Skip to main content

Struts2 - Working with Struts2 Action

First up, actions do the core work for  each request. They contain the business logic, hold the data and then select the result that should render the result page. Struts2 is an action-oriented Framework and actions are at its heart.

What does an action do?
Actions do three things. First, as you probably understand by now, an action's most important role, from the perspective of the framework's architecutre, is encapsulating the actual work to be done for a given request.
The second  major role is to serve as a data carrier in the framework's automatic transfer of data from the request to the view.
Finally, the action must assist the framework in determining which result should render the view that will be returned in the request response.

Whether you declare your action components with XML or Java annotations, when the framework creates your application's architecture, it'll organize your actions and other components into logical containers called packages. Many important operational attributes, such as the URL namespace to which actions will be mapped, are defined at the package level.  And, importantly, packages provide a mechanism for inheritance, which among other things allows you to inherit the components already defined by the framework.

Implementing actions
Implementing Struts 2 actions is easy. Basically, any class can be an action if it wants. It simply must provide an entry method for the framework to invoke when the action is executed. Struts2 Actions don't have to implment the Action interface. any object can informally honor the contract with the framework by simply implementing an execute() method that returns a control string.

The ActionSupport class
The ActionSupport class is a convenience class that provides default implementations of the Action Interface and several other useful interfaces, giving us such things as data validatoin and localization of error messages.  If your actions extends this class, they automatically gain the use of these implementations.


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…