Services Oriented Architectures

by Sandeep Desai (http://www.thedesai.net/sandeep)

SOA is an abstract architectural concept in which automation logic is decomposed into individual services

• Loosely Coupled (using XML)
• Composable
• Interoperable (using SOAP)
• Reusable
• Discoverable (using UDDI)

SOA is built primarily using Web services framework consisting of WSDL, SOAP, XML

SOAP defines a standard format for the message exchange

SOAP Version 1.2 is a lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. It uses XML technologies to define an extensible messaging framework providing a message construct that can be exchanged over a variety of underlying protocols. The framework has been designed to be independent of any particular programming model and other implementation specific semantics.

• Envelope
• Root element of the SOAP XML
• Header
• Optional element
• Processing instructions for intermediaries and receiver
• Message routing information
• Security
• Context and transaction management information
• Body
• Mandatory element
• Contains the message payload

WSDL is a language independent definition to describe the Web service

• An XML grammar for describing a Web service
• Port defines physical location of the service
• May use XSD to formalize the message structure
• Google Search API WSDL

WS Standards

• Web Services Distributed Management
• Web Services Orchestration
• Web Service Transactions
• Web Service Policy
• Web Services Security (WS XML sent with SOAP XML)
• Web Services Reliable Messaging

BPEL (Business Process Execution Language)

• based on XML Schema, SOAP, WSDL
• Workflow
• send XML message
• Manipulate XML data structures
• Receive asynchronous messages
• Manage events and exceptions
• Define parallel sequence of execution

ESB (Enterprise Service Bus)

• Core platform of SOA deployment
• Intermediary layer that makes services widely available
• Routes messages
• Performs message transformation
• Standard based application integration
• Connects to resources using specific adapters or protocols
• Manages Security and QoS

Development approaches

• Top Down/Contract Driven i.e. WSDL to Java
• Bottom UP i.e. Java to WSDL

SOA 2.0

• Service and event driven architecture
• Components to respond to events and alerts instead of requests only

REST

• Simpler than SOAP
• No SOAP style body and envelope
• Request is simple HTTP GET or POST. No security

JAX-RPC Java Based API for working with SOAP has client stub and server endpoint. Uses WSDL

Oracle JDeveloper

• has a HTTP Analyzer to see SOAP message and response
• WSA (Web Services Assembler) java –jar wsa.jar
• Oracle Web Services Manager to manage web services (security, reliability etc)

Standards

• W3C: HTTP, HTML, XML, SOAP, WSDL, WS-Choreography, WS-Adressing, WS-Policy, XML Encryption, XML Signature
• OASIS: UDDI, WS-Security, WS-BPEL, WS-Notification, WS-Reliability, …
• WS-I: Web services Interoperability Organization

JBI (Java Business Integration)

JDeveloper Web Services

To create secure web services using WS-Security

Create keystore with following command

keytool -genkey -dname "CN=sandeep, OU=sandeepDept, O=sandeepOrg, L=sandeepHome, S=Florida, C=US" -keyalg RSA -sigalg Sha1WithRSA -keystore mytestkeystore.jks -alias saturn

Java Web Service Code

package net.thedesai.soa;

import java.util.ArrayList;

import java.util.Calendar;

import java.util.GregorianCalendar;

import java.util.List;

import javax.jws.WebService;

@WebService(name = "GetDateWS", serviceName = "GetDateWS")

public class GetDates {

public GetDates() {

}

public Calendar getDate() {

return Calendar.getInstance();

}

public Calendar getDateHence(int daysHence) {

GregorianCalendar myCalendar = new GregorianCalendar();

myCalendar.add(GregorianCalendar.DATE, daysHence);

return myCalendar;

}

public String sayHello() {

return "Hello!";

}

public List<Person> getPersons() {

List<Person> persons = new ArrayList();

persons.add(new Person("foo", 123));

persons.add(new Person("bar", 456));

return persons;

