Developing Web Services from Scratch - For DBAs and Database Developers

Raastech, Inc.
2201 Cooperative Way, Suite 600
Herndon, VA 20171
+1-703-884-2223
info@raastech.com
Developing Web Services from Scratch
For DBAs and Database Developers
BGOUG Spring 2017 Conference
Hotel RIU Pravets Resort
Saturday, June 3, 2017
16:00 - 17:00
Hall B

© Raastech, Inc. 2017 | All rights reserved. Slide 2 of 61@Raastech
Agenda
1. Introduction
2. Introducing Web Services
3. Accessing a Web Service
4. Anatomy of a WSDL
5. Getting Started: Concepts
6. Live Development Demo
 Java Web Service: Top-Down Development
 Java Web Service: Bottom-Up Development
 BPEL Web Service
7. Recap & Summary

About Me
 Ahmed Aboulnaga @Ahmed_Aboulnaga
 18+ years Oracle experience
 Author of “Oracle SOA Suite 11g Administrator’s Handbook”
 Author of “Oracle SOA Suite 12c Administrator’s Guide”
 OCE (SOA Foundation Practitioner)
 Oracle ACE

About Raastech
 Small systems integrator founded in 2009
 Headquartered in the Washington DC area
 Specializes in Oracle Fusion Middleware
 Oracle Gold Partner
 Oracle SOA Specialized

Why This Presentation
 Learn to develop a web service from scratch
 Lot of PL/SQL developers are intimidated by SOA development
 Presentation is specific to SOAP, but concepts are similar for REST

 How application access was previously developed
PL/SQL
ProcedurePL/SQL
Procedure
SQL
Developer
Java
Application
.NET
Application
ODBC driver
JDBC driver
SQL*NET
(internal)
Custom Drivers

 ProC anyone?
 Must be aware of the
technology of the target system
implementation and import the
necessary libraries and drivers
compatible with that technology
PL/SQL
ApplicationJava
Application
AS/400
Mainframe
.NET
Application
.NET drivers
IBM JARs
JDBC driver
Specific Target Implementation

 Standardization on SOAP over HTTP
Web
ServiceAny
Application
Java
Application
.NET
Application
SOAP over HTTP
SOAP over HTTP
SOAP over HTTP
SOAP over HTTP

 No need to worry about
implementation technology
of target applications
AWS
Java
Application
SalesForce
Paypal
SOAP over HTTP
SOAP over HTTP
SOAP over HTTP
Agnostic Target Implementation

CREATE PROCEDURE getWeather (
zipcode IN VARCHAR2,
temperature OUT NUMBER)
IS
BEGIN
temperature := '35';
END;
CREATE PROCEDURE setWeather (
zipcode IN VARCHAR2,
temperature IN NUMBER)
IS
BEGIN
INSERT INTO temperature
VALUES (zipcode, temperature);
END;
Request-Response
Synchronous
1-way
Asynchronous
PL/SQL Samples

PL/SQL
Procedure
PL/SQL
Procedure
PL/SQL
Procedure
PL/SQL
Procedure
Synchronous vs. Asynchronous

 Now that business functionality is exposed as web services, these
services need to be consumed somehow.
 Since web services are standards based, they can be invoked via the
majority of programming languages or through other services.
Web Service Clients

soapUI

 The web service interface is accessible via an HTTP URL:
http://admin.raastech.com:7001/GetWeather/WeatherPort?WSDL
 The web service implementation may or may not reside on the same
service:
<soap:address location="http://srv.raastech.com:8888/GetWeather/WeatherPort"/>
 Often impossible to tell what underlying language was used to create
the web service.
Accessing a WSDL

<definitions name="Weather">
<types>
<schema>
<element name="zip" type="string"/>
<element name="temp" type="string"/>
</schema>
</types>
<message name="zipReq"><part name="parameters" element="zip"/></message>
<message name="tempResp"><part name="parameters" element="temp"/></message>
<portType name="WeatherPort">
<operation name="getWeather">
<input message="zipReq"/>
<output message="tempResp"/>
</operation>
</portType>
<binding name="WeatherBinding" type="WeatherPort">
<input name="zipReq"/>
<output name="tempResp"/>
</operation>
</binding>
<service name="WeatherService">
<port name="WeatherPort" binding="WeatherBinding">
<soap:address location="http://localhost/wc/weather"/>
</port>
</service>
</definitions>
The WSDL is the
interface to the
web service.
Implementation
details of the web
service is unknown.
Dissecting a WSDL: Interface

