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From conflue...@apache.org
Subject [CONF] Apache Tuscany: SCA Java implementation.spring (page edited)
Date Tue, 19 Aug 2008 16:10:03 GMT
SCA Java implementation.spring (TUSCANY) edited by Simon Laws
      Page: http://cwiki.apache.org/confluence/display/TUSCANY/SCA+Java+implementation.spring
   Changes: http://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=66253&originalVersion=2&revisedVersion=3






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{include: SCA Java Subproject Menu}
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h2. <implementation.spring>

The Tuscany Java SCA runtime supports components implemented with Spring Framework by using
the <implementation.spring> SCDL extension.

Spring Framework are used with SCA by integration Spring at the SCA Composite level, where
a Spring application context provides a complete composite, exposing services and using references
via SCA. This means that a Spring application context defines the internal structure of a
composite implementation.

The Spring Component implementation is one of the SCA extensions which is being formalized
in the OASIS Open Composite Services Architecture with a published [specifications |http://www.oasis-opencsa.org/sca-spring]
document.

h3. How Spring Application Context is used as SCA Composite Implementation?

* A Spring Application Context is used as an implementation within an SCA composite component.

* A component that uses Spring for an implementation can wire SCA services and references
without introducing SCA metadata into the Spring configuration. The Spring context knows very
little about the SCA environment. 
* All policy enforcement occurs in the SCA runtime implementation and does not enter into
theSpring space.
* It should be possible to generate an SCA Composite from any Spring context and use that
composite within an SCA assembly.

h3. How to Use Spring Component Implementation

The Spring component implementation SCDL has the following format:

{code}
   <implementation.spring location="targetURI" />
{code}

Where the location attribute of that element specifies the target uri of an archive file or
directory or the fully qualified path that contains the Spring application context files.


An example of all the three ways of specifying the target uri in the location attribute is
shown below

a) Specifying Fully Qualified Path:
{code}
   <implementation.spring location="./spring/application-context.xml" />
{code}

b) Specifying a Directory:
{code}
   <implementation.spring location="./spring" />
{code}

Here the target uri specifies the resource as a directory named "spring", where all the spring
related files are available.

c) Specifying an Archive file:
{code}
   <implementation.spring location="./spring.jar" />
{code}

Here the target uri specifies the resource as an archive file name "spring.jar", where all
the spring related files are available.

*IMPORTANT NOTE:* In case of b) and c), If the resource identified by the location attribute
is an archive file then the file META-INF/MANIFEST.MF is read from the archive. If the location
URI identifies a directory, then META-INF/MANIFEST.MF must exist underneath that directory.

If the manifest file contains a header "Spring-Context" of the format: +Spring-Context ::=
path ( ';' path )*+

Where path is a relative path with respect to the location URI, then the set of paths specified
in the header identify the context configuration files. If there is no MANIFEST.MF file or
no Spring-Context header within that file, then the default behaviour is to build an application
context using application-context.xml file in the META-INF/spring directory.


h3. Some Examples:

h4. Spring BigBank Sample
The spring-bigbank sample demonstrates most of the functionality that being specified in the
[specifications |http://www.oasis-opencsa.org/sca-spring] demostrating how the Spring Framework
can be used with SCA.

See the [simple-bigbank-spring |http://svn.apache.org/repos/asf/tuscany/java/sca/samples/simple-bigbank-spring/]
sample for a complete example.

h4. Direct use of SCA references within a Spring configuration
The references like addService, subtractService, multiplyService and divideService defined
by SCA composite as shown below

{code}
<composite>

    <component name="CalculatorServiceComponent">
         <implementation.spring location="META-INF/spring/CalculatorService-context.xml"/>


        <reference name="addService" target="AddServiceComponent" />
        <reference name="subtractService" target="SubtractServiceComponent" />
        <reference name="multiplyService" target="MultiplyServiceComponent" />
        <reference name="divideService" target="DivideServiceComponent" />
    </component>

    <component name="AddServiceComponent">
        <tuscany:implementation.script script="calculator/AddServiceImpl.js"/>
    </component>

    <component name="SubtractServiceComponent">
        <tuscany:implementation.script script="calculator/SubtractServiceImpl.rb"/>
    </component>

    <component name="MultiplyServiceComponent">
        <tuscany:implementation.script script="calculator/MultiplyServiceImpl.py"/>
    </component>

    <component name="DivideServiceComponent">
        <tuscany:implementation.script script="calculator/DivideServiceImpl.groovy"/>
    </component>

</composite>
{code}

can be directly used by Spring Application Context as shown here...

