Volume Number: 17 (2001)
Issue Number: 10
Column Tag: Beginning WebObjects 5
by Emmanuel Proulx
The Project Builder is the central tool for developing WebObjects applications, so this article talks about how to use this tool. The first thing you're going to do is open the Project Builder, by going to your disk, under the folder /Developer/Applications, and double-clicking on Project Builder.
Currently there's no project opened. Let's make a blank one. For now, don't try to understand the different options, as we'll cover them all later. In the menu, choose File | New Project. The dialog that pops up contains many different types of projects: WebObjects, Carbon, Cocoa, bundles, frameworks, Applet, driver, C++, and many more.
WebObjects is the development platform for the Mac OS X operating system, and it can produce many kinds of projects. This column is scoped to help you develop Web applications using Java, so for now let's concentrate on this kind of project:
Select the WebObjects Application project type and click Next.
Enter the project name and location. This column assumes the project name is Find-A-Luv, under the folder ~/projects/Find-A-Luv. (Create the ‘projects' folder under the home folder). Click on Finish.
The window that comes up next is the Project Builder, containing the project you just created:
This window is crowded with controls, which we'll cover shortly.
The Project Viewer is an IDE (Integrated Development Environment) for the Mac OS X operating system. Its graphical user interfaces resembles a Web browser. It is in fact a file browser; it lets you see the files of the project. The left part of the Project Builder ("Groups & Files") lets you select files, organizing them in a tree-like fashion into categories. I will refer to that part as the file browser tab. The right pane lets you edit the selected file - I call it the editor. Finally, the toolbar has buttons to build and run your project.
File Browser Tab
A project is a set of files that are used by a Web application. As explained in the introduction, and as you can see in the first level of the file browser, many types of files are necessary. Here's how they are classified in the Project Builder:
When you expand one of the categories of the first level, you can see other categories or files you may select. When you click on anything in the file browser, you will see the file appear in the editor pane.
Items in the file browser can be clicked on, double-clicked on or dragged around, just like icons of the operating system.
WARNING: If you drag something out of the file browser pane, it will be moved out of the project. The file will no longer be available in the project. If you want to copy the file, don't use the Project Builder. Use the operating system (Finder) to access the project's folder, and then copy the file from there.
The same is true when dragging files into the file browser. The file gets added to the project.
WARNING: If you drag something into the file browser pane, by default the file will not get copied. It will only be referenced. This means if you change, move or delete the file, the project will be affected. When you want to put the file inside the project, copy it into the project's folder first, and then drag it to the proper location in the file browser.
There will be more information on file management in a future article.
Editor
The second item in this window is the Editor. It works just like any text editor, except for a few features, like colored Java syntax and automatic indentation.
Toolbar
The last item of this window is the toolbar. Let's briefly describe the buttons. We'll deal with what they do in great detail subsequently.
Other elements of the Project Builder window are:
The Hello World Code
Enough talking. Now is time to write you first piece of code.
Open your Project Builder, pointing to the Find-A-Luv project. In the file browser tab, expand "Classes". Then, select Main.java. In the editor, you can see that file ready to be edited.
Although this class' name is Main, it has nothing to do with Java's public static void main(String []) member function. The class Main is associated with the Web Component of the same name, and for every instance of that Web Component, a new instance of the class is created too. The good news is, the Main page is the default home page for the project. So the Main class will be instantiated automatically when a user accesses your site through the ‘front door'.
We're going to make a plain Hello World example program right in here, in the constructor of the class:
Listing 1. Main.java
Main Web component
This code sample shows where to add the line that prints "hello world".
// Main.java: Class file for WO Component ‘Main'
// Project Find-A-Luv
//
// Created by eproulx on Wed May 16 2001
//
import com.webobjects.foundation.*;
import com.webobjects.appserver.*;
import com.webobjects.eocontrol.*;
import com.webobjects.eoaccess.*;
public class Main extends WOComponent {
public Main(WOContext context) {
super(context);
System.out.println("Hello World!");
}
}Ę
Bear in mind two things before we move on: first, you can use any classes of the standard JDK 1.3 here. That's good to know because we don't have to rely on any third-party tools and libraries to do most of the work. For example, here we printed to the Console using the System class.
Second, you must know that your development environment is emulating the Web server environment. That means if you try to use any visible objects, like AWT or Swing dialogs and frames, the user will never see them. The only person that will see even just "Hello World!" is the operator guy in the Web server room. Anything you do must be just non-interactive non-graphical pure processing code (server-side processing, or business logic). The real interaction takes place when dealing with Web Components (the Web pages).
