Apple WebObjects 5 Bedienungsanleitung PDF herunterladen (Seite 38)

38 A Programmer’s View of WebObjects

 Apple Computer, Inc. January 2002

CHAPTER 4

HTML-Based Applications

These advantages are discussed in more detail in the sections that follow.

Separating Presentation Code from Event-Handling

Logic

In WebObjects, a Web page is represented by a component, an object that has both

content and behavior. A component can also represent a portion of a page but

usually represents an entire page, so the word page is used interchangeably with the

word component.

Components consist of

■ a template in HTML code that specifies how the component looks. This file

can be edited by any HTML editor or text editor.

■ event-handling logic that specifies how the component acts. You specify this

with a standard Java source file.

■ bindings that associate the component’s layout specification (HTML code)

with its event-handling methods. These bindings are stored in a text file.

Separating the presentation code, event-handling logic, and bindings makes it

much easier to maintain a Web application. A graphic artist can modify the

presentation code, thus modifying the appearance of the page, without breaking its

event-handling logic. A programmer can completely rewrite the event-handling

logic without accidentally changing the page’s layout.

You do not need to edit all three files separately. WebObjects Builder, a graphical

component editing tool provided with WebObjects Development, edits the

template, bindings, and event-handling code files simultaneously, relieving you of

having to manually synchronize them. WebObjects Builder is described in more

detail in “WebObjects Builder” (page 46).

Figure 4-1 (page 39) shows the three files in an example component.

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Apple WebObjects 5 Bedienungsanleitung Seite 38