Archive for the ‘SOA’ Category

Will Recession Provide a Boost to SOA?

Posted on 10/19/2008 , Alexander Ananiev, 1 Comment ( Add )

There is no doubt that IT budgets will be cut next year. The size of the cut is hard to predict, but I think that it could exceed the Gartner’s forecast.

This, however, could finally give a shot in the arm to the long stagnated SOA projects. What makes me say that? Well, as I’ve been advocating all along, SOA represents an inexpensive way of adding flexibility and achieving new goals. SOA does not have to require significant new investments. Done smartly, it could be a great way of implementing new functionality without ripping the existing systems apart, which is undoubtedly won’t fly in light of highly constrained budgets.

To prove this point, in spite of lackluster economy, the demand for SOA architects has been booming.

There is one caveat to this view – organizations need to stop approaching SOA from the infrastructure standpoint (i.e., what ESB product do I need?) and start using it as a solution to real business needs. I’m not entirely sure that it’s going to happen, but bad economy could be just the motivation for that.

You Ain’t Gonna Need ESB

Posted on 08/25/2007 , Alexander Ananiev, 1 Comment ( Add )

Bobby Wolf posted a great article about a wide-spread problem plaguing many SOA implementations: over-engineering of SOA infrastructure, meaning that people rollout products that are not particularly required to implement their business services. He specifically talks about ESBs, but I would say that "you ain't gonna need it" principle should be applied to any component of a SOA stack. For example, why implement a super-expensive BPM suite (or a BPEL engine) when an organization is simply trying to build some data services? Or why pay for a registry if there are only a handful of services in place?

What many people don't realize is just how many SOA-related features are already provided by application servers. Open-source Glassfish server supports JAXR Web services repositories, XSLT mediations, JBI integration and provides extensive Web services monitoring capabilities. It can be augmented by several open-source JBI-based ESBs, such as OpenESB. Other application servers provide similar set of features, although using different technologies (e.g., SCA instead of JBI in IBM products). With an application server being so powerful, there should be a very good reason and business rationale for upgrading to commercial SOA/integration products.

In my mind the right strategy for any SOA is to first implement some services that provide immediate value to the business stakeholders. These services should be implemented using the products already owned and used by an organization (or by using open source ones). After the initial success of this implementation, the organization can evaluate commercial products to see how these products will help implement next set of business requirements/goals more efficiently.

Is The End of SOAP Dominance Nearing?

Posted on 08/11/2007 , Alexander Ananiev,

SOAP-based services currently dominate the enterprise landscape. Main reasons this are:

  • SOAP tight coupling with WSDL. Until recently, SOAP was the only supported WSDL binding. WSDL, with all of its issues (such as the convoluted structure), remains the only widely accepted vendor-neutral way of defining services.
  • In Java world, SOAP was promoted by adding its support to J2EE/Java EE via JAX-RPC and JAX-WS specifications. There is a way to create RESTful services using JAX-WS, however this approach has not gained wide acceptance due to a number of reasons (lack of standardized WSDL binding being one of them).
  • Solid support by software vendors. SOAP is supported in all application servers; there are plenty of development tools (including Eclipse and NetBeans) that can help with creating SOAP-based services.
  • Availability of a number of WS-* specifications that only work with SOAP. WS-* specs, such as WS-Security and WS-ReliableMessaging heavily rely on SOAP headers for passing message metadata.

SOAP, however, is far from perfect. It adds complexity and overhead and makes implementation of message intermediaries (e.g., gateway products) more difficult (XML message has to be parsed in order to obtain any information about the message, such as an operation name). On the other hand, the uptake of WS-* standards has been very slow, perhaps with the exception of WS-Security, so the benefit of WS-* integration with SOAP failed to materialize. Another supposed SOAP benefit is the protocol neutrality, i.e., a SOAP message looks the same over HTTP, JMS, RMI or any other supported protocol. However, most services are implemented using HTTP, or in some cases, JMS without any headers (unless WS-* is used), so this benefit has limited value.

So it is fair to say that in many instances, SOAP itself does not add any value to Web services implementation. Nevertheless, it's continued to be used because of the reasons listed above. But this situation might be changing in the future.

WSDL 2.0 fully supports HTTP binding. WSDL 2.0 stirred a lot of controversy (I personally think that it's a step forward from WSDL 1), however, it was finally accepted as a W3C recommendation in June, so we can fully expect that vendors support will follow.

Additionally, JAX-RS specification was created and included into Java EE 6. This will also promote development of RESTful services behind the firewall.

