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Managing State

Most applications must be able to preserve some application state between a user's requests. For example, if you're writing a catalog application, you must keep track of the items that the user has selected before the user actually fills out the purchasing information. By default, WebObjects stores application state on the server. If this doesn't meet your needs, WebObjects provides several alternatives strategies for storing state.

This chapter describes why, when, and how to store state in a WebObjects application. It compares all of the available state-storage strategies, shows you how to implement your own state-storage strategy, plus it describes how to control the amount of application state stored.

If you're fairly new to WebObjects programming, you'll probably just want to read the first three sections of this chapter and skip the rest. As you begin to write larger, more complex applications, memory demands and performance become an issue. At that point, you should read the rest of this chapter to learn about alternative state-storage strategies and how you can control the amount of state stored.

Before reading this chapter, you should be familiar with concepts presented in the chapter "WebObjects Viewed Through Its Classes."

Why Do You Need to Store State

When Do You Need to Store State

Objects and State

The Application Object and Application State

The Session Object and Session State

Component Objects and Component State

State Storage Strategies

Comparison of Storage Options

A Closer Look at Storage Strategies

State in the Server

State in the Page

State in Cookies

Custom State-Storage Options

Storing State for Custom Objects

Archiving Custom Objects in a Database Application

Archiving Custom Objects in Other Applications

Controlling Session State

Setting Session Time-Out

Using awake and sleep

Controlling Component State

Managing Component Resources

Adjusting the Page Cache Size

Using awake and sleep

pageWithName: and Page Caching

Client-Side Page Caching

Page Refresh and WODisplayGroup

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