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| </head> |
| <body class="article"> |
| <div id="header"> |
| </div> |
| <div id="content"> |
| <div class="paragraph"> |
| <p><a id="architecture"></a></p> |
| </div> |
| <div class="sect1"> |
| <h2 id="_deployment_architecture">Deployment Architecture</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>The Virgo for Apache Tomcat offers several choices when it comes to deploying applications. Each |
| choice offers certain advantages, and it is important to understand those in order to make |
| the right choice for your application. In this chapter, we take a closer look at the choices |
| offered, compare them, and provide guidelines in choosing the right one based on your |
| specific needs.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The VTS supports standard self-contained WAR files thus allowing you to |
| use the Virgo for Apache Tomcat as an enhanced web server. The VTS also supports the |
| <strong>Shared Libraries</strong> WAR format which allows for slimmer WAR files that |
| depend on OSGi bundles instead of including JAR files inside the WAR. The <strong>Shared |
| Services</strong> WAR format allows developers to further reduce the complexity of |
| standard WARs by deploying services and infrastructure bundles alongside the WAR. A shared |
| services WAR will then consume the services published by those bundles. To complete the |
| picture, the VTS supports the new OSGi-standard <strong>Web Application |
| Bundle</strong> deployment format for web applications that builds on the benefits |
| provided by a shared services WAR. In addition to this, VTS provides |
| additional conveniences for developing and deploying Spring MVC-based web applications.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For applications consisting of multiple bundles and web applications, plans and the PAR |
| format are the primary deployment models that take advantage of OSGi capabilities. We will |
| explore all of these formats and their suitability later in this guide.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-deployment-formats"></a></p> |
| </div> |
| <div class="sect2"> |
| <h3 id="_supported_deployment_formats">Supported Deployment Formats</h3> |
| <div class="paragraph"> |
| <p>The Virgo for Apache Tomcat supports applications packaged in the following formats:</p> |
| </div> |
| <div class="olist arabic"> |
| <ol class="arabic"> |
| <li> |
| <p><a href="#architecture-raw-osgi-bundles">Raw OSGi Bundles</a></p> |
| </li> |
| <li> |
| <p><a href="#architecture-wars">Java EE WAR</a></p> |
| </li> |
| <li> |
| <p><a href="#architecture-war-gemini">Web Application Bundles</a></p> |
| </li> |
| <li> |
| <p><a href="#architecture-pars">PARs</a></p> |
| </li> |
| <li> |
| <p><a href="#architecture-plans">Plans</a></p> |
| </li> |
| <li> |
| <p><a href="#architecture-configurations">Configurations</a></p> |
| </li> |
| </ol> |
| </div> |
| <div class="paragraph"> |
| <p>When you deploy an application to the VTS, each deployment artifact |
| (e.g., a single bundle, WAR, PAR, or plan) passes through a deployment pipeline. This |
| deployment pipeline is responsible for processing applications of certain types (i.e., |
| application type). The 3.7.0.RC01 release of the VTS natively |
| supports deployers analogous to each of the aforementioned packaging options.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Let’s take a closer look now at each of the supported deployment and packaging |
| options to explore which one is best suited to your application.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-raw-osgi-bundles"></a></p> |
| </div> |
| <div class="sect3"> |
| <h4 id="_raw_osgi_bundles">Raw OSGi Bundles</h4> |
| <div class="paragraph"> |
| <p>At its core, the Virgo for Apache Tomcat is an OSGi container. Thus any OSGi-compliant |
| bundle can be deployed directly on the VTS unmodified. You’ll |
| typically deploy an application as a single bundle or a set of stand-alone bundles |
| if you’d like to publish or consume services globally within the container via |
| the OSGi Service Registry.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-wars"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_war_deployment_formats">WAR Deployment Formats</h4> |
| <div class="paragraph"> |
| <p>For Web Application Archives (WAR), the Virgo for Apache Tomcat provides support for the |
| following three formats.</p> |
| </div> |
| <div class="olist arabic"> |
| <ol class="arabic"> |
| <li> |
| <p><a href="#architecture-standard-war">Standard WAR</a></p> |
| </li> |
| <li> |
| <p><a href="#architecture-shared-libraries-war">Shared Libraries WAR</a></p> |
