Welcome!

Weblogic Authors: Yeshim Deniz, Elizabeth White, Michael Meiner, Michael Bushong, Avi Rosenthal

Related Topics: Weblogic

Weblogic: Article

Developing JAX-RPC-based Web Services

Developing JAX-RPC-based Web Services

Web services are a type of service that can be shared by and used as components of distributed, Web-based applications. They are based on a collection of standards and protocols that allow us to make processing requests to remote systems by speaking a common, nonproprietary language and using common protocols (like HTTP, SOAP).

The Java API for XML-based remote procedure calls (JAX-RPC) simplifies the process of building Web services that incorporate XML-based RPC. It defines mappings between Java types and XML types that attempt to hide the details of XML and provide a familiar method-call paradigm. This article looks at how developers can use JAX-RPC to implement and call SOAP-based Web services described by the Web Services Description Language (WSDL) on the BEA WebLogic platform.

JAX-RPC-Based Web Services
JAX-RPC fully embraces the heterogeneous nature of Web services. It allows a JAX-RPC client to talk to another Web service deployed on a different platform and coded in a different language. JAX-RPC provides the specification for invocation modes, client generation, parameter modes, mappings for Java to WSDL and WSDL to Java, and client-side APIs for invoking the Web service.

Invocation Modes and Clients
JAX-RPC supports three kinds of Web services invocation modes:

  • Synchronous request-response: A client invokes a remote method on a Web service; the thread blocks while it is processed by the Web service and receives a return value or an exception.
  • One-way RPC mode: A client invokes a remote method on a Web service in one-way mode; the thread does not block and continues execution. The client gets no return value.
  • Nonblocking RPC mode: A client invokes a remote method on a Web service and continues processing in the same thread. Later, the client processes the remote method by performing blocking, receive, or polling for return values.

    With these modes, JAX-RPC supports two types of Java client applications - namely, static client and dynamic client. In this article, we will see how both Java clients can be written or generated using synchronous request-response mode on the WebLogic platform.

    Parameter Modes
    The Web service invocation based on JAX-RPC uses pass-by-copy semantics for parameter passing. It does not support the pass-by-reference way of parameter passing. The following types of parameters are supported by jax-rpc:

  • IN type: An IN parameter is passed as copy. The value of the IN parameter is copied before a Web service invocation. The return value is created as a copy and returned to the Web service client.
  • OUT type: An OUT parameter is passed as copy without any input value to the Web service method. The Web service method fills the OUT parameter and returns it to the client.
  • INOUT type: An INOUT parameter is passed as copy with an input value to the Web service method. The Web service method uses the input value, processes it, fills the INOUT parameter with a new value, and returns it to the client.

    The parameter passing mode for out and inout parameters uses holder classes. Holder classes enable the mapping to preserve the intended WSDL signature and parameter-passing semantics. The JAX-RPC specification includes "holder classes" for the mapping of simple XML types to the Java data types. The holder classes for primitive ones (e.g., int, float, etc.) are available with JAX-RPC implementation under the avax.xml.rpc.holders package. For the complex XML data types, the name of the holder class is constructed by appending Holder to the name of the corresponding Java class. These generated holder classes are packaged as part of the generated subpackage named holders in the WSDL-to-Java mapping.

    Each holder class provides the following methods and fields:

  • A public field named "value": The mapped Java type
  • A default constructor: Initializes the value field to a default value
  • A constructor: Sets the value field to the passed parameter

    Web Service Invocation
    BEA WebLogic 7.0 comes with a JAX-RPC 1.0-compliant runtime engine, which has both client-side and service-side libraries and deployment tools. Figure 1 shows a normal Web service invocation flow for synchronous request-response mode. The client application uses WebLogic's JAX-RPC runtime to perform a remote procedure call to invoke a method on the Web service. The runtime serializes Java objects to the SOAP message, which is sent to the Web service end point using HTTP transport. On the Web service side, WebLogic Platform receives this request and the service side JAX-RPC runtime deserializes the SOAP message into Java types and invokes the method on the Web service. The Web service, after processing the request, sends the response back to the client in a similar fashion.

    I have explained the simple Web service invocation based on JAX-RPC. The remainder of this article develops a sample Web service, and a static and dynamic client for it, on the WebLogic platform.

    An Order Processing Web Service
    I chose an order processing example for its proximity to a real busines-use case. This Web service will be capable of processing and updating a given "Order" using two methods - processOrder and updateOrder. ProcessOrder will take orderID string as an IN parameter and Order object as an OUT parameter. It will return status string as the return parameter. The updateOrder will take Order object as the INOUT parameter, update the orderDate, and return the Order object back to client. As both methods use a complex datatype, Order, that is also an OUT/INOUT parameter, a holder class has to be developed. The Order class and its holder class are shown in Listings 1 and 2 (the complete code can be found on the Web at www.sys-con.com/weblogic/sourcec.cfm):

    Now let's develop our Web service for the described functionality. The code is shown in Listing 3.

