Tuscany SCA Java - FAQ (TUSCANY) edited by Simon Laws
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http://cwiki.apache.org/confluence/display/TUSCANY/Tuscany+SCA+Java+-+FAQ
Changes:
http://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=35040&originalVersion=23&revisedVersion=24
Content:
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{include: SCA Java Subproject Menu}
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Welcome to the Apache Tuscany Java SCA FAQ page. Please help to keep the
information on this page current.
\\
{panel:title=Apache Tuscany SCA Frequently Asked
Questions|borderStyle=solid|borderColor=#C3CDA1|titleBGColor=#C3CDA1|bgColor=#ECF4D1}
* [Build Questions|#Build Questions]
** [What version of Java do I need? |#BuildA]
** [What version of Maven do I need? |#BuildB]
** [Why does the Tuscany code I checked out of Subversion not build? |#BuildC]
** [Java Heap Error during compilation|#BuildD]
** [How do I generate Eclipse projects from the source distribution or from
Subversion trunk?|#BuildE]
** [How do I generate an Eclipse WTP project for the WebApp samples?|#BuildF]
** [When running the WSConfidentialityTestCase using IBM JDK I experience
java.lang.ExceptionInInitializerError arising from the base
java.security.InvalidKeyException: Public key presented not for certificate
signature - how do I get over this?|#BuildG]
** [How do I run the samples from a release candidate before the maven
artifacts have been published?|#BuildH]
* [Implementation Java Questions|#Implementation JavaQuestions]
** [What is the format for specifying multiple interfaces with the @Service
annotation? |#ImplementationJavaA]** [Why are references not being injected
into my component? |#ImplementationJavaB]
* [Binding Questions|#Binding Questions]
** [Can I use the EJB binding to publish an SCA services as an SLSB? |#BindingA]
* [DataBinding Questions|#DataBinding Questions]
** [What is the difference between Logical Type and Physical
Type?|#DataBindingA]
* [Contribution Questions|#Contribution Questions]
** [What is META-INF/sca-contribution.xml for?|#ContributionA]
** [What is What is META-INF/sca-deployables/ for?|#ContributionB]
* [Specification Questions|#Specification Questions]
** [Where are the specifications that Tuscany implements?|#SpecificationA]\\
{panel}
h2. {anchor:Build Questions}
{bgcolor:#C3CDA1}Build Questions
{bgcolor}
h3. {anchor:BuildA}
{bgcolor:#C3CDA1}What version of Java do I need?
{bgcolor}
Both IBM and Sun JDK 1.5 are known to work and are used regularly by our
development community.
JDK1.4 will not work as the Tuscany SCA code base relies on some of the
features of JDK1.5 such as generics and annotations.
JDK1.6 has proven problematic due to some issues with bundled XML stream
parsing support that clashes with the support that Tuscany gets from elsewhere.
This issue is under investigation. If you are getting errors starting with the
following stack trace this is likely to be because you are using JDK 1.6
javax.xml.stream.FactoryConfigurationError: Provider
javax.xml.stream.XMLInputFactory could not be
instantiated: java.lang.InstantiationException
at
javax.xml.stream.XMLInputFactory.newInstance(XMLInputFactory.java:158)
h3. {anchor:BuildB}
{bgcolor:#C3CDA1}What version of Maven do I need?
{bgcolor}
To build the Apache Tuscany source code that you have checked out of subversion
you need to install Maven. The build is know to work relatively reliably with
Maven 2.0.5. People have had it working with later versions but it you are
encountering unpredicatbility in the build then give 2.0.5 a go.
h3. {anchor:BuildC}
{bgcolor:#C3CDA1}Why does the Tuscany code I checked out of Subversion not
build?
{bgcolor}
If you are taking code out of the trunk of the Tuscany Subversion repository
then you may have been unlucky and picked up a revision of the code where the
build is broken. As trunk is where the development takes place this happens now
and again although the development community tries to avoid build breaks if at
all possible and tries to fix them quickly when they do happen.
