// calls to other methods go here if we have implemented SubtractService, MultiplyService, DivideService
scaDomain.close();
}
}
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You can see that we start by using a static method on SCADomain to create a new instance of itself. The SCADomain is a concept in SCA that represents the boundary of an SCA system. This could be distributed across many processors but that's not implemented in Tuscany yet so lets concentrate on getting this working inside a single Java VM. The parameter "Calculator.composite" refers to an XML file that tells SCA how the components in our calculator application are assembled into a working applcation. Here is the XML that's inside Calculator.composite. Code Block |
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<composite xmlns="http://www.osoa.org/xmlns/sca/1.0"
name="Calculator">
<component name="CalculatorServiceComponent">
<implementation.java class="calculator.CalculatorServiceImpl"/>
<reference name="addService" target="AddServiceComponent" />
<!-- references to SubtractComponent, MultiplyComponent and DivideComponent -->
</component>
<component name="AddServiceComponent">
<implementation.java class="calculator.AddServiceImpl"/>
</component>
<!-- definitions of SubtractComponent, MultiplyComponent and DivideComponent -->
</composite>
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You can see that we define two components here and specify the Java implementation classes that Tuscany SCA needs to load to make them work. These are the classes we have just implemented. Also note that the CalculatorServiceComponent has a reference named "addService". In the XML, this reference targets the AddServiceComponent. It is no coincidence that the reference name, "addService", matches the name of the addService field we created when we implemented CalculatorServiceImpl. The Tuscany SCA runtime parses the information from the XML composite file and uses it to build the objects and relationships that represent our calculator application. It first creates instances of AddServiceImpl and CalcualtorSreviceImpl. It then injects a reference to the AddServiceImpl object into the addService field in the CalculatorServiceImpl object. This is equivalent to this piece of code from our normal Java client. Code Block |
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CalculatorServiceImpl calculatorService = new CalculatorServiceImpl();
AddService addService = new AddServiceImpl();
calculatorService.setAddService(addService);
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Once the composite file is loaded into the SCADomain our client code asks the SCADomain to give us a reference to the component called "CalculatorServiceComponent". Code Block |
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CalculatorService calculatorService = scaDomain.getService(CalculatorService.class, "CalculatorServiceComponent");
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We can now use this reference as though we had created it ouselves, for example, from the CalculatorServiceImpl.add() method implementation. Code Block |
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return addService.add(n1, n2);
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The SCA specifications often descibe SCA applications is diagramatic form. This often helps give a quick overview of what components ar part of an application and how they are wired together. If we draw a diagram of what we have build in the calculator sample we come up with something like. Image Added
You will notice that diagrams are provided with all of our samples. If you like to take a visual approach to things this may help you become quickly familiar with the components in the samples. Take a look at the ".png" files in the top level directory of each sample. Step 4 - Deploying the applcation: So as long as the "Calculator.composite" file is present on our class path, along with the rest of the tuscany jars, we can run our sample as we did previously. The samples come with an Ant build.xml file that allows the sample files to be rebuilt so if you want to experiment with the sample code you can do so and then recompile it. Once recompiled you can run it as before in the Running The Calculator Sample section, for example, we provide a run target in the Ant build.xml file so the calculator sample can also be run using. Background Color |
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| What Next? |
Looking back, the client code we have written to start the calculator application using the Tuscany SCA runtime is no longer than a normal Java client for the application. However we do now have the XML composite file that describes how our application is assembled. This concept of assembly is a great advantage as our applications become more complex and we want to change them, reuse them, integrate them with other applications or just further develop them using a programming model consistent with all our other SCA applications. Regardless of what language is used to implement each of them. For example, lets say our calculator sample is so poweful and popular that we want to put it on the company intranet and let other people access it as a service directly from their browser based Web2.0 applications. It's at this point we would normally start reaching for the text books to work out how to make this happen. As we have an XML file that describes our application it's easy in Tuscany SCA. The following should do the trick. Code Block |
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<composite xmlns="http://www.osoa.org/xmlns/sca/1.0"
name="Calculator">
<service name="CalculatorService" promote="CalculatorServiceComponent/CalculatorService">
<interface.java interface="calculator.CalculatorService"/>
<binding.jsonrpc/>
</service>
<component name="CalculatorServiceComponent">
<implementation.java class="calculator.CalculatorServiceImpl"/>
<reference name="addService" target="AddServiceComponent" />
<!-- references to SubtractComponent, MultiplyComponent and DivideComponent -->
</component>
<component name="AddServiceComponent">
<implementation.java class="calculator.AddServiceImpl"/>
</component>
<!-- definitions of SubtractComponent, MultiplyComponent and DivideComponent -->
</composite>
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All we have done is added the <service> element which tells Tuscany SCA how to expose our CalculatorServiceComponent as a JSONRPC service. Note that we didn't have to change the Java code of our components. This is just a configuration change. The helloworld-jsonrpc sample shows a working example of the jsonrpc binding. TODO - we don't have a JSONRPC version of the calculator sample If we really wanted a SOAP/HTTP web service we can do that easily too. The helloworld-ws-service and helloworld-ws-reference samples show you how to work with web services. TODO - we don't have a web services version of the calcualtor sample SCA allows other kinds of flexibility. We can rewire our components, for example, using a one of the remote bindings, like RMI, we could have the CalculatorServiceComponent running on one machine wired to a remote version of the application running on another machine. The calculator-rmi-service and calculator-rmi-reference samples show the RMI binding at work. We could also introduce components implemented in different languages, for example, let's add the SubtractServiceComponent implemented in Ruby. Code Block |