| </li> |
| <li> |
| <p><a href="#architecture-shared-services-war">Shared Services WAR</a></p> |
| </li> |
| </ol> |
| </div> |
| <div class="paragraph"> |
| <p>Each of these formats plays a distinct role in the incremental migration path |
| from a standard Java EE WAR to an OSGi-ified web application.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-standard-war"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_standard_war">Standard WAR</h4> |
| <div class="paragraph"> |
| <p>Standard WAR files are supported directly in the VTS. At |
| deployment time, the WAR file is transformed into an OSGi bundle and installed |
| into Tomcat. All the standard WAR contracts are honoured, and your existing WAR |
| files should just drop in and deploy without change. Support for standard, |
| unmodified WAR files allows you to try out the Virgo for Apache Tomcat on your existing |
| web applications and then gradually migrate toward the <strong>Shared |
| Libraries WAR</strong> and <strong>Shared Services WAR</strong> formats.</p> |
| </div> |
| <div class="paragraph"> |
| <p>In addition to the standard support for WARs that you would expect from |
| Tomcat, the VTS also enables the following features:</p> |
| </div> |
| <div class="olist arabic"> |
| <ol class="arabic"> |
| <li> |
| <p>Spring-driven load-time weaving (see Section 6.8.4, “Load-time weaving |
| with AspectJ in the Spring Framework"). |
| Diagnostic information such as FFDC (first failure data capture)</p> |
| </li> |
| <li> |
| <p>The main benefit of this application style is familiarity — developers know |
| how to create a WAR file! You can take advantage of the |
| VTS’s added feature set without modifying the |
| application. The application can also be deployed on other Servlet containers or |
| Java EE application servers.</p> |
| </li> |
| </ol> |
| </div> |
| <div class="paragraph"> |
| <p>You may choose this application style if the application is fairly simple and |
| small. You may also prefer this style even for large and complex applications as |
| a starting point and migrate to the other styles over time as discussed in <a href="#migrating-to-osgi">[migrating-to-osgi]</a>.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-shared-libraries-war"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_shared_libraries_war">Shared Libraries WAR</h4> |
| <div class="paragraph"> |
| <p>If you have experience with developing and packaging web applications using |
| the standard WAR format, you’re certainly familiar with the pains of |
| library bloat. So, unless you’re installing shared libraries in a common |
| library folder for your Servlet container, you have to pack all JARs required by |
| your web application in <code>/WEB-INF/lib</code>. Prior to the release of |
| the Virgo for Apache Tomcat, such library bloat has essentially been the norm for web |
| applications, but now there is a better solution! The Shared Libraries WAR |
| format reduces your application’s deployment footprint and eradicates |
| library bloat by allowing you to declare dependencies on libraries via standard |
| OSGi manifest headers such as <code>Import-Package</code> and <code>Require-Bundle</code> . The VTS provides additional |
| support for simplifying dependency management via the <code>Import-Library</code> and <code>Import-Bundle</code> manifest headers |
| which are essentially macros that get expanded into OSGi-compliant <code>Import-Package</code> statements.</p> |
| </div> |
| <div class="admonitionblock tip"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <div class="title">Tip</div> |
| </td> |
| <td class="content"> |
| <div class="paragraph"> |
| <p>For detailed information on which libraries are already available, check |
| out the <a href="http://www.eclipse.org/ebr">EBR</a>.</p> |
| </div> |
| </td> |
| </tr> |
| </table> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-shared-services-war"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_shared_services_war">Shared Services WAR</h4> |
| <div class="paragraph"> |
| <p>Once you’ve begun taking advantage of declarative dependency management |
| with a Shared Libraries WAR, you’ll likely find yourself wanting to take |
| the next step toward reaping further benefits of an OSGi container: sharing |
| services between your OSGi-compliant bundles and your web applications. By |
| building on the power and simplicity of Gemini Blueprint, the <strong>Shared Services |
| WAR</strong> format puts the OSGi Service Registry at your finger tips. As |
| a best practice you’ll typically publish services from your domain, |
