Release 2 (9.0.2)
Part Number A95109-01
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| Oracle9i Application Server Migrating From WebLogic Release 2 (9.0.2) Part Number A95109-01 |
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This chapter provides an overview of the issues involved in migrating J2EE web applications from WebLogic Server 6.0 to Oracle9i Application Server (Oracle9iAS) Release 2, and the effort required.
The chapter contains these topics:sv
The application server market is evolving rapidly. In particular, the most significant development over the last few years is the emergence of Sun Microsystems' Java 2 Platform, Enterprise Edition (J2EE) Specification that promises to create a level of cross-vendor standardization.
The J2EE platform and component specifications define, among other things, a standard platform for developing and deploying multi-tier, web-based, enterprise applications.
J2EE provides a solution to the problems encountered by companies moving to a multi-tier computing model. The problems addressed include reliability, scalability, security, application deployment, transaction processing, web interface design, and timely software development. It builds upon the Java 2 Platform, Standard Edition (J2SE) to enable Sun Microsystems' "Write Once, Run Anywhere" paradigm for multi-tier computing.
J2EE consists of the components described in Table 1-1:
The J2EE application model is a multi-tier application model. Application components are managed in the middle tier by containers. A container is a standard runtime environment that provides services, including life cycle management, deployment, and security services, to application components. This container-based model separates business logic from system infrastructure.
The J2EE platform consists of a runtime environment and a standard set of services that provide the necessary functionality for developing multi-tiered, web-based, enterprise applications.
The J2EE platform consists of the components described in Table 1-2.
An application server is software that runs between web-based client programs and back-end databases and legacy applications. It helps separate system complexity from business logic, enabling developers to focus on solving business problems. An application server helps reduce the size and complexity of client programs by enabling these programs to share capabilities and resources in an organized and efficient way.
Application servers provide benefits in the areas of usability, flexibility, scalability, maintainability, and interoperability.
Oracle9iAS is a comprehensive, integrated application server that provides all of the infrastructure and functionality needed to run every successful e-Business. All development teams face a similar set of challenges--the need to rapidly deliver web sites and applications that run fast over any network and on every device; while providing business intelligence to support operational adjustments and strategic decisions. Oracle9iAS enables teams to address all of these e-business challenges.
Oracle9iAS has generated a great deal of interest in the application server market, and many organizations are embracing it to deploy their web-based, enterprise applications.
Oracle9iAS offers the only integrated infrastructure to develop and deploy web sites and applications. It provides a complete J2EE platform for developing enterprise Java applications. Oracle9iAS enables developers to develop web applications in any language including Java, Perl, PL/SQL, XML, and Forms. It enables the reduction of development and deployment costs through a single, unified platform for Java, XML, and SQL.
The J2EE server implementation in Oracle9iAS is called Oracle9iAS Containers for J2EE (OC4J). OC4J runs on the standard JDK and is extremely lightweight, provides high performance and scalability, and is simple to deploy and manage. With Oracle9iAS Release 2, the OC4J supports J2EE 1.2 with support for some J2EE 1.3 features.
This migration guide seeks to help you understand the migration challenges you may face when migrating your J2EE applications from Weblogic Server 6.0 to Oracle9iAS.
The varying degrees of compliance to J2EE standards can make migrating applications from one application server to another a daunting task. Some of the challenges in migrating J2EE applications from one application server to another are:
These challenges make the migration path daunting, uncertain, and difficult to reliably plan and schedule. This chapter addresses the challenges in migrating your applications from WebLogic Server 6.0 to Oracle9iAS, providing an approach to migration with solutions based on the J2EE version 1.2 specification.
The J2EE platform provides a multi-tiered, distributed application model. Central to the J2EE component-based development model is the notion of containers. Containers are standardized runtime environments that provide specific services to components. Thus, Enterprise JavaBeans (EJB) developed for a specific purpose in any organization can expect generic services such as transaction and EJB life cycle management to be available on any J2EE platform from any vendor.
Containers also provide standardized access to enterprise information systems; for example, providing RDBMS access through the JDBC API. Containers also provide a mechanism for selecting application behavior at assembly or deployment time.
As shown in Figure 1-1, the J2EE application architecture is a multi-tiered application model. In the middle tier, components are managed by containers; for example, J2EE web containers invoke servlet behavior, and EJB containers manage life cycle and transactions for EJBs. The container-based model separates business logic from system infrastructure.
In quantifying the migration effort, it is helpful to examine the application components to be migrated with the following issues in mind:
Code may not be portable because it contains embedded references to vendor-specific extensions to the J2EE specification. Evaluating and planning for code modifications may be a significant part of the migration effort.
If vendor-specific extensions are in use, migration of those components becomes difficult or unfeasible. Complete redesign toward J2EE specifications is not addressed in this document. If vendor-specific extensions are in use, they may need to be redesigned and reimplemented, rather than being identified as migration candidates.
If a component is largely non-compliant with the J2EE specification, this guide will not be helpful in determining the migration path to Oracle9iAS. If the J2EE specification version of the component is not v1.2 (the version on which this guide is based), then the specification implementation differences will need to be addressed.
The approach in developing this migration guide was to document our experience migrating web application components from WebLogic Server 6.0 to Oracle9iAS. Examples shipped with WebLogic Server 6.0 were selected, tested on WebLogic Server 6.0, and migrated to Oracle9iAS. Issues encountered in the migration of these examples are the basis for this document.
Moving from WebLogic Server 6.0 to Oracle9iAS is a relatively simple process. Standard J2EE applications, using no proprietary APIs, can be deployed with no required code changes. The only actions required are configuration and deployment. Those applications using proprietary utilities or APIs can be ported easily.
This guide details the migration of components from WebLogic Server 6.0 to Oracle9iAS. While it does not claim to be an exhaustive source of solutions for every possible configuration, it provides solutions for some of the migration issues listed above, which will surface, along with others, in your migration effort. The information in this guide helps you to assess the WebLogic Server 6.0 applications and plan and execute their migration to Oracle9iAS. The material in this guide supports these high-level tasks:
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