{code}
<beans>

    <sca:service name="CalculatorService"
        type="bigbank.calculator.CalculatorService" target="CalculatorServiceBean"/>

    <bean id="CalculatorServiceBean" class="bigbank.calculator.CalculatorServiceImpl">
        <!-- Here are some implicit references - a property with a ref not satisifed within
the
         * Spring application context.
         -->
        <property name="addService" ref="addService"/>
        <property name="subtractService" ref="subtractService"/>
        <property name="multiplyService" ref="multiplyService"/>
        <property name="divideService" ref="divideService"/>
    </bean>

</beans>
{code}

See the [spring-bigbank-calculator |http://svn.apache.org/repos/asf/tuscany/java/sca/samples/spring-bigbank-calculator/]
sample for a complete example of using SCA references directly.

h4. Explicit declaration of SCA related beans inside a Spring Application Context
It is also possible to explicitly declare SCA-related beans inside a Spring configuration
to proxy SCA references. The primary reason you may do this is to enable the Spring container
to decorate the bean (using Spring AOP for example).

The references checkingAccountService, calculatorService and stockQuoteService defined by
SCA composite as shown below

{code}
<composite name="BigBank">

    <component name="AccountServiceComponent">
        <implementation.spring location="spring-context/Account-spring-context.xml"/>
        
        <service name="AccountService">
            <interface.java interface="bigbank.account.AccountService"/>
        </service>

        <reference name="savingsAccountService" target="SavingsAccountServiceComponent"/>
        
        <reference name="checkingAccountService">
          <interface.java interface="bigbank.account.checking.CheckingAccountService"/>
          <binding.jms initialContextFactory="org.apache.activemq.jndi.ActiveMQInitialContextFactory"
                       jndiURL="tcp://localhost:61619">
              <destination name="RequestQueue" create="always"/>
              <response>
                  <destination name="ResponseQueue" create="always"/>
              </response> 
          </binding.jms>
        </reference>
        
        <reference name="stockAccountService" target="StockAccountServiceComponent"/>
        
        <reference name="calculatorService">
            <tuscany:binding.rmi host="localhost" port="8099" serviceName="CalculatorRMIService"/>
        </reference>      
        
        <reference name="stockQuoteService">
            <binding.ws uri="http://localhost:8081/services/StockQuoteWebService"/>
        </reference>
    </component>

    <component name="SavingsAccountServiceComponent">
        <implementation.composite name="bbsv:SavingsAccountDept"/>
    </component>

    <component name="StockAccountServiceComponent">
        <implementation.composite name="bbst:StockAccountDept"/>
    </component>

</composite>
{code}

can be declared explicit as SCA beans in Spring Application Context as shown below using the
Spring SCA Namespace schema..

{code}
<beans>
   <bean id="AccountServiceBean" class="bigbank.account.AccountServiceImpl">     
        <property name="calculatorService" ref="calculatorService"/>
        <property name="stockQuoteService" ref="stockQuoteService"/>
        <property name="checkingAccountService" ref="checkingAccountService"/>
        
        <!-- Here are some implicit references & properties - a property with a ref
not satisifed 
        * within the Spring application context.
         -->
        <property name="savingsAccountService" ref="savingsAccountService"/>
        <property name="stockAccountService" ref="stockAccountService"/>           
  
        <property name="currency" value="EURO"/>
    </bean>
    
    <sca:reference name="checkingAccountService" type="bigbank.account.checking.CheckingAccountService"/>
    
    <sca:reference name="calculatorService" type="bigbank.calculator.CalculatorService"/>
    
    <sca:reference name="stockQuoteService" type="bigbank.stockquote.StockQuoteService"/>
</beans>
{code}

See the [simple-bigbank-spring |http://svn.apache.org/repos/asf/tuscany/java/sca/samples/simple-bigbank-spring/]
sample for a complete example of using explicit declaration of SCA related beans.

h4. Using SCA Bindings for Spring Implementation

We know that a component that uses Spring for an implementation can wire SCA services and
references without introducing SCA metadata into the Spring configuration. The Spring context
knows very little about the SCA environment. Hence the SpringComponent implementation remains
the same as shown from some of the examples above but different bindings are chosen at the
SCA Composite level as shown below.