| service, and infrastructure bundles via <code><osgi:service …​></code> and then consume them in your web application’s |
| ApplicationContext via <code><osgi:reference …​ ></code>. Doing so |
| promotes programming to interfaces and allows you to completely decouple your |
| web-specific deployment artifacts from your domain model, service layer, etc., |
| and that’s certainly a step in the right direction. Of the three supported |
| WAR deployment formats, the Shared Services WAR is by far the most attractive in |
| terms of modularity and reduced overall footprint of your web applications.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-war-gemini"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_wars_and_the_gemini_web_container">WARs and the Gemini Web Container</h4> |
| <div class="paragraph"> |
| <p>Virgo for Apache Tomcat fully supports the OSGi Web Applications standard. Using the |
| reference implementation from Gemini Web that was developed by SpringSource from |
| an offshoot of the original VTS codebase. This RI is now fully |
| integrated in VTS as the basis of the support for web |
| application deployment.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The OSGi Web Applications specification introduces the concept of a <strong>Web |
| Application Bundle</strong>, which is a WAR that is also a bundle. The |
| specification defines how WAR files are transformed into bundles automatically |
| as needed.</p> |
| </div> |
| <div class="paragraph"> |
| <p>You can find an introduction to the Web Container in blog entries written by |
| the Virgo team <a href="http://blog.springsource.com/2009/05/27/introduction-to-the-osgi-web-container/">here</a> |
| and <a href="http://blog.springsource.com/2009/06/01/what-the-osgi-web-container-means-for-dm-server/">here</a>.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-war-gemini-extensions"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_extensions_to_the_web_container">Extensions to the Web Container</h4> |
| <div class="paragraph"> |
| <p>Virgo for Apache Tomcat provides a variety of extensions to the Web Container that |
| allow you to construct sophisticated applications. The table below |
| summarises the extensions that are available or in development.</p> |
| </div> |
| <table class="tableblock frame-all grid-all spread"> |
| <colgroup> |
| <col style="width: 50%;"> |
| <col style="width: 50%;"> |
| </colgroup> |
| <thead> |
| <tr> |
| <th class="tableblock halign-left valign-top">Feature</th> |
| <th class="tableblock halign-left valign-top">Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Instrumentable ClassLoaders</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">All web bundle ClassLoaders are |
| instrumentable by Spring’s load-time weaving infrastructure.</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Support for exploded bundles/WARs</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Bundles/WARs in directory form can |
| be deployed as Web Application Bundles</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Support for scanning TLDs in dependencies</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">As per the Web Application |
| specification, all TLDs located inside a web bundle are located using |
| the rules defined in the JSP 2.1 specification. In |
| VTS, the dependencies of a Web Application |
| Bundle are also scanned for TLDs following the rules outlined in JSP 2.1</p></td> |
| </tr> |
| </tbody> |
| </table> |
| <div class="paragraph"> |
| <p><a id="architecture-pars"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_par">PAR</h4> |
| <div class="paragraph"> |
| <p>A PAR is a standard JAR which contains all of the modules of your application |
| (e.g., service, domain, and infrastructure bundles as well as a WAR or web module |
| for web applications) in a single deployment unit. This allows you to deploy, |
| refresh, and undeploy your entire application as a single entity. If you are |
| familiar with Java EE, it is worth noting that a PAR can be considered a replacement |
| for an EAR (Enterprise Archive) within the context of an OSGi container. As an added |
| bonus, modules within a PAR can be refreshed independently and on-the-fly, for |
| example via the Virgo Eclipse IDE Tooling (see the Virgo Tools Guide).</p> |
| </div> |
| <div class="paragraph"> |
| <p>Many of the benefits of the PAR format are due to the underlying OSGi |
| infrastructure, including:</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p>Fundamentally modularized applications: instead of relying on fuzzy |
| boundaries between logical modules in a monolithic application, this |