Save your code now - menu File | Save (or (-S).
Building
You are now ready to compile your project. Go to the toolbar, and click on the button with the hammer . The Build tab comes up, as shown below:
Obviously, the build has failed for this example (look at the status bar).
Let's examine the build tab. The lower half shows the compiler output. But you shouldn't have to look there, because the upper half of the build tab displays the compilation errors. In this example, there was a syntax error in the file Main.java. Clicking on the compilation error actually opens the right file and points you to the line where the error is. This is very handy.
If there were errors when you clicked on the build button, I will trust your programmer aptitudes for fixing them now. If there are no errors after the compilation, you are ready to go to the next step.
PREFERENCE: You can customize the behavior of the build process by going to menu Project Builder | Preferences, then by selecting the Build category. One of my favorite settings is to change the "Unsaved files" option to "Always Save". This way, whenever I build my project, I don't get the annoying dialog popping up asking "Save before building?"
Running
Let's see how well your "Hello World" program works. Go to the Project Builder and click on the toolbar button with the computer monitor . This opens the Run tab, as shown next:
I like to call the run tab "the Console". It displays the runtime messages, like the ones from WebObjects itself, System.err messages and guess what else? The System.out messages.
When you run the "Hello World" example, the Console displays lots of message - don't worry about these. Three things happen when you click on the Run button:
The WebObjects server is started.
Your Web application is deployed to that server.
Your Web browser pops up, pointing to the application.
The application is not displayed right away in the browser. We are redirected to it, with a page saying "One moment please...". This is just a redirection page generated by WebObjects. Immediately after that, a blank page appears. What page is this? This is the default page for your Web application, the "Main" Web Component. Does that means an instance of the Main class was created, and that the constructor we wrote was called? Go back to the Console to check it out.
Success! The words "Hello World" are displayed.
TRICK: "Compiling and running" is a common task that you will do so often, it deserves a shortcut. You can save a lot of mouse clicks by typing (-R.
You can now close the Web browser if you want. To stop the server, go back to the Console again, and click on the stop button . This will bring you back to the build tab.
When it comes to getting help with WebObjects, you have many choices. Often, any one source of information will do the trick, but usually one source is always better then the others for finding the specific information you're looking for. It's like wanting to listen to music and owning tons of CDs. You could pick up any one, but you have your favorite ones depending on the mood you're in right now.
Let's take a good look at each of these sources of information and check out what they do best.
Project Builder Help Menu
This contains these items:
The help topics appear in the Mac OS X Help Viewer program, except for the release notes, which appear inside the Project Builder editor.
For API, you must know the name of the class or method you wish to look up.
WebObjects Builder Help
We'll see the WebObjects Builder in a coming article, but I wanted to introduce its Help menu right away because I prefer using it instead of the Project Builder Help menu. It contains way more material, and it brings up the Web browser right away. Invoke it from within the WebObjects Builder by going to menu Help | Help Topics or by pressing F1.
Also, the WebObjects Builder help page contains an item called "Updated Docs at Apple", that brings you the exact same help contents but with all the fixes and updates that Apple introduced over time. Be sure to bookmark that page!
Lastly, it contains a link to Apple's Search Engine when clicking on the item "WEB SITE SEARCH". Note that you have to specify what you are searching for (in the subject field, select "WebObjects Documentation").
Oh and there's also the WebObjects Builder's "tip of the day" dialog that shows up every time you start it. I'll let you explore it yourself.
Java Browser
Imagine a situation where you know what class (and what package) you want to use, but you can't remember the exact syntax for a member variable or method, or even the types and order of a method's parameters. It doesn't have to be a WebObjects class; you could want to know that for any class.
You could bring up the API help documents, but instead I suggest you fire up the Java Browser. This tool lets you explore all available packages, and view the class interfaces. I use this very often.
To open the Java Browser, open the folder /Developer/Applications, and double-click on Java Browser. A window comes up, and you can now navigate through all packages and classes that are in the classpath. Most of the WebObjects-specific classes are located under the package com.apple.
Inspector attributes helpĘ
When using the Inspector (a window that floats above tools, and show you the properties of the selected object), you can sometimes see a button in the lowest part that looks like this: . When an item is selected in the Inspector, clicking on this button will bring up the related help. This help mechanism is very specific to the context, as opposed to the previous approaches.
Help on the Web
There are several sources of help available on the Internet:
We'll cover project management, and introduce Web components.
Emmanuel Proulx is a Course Writer, Author and Web Developer, working in the domain of Java Application Servers. He can be reached at emmanuelp@theglobe.com.