There are may and various other things that can cause your build to break. Its
worth checking on the mail list that the trunk is building. Assuming that it is
we will usually ask you to do the following as a basic level set.
Stop any ide you may have running
Check out the latest trunk revision
cd mytuscanydir
svn checkout [https://svn.apache.org/repos/asf/incubator/tuscany/java/]
or (if you already have a version of the code)
svn update [https://svn.apache.org/repos/asf/incubator/tuscany/java/]
Clean all the maven projects
cd mytuscanydir/sca
mvn clean
Remove all the sca artifacts from the local maven repository by removing (or
renaming) all of the directories under
.m2\repository\org\apache\tuscany\sca
Rebuild sca
cd mytuscanydir/sca
mvn
If it still doesn't work then get back on the mail list
h3. {anchor:BuildD}
{bgcolor:#C3CDA1}Java Heap error during compilation
{bgcolor}
I always get a "Java heap space" error during the build while the itests are
running these days. Runs fine if I build from within the itests folder but
building from the top sca folder always fails.
try "MAVEN_OPTS="-Xmx1024m \-Xms512m" or You can also increase the memory
options in the sca pom [1], in the surefire plugin configuration section.
[1] [https://svn.apache.org/repos/asf/incubator/tuscany/java/sca/pom.xml]
h3. {anchor:BuildE}
{bgcolor:#C3CDA1}How do I generate Eclipse projects from the source
distribution or from Subversion trunk?
{bgcolor}
If you have unpacked the source distribution or have checked out all of the
code under the tuscany/java/sca directory in subversion then you should end up
with a source directory containing something like:
{noformat}
demos
distribution
itest
modules
samples
tools
pom.xml
{noformat}
You can build the source from using maven with the command
{code}
mvn
{code}
You can also build Eclipse projects for all the modules in the project using
the command
{code}
mvn -Peclipse eclipse:eclipse
{code}
This builds ".classpath" and ".project" files for each modules. The easiest
thing to do is import all of these generated projects. In Eclipse choose
"File/Import/Existing Projects Into Workspace". From the wizard select your
source directory and Eclipse should now find all of the Eclipse projects that
have been generated.
If you imported all modules into Eclipse you should find that project
dependencies are satisfied by reference to other Tuscany SCA projects in your
workspace. This is convenient for debugging as all Tuscany SCA source it now
available in your workspace.
h3. {anchor:BuildF}
{bgcolor:#C3CDA1}How do I generate an Eclipse WTP project for the WebApp
samples?
{bgcolor}
If you're using Eclipse WTP and want to get WTP Web Projects generated for our
Webapp samples you can simply pass a \-Dwtpversion=1.5 option tothe usual mvn
eclipse:eclipse command, like this:
{code}
mvn -Dwtpversion=1.5 -Peclipse eclipse:eclipse
{code}
The magic \-Dwtpversion=1.5 option will add the WTP Web project nature to all
the Eclipse projects with <packaging>war</packaging> in their Maven pom.xml.
You'll then be able to add these projects to a WTP Tomcat or Geronimo Server
configuration, to publish and run them straight from your Eclipse workspace.
h3. {anchor:BuildG}
{bgcolor:#C3CDA1}When running the WSConfidentialityTestCase using IBM JDK I
experience java.lang.ExceptionInInitializerError arising from the base
java.security.InvalidKeyException: Public key presented not for certificate
signature - how do I get over this?
{bgcolor}
To get over this exception please go over to the jre\lib\security\java.security
of the IBM JDK installation and set up the security providers as follows.
{noformat}
#
# List of providers and their preference orders:
#
security.provider.1=org.bouncycastle.jce.provider.BouncyCastleProvider
security.provider.3=com.ibm.jsse2.IBMJSSEProvider2
security.provider.2=com.ibm.crypto.provider.IBMJCE
security.provider.4=com.ibm.security.jgss.IBMJGSSProvider
security.provider.5=com.ibm.security.cert.IBMCertPath
security.provider.6=com.ibm.security.sasl.IBMSASL
{noformat}
h3. {anchor:BuildH}
{bgcolor:#C3CDA1}How do I run the samples from a release candidate before the
maven artifacts have been published?