Currently, there a preconceived notion that REST is only good for Internet/WEB 2.0 environment, whereas enterprise services should all be using SOAP. The emergence of the two new standards will help change this notion.

Ideally, developers should be able to use the simplest binding that gets the job done. HTTP/REST can be a good choice for many "query-style" services. Services that accept more complex data can use "Plain Old XML" over HTTP post. Finally, services that have to rely on WS-* specifications will utilize SOAP. In all these cases, developers should be able to use same set of APIs for invoking the service and same set of annotations (obviously, with different parameters) for creating the service.

Perhaps this is how Web service development will be done in the future, but we are certainly not there yet.

Improve Your Application Performance with XML Appliance

Posted on 07/29/2007 , Alexander Ananiev, 1 Comment ( Add )

XML appliances are capable of extremely fast XML parsing and transformation (sometimes the term "wire-speed" is used). The speed is achieved by using hardware acceleration, specially written XML parsers and XSLT engines (you won’t find Xerces on these devices) and optimized operating system (usually, a trimmed-down version of Linux or BSD).

How fast are XML appliances? I’m not aware of published benchmarks; however, I did have a chance to conduct an informal performance testing of DataPower XI50 for a client and the results were quite impressive; for example we saw little to no overhead validating medium-size XML schemas.

Clearly, offloading as much XML processing as possible to an appliance could be a performance booster. So what kind of processing could be done on the device? Here are my recommendations based on the capabilities of the DataPower appliance; the situation could be slightly different with devices from other vendors. (more…)

Using Maven Repository as Web Services Registry

Posted on 07/01/2007 , Alexander Ananiev, 6 Comments ( Add )

A Web services registry is arguably one of the most important components of SOA. The registry provides a single source of information about all services in an enterprise.

There are a number of commercial registry/repository products but all of them are quite pricey. Also, smaller organizations or organizations just starting with SOA may not need the full power of a commercial registry/repository product; most of it functionality will remain unutilized. On the other hand, existing registries do not do a particularly good job of managing dependencies between services as well as between service consumers and service providers. Dependency management must be a key consideration in SOA since, unlike in the case of monolithic applications, an SOA consists of a large number of “moving parts”, that is, services. In a well developed SOA most services depend on other services and these services in turn may rely on some other services. Being able to manage and analyze services dependencies is required in order to be able to implement robust and maintainable SOA.

Open source Maven project has become something close to a de-facto standard in the area of dependency management for building Java-based projects and components. (more…)

XML Appliances Begin Supporting Java

Posted on 06/21/2007 , Alexander Ananiev,

Layer7 announced that its appliances will support Java-based custom assertions. Details are sketchy at this point but apparently Layer7 will provide a proprietary SDK for developing assertions. This could be much more powerful mechanism than XSLT-only facilities in IBM DataPower.

So how long before appliances begin supporting JBI and SCA components? The trick here of course is to make sure that an appliance is still a robust low-maintenance device that can't be brought down by a rogue application thread. But if Layer7 was able to figure it out for Java in general (I wonder if they use a general Sun JDK or some kind of a special JDK build), there is no reason why an appliance can't start supporting more advanced specifications such as JBI/SCA.

Comparison of SOA Suites

Posted on 06/17/2007 , Alexander Ananiev, 10 Comments ( Add )

Several SOA vendors are trying to put together comprehensive suites of SOA products that in theory should be capable of addressing all aspects of SOA, including governance, integration, business process management and others.

Formation of SOA suites is having a tremendous impacts on how SOA products are selected as many organizations are being tempted to settle for "one stop shop" approach as opposed to doing proper product evaluation within each SOA product category. (Interesting discussion about SOA suites is available at ZDNet).

So what is a SOA suite and how offerings from different vendors support different aspects of SOA? The table below attempts to answer this question. (more…)

SCA and JBI Mean Nothing for SOA?

Posted on 06/06/2007 , Alexander Ananiev, 3 Comments ( Add )

There is an interesting and somewhat controversial interview with ZapThink's Jason Bloomberg where he claims that SCA and JBI are just going to "muddy the waters" as opposed to provide real help to SOA architects.

I certainly agree with his assessment that SCA (can't really speak about JBI) is more of a generic component-centric programming model than a SOA implementation framework. I blogged about it before. However, I do think that SCA is going to provide a lot of value in the area of application architecture and just general component reuse. A technology or a framework does not have to be about SOA to be useful.

Will JAX-WS Become the Primary Mechanism for Invoking RESTful Services?