| style promotes physically separated modules in the form of OSGi bundles. |
| Then each module may be developed separately, promoting parallel |
| development and loose coupling.</p> |
| </li> |
| <li> |
| <p>Robust versioning of various modules: the versioning capability |
| offered by OSGi is much more comprehensive than alternatives. Each |
| module can specify a version range for each of its dependencies. Bundles |
| are isolated from each other in such a way that multiple versions of a |
| bundle may be used simultaneously in an application.</p> |
| </li> |
| <li> |
| <p>Improved manageability: each bundle may be deployed or undeployed in |
| a running application. This allows modifying the existing application to |
| fix bugs, improve performance, and even to add new features without |
| having to restart the application.</p> |
| </li> |
| </ul> |
| </div> |
| <div class="paragraph"> |
| <p>Furthermore, PARs scope the bundles of your application within the |
| VTS. Scoping provides both a physical and logical application |
| boundary, effectively shielding the internals of your application from other PARs |
| deployed within the VTS. This means your application doesn’t |
| have to worry about clashing with other running applications (e.g., in the OSGi |
| Service Registry). You get support for load-time weaving, classpath scanning, |
| context class loading, etc., and the VTS does the heavy lifting for |
| you to make all this work seamlessly in an OSGi environment. If you want to take |
| full advantage of all that the Virgo for Apache Tomcat and OSGi have to offer, packaging and |
| deploying your applications as a PAR is a good choice, although plans are an even |
| better one, as described in the next section.</p> |
| </div> |
| <div class="admonitionblock tip"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <div class="title">Tip</div> |
| </td> |
| <td class="content"> |
| <div class="title">OSGi != multiple JARs</div> |
| <div class="paragraph"> |
| <p>Note that while physically separated modules can, in theory, be implemented |
| simply using multiple JARs, complex versioning requirements often make this |
| impractical. For example, consider the situation depicted in the diagram below.</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p>Bundle A depends on version <code>1.0.0</code> of bundle <code>B</code> and version <code>2.0.0</code> of bundle <code>C</code>.</p> |
| </li> |
| <li> |
| <p>Bundle B depends on version <code>1.0.0</code> of bundle <code>C</code>.</p> |
| </li> |
| </ul> |
| </div> |
| <div class="paragraph"> |
| <p>Suppose that versions <code>1.0.0</code> and <code>2.0.0</code> of bundle <code>C</code> are neither |
| backward nor forward compatible. Traditional monolithic applications cannot |
| handle such situations: either bundle <code>A</code> or bundle <code>B</code> would need reworking which |
| undermines truly independent development. OSGi’s versioning scheme enables |
| this scenario to be implemented in a robust manner. If it is desirable to rework |
| the application to share a single version of <code>C</code>, then this can be planned in and |
| is not forced.</p> |
| </div> |
| <div class="imageblock"> |
| <div class="content"> |
| <img src="assets/images/architecture-bundle-versioning.png" alt="architecture bundle versioning"> |
| </div> |
| </div> |
| </td> |
| </tr> |
| </table> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-plans"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_plans">Plans</h4> |
| <div class="paragraph"> |
| <p>A plan is similar to a PAR in that it encapsulates all of the artifacts of your |
| application in a single deployment unit. The main difference, however, is that a |
| plan is simply an XML file that lists the artifacts of your application; a PAR, by |
| contrast, is an actual JAR file that physically contains the artifacts. Just like a |
| PAR, you deploy, refresh, and undeploy a plan as a single entity. We highly |
| recommends the use of plans for creating applications.</p> |
| </div> |
| <div class="paragraph"> |
| <p>When you create a plan, you can specify that the included bundles and services |
| are in a scope that isolates them from the rest of Virgo for Apache Tomcat and its |
| deployments. This scoping ensures that the bundles wire to each other and see each |
| other’s services in preference to services from outside the scope. Scoping |
| also prevents application code from leaking into the global scope or scope of |
| another application. In addition, a plan can link the lifecycle of a group of |
| bundles together atomically, which ensures that start, stop, and uninstall |
