Spring’s core support includes its capability of configuring application, enterprise integration, its testing capabilities and data access methodologies. In Chapter 4, I introduced you to various configuration styles available in Spring. In Chapter 5, I continued on to explain the various simplifications that you can do in your application. In this Chapter I will be covering enterprise integration which is one of the core support provided by the spring framework in detail.
I always like to call an application enterprise. For an application to be called enterprise, it needs to have enterprise components/objects on which it is built. I call an object enterprise when it has capability to handle transactions, capable of existing in a secured environment, has capability to integrate with other system, and so forth.
Using Spring framework, you can make simple POJOs getting transformed into what I call as enterprise objects, with minimal involvement of developers. Developers spend more time writing the actual business logic and the Spring container does all the magic behind the scenes.
Spring framework provides comprehensive infrastructural support for what we call an enterprise application. One such important component in any enterprise application is its capability to integrate. Spring handles plumbing involved in integrating various components in an enterprise application so that you can focus on actual business logic/business use case. Integrating enterprise application can be done in many ways. Each way has its own advantages and disadvantages. We will be discussing the various enterprise integration styles available in some detail in subsequent sections and will also cover the support rendered by Spring to achieve these integration styles in your enterprise application.
Enterprise Application Integration (EAI) is an application of technology defined as the integration of data and services between applications. The patterns of modern day EAI are usually attributed to Enterprise Integration Patterns, by Gregor Hohpe, et. al., that categorizes and explains many of the integration patterns common to integration solutions. Hohpe, et. al., list four types of integration styles:
1. Shared Database: two systems query the same database for data to be passed. An example of this is when you have two EARs deployed whose entity classes (JPA, Hibernate, etc.) shared common tables for performing various business processes.
2. Remote Procedure Call: each of two systems expose services that the other can call. An example of this is EJB services, or SOAP and REST services.
3. Messaging: two systems connect to a common messaging system and exchange data and invoke behavior using messages. An example of this is the familiar hub-and-spoke JMS architecture.
4. File Transfer: two systems produce files whose payload is the message to be processed by the other system. An example of this is polling a directory or an FTP directory for a file and putting appropriate business logic and processing it.
These styles are disparate because no one solution will work all the time. According to requirement in your application, choose the right style which best fits your requirement. These architectural styles are different with each having its own unique advantages and disadvantages. The standards in JEE fall short to some extent and don’t provide complete solution when integration with other systems.
Integration between two systems can be as simple as joining two tables. Nevertheless, there arise several issues when you try to integrate two systems using this integration methodology. First of all it is difficult to come up with a single schema that will suit the needs of both the application and second is the creation of interdependencies between two systems having diverse requirements and mixing it could as good as mixing oil and water. That means it will never gel together in the ideal enterprise application as we think.
Having said that Shared database has its own advantages like it’s simple and transactional. Some of the disadvantages which can be attributed to this style of integration are that it could be slower and retard or obstruct the database schema evolution over a period of time with more and more features added onto the enterprise application due to changing business dynamics.
Figure 6-1. Shared Database Integration style
Spring framework provides extensive support for this integration style. The support by Spring for this integration style is as below:
- Extensive support for transaction management
- Ease of using JDBC using JdbcTemplate
- Support for Object Relational Mapping (ORM) integration
- DataAccessException hierarchy makes exception handling easy
- Spring Data, an umbrella project in the Spring framework
These will be explained to some extent in the following sections.
Transaction management is critical in any form of applications that will interact with the database. The application has to ensure that the data is consistent and the integrity of the data is maintained.
Comprehensive transaction support is among the most convincing reasons for using the Spring framework. The Spring framework provides a consistent abstraction for transaction management that delivers various benefits. Some of which are:
- Consistent programming model across different transaction APIs such as Java Transaction API (JTA), Java Database Connectivity (JDBC), Hibernate, Java Persistence API (JPA), and Java Data Objects (JDO)
- Declarative transaction management
- Simpler API to code on
- Excellent integration with Spring’s data access abstractions
We will be covering Spring’s support for managing transactions in Chapter 8, “Data Access” in detail. I just wanted to bring in this point here so that you will be able to link when we discuss this topic later in subsequent chapter.
Using conventional could be clumsy and not so clear way of doing things. Spring makes coding in JDBC easy and elegant using JdbcTemplate.
We will be covering Spring’s support for JDBC in Chapter 8, “Data Access” in detail.
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