{bgcolor}
The samples in the binary distribution won't build with mvn till we actually
release and the artifacts get published to the live maven repository. To test
things you can bypass this by setting up a mirror pointing to the release
candidate maven repository. You do that by adding the following to your maven
settings.xml file:
{code}
<mirrors>
<mirror>
<id>ant.staging</id>
<url>http://people.apache.org/~antelder/tuscany/1.0-RC1a/maven</url>
<mirrorOf>apache.incubator</mirrorOf>
</mirror>
{code}
The settings.xml is in a .m2 folder in your home directory, eg mines at:
"C:\Documents and Settings\Administrator\.m2". If you don't have one then we've
an example at:
[settings.xml|https://svn.apache.org/repos/asf/incubator/tuscany/java/etc/settings.xml]
h2. {anchor:Implementation JavaQuestions}
{bgcolor:#C3CDA1}Implementation Java Questions
{bgcolor}
h3. {anchor:ImplementationJavaA}
{bgcolor:#C3CDA1}What is the format for specifying multiple interfaces with the
@Service annotation?
{bgcolor}
{code}
@Service(interfaces={Interface1.class, Interface2.class, Interface3.class} )
public class ServiceImpl implements Interface1, Interface2, Interface3{
...
}
{code}
h3. {anchor:ImplementationJavaB}
{bgcolor:#C3CDA1}Why are references not being injected into my component?
{bgcolor}
If you have a component implementation that looks something like...
{code}
public class ServiceImpl implements ServiceInterface1{
@Reference
ServiceInterface2 serviceReference1;
@Reference
private ServiceInterface2 serviceReference2;
@Reference
protected ServiceInterface2 serviceReference3;
@Reference
public ServiceInterface2 serviceReference4;
...
}
{code}
Then in you operation you will find that serviceReference1 and
serviceReference2 are null because SCA will only inject references into fields
marked protected or public. This is true for the other injecting annotations,
for example, @Callback, @ConversationId and @Context.
h2. {anchor:Binding Questions}
{bgcolor:#C3CDA1}Binding Questions
{bgcolor}
h3. {anchor:BindingA}
{bgcolor:#C3CDA1}Can I use the EJB binding to publish an SCA services as an
SLSB?
{bgcolor}
Unfortunately, we only have the reference binding support for SLSB (call
SLSB from SCA) in Tuscany at this moment. Any contribution to support SLSB
service binding is welcome. :-)
h2. {anchor:DataBinding Questions}
{bgcolor:#C3CDA1}DataBinding Questions
{bgcolor}
h3. {anchor:DataBindingA}
{bgcolor:#C3CDA1}What is he difference between Logical Type and Physical Type?
{bgcolor}
The logical type represents the data type the user thinks is flowing across a
wire. This could be a Java type, a XML type, a CORBA type, whatever depending
on the /logical/ service contract defined in the assembly.
The physical type is the actual representation of that type that is flowed by
the runtime. In the Java runtime this will always be a Java type (i.e. some
subclass of Object). In some cases it will be the same as the logical type -
e.g. when a Java component calls another Java component over a local wire using
a Java interface then both logical and physical types will be the same. In many
cases though they will be different - for example, if the service contract was
WSDL then the logical type would be the XML type used by the WSDL.
Within the runtime the same logical type may have different physical forms.
For example, the same XML document could be represented physically as a DOM, a
StAX stream, an SDO, a JAXB object, or an AXIOM stream. The framework supports
conversion between these different physical forms.
{quote}
{quote}
# *What is the role of a data mediator interceptor? Can you cite an example of
how mediation works say for a component A with reference R that references a
service S in component B.?*
The interceptor gets added by the connector. A's outbound wire and B's inbound
wire describe the datatypes their implementations can support. When the wire
ends are connected the connector adds the interceptor if mediation is needed.
One job of a transport binding is to convert an in-memory physical
representation to a suitable set of bits on the network (aka serialization and
deserialization). Rather than reinvent the different transports we reuse
existing implementations such as Axis2 or RMI. As such we need to convert the
physical representation on our internal wire with that used by the transport.
