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APPENDIX B n HIBERNATE TOOLS 269 n HIBERNATE TOOLS 269 You should be aware that Eclipse user libraries are not a Java standard, and do not exist as independent entities. They are merely a grouping of paths to JAR files to make configuring Eclipse projects more convenient. The user library will not reflect changes made to the underlying JAR files themselves (moving or deleting them, for instance). Because user libraries belong to the Eclipse workspace, rather than to the individual projects, you can create a library from the Window Preferences menu before you have created any projects. You should then drill down through the tree view to select the Java Build Path User Libraries node. Initially there are no user libraries configured. You will need to click the add button to create your own. You will be prompted for a name for the library. The first library will contain the JAR files for the Hibernate core. We recommend including the full version number in the library name so that you will be able to readily distinguish between versions if you are managing more than one Eclipse project in the same workspace over an extended period of time. (Hibernate updates come thick and fast!) The library name will be added to the list of libraries, but it does not yet contain any JAR files. You should select the library name in the list, and then click the Add Jars button. You now want to add all the core Hibernate 3 JAR files to the library. You can add multiple files, but not directories, so this must be carried out in two steps. You will be presented with a normal file-selection dialog. You should navigate to your core Hibernate install directory and select the hibernate3.jar file. You should select the library name and again click Add Jars, but now navigate to the lib subdirectory beneath the core Hibernate install directory. Select all the JAR files in this directory and add them to the library. Having created the core Hibernate user library, you should repeat the process to create the Hibernate Annotations user library with an appropriate version number.1 Figure B-5 shows part of an exploded view of the resulting pair of user libraries. Figure B-5. The two user libraries 1. Naturally, this step is not essential if you do not intend to use Hibernate annotations in your project. Our example assumes throughout that you will be using annotations for the project s mappings.
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268 APPENDIX B n HIBERNATE TOOLS APPENDIX B n HIBERNATE TOOLS At this point, you will have successfully completed the installation of the Hibernate Tools plug-in. There will be no immediate visible change to the layout of the workbench however, as you will see in the next step, there should be some new options for you, accessible via the various menus including a new Eclipse perspective onto some of the Hibernate workbench views. nNote If you are unable or unwilling to install the software directly from Eclipse, it is also possible to download the tools as a ZIP file from the Hibernate site and copy the plug-ins directory from the archive directly over the top of Eclipse s own plug-ins directory. You should then restart Eclipse for the changes to take effect. We do not recommend that you try this approach unless you are already comfortable with the process of installing Eclipse plug-ins in this manner. The Eclipse plug-in installation process is now quite streamlined, so it is unlikely that you will encounter any serious problems. However, if you do have problems, first check that you have the correct versions of the downloads described here, and check that you have followed the installation steps as given previously. If you are still encountering problems, you should search the Tools forum on the Hibernate Forums page (http://forum.hibernate.org) to see if other users have encountered the same problems. You should also check the Hibernate bug database (www.hibernate.org/217.html) to see if there are known problems that match yours. The Boilerplate Project Configuration Now that the tools plug-in has been installed, you are ready to set up a project that will take advantage of it. As a first step, we recommend configuring a user library to make adding the appropriate JAR files to new projects more straightforward, and to make the resulting project view less cluttered. Figure B-4 compares the view of the project s contents with and without the use of user libraries. Figure B-4. An Eclipse project using user libraries (left) compared with one using JAR files directly (right)
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APPENDIX B n HIBERNATE TOOLS 267 n HIBERNATE TOOLS 267 Figure B-2. Specifying the new download site You will then be returned to the list of sites shown in Figure B-3, where you should uncheck the Eclipse download site, as you will only be installing the Hibernate Tools plug-in. Figure B-3. Deselect the Eclipse update site. Click the Next button, and Eclipse will download the list of available updates from the updates site that you have provided. If you have not provided the correct site name, or you have other connectivity issues, you will not be able to reach this step. If you are experiencing problems, go back and check that you have configured any necessary proxy settings, and that all the appropriate URLs have been entered correctly. Once you successfully reach this step, you should select the Hibernate Tools check box and click Next. Eclipse now lists the features that will be installed and prompts you to accept the license that applies to the plug-in features. You must accept the terms and conditions of the license to proceed beyond this step. Once you have checked the Accept radio button, click the Next button. You will now be presented confirmation of the features to be installed, and given the option of installing the features to a nonstandard location. (We always accept the default installation into the Eclipse plug-ins directory.) Click Finish to proceed. Currently, the Hibernate Tools plug-in is not digitally signed. Eclipse warns you of this. In principle, it is possible that a malicious third party with access to servers between you and the Eclipse download site could substitute their own code for the Eclipse tools. In practice this is unlikely, but it is to be hoped that the Hibernate or JBoss teams will start code signing their final releases. To proceed with the plug-in installation, you must accept the verification prompt. Finally, Eclipse prompts you to restart or apply the changes directly. Generally when installing Eclipse plug-ins, it is safest to select the restart option. Though we know of no specific problems with the Hibernate Tools, we recommend choosing restart here anyway it won t be necessary to reboot the PC, though!