    The next step is to compile and deploy it on the WebLogic platform. WebLogic comes with some easy-to-use deployment tools using Ant (Apache's build tool) and includes predefined tasks for deploying the service on WebLogic Server 7.0. The sample "build.xml" is shown in Listing 4. This build file will generate an EAR file that will store information about the service endpoint, deployment descriptor (web-services.xml), and serializer and deserializer code (OrderCodec class); and will even generate a static client in the sample.client package and bundle it in a JAR file. The deployment descriptor (web-services.xml; it can be found in 'web-services.war' in 'ws_order.ear') has to be changed for the style of the parameter so the first method is OUT and the second method is INOUT. Once these changes are complete, repackage whole files into the EAR file (ws_order.ear) and deploy it using WebLogic's admin console. The OrderProcessing service will be available at the following URL:

    http://<your_machine_name>:<port-num>/
    <contextURI>/<serviceURI>

    In our case it may look like :

    http://localhost:7001/WebServices/OrderProcessing

    OrderProcessing Web Service Clients
    Static Client

    The static client to invoke a Web service uses a more strongly typed Java interface. On WebLogic, writing a static client is really easy as the Ant tasks specified above generate the client JAR, which has the following:

  • A Web service-specific implementation of the Service interface, which acts a stub factory
  • Serialization class for non-built-in data types and their Java representations
  • An interface and implementation of each SOAP port

    A client application has to use the generated classes in the client JAR. The static client is invoking the processOrder () method of the OrderProcessing Web service (see Listing 5).

    Dynamic Client
    A dynamic client is analogous to looking up and invoking the Java class methods using the reflection APIs. All the information like target endpoint and method parameters must be set explicitly. Listing 6 shows you how to write a dynamic client for invoking the updateOrder method OrderProcessing Web service.

    Running the Client
    For running both types of client, set the environment using a WebLogic-specific "setWLSEnv.bat" file. This .bat/.sh will set the classpath variable to include JAX-RPC-related jar files. Additionally, we have to add a client-specific JAR file generated by running the ant task earlier. After the environment is set, simply give the following commands:

    For the static client:
    <prompt>java sample.client.StaticClient

    For the dynamic client:
    <prompt>java sample.client.DynamicClient

    Conclusion
    In this article I tried to demonstrate how to develop JAX-RPC-based Web services. The method described here gives the developer the freedom to write client and Web services in a way that hides all the complexities of serializing objects on-the-wire XML format. For the developer, it will simply appear to be a Java method invocation. This article also highlights how easy it is to expose a given "Java class" as a Web service.

    References

  • http://e-docs.bea.com/wls/docs70/webserv/index.html
  • http://java.sun.com/xml/jaxrpc
  • More Stories By Rajesh Sumra

    Rajesh Sumra is a Senior Software Engineer in the Wireless Solutions Lab, Hewlett Packard. He holds a Masters degree in Information Technology from IIIT, Bangalore. He has been working with the e-speak project for more than a year and later been involved in developing UDDI Server functionalities for the HP's UDDI Server. Currently he is involved in designing and developing an Web services based framework for mobile infrastructure.

    Comments (0)

    Share your thoughts on this story.

