Home > Articles > Web Development

  • Print
  • + Share This
This chapter is from the book

7.5 Service Composability

The composability of a service is an implicit byproduct of the extent to which the other service-orientation design principles have been successfully applied. The ability to compose services into new, higher-level services is an inherent, logical consequence if the other design principles outlined in this chapter are followed. For example, a service contract that is standardized allows interaction and composition between services implemented in different languages using different runtime environments. Decoupling a service implementation from its contract allows the same logic to be reused in other compositions.

With regards to the implications that service composability has for the service contract, this section highlights some of the issues and requirements for the runtime environment in which the services run. See Chapter 11 for further exploration of service composition with Java.

Runtime Environment Efficiency

A highly efficient and robust runtime environment is required for service compositions. The ability for services to participate in multiple compositions places severe challenges on runtime environments and must be taken into account when designing a service inventory.

If a service is used by multiple compositions, applying different non-functional characteristics can be necessary. One composition rarely invokes a service with no particular requirement for fast response times, whereas another composition using the same service can require support for high transaction loads with short response times. Similarly, one composition can require a reliable connection between the composition controller and its members, whereas another can be tolerant of lost messages. Applying different QoS definitions to the same service, depending on the composition, must be possible without requiring code changes in the service logic itself.

Java, as a programming language, has no built-in features that help or hinder the runtime environment. In most cases, Java-based services are hosted in a Java EE-compliant application server or an alleged Web server environment, which is Java SE-compliant. In either case, the runtime environments provide advantages over other traditional server platforms in terms of composability.

Java EE defines the management of solution logic according to the roles people perform, such as component provider, deployer, and assembler. As a result, much of the information on the execution of solution logic at runtime is not hardcoded into the logic itself but is instead stored in declarative configuration files, called deployment descriptors. The same piece of Java code can be used differently with different deployment descriptors and changed at runtime without requiring recompilation of the code. Despite being undefined by the Java EE standard, most Java EE application servers support defining individual server instances with specific runtime definitions. One instance usually runs in one process with its own configuration for elements like thread pools or memory heap sizes. In many cases, instances can be clustered to provide one logical application server across multiple physical processes or machines.

Separating runtime information about a component from its actual logic is possible because the Java EE application server runs as a container. This means that all incoming and outgoing data is intercepted and processed by the application server based on the current configuration. For example, if a certain piece of Java logic can only run within the scope of a transaction, the container can be configured to ensure a transaction is present whenever this piece of logic is invoked.

The same approaches to the runtime environment apply to Web services on two levels:

  1. The runtime environment that processes an incoming message, such as a SOAP or REST request message, can perform several tasks before forwarding the request to the actual service. These tasks include the ability to decrypt data sent in an encrypted form, establish handshaking between service consumer and service by returning acknowledgement that the message has been received, interpret information in the request message header indicating that the invocation of the service must be part of a distributed transaction, and convert incoming XML data into Java objects.
  2. For SOAP-based Web services, JAX-RPC and JAX-WS provide a mechanism and an API that allow the insertion of custom logic to parse, interpret, or change incoming and outgoing messages. The custom logic runs inside a handler. For JAX-RS-based implementations of REST services, such interception logic can be implemented by developers in special entity handlers known as entity providers. The JAX-RS 2.0 release provides added filters and interceptors otherwise not included in previous versions.

Both approaches are similar regardless of the Web services used. One is controlled by the user of the system, whereas the other is implicitly included with the runtime. Reading and manipulating incoming and outgoing messages separate from the service logic is crucial to supporting the Service Composability principle. Composing hosted services, including both composition members and composition controllers, is supported by the concept of containers and deployment descriptors and enhanced by SOAP-based Web services, such as handlers.

Ultimately, implementing a highly efficient runtime allows the developer to focus on the business logic of the actual service implementation, leaving everything else to the underlying Java platform. More advanced technologies, such as the SCA, expand on this concept by separating core business logic implementation further away from aspects of a service component, such as the protocol bindings used to interact with service consumers and other services used to fulfill functionality.

Service Contract Flexibility

Service contracts can be designed to increase the ability of a service for multiple compositions. Generally, multiple compositions are only applicable to the composition members for increasing the reusability of a service in different business contexts or business tasks. A service contract can be rewritten to enable reuse of a service without changing the core functionality of the service.

To write a flexible service contract that is reusable, recall the following approaches:

  • Use generic data types or supertypes instead of concrete subtypes. If an enterprise deals with both commercial customers (CommercialCustomer) and personal customers (PersonalCustomer), evaluate whether a common supertype can be established for both (Customer) to be used in the service contract. JAXB supports polymorphism to ensure that the appropriate Java object is created when a message containing a subtype is received.
  • Decouple the service contract from its underlying runtime platform by hiding details about QoS characteristics, which can change over time and will vary depending on service consumer requirements and how a service is deployed.
  • Decouple the service implementation from its contract by utilizing generic APIs, such as the JAX-WS Provider API for SOAP-based Web services. For REST services, deal with generic Java types in resource methods, such as String, byte[], and InputStream. Note that generated generic service consumer or service logic results in additional code that must be developed and tested.

Standards-Based Runtime

Composition members and controllers benefit from a runtime environment that supports a wide range of accepted standards. Composing services means the services interact and interoperate. Interoperability of services is supported by a runtime environment upheld by relevant standards, such as the WS-I. Java’s APIs for SOAP-based Web services, JAX-RPC and JAX-WS, require support for the WS-I Basic Profile, which allow services to be designed with a high degree of interoperability. REST services achieve full interoperability inherently through HTTP.

Advanced standards relevant in a composition of services include the WS-Security standards for which a WS-I profile also exists, the WS-Transaction and related standards, WS-Addressing, and WS-ReliableMessaging, which supports the reliable exchange of messages between services. These advanced standards are combined in another WS-I profile known as the Reliable Secure profile.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020