Page History

Anchor
Intro Intro

Background Color
color #C3CDA1
Introduction

This user guide will help you become familiar with SCA concepts and walks you through an example that demonstrates how to build an SCA application. It also describes the different environments that Tuscany supports (such as command line clients or web applications) and how to package up applications to run in these environments.

There's nothing to it really! Building SCA applications is easy. One of the main goals of Tuscany and SCA is to avoid imposing rules and requirements on how people write applications. We want to let people write application code the way they want without being concerned about the environment in which it will be used. After all, writing code to handle plumbing just gets in the way of writing the interesting stuff. So basically, you write the code for interesting bits, and Tuscany provides the environment that lets it run. Therefore, this guide is just an example of how an SCA application can be developed and is not a rule.

Anchor
Quick Guide to SCA Quick Guide to SCA

Background Color
color #C3CDA1
Quick Guide to SCA

The quick guide to SCA gives you an overview of SCA concepts and prepares you to work on the example below. You can skip this step if you are already familiar with SCA.

For more details on SCA please refer to the specifications at Open SOA web site.

Anchor
Example Walkthrough Example Walkthrough

Background Color
color #C3CDA1
Example Walkthrough

Anchor
Overview of Example Overview of Example

Background Color
color #C3CDA1
Overview of Example

We will use the calculator sample to walk through the steps for building an SCA application. As the name indicates, this example performs typical calculator operations. It is given two numbers and asked to perform an operation on them. Our calculator will handle add, subtract, multiply and divide.

We start with a simple variation of the calculator example and extend it to include more advanced SCA features.

Anchor
Getting Set Up Getting Set Up

Background Color
color #C3CDA1
Getting Set Up

• Download Tuscany Java SCA release.
  Please download the latest binary release. You can use the source code release but you will have to use Maven at all stages.
• Download prerequisites
  • Java 5
  • Maven 2.0.4+

If you want to build the sample with Ant rather than Maven you will need to download Ant instead

• • Ant 1.7.0

Anchor
Running The Calculator Sample Running The Calculator Sample

Background Color
color #C3CDA1
Running The Calculator Sample

Calculator is provided as a sample under SCA Java binary distribution. Let's first run the sample before we go about
building it. It is easy!

• Go to the directory ..\samples\calculator

  Code Block
  ant run

Alternatively if you want to run the sample directly from the command line try the following.

• if you are using Windows issue the command:

  Code Block

• java -cp ..\..\lib\tuscany-sca-manifest.jar;target\sample-calculator.jar calculator.CalculatorClient

• if you are using *nix issue the command:

  Code Block
  java -cp ../../lib/tuscany-sca-manifest.jar:target/sample-calculator.jar calculator.CalculatorClient

You

should

see

the

following

result:

3

+

2=5.0

3

-

2=1.0

3

*

2=6.0

3

/

2=1.5

If

you

are

using

the

source

disitribution

then

we

suggest

you

use

Maven

to

build

and

run

the

calculator

sample

because

the

tuscany-sca-manifest.jar

is

not

provided

with

the

source

distribution.

This

jar

is

part

of

the

binary

distribution

and

collects

together

all

of

the

tuscany

jars

in

one

place

so

that

the

java

command

line

is

nice

and

short

when

running

samples.

Anchor
Building The Calculator Sample In Java Building The Calculator Sample In Java

Background Color
color #C3CDA1
Building The Calculator Sample In Java

What you will learn

This example illustrates how to define your application while staying focused on the business logic. It walks you through the steps of building a composite application called calculator. All connections between the components within the composite are local and defined using Java interfaces.

Example walk-through

Step 1 - Define what building blocks are needed: Think about how your application can be broken down into smaller functions/services. Each block is a logical unit of operation that can be used in the overall application. In this case, calculator application can be divided into five blocks: AddService block, SubstractService block, MultiplyService block and DivideService block and a main block that takes a request and routes it to the right operation. We have called this main block the CalculatorService
Image Added

(?)TODO - need to update the diagram to change Add -> AddService etc. Who has the editable version?

Step 2 - Implement each block: Now that you have identified the blocks of functionality in your application, you are ready to create each block. In SCA the blocks of functionality are referred to as components so let's look at how we implement a component. We'll take the AddService component as our first example.

The AddService component will provide a service that adds two numbers together. The CalcualtorService component uses the AddService component whenever it is asked to perform additions. If we were writing the AddService component in plain old Java we would start by describing a (Java) interface.

public interface AddService {

    double add(double n1, double n2);
}

Now,

we

provide

an

implementation

of

this

interface.

public class AddServiceImpl implements AddService {

    public double add(double n1, double n2) {
        return n1 + n2;
    }
}

But

wait!

Aren't

we

writing

an

SCA

component?

It

must

be

more

complicated

that

that

-

the

mere,

plain

old

Java

interface

and

implementation,

right?

Well,

actually

an

SCA

component

can

just

be

plain

old

Java

so

we

have

just

done

all

the

coding

we

needed

to

implement

the

SCA

AddService

component.

We

can

use

SCA

to

expose

the

service

that

the

AddService

component

provides

over

any

of

the

supported

bindings,

for

example,

WebServices,

JMS

or

RMI,

without

changing

out

the

AddService

implementation.