    Add your comment
    You must be signed in to add a comment. Sign-in | Register

    In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


    @ThingsExpo Stories
    Nordstrom is transforming the way that they do business and the cloud is the key to enabling speed and hyper personalized customer experiences. In his session at 21st Cloud Expo, Ken Schow, VP of Engineering at Nordstrom, will discuss some of the key learnings and common pitfalls of large enterprises moving to the cloud. This includes strategies around choosing a cloud provider(s), architecture, and lessons learned. In addition, he’ll go over some of the best practices for structured team migrat...
    As businesses evolve, they need technology that is simple to help them succeed today and flexible enough to help them build for tomorrow. Chrome is fit for the workplace of the future — providing a secure, consistent user experience across a range of devices that can be used anywhere. In her session at 21st Cloud Expo, Vidya Nagarajan, a Senior Product Manager at Google, will take a look at various options as to how ChromeOS can be leveraged to interact with people on the devices, and formats th...
    SYS-CON Events announced today that Yuasa System will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Yuasa System is introducing a multi-purpose endurance testing system for flexible displays, OLED devices, flexible substrates, flat cables, and films in smartphones, wearables, automobiles, and healthcare.
    Join IBM November 1 at 21st Cloud Expo at the Santa Clara Convention Center in Santa Clara, CA, and learn how IBM Watson can bring cognitive services and AI to intelligent, unmanned systems. Cognitive analysis impacts today’s systems with unparalleled ability that were previously available only to manned, back-end operations. Thanks to cloud processing, IBM Watson can bring cognitive services and AI to intelligent, unmanned systems. Imagine a robot vacuum that becomes your personal assistant tha...
    Organizations do not need a Big Data strategy; they need a business strategy that incorporates Big Data. Most organizations lack a road map for using Big Data to optimize key business processes, deliver a differentiated customer experience, or uncover new business opportunities. They do not understand what’s possible with respect to integrating Big Data into the business model.
    Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, will discuss how from store operations...
    Recently, REAN Cloud built a digital concierge for a North Carolina hospital that had observed that most patient call button questions were repetitive. In addition, the paper-based process used to measure patient health metrics was laborious, not in real-time and sometimes error-prone. In their session at 21st Cloud Expo, Sean Finnerty, Executive Director, Practice Lead, Health Care & Life Science at REAN Cloud, and Dr. S.P.T. Krishnan, Principal Architect at REAN Cloud, will discuss how they bu...
    SYS-CON Events announced today that Dasher Technologies will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Dasher Technologies, Inc. ® is a premier IT solution provider that delivers expert technical resources along with trusted account executives to architect and deliver complete IT solutions and services to help our clients execute their goals, plans and objectives. Since 1999, we'v...
    SYS-CON Events announced today that TidalScale, a leading provider of systems and services, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. TidalScale has been involved in shaping the computing landscape. They've designed, developed and deployed some of the most important and successful systems and services in the history of the computing industry - internet, Ethernet, operating s...
    Enterprises have taken advantage of IoT to achieve important revenue and cost advantages. What is less apparent is how incumbent enterprises operating at scale have, following success with IoT, built analytic, operations management and software development capabilities – ranging from autonomous vehicles to manageable robotics installations. They have embraced these capabilities as if they were Silicon Valley startups. As a result, many firms employ new business models that place enormous impor...
    SYS-CON Events announced today that Taica will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Taica manufacturers Alpha-GEL brand silicone components and materials, which maintain outstanding performance over a wide temperature range -40C to +200C. For more information, visit http://www.taica.co.jp/english/.
    SYS-CON Events announced today that MIRAI Inc. will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MIRAI Inc. are IT consultants from the public sector whose mission is to solve social issues by technology and innovation and to create a meaningful future for people.
    As hybrid cloud becomes the de-facto standard mode of operation for most enterprises, new challenges arise on how to efficiently and economically share data across environments. In his session at 21st Cloud Expo, Dr. Allon Cohen, VP of Product at Elastifile, will explore new techniques and best practices that help enterprise IT benefit from the advantages of hybrid cloud environments by enabling data availability for both legacy enterprise and cloud-native mission critical applications. By rev...
    With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
    SYS-CON Events announced today that Datera will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Datera offers a radically new approach to data management, where innovative software makes data infrastructure invisible, elastic and able to perform at the highest level. It eliminates hardware lock-in and gives IT organizations the choice to source x86 server nodes, with business model option...
    Infoblox delivers Actionable Network Intelligence to enterprise, government, and service provider customers around the world. They are the industry leader in DNS, DHCP, and IP address management, the category known as DDI. We empower thousands of organizations to control and secure their networks from the core-enabling them to increase efficiency and visibility, improve customer service, and meet compliance requirements.
    Digital transformation is changing the face of business. The IDC predicts that enterprises will commit to a massive new scale of digital transformation, to stake out leadership positions in the "digital transformation economy." Accordingly, attendees at the upcoming Cloud Expo | @ThingsExpo at the Santa Clara Convention Center in Santa Clara, CA, Oct 31-Nov 2, will find fresh new content in a new track called Enterprise Cloud & Digital Transformation.
    SYS-CON Events announced today that N3N will exhibit at SYS-CON's @ThingsExpo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. N3N’s solutions increase the effectiveness of operations and control centers, increase the value of IoT investments, and facilitate real-time operational decision making. N3N enables operations teams with a four dimensional digital “big board” that consolidates real-time live video feeds alongside IoT sensor data a...
    SYS-CON Events announced today that NetApp has been named “Bronze Sponsor” of SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. NetApp is the data authority for hybrid cloud. NetApp provides a full range of hybrid cloud data services that simplify management of applications and data across cloud and on-premises environments to accelerate digital transformation. Together with their partners, NetApp emp...
    Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...