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266 APPENDIX B n HIBERNATE TOOLS APPENDIX B n HIBERNATE TOOLS Kit, or SDK) as the basis for installing Hibernate Tools. At the time of writing, the latest version of the SDK is 3.1.2. Eclipse can be downloaded from the Eclipse Foundation web site (www.eclipse.org). You will find a file named eclipse-SDK-3.1.2-win32.zip in the Downloads section. The Hibernate team is now employed by JBoss, who provides a branded version of Eclipse that includes the Hibernate plug-ins, including several JBoss-specific ones. This can be downloaded from the JBoss web site (http://download.jboss.com/jbosside/builds). If you choose to use this version of Eclipse, then you can omit the installation steps described in the next section. Installing the Plug-In We will now walk you through the process of installing the plug-in using Eclipse s standard updates feature. Select the Find and Install menu option from the Help Software Updates menu. You should then select the option to search for new features, as Hibernate is not a standard Eclipse SDK component. By default, Eclipse will only be aware of the Eclipse Foundation web site as a source of new Eclipse features. Click the New Remote Site button shown in the upper right of Figure B-1 to add the site from which you will obtain the Hibernate Tools plug-in. Figure B-1. By default, only www.eclipse.orgis available as a download site. You will now need to enter the URL for the site from which Eclipse will obtain the plug-in, and an informal name for the site, into the dialog shown in Figure B-2. Presently, the download site is at http://download.jboss.org/jbosside/updates/development this is unlikely to change, but if you encounter problems, you should check the http://tools.hibernate.org web site to make sure that this is still listed as the update site.
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Hibernate Tools APPENDIX B n n n Hibernate Tools APPENDIX B n n n The Hibernate Tools toolset really consists of two quite distinct tools: a set of plug-ins to enhance the Eclipse integrated development environment (IDE), and a set of tasks for the Ant build tool. They are packaged together because they share significant chunks of implementation despite their very different fa ades. We have already used one of the Ant tasks from Hibernate Tools in earlier chapters to generate our database schemas. In this appendix, we will discuss the other available tasks. First, however, we will discuss the use of the toolset as a plug-in for Eclipse. nCaution At the time of writing, Hibernate Tools is at an advanced beta stage of development. You should be aware that you may encounter rough edges and bugs when using these tools. Currently, the Ant tasks are more polished than the Eclipse plug-ins. Even so, we think that it is well worth familiarizing yourself with all these tools and even using them in production, as most of the problems can be worked around. It is beyond the scope of this book to attempt to teach you how to use Ant or Eclipse (although we do walk you through some of the less common configuration details). To get the most from this appendix, you should be familiar with both Ant and Eclipse although it is possible to use both parts of the plug-in independently. General information on the latest versions of Hibernate Tools, any changes or new features, the online documentation, and the locations of the various downloads are available from the Hibernate web site (http://tools.hibernate.org). The Eclipse Plug-In Eclipse is one of the best-known and liked Java development environments to emerge in recent years. Eclipse evolved originally as a proprietary component of IBM s WebSphere Application Developer (WSAD) environment. IBM chose to release Eclipse, the IDE, as an open source application. Thus, the open source Eclipse IDE emerged as a mature product virtually overnight. Eclipse is designed as a core application, the Eclipse platform, extended by various plug- ins, typically including Java Development Tools (JDT). For our purposes, we assume that you will start out with this combination (known rather confusingly as the Software Development
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264 APPENDIX A n MORE ADVANCED FEATURES APPENDIX A n MORE ADVANCED FEATURES Summary In this appendix, we have examined Hibernate s place in the new Enterprise Java Beans standard (EJB 3), and looked at alternative mechanisms for accessing Hibernate entities. We have shown how SQL and stored procedures can be integrated into the Hibernate environment, and we have discussed how events and listeners provide internal access to Hibernate s persistence mechanism.
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APPENDIX A n MORE ADVANCED FEATURES 263 n MORE ADVANCED FEATURES 263 { if( entity instanceof Booking ) { Booking booking = (Booking)entity; booking.setName(”unknown”); } // The flag can’t save us from ourselves here! return false; } Again, this is probably not the best way to make the changes, but it can be useful when you already have a considerable body of logic prepared to process the entity type. Overriding the Default Constructor Occasionally, you will find that it is necessary to persist a POJO that has no default constructor. Usually you will have access to the source code, and should just make the change directly. Occasionally, however, you may find that you are working with classes for which the source code is not available or that you are working with large bodies of generated objects for which it is extremely inconvenient to manage changes made to the source code. In these circumstances, it is possible to use an interceptor to replace the default object-creation logic. This technique can be used as long as you have some way of obtaining or applying default values for the parameters of the POJO s non-default constructor. Listing A-30 shows an example of the use of this technique to instantiate a POJO whose only constructor demands a String parameter. Listing A-30. Invoking a Non-Default Constructor private static class OverrideCtor implements Interceptor { public Object instantiate( String entityName, EntityMode entityMode, Serializable id) throws CallbackException { if( entityName.equals(MissingDefaultCtorClass.class.getName())) { // My call to CTor return new MissingDefaultCtorClass(”NOT SET”); } else { // Some other class -continue to default handling return null; } } // … the remaining default method declarations… }
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