Posted on 06/02/2007 , Alexander Ananiev, 3 Comments ( Add )

Developers working with REST and XML/HTTP services have traditionally used light-weight APIs, such as java.net classes or Apache HttpClient. Web services APIs provided by JAX-RPC were SOAP and "enterprise" only and they required J2EE libraries. The situation changed with the release of JAX-WS and its inclusion into Java SE 6. JAX-WS supports RESTful services; also, its Dispatch interface allows clients to work with XML directly as opposed to having to use object mapping or completely unwieldy SAAJ API. A nice example of using JAX-WS to implement a client for a RESTful service is available in Mark Hadley's blog.

However, I don't think that JAX-WS is going to become the primary way of implementing RESTful clients just yet. In many situations, HttpClient provides more flexibility and control over HTTP calls.

For example, it is very straightforward to turn on basic authentication for a client using HttpClient APIs: (more…)

Is ESB The Mediation Infrastructure of Web Services Platform?

Posted on 05/28/2007 , Alexander Ananiev, 1 Comment ( Add )

Lori MacVitte from F5 had a few comments about my post on using XML appliances in ESB capacity. While I don't completely agree with some of her specific points about what ESB capabilities are missing from XML appliances (for example, parallel processing is employed by most appliance vendors, transactionality is also supported for relevant protocols (although no XML appliance can act as an XA transaction coordinator)), the overall observation is correct – there is (and there always will be) a big difference between software-based ESBs and hardware-based XML appliances.

Software ESBs are implemented on top of application servers or messaging products. As such, they are infinitely flexible. Even if certain feature (e.g., some fancy transformation) is not supported by the ESB product out of the box, it can always be custom-developed using Java or other language supported by the product. This custom code can use all the facilities of the underlying application server, such as transaction management, connection pooling and so forth. (more…)

Is XML Appliance the Ultimate ESB?

Posted on 05/23/2007 , Alexander Ananiev, 7 Comments ( Add )

IBM recently announced that DataPower XI50 appliance now supports transformations developed using WebSphere Transformation Extender design studio. This is the same technology used in the Message Broker product. Additionally, support for WebSphere Registry and Repository has been added. From the announcement:

New offerings being announced today include the WebSphere DataPower Integration Appliance XI50, which now supports direct database connectivity including IBM's DB2 data server extending the XI50's enterprise service bus capabilities. It also adds support for WebSphere Transformation Extender design studio providing common data transformation tooling across IBM's ESB portfolio. The XI50, along with a new version of the WebSphere DataPower XML Security Appliance XS40, now integrates with the IBM WebSphere Service Registry and Repository (WSRR) to offer enhanced governance capabilities and improve service interoperability, reuse and connectivity.

So why is it significant? (more…)

Finally, Somebody is Thinking about Batch Processing

Posted on 05/20/2007 , Alexander Ananiev,

Batch processing (a.k.a. "bulk processing") is dull and boring compared to the new world of SOA, Software as a Service and Web 2.0. It’s hardly ever mentioned these days, so one can get an impression that batch processing all but disappeared from an enterprise and got replaced by “enterprise mashups”, or, at the very least, Web services.

Of course, nothing can be further from the truth. While Web services indeed begin playing a key role in many organizations, batch files still remain one of the most widespread form of system integration due to a large number of "legacy" systems that rely on it. At the same time, batch processing presents certain challenges to developers; these challenges include high volume/high throughput requirements since batch processing is inherently “spiky”, ability to deal with failures, which usually requires checkpoint/restart capabilities and many others.

The way batch files are processed varies greatly from system to system; in most cases developers end up creating their own custom frameworks to handle batch processing requirements. (more…)

soapUI vs. JUnit

Posted on 04/28/2007 , Alexander Ananiev, 12 Comments ( Add )

Open source soapUI tool has a number of benefits over developing test cases in Java using JUnit framework. Some of these benefits include:

  • Use of UI for creating/configuring tests. This makes it possible for non-programmers to develop tests, which means that testing of Web services can be performed by a QA/system test group.
  • Auto-generation of test messages based on WSDL.
  • Ability to externalize test data using property files.
  • Built-in assertions, such as checking for SOAP faults and validity of the schema.
  • Built-in stress testing capabilities.
  • Management of endpoint URLs.

Overall, soapUI allows developers and testers to create tests quicker and also makes tests easier to manage and update.

However, one needs to understand shortcomings of this approach. soapUI uses its own Web services client. The way it creates test messages is different from how regular (JAX-WS-based and other) Web services clients work. soapUI completely skips the step of generating Java classes from WSDL. It does not have to deal with XML marshalling/unmarshalling from/to Java objects. As a result, you are not invoking your service the way it will be invoked by real Web service consumers.