| events on a single artifact in the plan are escalated to all artifacts in the plan. |
| You can, however, disable both of these features by simply setting an attribute in |
| the plan.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The general benefits of using plans are similar to those of using PARs; see <a href="#architecture-pars">PAR</a> for details. Plans offer added benefits, |
| however, such as the ability to control the deployment order of your application: |
| the order in which you list artifacts in the plan’s XML file is the order in |
| which VTS deploys them. Additionally, because plans specify the |
| artifacts that make up an application by reference, it is easier to share artifacts |
| between plans as well as update individual parts of a plan without having to |
| physically repackage (re-JAR) it.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-configurations"></a></p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="_configurations">Configurations</h4> |
| <div class="paragraph"> |
| <p>A Configuration is simply a Java properties file. When deployed it will be |
| recognised by the deployer and installed in to <strong>Configuration |
| Admin</strong> for later use by your applications. VTS supports |
| both singleton (ManagedService) and factory (ManagedServiceFactory) configurations. |
| (see section 104.6 in the Compendium Specification)</p> |
| </div> |
| <div class="paragraph"> |
| <p>For a singleton configuration the name that it will be installed under is its filename |
| minus the <code>.properties</code> extension. Factory Configuration is supported by |
| specifying the <strong>service.factoryPid</strong> property. In this case the actual PID will |
| be created by <strong>Configuration Admin</strong> (see section 104.6 in the |
| Compendium Specification).</p> |
| </div> |
| <div class="paragraph"> |
| <p>How to consume configuration data is discussed <a href="#developing-applications-configuration-artifacts">later</a>.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-dependency-types"></a></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect2"> |
| <h3 id="_dependency_types">Dependency Types</h3> |
| <div class="paragraph"> |
| <p>In an OSGi environment, there are two kinds of dependencies between various bundles: |
| <strong>type</strong> dependency and <strong>service</strong> dependency.</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p><strong>Type dependency</strong>: A bundle may depend on a |
| type exported by another bundle thus creating a type dependency. Type |
| dependencies are managed through <code>Import-Package</code> and |
| <code>Export-Package</code> directives in the OSGi manifest. This |
| kind of dependency is similar to a JAR file using types in other JAR files |
| from the classpath. However, as we’ve seen earlier, there are |
| significant differences.</p> |
| </li> |
| <li> |
| <p><strong>Service dependency</strong>: A bundle may also |
| publish services (preferably using Gemini Blueprint), and other bundles may consume |
| those services. If two bundles depend on the same service, both will be |
| communicating effectively to the same object. More specifically, any state |
| for that service will be shared between all the clients of that service. |
| This kind of arrangement is similar to the commonly seen client-server |
| interaction through mechanisms such as RMI or Web Services.</p> |
| </li> |
| </ul> |
| </div> |
| </div> |
| <div class="sect2"> |
| <h3 id="_regions">Regions</h3> |
| <div class="paragraph"> |
| <p>Conceptually, the Eclipse Virgo can be divided into two separate subsystems, called Regions. This |
| provides a way to keep the Virgo Kernel separate from user applications. Read more about Regions |
| and the two in Virgo in the <a href="http://www.eclipse.org/virgo/documentation/virgo-documentation-3.7.0.RC01/docs/virgo-user-guide/html/index.html">User Guide</a> |
| concepts section.</p> |
| </div> |
| <div class="paragraph"> |
| <p><a id="architecture-forming-bundles"></a></p> |
| </div> |
| </div> |
| <div class="sect2"> |
| <h3 id="_a_guide_to_forming_bundles">A Guide to Forming Bundles</h3> |
| <div class="paragraph"> |
| <p>So what makes an application suitable for deployment on the Virgo for Apache Tomcat? Since |
| OSGi is at the heart of the VTS, modular applications consisting of |
| bundles, which each represent distinct functionality and well-defined boundaries, can |
| take maximum advantage of the OSGi container’s capabilities. The core ideas behind |
| forming bundles require following good software engineering practices: separation of |