<types>
<schema>
</schema>
</types>
</operation>
</portType>
</operation>
</binding>
</port>
</service>
</definitions>
Location is referred
to as the “endpoint”.
Identifies where the
actual code resides.
Dissecting a WSDL: Endpoints

<types>
<schema>
</schema>
</types>
</operation>
</portType>
</operation>
</binding>
</port>
</service>
</definitions>
This web service
has a single
operation, with an
input and an output
(i.e., synchronous).
Dissecting a WSDL: Operations

<types>
<schema>
</schema>
</types>
</operation>
</portType>
</operation>
</binding>
</port>
</service>
</definitions>
The type of the
message is defined
in the “schema”.
Dissecting a WSDL: Messages

JavaBPEL
getCustomerSoapUI
getCustomerSoapUI
Today’s Live Development Demo

 http://www.w3schools.com/xml/default.asp
 http://www.w3schools.com/schema/default.asp
 http://www.w3schools.com/xpath/default.asp
 http://www.w3schools.com/xsl/default.asp
 http://www.w3schools.com/xquery/default.asp
 http://www.w3schools.com/webservices/default.asp
 http://www.w3schools.com/webservices/ws_wsdl_intro.asp
 http://www.w3schools.com/webservices/ws_soap_intro.asp
 http://blog.raastech.com/2009/01/creating-top-down-java-web-service-for.html
 http://blog.raastech.com/2009/03/creating-bottom-up-java-web-service-for.html
w3schools References

 XML stands for “EXtensible Markup Language”.
 XML was designed to transport and store data.
 XML is designed to be self-descriptive.
 XML was originally designed to transport and store data.
 XML does not contain any logic.
Introduction to XML

 XML documents follow a tree structure.
 Every XML document must have 1 root element.
 The root element is the parent of all other elements.
<Customer>
<Name>John Doe</Name>
<OrderNumber>61237</OrderNumber>
<Items>
<Item quantity="2">Book</Item>
</Items>
</Customer>
XML Structure – Root Element

 Comments
<Customer>

<Items>
</Items>
</Customer>
XML Structure – Comments

 XML documents must have open and close tags.
 Valid HTML, but invalid XML:
<li> XML is easy
XML Structure – Tags

 Open and close tags must have matching case
<Customer>John Doe</customer>

 XML elements must be properly nested
<b><u>Hello World</b><u>

 Entity reference.
< < less than
> > greater than
& & ampersand
' ' apostrophe
" " quotation mark
XML Structure – Entity Reference

 Unlike HTML, whitespace is preserved in XML.
<Customer>
<Name>John Doe
is a person. His age is 20.</Name>
</Customer>
XML Structure – Whitespace

 Attributes
<Customer OrderNumber="61237">
<Items>
<Item quantity="1">Binder</Item>
</Items>
</Customer>
XML Structure – Attributes

 Should you use elements or attributes when designing XML
documents?
<Customer>
<Items>
</Items>
</Customer>
<Customer OrderNumber="61237">
<Items>
</Items>
</Customer>
XML Structure – Attributes vs. Elements

 Namespaces are identifiers.
<Customers>
<e:Customer xmlns:e="http://raastech.com/Employees">
<e:Name>John Doe</e:Name>
</e:Customer>
<p:Customer xmlns:p="http://raastech.com/Partners">
<p:Name>Jane Doe</p:Name>
</p:Customer>
<Customers>
XML Structure – Namespaces

 Default namespace; no need to prefix all child elements.
<Customer xmlns="http://raastech.com/Employees">
</Customer>
XML Structure – Default Namespace

 XML Schema defines elements in an XML document.
 XML Schema defines attributes in an XML document.
 XML Schema defines child elements, and optionally their number
and order.
 XML Schema defines data types for both elements and attributes.
 XML Schema defines default and fixed values for elements and
attributes.
Introduction to XML Schema

 XML Schemas are well-formed XML documents and are extensible.
 They are typically saved as .xsd files.
 The root element of every XML Schema is the <schema> element.
 The <schema> element may include attributes such as the XML
namespace.
Introduction to XML Schema

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xs:element name="Customer">
<xs:complexType>
<xs:sequence>
<xs:element name="OrderNumber" type="xs:string"/>
<xs:element name="Name" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
Example of an XML Schema

 A simple element contains only plain text that can be defined in one
of several predefined data types (or custom types).
 The predefined data types in XML Schema include:
 string
 decimal
 integer
 boolean
 date
 time
Simple Element