Technically, it may not be an issue in a majority of cases. The fact that soapUI is able to parse your WSDL/schema and generate test message means that you have a valid WSDL that should also be consumable by other technologies. However, it is possible that your WSDL/ schema may lead to sub-optimal (albeit perfectly valid) generated classes. For example, the schema that defines <addresses><address>...</address>...</addresses> XML will result in JAXB compiler generating Addresses class that returns the list of type Address. This may or may not be how you want Java classes to look like for the clients. Perhaps you may want to consider to get rid of <addresses> so that no extra class is generated.

In other words, using soapUI (or similar UI-based Web services testing tools, such as SOAPScope) does not allow you to understand all the details of how your Web service will be consumed in the real world.

Another advantage of JUnit test cases is that they can be used as examples illustrating the use of your service. The test classes can be published along with other Web service documentation or handed over to consumers to help them jump-start their client implementations. Unfortunately, soapUI test cases can't be used for this purpose.

The shortcomings of visual testing tools such as soapUI can be addressed by complementing soapUI tests with JUnit tests. I usually start with soapUI since it is so easy to get up and running with it. Once soapUI test is implemented, I go back to Java, generate Web services client classes from WSDL and implement a JUnit test class. The logic that goes into a JUnit test class obviously depends upon a Web service. But at the very least, there should be one JUnit test per service that invokes the service using generated classes and libraries provided by your Web service product of choice. This way, we can see exactly how our services will be consumed by our clients.

Create JAX-WS Service in 5 Minutes (Tutorial)

Posted on 04/19/2007 , Alexander Ananiev, 49 Comments ( Add )

This is a brief tutorial describing how to create a Web service using WSDL and annotations. The approach presented here allows you to design and implement your WSDL/Schema and Java classes independently without having to generate anything. You can then use annotations to map Java classes to appropriate WSDL and Schema elements.
Since JAXB and JAX-WS have sensible defaults, the number of annotations can be kept to the minimum.

In my opinion, it is always best to develop WSDL and schemas by hand to ensure that the service contract is appropriately defined and also that the schema can be re-used (by other services) and extended if necessary. I do not recommend using annotations for automatically producing WSDL and schemas at runtime as this leads to simplistic schemas and WSDLs.

Generating classes from WSDL/schema sometimes makes sense, say in situations when you have to use a pre-defined schema. However, as with any code generation, it creates a maitainance problem especially if there is a need to put behavior into generated classes. So it is desirable to be able to evolve object model and service implementation classes independently from WSDL/schemas. You can do it quite easily by following the steps below.

Even though I use the word "create" when describing some of the steps, the same approach will also work for updates or refactoring caused by changes in service requirements.

The steps are the following:

  • Design your service interface. In our case the service has a single "add" operation that accepts a "person" document, adds it to a database and returns back the status:
    public String add( Person person )
  • Design your data/object model. In our case Person class has three fields (ssn, firstName, lastName) and the list of addresses. Real world examples will certainly be more complex, but this is good enough for our purposes.
  • Define XML schema based on your object model. Use strict datatypes where possible. For example, we use xsd:token instead of xsd:string since "token" does not allow carriage return, tabs, and leading spaces:
  •     <xsd:element name="person">
            <xsd:complexType >
                <xsd:sequence>
                    <xsd:element name="ssn" type="xsd:token" 
                            minOccurs="1" maxOccurs="1"/>
                    <xsd:element name="firstName" type="xsd:token" 
                            minOccurs="1" maxOccurs="1"/>
                    <xsd:element name="lastName" type="xsd:token" 
                            minOccurs="1" maxOccurs="1" />
                    <xsd:element name="address" type="Address" 
                            minOccurs="1" maxOccurs="unbounded"/> 
                </xsd:sequence>
            </xsd:complexType>
        </xsd:element>
      

    Complete schema file

  • Create an XML file for your schema so you can test the schema. You can generate an XML instance document automatically from Eclipse (assuming you're using Eclipse Web Tool Platform) by right-clicking on the schema in navigator and selecting "generate". Test the schema by changing data and making sure that you're getting correct validation errors.
  • Sample XML file

  • Create WSDL. Our WSDL imports the schema that we just created. Note that the WSDL target namespace is different from the schema namespace since the same schema can be reused by different WSDLs:
  •     <wsdl:definitions 
              targetNamespace="http://personservice" 
              xmlns="http://personservice" 
              xmlns:pers="http://person"
              xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" 
              xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" 
              xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/" 
              xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      
          <wsdl:types>
                <xsd:import namespace="http://person" 
                        schemaLocation="person.xsd" />
                <!-- Return value -->
                <xsd:element name="status" type="xsd:string" />
          </wsdl:types>
          ...
      

