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【正文】 k with Hibernate, since I39。ve done so much of that recently in putting together the Developer39。s Notebook. It turns out there are several such efforts underway。 in this article we will explore one of themthe Hibernate Synchronizer.Hibernate SynchronizerOf the plugins I39。ve found so far, the Hibernate Synchronizer interested me most because it seems to best support the kind of mappingcentric workflow I adopted throughout my Developer39。s Notebook. (Hibernate can be used in many different ways, so check out the other plugins available。 these may be more helpful if your environment calls for another approach.) In fact, the Hibernate Synchronizer plugin removes the need for you to think about updating your Java code when you change your mapping document. In a very Eclipselike way, it automatically updates the Java code as you edit the mapping. But it goes even farther than Hibernate39。s builtin code generation tools by creating a pair of classes for each mapped object. It owns a base class, which it rewrites at will as you change the mapping, and gives you a subclass that extends this base class, where you can put business logic and other code, without fear that it will ever get changed out from under you. As befits an approach centered around the Hibernate mapping document, Hibernate Synchronizer includes a new editor ponent for Eclipse that provides intelligent assistance and code pletion for such documents. A nice DTDdriven XML editor, such as the aforementioned XMLBuddy, can do some of this for you, but Hibernate Synchronizer uses its semantic understanding of the documents to go much further. It also offers a graphical view of the properties and relations in the mapping, wizard interfaces for creating new elements, and other such niceties. And, as mentioned, in its default configuration the editor automatically regenerates the dataaccess classes as you edit their mapping documents. There are other pieces to Hibernate Synchronizer, too. It adds a section to Eclipse39。s New menu that provides wizards for creating Hibernate configuration and mapping files, and adds contextual menu entries in the package explorer and in other appropriate places, providing easy access to relevant Hibernate operations.OK, enough abstract description, time to get down to the practical stuff! After all, you were already probably interested in this, or you wouldn39。t have started to read the article. So how do you get and play with Hibernate Synchronizer?InstallationHibernate Synchronizer is installed using Eclipse39。s builtin Update Manager. The plugin offers separate update sites for users of Eclipse and the forthing Eclipse 3. Because I39。m using Eclipse for missioncritical work, I39。m still using the production release, . As I write this, Eclipse 3 has entered its release candidate phase, and I am very much looking forward to being able to upgrade to a production release of version 3 when I return from JavaOne later this summer. (The main reason I mention this is to emphasize that the following instructions are written from an Eclipse 2 perspective。 some mands and screens are undoubtedly different in Eclipse 3, so if you39。re using it, be sure to apply your own judgment in following these steps! If it helps, my impression is that Hibernate Synchronizer39。s own install instructions are written for Eclipse 3.)Fire up Eclipse and open the Update Manager by choosing Help Software Updates Update Manager. Once the Install/Update perspective opens up, rightclick (or controlclick, if you39。re using a onebutton mouse) in the Feature Updates view and choose New Site Bookmark. Figure 1. Adding the Hibernate Synchronizer plugin site to the Update ManagerIn the resulting dialog, enter the URL for the version of the plugin that you need. The URL to be entered depends on your Eclipse version:Eclipse : Eclipse 3: You also need to assign a name for the new bookmark. Hibernate Synchronizer makes a lot of sense. Once you click Finish, the new bookmark will appear in the Feature Updates actually install the plugin, click on the disclosure triangle to the left of the bookmark, and again on the next one that appears inside of it, until you can see the icon for the plugin itself. When you click on that, the Preview view will update to show you an interface that allows you to install the Install Now to actually install it, and let Eclipse walk you through the TradeOffs, below, for some discussion about this license agreement. You may wish to read it carefully before deciding to use Hibernate Synchronizer in a project of your own. I think it39。s probably fine, but it is confusingly based on the GPL without actually being open source. Now that the plugin is installed, you need to quit and relaunch Eclipse for it to take effect. The dialog seems to imply that Eclipse will restart itself, but in my experience, clicking Yes merely causes the environment to quit, and you have to relaunch it manually. This may be a limitation of Eclipse 39。s Mac OS X implementation。 Eclipse 3 is going to be the first release that promises firstclass support for OS X. In any case, this is a very minor issue. If you need to restart Eclipse, do so now, because it39。s time to start configuring the plugin to put it through its paces! ConfigurationOnce Eclipse es back up, you can close the Install/Update perspective. Open a Java project that uses Hibernate. If you39。ve been going through the examples in the Developer39。s Notebook, you39。ll have several directories from which to choose. I39。ll be looking at the examples as they exist in Chapter 3, which is the sample chapter available online. You can also download the source for all of the examples from the book39。s site. If you39。re creating a new Eclipse project to work with one of the example source directories, just choose File New Project, specify that you want to create a Java project and click Next, give it a name (Hibernate Ch3 in my c