NOTE: All kind of bindings supported by SCA can be used for Spring Implementation as the bindings
are independent of Spring context. Few examples can be seen below.

h5. Working with SCA WebServices Binding

Declaring Service

{code}
<composite name="StockQuote">
    
    <service name="StockQuoteService" promote="StockQuoteServiceComponent">
        <interface.java interface="bigbank.stockquote.StockQuoteService"/>
        <binding.ws uri="http://localhost:8081/services/StockQuoteWebService"/>
    </service>

    <component name="StockQuoteServiceComponent">
        <implementation.spring location="META-INF/spring/StockQuoteService-context.xml"/>
    </component>

</composite>
{code}

Declaring Reference

{code}
<component name="AccountServiceComponent">
    <implementation.spring location="spring-context/Account-spring-context.xml"/>

    <reference name="stockQuoteService">
       <binding.ws uri="http://localhost:8081/services/StockQuoteWebService"/>
    </reference>
</component>
{code}

See the [spring-bigbank-stockquote | http://svn.apache.org/repos/asf/tuscany/java/sca/samples/spring-bigbank-stockquote/]
sample for a complete example of using SCA Web Service binding.

h5. Working with SCA RMI Binding

Declaring Service

{code}
<composite name="Calculator">
    <service name="CalculatorService" promote="CalculatorServiceComponent">
        <interface.java interface="bigbank.calculator.CalculatorService"/>
        <tuscany:binding.rmi host="localhost" port="8099" serviceName="CalculatorRMIService"/>
    </service>

    <component name="CalculatorServiceComponent">
        <implementation.spring location="META-INF/spring/CalculatorService-context.xml"/>
        <reference name="addService" target="AddServiceComponent" />
        <reference name="subtractService" target="SubtractServiceComponent" />
        <reference name="multiplyService" target="MultiplyServiceComponent" />
        <reference name="divideService" target="DivideServiceComponent" />
    </component>
</composite>
{code}

Declaring Reference

{code}
<component name="AccountServiceComponent">
    <implementation.spring location="spring-context/Account-spring-context.xml"/>
    
    <reference name="calculatorService">
        <tuscany:binding.rmi host="localhost" port="8099" serviceName="CalculatorRMIService"/>
    </reference>
</component>
{code}

See the [spring-bigbank-calculator |http://svn.apache.org/repos/asf/tuscany/java/sca/samples/spring-bigbank-calculator/]
sample for a complete example of using SCA RMI binding.

h3. Spring SCA Namespace schema

{code}
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns="http://www.springframework.org/schema/sca"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema" attributeFormDefault="unqualified"
	elementFormDefault="qualified" targetNamespace="http://www.springframework.org/schema/sca">
	<xsd:element name="composite">
		<xsd:complexType>
			<xsd:attribute name="component" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="sca-adapter-class" use="optional">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
		</xsd:complexType>
	</xsd:element>
	<xsd:element name="reference">
		<xsd:complexType>
			<xsd:attribute name="name" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="type" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="default" use="optional">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
		</xsd:complexType>
	</xsd:element>
	<xsd:element name="property">
		<xsd:complexType>
			<xsd:attribute name="id" use="optional">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="name" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="type" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
		</xsd:complexType>
	</xsd:element>
	<xsd:element name="service">
		<xsd:complexType>
			<xsd:attribute name="name" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="type" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="target" use="required">
				<xsd:simpleType><xsd:restriction base="xsd:string" /></xsd:simpleType>
			</xsd:attribute>
		</xsd:complexType>
	</xsd:element>
</xsd:schema>
{code}

h3. References

[1] SCA Spring Component Implementation Specification - http://www.oasis-opencsa.org/sca-spring
[2] Spring Framework - http://static.springframework.org/spring/docs/2.0.x/reference/index.html

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