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<composite xmlns="http://www.osoa.org/xmlns/sca/1.0"
name="Calculator">
<component name="CalculatorServiceComponent">
<implementation.java class="calculator.CalculatorServiceImpl"/>
<reference name="addService" target="AddServiceComponent" />
<reference name="subtractService" target="SubtractServiceComponent" />
<!-- references to MultiplyComponent and DivideComponent -->
</component>
<component name="AddServiceComponent">
<implementation.java class="calculator.AddServiceImpl"/>
</component>
<component name="SubtractServiceComponent">
<implementation.script script="calculator/SubtractServiceImpl.rb"/>
</component>
<!-- definitions of MultiplyComponent and DivideComponent -->
</composite>
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Of course we need the Ruby code that implements the component. Code Block |
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def subtract(n1, n2)
return n1 - n2
end
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The Tuscany SCA runtime handles wiring Java components to Ruby components and performs any required data transformations. The calculator-script sample shows different script languages in use. So, now that our application is desribed as an SCA assembly there are lots of possibilities as we futher develop it and integration it with other applications. The following sections provide more detail on the features provided by Tuscany SCA. Anchor |
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| Tuscany SCA Extensions |
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| Tuscany SCA Extensions |
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| Tuscany SCA Extensions |
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| The Extensible Runtime |
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| The Extensible Runtime |
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| The Extensible Runtime |
The Tuscany SCA runtime comprises a small set of core software which deals with: - Managing extesions to the Tuscany SCA Runtime(core)
- Building and in memory assembly model of SCA applications (assembly)
- Processing SCA applcations that are contributed (contribution)
- Supporting databindings (databinding)
- Supporting Tuscany SCA when its embedded in other environments (embedded)
- Supporting Tuscany SCA when its running in a servlet container (http)
The collections of interfaces that describe these features are referred to as the System Programming Interface (SPI). The developer guide discusses them in more detail but from a user perspective the important thing to realize is that the majority of interesting functionality in Tuscany SCA is provided by extensions which build upon this core SPI. These extensions provide Tuscany SCA with its ability to support a wide variety features. - Implementation types
- Binding types
- Databinding types
- Interface description styles
- Hosting environments
So to undestand how to use the Tuscany SCA runtime is to understand how to use its extensions. Anchor |
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| Available Extensions |
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| Available Extensions |
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| Available Extensions |
More often than not using an extension involves adding information to you SCDL files or your implementation files but this is not always the case. The links below describe each of the extensions and how they can be used and configured. HTML Table |
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| Table Row (tr) |
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Table Cell (td) |
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| Implementation Types |
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| Implementation Types |
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| Implementation Types |
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Table Row (tr) |
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Table Cell (td) |
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Support for SCA components implemented with Java classes |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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Support for SCA components implemented with scripting languages |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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Support for SCA components implemented with Spring Framework |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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Anchor |
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| Protocol Bindings |
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| Protocol Bindings |
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| Protocol Bindings |
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Table Row (tr) |
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Table Cell (td) |
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Communication with AJAX clients |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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Asynchronous JMS messaging |
Table Cell (td) |
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Under development |
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Table Row (tr) |
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Table Cell (td) |
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The JSON-RPC protocol |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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The Java RMI protocol |
Table Cell (td) |
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Available from 0.90 |
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Table Cell (td) |
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SOAP/HTTP web services |
Table Cell (td) |
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Available from 0.90 |
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| Data Bindings |
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| Data Bindings |
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| Data Bindings |
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Table Row (tr) |
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Table Cell (td) |
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databinding-axiom |
Table Cell (td) |