 String
<someelement>Hello World</someelement>
 Decimal
<someelement>12.50</someelement>
 Integer
<someelement>12</someelement>
 Boolean
<someelement>true</someelement>
Data Types

 Date
<someelement>2002-09-24Z</someelement>
<someelement>2008-07-24-06:00</someelement>
 Time
<someelement>08:00:00</someelement>
 DateTime
<someelement>2008-07-24T08:00:00</someelement>
Data Types

 Restrictions are also referred to as facets.
 Examples include:
 minInclusive
 maxInclusive
 Enumeration
 fractionDigits
 Length
 maxInclusive
 maxExclusive
 maxLength
 minLength
 totalDigits
Restrictions

 Complex elements are XML elements that contains other elements
or attributes.
<xs:element name="Customer">
<xs:complexType>
<xs:sequence>
<xs:element name="Name" type="xs:string"/>
<xs:element name="Item" type="xs:ItemType" minOccurs="1" maxOccurs="5"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:complexType name="ItemType">
<xs:sequence>
<xs:element name="Item" type="xs:string"/>
<xs:element name="Price" type="xs:decimal"/>
</xs:sequence>
</xs:complexType>
Complex Element

 SOAP stands for Simple Object Access Protocol.
 It is a communication protocol and allows XML documents to be
exchange over HTTP.
 As a result, it is platform and technology independent, and ideal for
Internet-based communication.
 A SOAP message is an XML document that contains the following:
 Envelope
 Header
 Body
 Fault
Introduction to SOAP

 Envelope
 Root element of a SOAP message.
 xmlns:soap namespace should always have the value of
http://www.w3.org/2001/12/soap-envelope.
 Header
 Optional.
 Could include information such as authentication information.
 First child element of the Envelope element.
 Body
 Required.
 Contains the content of the SOAP message (i.e., the payload).
SOAP Message

 Example:
<soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope">
<soap:Header>
</soap:Header>
<soap:Body>
<m:Customer xmlns:m="http://raastech.com/Customer">
<m:Name>John Doe</m:Name>
</m:Customer>
</soap:Body>
</soap:Envelope>
SOAP Message

 WSDL stands for Web Services Description Language.
 It is an XML document that describes a web service (i.e., it is the
interface specification for the web service).
 It specifies the location of the web service, the operations it
supports, and the message types.
Introduction to WSDL

 A top-down web service begins with a WSDL.
 Stubs for the underlying Java classes are created.
 Live Development Demo
Java Web Service Development: Top-Down
WSDL
(interface)
Java
(Class)
WSDL
(interface)
Create interface first Java class stub auto-created
Webservice
development
(top-down)

 A bottom-up web service begins with an already existing Java class.
 Class and methods are easily exposed as a web service interface.
Java Web Service Development: Bottom-Up
Java
(class)
WSDL
(interface)
Java
(class)
WSDL auto-generated
from Java class
Create Java class first
Webservice
development
(bottom-up)

BPEL Web Service Development

{
"Customer":
{
"FirstName":"John",
"LastName":"Doe"
}
}
<soap:Envelope
xmlns:soap="http://www.w3.org/2001/12/soap-envelope">
<soap:Body>
<m:Customer xmlns:m="http://raastech.com/Customer">
<m:FirstName>John</m:FirstName>
<m:LastName>Doe</m:LastName>
</m:Customer>
</soap:Body>
SOAP/XML Message
 Strong message type validation
 Based on XML standard
 Wide usage and adoption
 Not size-friendly:
 Size of data: 7 bytes
 Size of message: 236 bytes
REST/JSON Message
 Lightweight and efficient (mobile!)
 Growing usage and adoption
 Most moving to REST now
 Size-friendly:
 Size of data: 7 bytes
 Size of message: 50 bytes
SOAP vs. REST

 http://www.ateam-oracle.com/performance-study-rest-vs-soap-for-mobile-applications/
SOAP vs. REST

 Why has web services become the accepted standard?
 Are you more familiar with XML terminology?
 What is a popular SOAP client testing tool?
 What are the components of a SOAP message?
 Can you understand a WSDL when you look at it now?
 What is the difference between top-down and bottom-up web service
development?
 What is REST?
Recap

Contact Information
 Ahmed Aboulnaga
 Technical Director
 @Ahmed_Aboulnaga
 ahmed.aboulnaga@raastech.com

Q&A

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