Java annotation-based

The annotation declarative approach configures the transaction attributes via annotations in the Java source file. Annotation-based declarative transaction management is more popular than XML-based because of following:

• Easier to use
• Transaction semantics close to affected Java source code making the code well documented

The steps to be followed for adding declarative transaction management to your application can be summarized using the following steps:

1. Define a transaction manager in Spring configuration file (This is still required in annotation-based transaction style as well)

[xml]

[/xml]

1. Turn on support for transaction annotations in your Java source code, in the Spring configuration file

[xml][/xml]

1. Add the @Transactional annotation to the method defined in your service class or the service class itself

[java]@Transactional

public class LoyaltyService{

Double getLoyaltyPoints(String customerCode) {

//Some code….

}

}[/java]

@Transactional in Detail

The annotation @Transactional can be applied to a method or at the class level. If applied to a class, all the public methods within the class will inherit the @Transactional annotation. It is also possible to configure the isolation level and the propagation nature. If not specified, the propagation defaults to REQUIRED and for the isolation level, it uses the database isolation level. The various default settings can be summarized as follows:

• Isolation level is defaulted to ISOLATION_DEFAULT.
• Propagation setting is defaulted to PROPAGATION_REQUIRED.
• Transaction setting is read/write in nature.
• Any RuntimeException triggers rollback, and any checked Exception does not.
• Transaction timeout defaults to the default timeout of the underlying transaction system or to none if timeouts are not supported by the underlying transaction system.

@Transactional Settings

By default, attribute “proxy-target-class” in is set to false, such that only interfaces with @Transactional annotations are proxied. This is useful if you divide your service architecture into a service interface and an implementation. If this is not the case, it is required to set this attribute to true for class-based proxies to be created.

[xml][/xml]

@Transactional annotation has other properties which can be used to control the transaction behaviour in your services. Some of the commonly used ones are:

• readOnly

[xml]@Transactional(readOnly=true)[/xml]

• propagation

[xml]@Transactional(propagation=Propagation.REQUIRES_NEW)[/xml]

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Tomcy John

Blogger & Author at javacodebook

He is an Enterprise Java Specialist holding a degree in Engineering (B-Tech) with over 10 years of experience in several industries. He's currently working as Principal Architect at Emirates Group IT since 2005. Prior to this he has worked with Oracle Corporation and Ernst & Young. His main specialization is on various web technologies and acts as chief mentor and Architect to facilitate incorporating Spring as Corporate Standard in the organization.

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