Hibernate saveOrUpdate trap for web developers and StaleStateException
Summary: Hibernate users should be aware of saveOrUpdate method if they continue to use the same persistent object even if a transaction failed at some point.
Details:
Suppose you have a persistent object bound to your web(like JSF) views. Entered some data (which will lead to a db ConstraintViolationException) and tried to save it (at your DAO service) by using saveOrUpdate method. As we expected, it will throw a ConstraintViolationException and you'll rollback the transaction.
Then, go back to the entry page, correct the wrong field value at the same object, and try to save it again. You'll get a StaleStateException since saveOrUpdate method assigned identifier values automatically to your new object when you attempt to save it first. Later, when the save operation failed, it didn't roll back your object's state to its initial state. The summary of the flow causing this error is as below;
Hibernate Annotations is my preferred way to map my entity classes, since they don't require any external file (thus keeping mapping info in your Java files), is fully integrated with all Hibernate mapping capabilities and Hibernate documentation encourages us to use this kind of configuration because it's more efficient.
Annotation driven mapping in Hibernate uses the standard JPA API annotations and introduce some specific extensions to deal with some Hibernate features. You can find a full reference in the official documentation.
A common requirement in developing enterprise applications is to ensure audit logs are available for data security and traceability–who made the changes, when they were made, and what files or sections were changed. This requirement is not only dictated by corporate IT policies, but also required by government laws. Considering that most enterprise applications have at least 50 domain objects, implementing audit logs on each of them can be time-consuming. So, a generic solution must be established to minimize coding when creating audit logs.
Many enterprise business applications have such requirements that they should log their users' operations; who performs and when, records that are inserted into, deleted from database, or are changed during those operations, with a meaningful description about current state of those records. Hibernate already provides an interceptor mechanism at SessionFactory level. Hibernate fires events indicating new records are inserted, old ones are deleted, detection of updates, and other events related with transaction status, session flush etc. By that way one can easily track changes on persistent entities in his application.
With the addition of generics in Java 5, writing a custom DAO for each domain object is no longer required. There are a wide variety of articles on creating generic DAOs, but my current project uses the approach from this IBM DeveloperWorks article. This approach was choses mainly because of the clearly written article and the integration with Spring. You should be able to extend any generic DAO based on Spring to implement the stored procedure configuration.
Thought I've bookmarked this a long time ago... "With the adoption of Java™ 5 generics, the idea of a generic typesafe Data Access Object (DAO) implementation has become feasible. In this article, system architect Per Mellqvist presents a generic DAO implementation class based on Hibernate. He then shows you how to use Spring AOP introductions to add a typesafe interface to the class for query execution."
About
AutoDAO is a Generic DAO on steroids implementation for Java.
This project was inspired by Don't repeat the DAO! article by Per Mellqvist.
Main features
* Ready to use CRUD operations
* Zero persistence code for common DAO queries
* Annotation-driven auto-configuration
* Spring Framework custom namespace for easy to use configuration
* Hibernate/JPA support
What does it do?
Given an accessible database schema, the Hibernate POJO Generator produces all the Java code necessary to access each field in each table via the Hibernate persistence framework. Additionally, the generator also creates all the necessary helper classes and test units for each component.
This article demonstrates a brand new open source library for unit testing, called Unitils. Unitils helps you in writing simple and maintainable unit tests with JUnit or TestNG . It glues together some widely used test libraries like DbUnit and EasyMock and offers integration with Spring and Hibernate . Unitils encourages applying good practices and unit testing guidelines. The ideas behind the code are based on the authors' concrete experience on enterprise projects.
Unitils offers following features
* Equality assertion through reflection, with options like ignoring Java default/null values and ignoring order of collections
* Support for database testing involving test data management with DbUnit, automatic maintenance of unit test databases and automatic constraints disabling
* Hibernate integration features such as session management and testing the mapping with the database
* Integration with Spring, involving ApplicationContext management and injection of spring managed beans
* Integration with EasyMock and injection of mocks into other objects
As also described in the Hibernate book from King and Bauer: "With the adoption of Java™ 5 generics, the idea of a generic typesafe Data Access Object (DAO) implementation has become feasible. In this article, system architect Per Mellqvist presents a generic DAO implementation class based on Hibernate. He then shows you how to use Spring AOP introductions to add a typesafe interface to the class for query execution."