Let's

take

a

look

at

the

CalculatorService

component.

This

is

interesting

because

it's

going

to

call

the

AddService

component.

In

the

full

application

it

will

call

the

SubtractService,

MultiplyService

and

DivideService

components

as

well,

but

we

will

ignore

these

for

the

time

being

as

they

follow

the

same

pattern

as

we

will

implement

for

the

AddService

component.

Again

we

will

start

by

defining

an

interface

because

CalcultorService

is

itself

providing

an

interface

that

others

will

call.

public interface CalculatorService {

    double add(double n1, double n2);
    double subtract(double n1, double n2);
    double multiply(double n1, double n2);
    double divide(double n1, double n2);
}

Now

we

implement

this

interface.

public class CalculatorServiceImpl implements CalculatorService {

    private AddService addService;
    private SubtractService subtractService;
    private MultiplyService multiplyService;
    private DivideService divideService;
   
    public void setAddService(AddService addService) {
        this.addService = addService;
    }

    ...set methods for the other attributes would go here

    public double add(double n1, double n2) {
        return addService.add(n1, n2);
    }

    ...implementations of the other methods would go here
}

Step 3 - Assembling the application:
So all well and good but how do we actually run these two components. Well of course the java programmer in us want's to get down to it, write a mainline to connect our two components together and run then. We could still do that easily in this case.

public class CalculatorClient {
    public static void main(String[] args) throws Exception {

        CalculatorServiceImpl calculatorService = new CalculatorServiceImpl();
        AddService            addService        = new AddServiceImpl();
        calculatorService.setAddService(addService);
      
        System.out.println("3 + 2=" + calculatorService.add(3, 2));
        // calls to other methods go here if we have implemented SubtractService, MultiplyService, DivideService
    }
}

But

this

doesn't

run

using

the

Tuscany

SCA

runtime and extending this code to provide web services interfaces, for example, would be a little more complicated. What do we have to do to make it run in Tuscany where we get all things like web service support for free? Well, not much actually. First let's change the client to fire up the Tuscany SCA runtime before calling our components.

public class CalculatorClient {
    public static void main(String[] args) throws Exception {

        SCADomain scaDomain = SCADomain.newInstance("Calculator.composite");
        CalculatorService calculatorService = scaDomain.getService(CalculatorService.class, "CalculatorServiceComponent");

        System.out.println("3 + 2=" + calculatorService.add(3, 2));
        // calls to other methods go here if we have implemented SubtractService, MultiplyService, DivideService

        scaDomain.close();
    }
}

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.

<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>

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.

        CalculatorServiceImpl calculatorService = new CalculatorServiceImpl();
        AddService            addService        = new AddServiceImpl();
        calculatorService.setAddService(addService);

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".

CalculatorService calculatorService = scaDomain.getService(CalculatorService.class, "CalculatorServiceComponent");

We can now use this reference as though we had created it ouselves, for example, from the CalculatorServiceImpl.add() method implementation.

return addService.add(n1, n2);

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.

ant compile

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.

ant run

Anchor
What Next What Next

Background Color
color #C3CDA1
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.

<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>

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.

<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>

Of

course

we

need

the

Ruby

code

that

implements

the

component.

def subtract(n1, n2)
    return n1 - n2
end

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
Tuscany SCA Extensions Tuscany SCA Extensions

Background Color
color #C3CDA1
Tuscany SCA Extensions

Anchor
The Extensible Runtime The Extensible Runtime

Background Color
color #C3CDA1
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
Available Extensions Available Extensions

Background Color
color #C3CDA1
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.

Anchor
Using Extensions Using Extensions

Background Color
color #C3CDA1
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;

META-INF/services/org.apache.tuscany.sca.core.ModuleActivator

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
Tuscany SCA And IDEs Tuscany SCA And IDEs

Background Color
color #C3CDA1
Tuscany SCA And IDEs

Anchor
Using The Samples In An IDE Without Maven Using The Samples In An IDE Without Maven

Background Color
color #C3CDA1
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
  my working dir/calculator

• Import all of the sample code and resources into this project, e.g.

  No Format
  Use the File,Import menu and then select tuscany_sca_install_dir/samples/calculator from the filesystem

• Configure the source path to include

  No Format
  tuscany_sca_install_dir/samples/calculator/src/main/java tuscany_sca_install_dir/samples/calculator/src/main/resources

• Configure the output folder to be

  No Format
  tuscany_sca_install_dir/samples/calculator/target

• Configure the build path to include all of the jars provided in

  No Format
  tuscany_sca_install_dir/lib

• If you select calculator.CalculatorClient.java and run as "Java Application" you should see

  No Format
  3 + 2=5.0 3 - 2=1.0 3 * 2=6.0 3 / 2=1.5

The details of how to do this for other development environments will vary but the process will be similar.

Anchor
Using The Samples In An IDE If You Have Maven Using The Samples In An IDE If You Have Maven

Background Color
color #C3CDA1
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;

cd sca 

If you are an Eclipse user do the following

mvn -Peclipse eclipse:eclipse  

If you are an IDEA user do the following

mvn idea:idea

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.