}

}

package net.thedesai.soa;

public class Person {

public Person() {}

public Person(String name, int salary) {

this.name = name;

this.salary = salary;

}

public int getSalary() { return salary; }

public void setSalary(int salary) { this.salary = salary; }

public String getName() { return name; }

public void setName(String name) { this.name = name; }

private int salary;

private String name;

}

WSDL Example (Generated from JDeveloper)

<definitions

name="GetDateWS"

targetNamespace="http://soa.thedesai.net/"

xmlns="http://schemas.xmlsoap.org/wsdl/"

xmlns:tns="http://soa.thedesai.net/"

xmlns:soap12="http://schemas.xmlsoap.org/wsdl/soap12/"

xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/"

xmlns:tns0="http://soa.thedesai.net/types/"

xmlns:xsd="http://www.w3.org/2001/XMLSchema"

xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"

xmlns:tns1="http://www.oracle.com/webservices/internal/literal"

>

<types>

<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://soa.thedesai.net/types/"

elementFormDefault="qualified" xmlns:tns="http://soa.thedesai.net/types/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:soap11-enc="http://schemas.xmlsoap.org/soap/encoding/"

xmlns:ns1="http://www.oracle.com/webservices/internal/literal">

<import namespace="http://soa.thedesai.net/"/>

<import namespace="http://www.oracle.com/webservices/internal/literal"/>

<complexType name="getDate">

<sequence/>

</complexType>

<complexType name="getDateResponse">

<sequence>

<element name="return" type="dateTime" nillable="true"/>

</sequence>

</complexType>

<complexType name="getDateHence">

<sequence>

<element name="param0" type="int"/>

</sequence>

</complexType>

<complexType name="getDateHenceResponse">

<sequence>

<element name="return" type="dateTime" nillable="true"/>

</sequence>

</complexType>

<complexType name="getPersons">

<sequence/>

</complexType>

<complexType name="getPersonsResponse">

<sequence>

<element name="return" type="ns1:list" nillable="true"/>

</sequence>

</complexType>

<complexType name="sayHello">

<sequence/>

</complexType>

<complexType name="sayHelloResponse">

<sequence>

<element name="return" type="string" nillable="true"/>

</sequence>

</complexType>

<complexType name="Person">

<sequence>

<element name="name" type="string" nillable="true"/>

<element name="salary" type="int"/>

</sequence>

</complexType>

</schema>

<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.oracle.com/webservices/internal/literal"

elementFormDefault="qualified" xmlns:tns="http://www.oracle.com/webservices/internal/literal"

xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:soap11-enc="http://schemas.xmlsoap.org/soap/encoding/">

<import namespace="http://soa.thedesai.net/"/>

<import namespace="http://soa.thedesai.net/types/"/>

<complexType name="list">

<complexContent>

<extension base="tns:collection">

<sequence/>

</extension>

</complexContent>

</complexType>

<complexType name="collection">

<sequence>

<element name="item" type="anyType" minOccurs="0" maxOccurs="unbounded"/>

</sequence>

</complexType>

</schema>

<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://soa.thedesai.net/"

elementFormDefault="qualified" xmlns:tns="http://soa.thedesai.net/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:soap11-enc="http://schemas.xmlsoap.org/soap/encoding/"