    Complete WSDL file

  • Create your object model classes and annotate them with appropriate JAXB annotations:
  •     // By default JAXB uses getters/setters for marshaling/unmarshaling
        // Using fields access allows us not to define getters/setters for 
        // all mapped instance variables.
        @XmlAccessorType(XmlAccessType.FIELD)
        // We need to provide the namespace, otherwise it defaults to
        // the package name
        @XmlRootElement(namespace="http://person")
        public class Person {
        
            // we only need annotations for variables that don't match 
            // element names
            private String ssn;
            private String firstName;
            private String lastName;
            
            @XmlElement(name = "address")
            protected List<Address> addresses;
          ...
      

    Person class
    Address class

  • Create ObjectFactory class. This class is required by JAXB and it should contain factory methods for all JAXB-mapped classes. ObjectFactory must resides in the same package with object model classes.
  •     @XmlRegistry
        public class ObjectFactory {
        
            public Person createPerson() {
                return new Person();
            }
            
            public Address createAddress() {
                return new Address();
            }
        }
      

    ObjectFactory class

  • Create Web Service implementation class. Note that with JAX-WS Service Endpoint Interface (SEI) is optional, so all you need is an implementation class:
  •       @WebService(
                  // all values must match corresponding attributes 
                  // and elements of the WSDL file
              
                  // Name of the port type in WSDL
                  name="PersonService",
                  // Target namespace of WSDL, could be 
                  // different from the schema namespace
                  targetNamespace="http://personservice",
                  serviceName="PersonServicePorts",
                  portName="PersonService",
                  // the file must be available to Web container
                  wsdlLocation="WEB-INF/wsdl/PersonService.wsdl"
          )
          
          /*
           * We'are using "bare" style since "add" operation 
           * takes only one argument, person document. Therefore, there 
           * is no need to "wrap" it by nesting it inside operation element.
           * Note that "wrapped" style is the default.
           */
          @SOAPBinding(parameterStyle=SOAPBinding.ParameterStyle.BARE)
          
          public class PersonService {
              
              @WebResult(name = "status")
              public String add( Person person ) {
                  
                  System.out.println("Adding person :"+person );
                  return "Added "+person.getFullName();
              }
          }
      

    PersonService class

  • Deploy your Web service to your application server or Web services container. Refer to your application server documentation for details.
  • Test the service. The easiest way to test the service is to use open source soapUI tool. You can install it as Eclipse plugin (there are also plugins for NetBeans and IDEA) following these instructions. In Eclipse, open SoapUI view, right click and create a project from your WSDL file. SoapUI will automatically create a sample SOAP request which you can update with your data. You can run it right away. Later, you can create a repeatable test suite with parametirized data using SoapUI properties and assertions:


SoapUI Project (you can import it into SoapUI).

You can also download all files in a zip file.

WS-I Basic Security Profile Has Been Released

Posted on 04/12/2007 , Alexander Ananiev,

The final version of Basic Security Profile 1.0 (BSP) was recently been released by WS-I. This is certainly a welcome event; WS-Security is broad and complex and it has been plagued by interoperability issues for quite some time (although the situation has improved in the last year or so). The BSP document seems to have pretty good level of details with plenty of good examples that are easy to follow.

I looked at a few messages generated by Axis used in conjunction with Apache WS-Security implementation called Rampart and at the first glance they seem to be compliant with BSP, although all my examples use WS-Security username token profile, which is the simplest form of passing credentials with WS-Security.

As an example, Rampart generates the correct form of the password tag, which includes "type" attribute (this attribute is not mandated by WS-Security, however, it is required by BSB):

<wsse:Password
      Type="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-username-token-profile-1.0#PasswordDigest">
      B5twk47KwSrjeg==
   </wsse:Password>

BSP is going to make the use of WS-Security more widespread, although this is not going to happen overnight. Currently, none of the public Web services (Yahoo, Ebay, Amazon) use WS-Security, which is not surprising since the standard is not fully supported by such languages as PHP, Python and Ruby (although some aspects of WS-Security are supported in PHP). Even platforms for commercial services, such as StrikeIron, don't use it (StrikeIron does support WS-Security for communication between its broker and service providers, but not for client calls).

In any event, I'm pretty confident that we can count on rising WS-Security adoption in an enterprise.