Skip to main content

Spring - Database Transaction (Part 1)

We will define a transaction as a unit of work that is made up of a set of operations, against one or more resources, that must be completed in its entirety.

The ACID properties:
Atomic, Consistent, Isolated, Durable Properties.

Atomicity: All individual steps of the transaction must complete. If one step fails, they must all fail or be undone.
consistency: Transactions must also leave any affected resources in a consistent state.
Isolation: Each transaction should operate isolated from each other and also in the required sequence.
Duration: the transactions should be durable.

Transaction propagation:
Each transaction has some attributes associated with it, like its status. This information is stored in what is called the transaction context. This context must be made available to any transaction manager that handles this transaction. The transaction context is associated iwth the thread that is executing.
In the case where there is a remote call when a transaction is active, the transaction context is passes along, propagated, to the remote process.  This allows the remote process to participate in the same transaction.
The propagation behavior is the attribute that can be used to define the scope of your transactions and how multiple transaction will interact with each other.

PROPAGATION_REQUIRED
 Support a current transaction, create a new one if none exists. Analogous to EJB transaction attribute of the same name. This is typically the default setting of a transaction definition.

PROPAGATION_SUPPORTS
 Support a current transaction, execute non-transactionally if none exists. Analogous to EJB transaction attribute of the same name.

PROPAGATION_MANDATORY
 Support a current transaction, throw an exception if none exists. Analogous to EJB transaction attribute of the same name.

PROPAGATION_REQUIRES_NEW
 Create a new transaction, suspending the current trans- action if one exists. Analogous to EJB transaction attribute of the same name.

PROPAGATION_NOT_SUPPORTED
 Execute non-transactionally, suspending the current trans- action if one exists. Analogous to EJB transaction attribute of the same name.

PROPAGATION_NEVER
 Execute non-transactionally, throw an exception if a trans- action exists. Analogous to EJB transaction attribute of the same name.

PROPAGATION_NESTED
 Execute within a nested transaction if a current transaction exists, or behave like PROPAGATION_REQUIRED otherwise. There is no analogous feature in EJB.

Isolation: the isolation attribute allows you to override the default isolation setting of your data source.
 ISOLATION_READ_UNCOMMITTED
 Dirty reads, non-repeatable reads, and phantom reads can occur.
ISOLATION_READ_COMMITTED
 Dirty reads are prevented; non-repeatable reads and phantom reads can occur.
ISOLATION_REPEATABLE_READ
 Dirty reads and non-repeatable reads are prevented; phantom reads can occur.
ISOLATION_SERIALIZABLE
 Dirty reads, non-repeatable reads, and phantom reads are prevented.

Read-Only
This flag can be set to true to indicate that the transaction does not modify any persistent state.  This is more of a hint because not all transactional resources can take advantage of this setting. It's particularly useful when using Hibernate because it tells Hibernate not to detect and flush changes within a read-only transaction.



Transaction Demarcation:
Whether you use local or global transactions, you must somehow inform the transaction manager when your transaction begins and when it ends. This is called transaction demarcation and there are two ways to accomplish this. You can either do it programmactically by using JDBC APIs , or you can take advantage of declarative transaction management that is offered by an EJB container as well as by the Spring Framework.

Declarative Transaction provide a very attractive alternative to the programmatic solutions. You can allow a framework to demarcate the transactions not having to include transaction management in your code makes your code much more readable and easier to maintain.

Comments

Popular posts from this blog

Stretch a row if data overflows in jasper reports

It is very common that some columns of the report need to stretch to show all the content in that column. But  if you just specify the property " stretch with overflow' to that column(we called text field in jasper report world) , it will just stretch that column and won't change other columns, so the row could be ridiculous. Haven't find the solution from internet yet. So I just review the properties in iReport one by one and find two useful properties(the bold highlighted in example below) which resolve the problems.   example:
<band height="20" splitType="Stretch"> <textField isStretchWithOverflow="true" pattern="" isBlankWhenNull="true"> <reportElement stretchType="RelativeToTallestObject" mode="Opaque" x="192" y="0" width="183" height="20"/> <box leftPadding="2"> <pen lineWidth="0.25"/> …

JasperReports - Configuration Reference

Spring - Operations with jdbcTemplate

This class manages all the database communication and exception handling using a java.sql.Connection that is obtained from the provided DataSource. JdbcTemplate is a stateless and threadsafe class and you can safely instantiate a single instance to be used for each DAO.


Use of Callback Methods
JdbcTemplate is based on a template style of programming common to many other parts of Spring. Some method calls are handled entirely by the JdbcTemplate, while others require the calling class to provide callback methods that contain the implementation for parts of the JDBC workflow. This is another form of Inversion of Control. Your application code hands over the responsibility of managing the database access to the template class. The template class in turn calls back to your application code when it needs some detail processing filled in. These callback methods are allowed to throw a java.sql.SQLException, since the framework will be able to catch this exception and use its built-in excepti…