xmlns:ns1="http://soa.thedesai.net/types/">

<import namespace="http://www.oracle.com/webservices/internal/literal"/>

<import namespace="http://soa.thedesai.net/types/"/>

<element name="getDate" type="ns1:getDate"/>

<element name="getDateResponse" type="ns1:getDateResponse"/>

<element name="getDateHence" type="ns1:getDateHence"/>

<element name="getDateHenceResponse" type="ns1:getDateHenceResponse"/>

<element name="getPersons" type="ns1:getPersons"/>

<element name="getPersonsResponse" type="ns1:getPersonsResponse"/>

<element name="sayHello" type="ns1:sayHello"/>

<element name="sayHelloResponse" type="ns1:sayHelloResponse"/>

</schema>

</types>

<message name="GetDateWS_getDate">

<part name="parameters" element="tns:getDate"/>

</message>

<message name="GetDateWS_getDateResponse">

<part name="parameters" element="tns:getDateResponse"/>

</message>

<message name="GetDateWS_getDateHence">

<part name="parameters" element="tns:getDateHence"/>

</message>

<message name="GetDateWS_getDateHenceResponse">

<part name="parameters" element="tns:getDateHenceResponse"/>

</message>

<message name="GetDateWS_getPersons">

<part name="parameters" element="tns:getPersons"/>

</message>

<message name="GetDateWS_getPersonsResponse">

<part name="parameters" element="tns:getPersonsResponse"/>

</message>

<message name="GetDateWS_sayHello">

<part name="parameters" element="tns:sayHello"/>

</message>

<message name="GetDateWS_sayHelloResponse">

<part name="parameters" element="tns:sayHelloResponse"/>

</message>

<portType name="GetDateWS">

<operation name="getDate">

<input message="tns:GetDateWS_getDate"/>

<output message="tns:GetDateWS_getDateResponse"/>

</operation>

<operation name="getDateHence">

<input message="tns:GetDateWS_getDateHence"/>

<output message="tns:GetDateWS_getDateHenceResponse"/>

</operation>

<operation name="getPersons">

<input message="tns:GetDateWS_getPersons"/>

<output message="tns:GetDateWS_getPersonsResponse"/>

</operation>

<operation name="sayHello">

<input message="tns:GetDateWS_sayHello"/>

<output message="tns:GetDateWS_sayHelloResponse"/>

</operation>

</portType>

<binding name="GetDateWSSoapHttp" type="tns:GetDateWS">

<soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>

<operation name="getDate">

<soap:operation soapAction=""/>

<input>

<soap:body use="literal" parts="parameters"/>

</input>

<output>

<soap:body use="literal" parts="parameters"/>

</output>

</operation>

<operation name="getDateHence">

<soap:operation soapAction=""/>

<input>

<soap:body use="literal" parts="parameters"/>

</input>

<output>

<soap:body use="literal" parts="parameters"/>

</output>

</operation>

<operation name="getPersons">

<soap:operation soapAction=""/>

<input>

<soap:body use="literal" parts="parameters"/>

</input>

<output>

<soap:body use="literal" parts="parameters"/>

</output>

</operation>

<operation name="sayHello">

<soap:operation soapAction=""/>

<input>

<soap:body use="literal" parts="parameters"/>

</input>

<output>

<soap:body use="literal" parts="parameters"/>

</output>

</operation>

</binding>

<service name="GetDateWS">

<port name="GetDateWSSoapHttpPort" binding="tns:GetDateWSSoapHttp">

<soap:address location="http://138.1.196.199:8888/soa-getdates-context-root/GetDateWSSoapHttpPort"/>

</port>

</service>

</definitions>

Links

• Web Services Top 10 FAQ (Good starting point for beginners)
• REST (Plain Old XML Web Services simpler than SOAP)
• Time for REST
• Oracle BPEL Cookbook
• Java Web Services
• Java Web Services Tutorial
• Java Blueprints Catalog
• Apache Web Services
• Web Services Org
• WS-NonExistentStandards

• Google Web Search API
• Creating Google Web Search Application using JDeveloper
• Developing Web services using JDeveloper
• Secure Web Services using JDeveloper

• Web Services Authentication and Identity Management (5 page article)
• SOA Methodology (Issues to look into when adopting SOA)
• Open Source SOA stack
• Creating Web Services with WSAD 5.0
• Introducing JAX-WS 2.0 with Java 6
• Architecting Security for Web Services

Books

• Designing Web Services with the J2EE(TM) 1.4 Platform : JAX-RPC, SOAP, and XML Technologies
• J2EE Web Services by Richard Monsoon-Haefel