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Support for AXIOM databinding |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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databinding-jaxb |
Table Cell (td) |
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Support for JAXB databinding |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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databinding-sdo |
Table Cell (td) |
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Support for SDO databinding |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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databinding-sdo-axiom |
Table Cell (td) |
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Support optimzed SDO to AXIOM transformation |
Table Cell (td) |
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Available from 0.90 |
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| Hosting Tuscany |
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| Hosting Tuscany |
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| Hosting Tuscany |
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A simple embedded host that boots Tuscany core and application from the same classpath |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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host-webapp |
Table Cell (td) |
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Intialises the Tuscany runtime for use in a Web Application |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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http-jetty |
Table Cell (td) |
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The integration between Tuscany and the Jetty web container |
Table Cell (td) |
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Available from 0.90 |
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Table Row (tr) |
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Table Cell (td) |
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http-tomcat |
Table Cell (td) |
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The integration between Tuscany and the Tomcat web container |
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Available from 0.90 |
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| Using Extensions |
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| Using Extensions |
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| Using Extensions |
Extensions are loaded into the Tuscany SCA runtime using the Java service loading mechanism. Each extension is packaged as a jar and provides a file; Code Block |
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META-INF/services/org.apache.tuscany.sca.core.ModuleActivator
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Using this information the Tuscany SCA runtime will load each extensions present on the the Java CLASSPATH. So if you want to use a particular feature make sure that it's available on your classpath. Conversely if you don't want a particular feature to be active remove it from the classpath. Writing a new extension is a subject in its own right and is described in the extension guide Anchor |
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| Tuscany SCA And IDEs |
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| Tuscany SCA And IDEs |
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| Tuscany SCA And IDEs |
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| Using The Samples In An IDE Without Maven |
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| Using The Samples In An IDE Without Maven |
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| Using The Samples In An IDE Without Maven |
We don't provide any IDE project files with our disitributions so you will have to import the sample files into your IDE manually. Here's an example of how it can be done using Eclipse. Here the directory tuscany_sca_install_dir is the directory whch holds the Tuscany SCA Java binary installation after it's been extracted from its archive file, for example, for the 0.90 release this will be tuscany-sca-0.90-incubating. In a new or existing workspace - Create a new java project to represent the sample you want to work on, e.g.
No Format |
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my working dir/calculator
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- Import all of the sample code and resources into this project, e.g.
No Format |
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Use the File,Import menu and then select tuscany_sca_install_dir/samples/calculator from the filesystem
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- Configure the source path to include
No Format |
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tuscany_sca_install_dir/samples/calculator/src/main/java
tuscany_sca_install_dir/samples/calculator/src/main/resources
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- Configure the output folder to be
No Format |
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tuscany_sca_install_dir/samples/calculator/target
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- Configure the build path to include all of the jars provided in
No Format |
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tuscany_sca_install_dir/lib
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- If you select calculator.CalculatorClient.java and run as "Java Application" you should see
No Format |
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3 + 2=5.0
3 - 2=1.0
3 * 2=6.0
3 / 2=1.5
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The details of how to do this for other development environments will vary but the process will be similar. Anchor |
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| Using The Samples In An IDE If You Have Maven |
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| Using The Samples In An IDE If You Have Maven |
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| Using The Samples In An IDE If You Have Maven |
If you are a Maven user you can use it to generate all of the IDE project files for you automatically. This works best if you generate IDE projects for all of the Apache Tuscany modules. You can then include the ones you are interested in working with in you IDE. To build IDE project files for all of the modules in Apache Tuscany SCA; If you are an Eclipse user do the following No Format |
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mvn -Peclipse eclipse:eclipse
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If you are an IDEA user do the following These commands generate project files for each module in Apache Tuscany SCA. The modules you are interested in can now be included in your IDE, for example, in Eclipse, if you create a new Java project and use the option to "create a new project from existing source" you can specify an SCA module directory, which includes the generated project files, and Eclipse will treat it like any other Java project. |