So, for example, Axis2 only understands AXIOM so in a reference we need to
convert the user's physical representation to AXIOM and in a service we need to
convert the AXIOM generated by the transport into the form the user's
implementation requires. The steps could be described as follows:
## A calls reference R with physical Java object X(java)
## X is placed on R's outbound wire
## data mediation converts X(java) to AXIOM object X(axiom)
## X(axiom) is placed on inbound wire for the Axis2 binding
## Axis2 binding serializes X(axiom) onto the network as XML
## Axis2 binding on the target deserializes the XML from the network to X(axiom)
## X(axiom) is placed on the outbound wire from the Axis2 binding
## data mediation converts X(axiom) to X(java) as needed by the target component
## X(java) is placed on B's inbound wire
## the target instance for B is invoked passing in X(java)
. An important thing to note here is that from the fabric's perspective we are
dealing with two physical wires: the wire on the client connecting the source
component A to the outbound Axis2 transport and the wire on the server
connecting the inbound Axis2 transport to the target component B.
>From a global perspective there is one logical wire from A to B but because A
>and B are located on two different runtimes that logical wire gets split into
>two physical wires A->net and net->B.
h2. {anchor:Contribution Questions}
{bgcolor:#C3CDA1}Contribution Questions
{bgcolor}
h3. {anchor:ContributionA}
{bgcolor:#C3CDA1}What is META-INF/sca-contribution.xml for?
{bgcolor}
The [SCA Assembly Model Specification
V1.00|http://www.osoa.org/display/Main/Service+Component+Architecture+Specifications]
describes this file in section 1.10.2.3. Any composites that are named in the
sca-contribution.xml file will be automatically be included in the deployable
list maintained by the contribution.
If you have a contribution in a directory say.
/my/contribution/dir
Then all composites, along with any other resources, under this directory will
be located by the contribution service. For example, assume we have
/my/contribution/dir/META-INF/sca-contribution.xml
/my/contribution/dir/mycomposite.composite
Where sca-contribution.xml is
<contribution xmlns="http://www.osoa.org/xmlns/sca/1.0";
targetNamespace="http://mycomposite";
xmlns:management="http://mycomposite";>
<deployable composite="mycomposite:MyComposite"/>
</contribution>
So in this case the contribution service will locate the file
mycomposite.composite and, assuming it contains a composite called
mycomposite:MyComposite, will present it as being deployable based on the
information in sca-contribution.xml.
h3. {anchor:ContributionB}
{bgcolor:#C3CDA1}What is META-INF/sca-deployables/ for?
{bgcolor}
This is a Tuscany specific shorthand for defining deployable components, i.e.
you won't find it in the SCA specifications.
If you have a contribution in a directory say.
/my/contribution/dir
Then all components in composites under this directory will be located by the
contribution service and any components in composites under the directory
/META-INF/sca-deployables/ will automatically be included in the deployable
list maintained by the contribution, for example
/my/contribution/dir/META-INF/sca-deployables/mycomposite.composite
h2. {anchor:Specification Questions}
{bgcolor:#C3CDA1}Specification Questions
{bgcolor}
h3. {anchor:SpecificationA}
{bgcolor:#C3CDA1}Where are the specifications that Tuscany implements?
{bgcolor}
You can find the 6 SCA technical committees here:
[http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=sca-assembly]
[http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=sca-policy]
[http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=sca-bindings]
[http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=sca-j]
[http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=sca-c-cpp]
[http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=sca-bpel]
Meeting minutes, documents, issues and so on are linked from the main page.
Mailing list archives can be found here:
[http://www.oasis-open.org/archives/sca-assembly/]
[http://www.oasis-open.org/archives/sca-policy/]
[http://www.oasis-open.org/archives/sca-bindings/]
[http://www.oasis-open.org/archives/sca-j/]
[http://www.oasis-open.org/archives/sca-c-cpp/]
[http://www.oasis-open.org/archives/sca-bpel/]
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