). However, the new Session and its fresh persistence context don t have this information. Neither does the detached object contain some internal list of all the modifications you ve made. Hibernate has to assume that an