| concerns, loose coupling, and communication through clear interfaces. In this section, |
| we look at a few approaches that you may use to create modular applications for |
| Virgo for Apache Tomcat deployment. Please consider the following discussion as guidelines and |
| not as rules.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Bundles can be formed along horizontal slices of layering and vertical slices of |
| function. The objective is to enable independent development of each bundle and minimize |
| the skills required to develop each bundle.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example, an application could have the following bundles: |
| <strong>infrastructure</strong>, <strong>domain</strong>, |
| <strong>repository</strong>, <strong>service</strong>, and |
| <strong>web</strong> as shown in the following diagram.</p> |
| </div> |
| <div class="imageblock"> |
| <div class="content"> |
| <img src="assets/images/bundle-dependencies-layers.png" alt="bundle dependencies layers"> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Each bundle consists of types appropriate for that layer and exports |
| packages and services to be used by other layers. Let’s examine each bundle in |
| more detail:</p> |
| </div> |
| <table class="tableblock frame-all grid-all spread"> |
| <caption class="title">Table 1. Bundles across layers</caption> |
| <colgroup> |
| <col style="width: 20%;"> |
| <col style="width: 20%;"> |
| <col style="width: 20%;"> |
| <col style="width: 20%;"> |
| <col style="width: 20%;"> |
| </colgroup> |
| <thead> |
| <tr> |
| <th class="tableblock halign-left valign-top">Bundles</th> |
| <th class="tableblock halign-left valign-top">Imported Packages</th> |
| <th class="tableblock halign-left valign-top">Exported Packages</th> |
| <th class="tableblock halign-center valign-top">Consumed Services</th> |
| <th class="tableblock halign-center valign-top">Published Services</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Infrastructure</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Third-party libraries</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Infrastructure interfaces</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">None</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">None</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Domain</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Depends: for example, |
| if JPA is used to |
| annotate persistent |
| types, then JPA |
| packages.</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Public domain types</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">None</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">None</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Web</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Domain, Service</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">None</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">Service beans</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">None</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Service</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Domain, |
| Infrastructure, |
| Repository</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Service interfaces</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">Repository beans</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">Service beans</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Repository</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Domain, |
| Third-party libraries, |
| ORM bundles, etc.</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Repository interfaces</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">DataSources, |
| ORM session/entity managers, |
| etc.</p></td> |
| <td class="tableblock halign-center valign-top"><p class="tableblock">Repository beans</p></td> |
| </tr> |
| </tbody> |
| </table> |
| <div class="paragraph"> |
| <p>Within each layer, you may create bundles for each subsystem representing a vertical |
| slice of business functionality. For example, as shown in the following figure, the |
| service layer is divided into two bundles each representing separate business |
| functions. |
| <span class="image"><img src="assets/images/bundle-dependencies-verticals.png" alt="bundle dependencies verticals"></span></p> |
| </div> |
| <div class="paragraph"> |
| <p>You can similarly separate the repositories, domain classes, and web controllers |
| based on the business role they play.</p> |
| </div> |
| </div> |
| </div> |
| </div> |
| </div> |
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| <div id="footer-text"> |
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