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The Application Object in JSP

By: Sathya Narayana in JSP Tutorials on 2010年10月24日 [フレーム]

The Application object in JSP is a global object that is shared across all servlets and JSP pages in a web application. It provides a way to store and share data across the entire application. The Application object is an instance of the javax.servlet.ServletContext interface.

Some common uses of the Application object in JSP include:

Storing global configuration settings that are used across the entire application, such as database connection information, email server settings, etc.
Storing data that is needed by multiple servlets or JSP pages, such as lookup tables, cached data, etc.
Providing a way to share objects between different parts of the application, such as objects that manage application-level resources like database connections, thread pools, etc.

To access the Application object in JSP, you can use the application implicit object, like this:

<%
 application.setAttribute("myData", someObject);
%>

This sets an attribute called myData on the Application object, with the value of someObject. To retrieve the attribute from another JSP page or servlet, you can use the getAttribute method, like this:

<%
 Object myData = application.getAttribute("myData");
%>

This retrieves the value of the myData attribute from the Application object. Note that any object stored in the Application object must be thread-safe, since it may be accessed by multiple threads simultaneously.

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