Introduction To Java Programming
Fall COMMON 1999
Session 21LF
Session 33LF
Session 41LF
Introduction To Java Programming
Introduction |
4 |
Goal |
4 |
Tools |
4 |
Setup |
4 |
Hints |
4 |
Getting Started: Java Programming Tips |
5 |
Anatomy of a Java Program |
5 |
Some AS/400 Specifics |
6 |
Exercise 1: Creating and Running the HelloWorld Application on Windows |
8 |
What This Exercise Is About |
8 |
What You Should Be Able To Do |
8 |
Introduction |
8 |
Exercise Instructions |
8 |
Open An Editor |
8 |
Enter And Compile The Source |
8 |
Run The HelloWorld Application |
9 |
Hints |
9 |
Exercise 2: Running the Hello World Application On the AS/400 |
10 |
What This Exercise Is About |
10 |
What You Should Be Able To Do |
10 |
Introduction |
10 |
Exercise Instructions |
10 |
Use the emulator to sign-on to the AS/400 |
10 |
Go back to the MS-DOS prompt of exercise 1 |
10 |
Return to the emulator |
11 |
Hints |
11 |
Exercise 3: AS/400 Java Programs |
12 |
What This Exercise Is About |
12 |
What You Should Be Able To Do |
12 |
Introduction |
12 |
Exercise Instructions |
12 |
CRTJVAPGM, DSPJVAPGM |
12 |
DLTJVAPGM |
13 |
Exercise 4: Create Your Own Home Page |
14 |
What This Exercise Is About |
14 |
What You Should Be Able To Do |
14 |
Introduction |
14 |
Exercise Instructions |
14 |
Start Netscape and Composer |
14 |
Adding Text To Your Web Page |
14 |
Adding A Link In Your Web Page To Another Web Page |
15 |
Saving Your Web Page |
16 |
Exercise 5: Creating The Hello World Applet |
17 |
What This Exercise Is About |
17 |
What You Should Be Able To Do |
17 |
Introduction |
17 |
Create The HelloWorldApplet Source File |
17 |
Enter And Compile The Source |
17 |
Insert The HelloWorldApplet Into Your Home Page |
18 |
Test The HelloWorldApplet |
19 |
Exercise 6: Creating The Hello World Servlet |
20 |
What This Exercise Is About |
20 |
What You Should Be Able To Do |
20 |
Introduction |
20 |
Create The HelloWorldServlet Source File |
20 |
Enter And Compile The Source |
20 |
Place the HelloWorldServlet onto the IBM Web Sphere web server. |
21 |
Run the HelloWorldServlet |
22 |
Bonus Lab 1: QShell |
23 |
What This Exercise Is About |
23 |
What You Should Be Able To Do |
23 |
Introduction |
23 |
Using QShell |
23 |
Introduction
Java is an exciting programming language that is quickly being accepted in the computing industry. Java offers a programmer the flexibility to create full fledged applications (both client and server), applets that can run inside of a World Wide Web browser and servlets that can run inside web server applications.
Goal
In this lab, you will work through a series of exercises that provide you with an opportunity to create Java applications that run on the AS/400 as well as Windows 95. You will also explore the differences between a Java applet, a Java application, and a Java servlet.
Tools
The tools that you will use for the exercises in this lab for the most part are quite primitive. The most basic editor and command line compiler are used to create Java source code and compile your Java programs. On Windows you will use Notepad or edit. To compile and run your Java code you will use the Java Development Kit.
Setup
During this lab you will need a userid and password for the AS/400 and you will need to know the name of the AS/400 system. The userid and password will be JAVAxx where xx is the number 01 to 99 (two digits number). This information will be given to you by your instructor. Please fill in this information below so that you have it for reference during the lab.
The name of my AS/400 is _________________________ (case sensitive)
My AS/400 userid is _______________________________
My AS/400 password is ____________________________
The AS/400 directory is /LABxxx/Javaxx (Javaxx is your ID)
The AS/400 library is LABxxx
The PC directory is C:\LABxxx
Hints
The most important tip that you should remember while performing the following exercises is that the Java language is HIGHLY case sensitive. Please be extra careful to double check the case of all code that you enter to ensure that you've input your code correctly.
At the end of the first two exercises is a list of additional hints. These hints apply to all exercises. Check them out if you have trouble with an exercise.
Getting Started: Java Programming Tips
Anatomy of a Java Program
A simple Java program is shown below.
// This is a simple Java program
// With this style of comments the double slash must be on every line
/*
With this style of comments you just need the beginning slash-star
and the ending star-slash
*/
// There are two ways to use this class. Since it has a "main" method,
// it can be run from the command line. It also has public constructors
// so it can be used by other Java classes. If used by other classes,
// main will not be called.
// This class uses classes in the java.io package
import java.io.*;
public class SimpleProgram extends Object
{
// The number of times this class is constructed. Since this
// variable is static, there is one value for all classes.
private static int useCount = 0;
// The value passed when another object constructs this class.
// Each class gets its own copy of this variable.
private int valuePassedOnConstructor = 0;
// A class constructor with one parameter. Constructor names
// match the class name.
public SimpleProgram(int value)
{
valuePassedOnConstructor = value;
useCount++;
}
// Main is the method called if the program is started from the
// command line ("java SimpleProgram"). Note it is static so it
// cannot access non-static variables.
public static void main(String[] args)
{
// Create a SimpleProgram object
SimpleProgram sp = new SimpleProgram(100);
// Call routine Main in SimpleProgram
sp.Main(args);
// Create another object to increment the use count
SimpleProgram sp2 = new SimpleProgram(200);
sp2.Main(args);
// Print the number of time this class was constructed.
System.out.println("Count = " + useCount);
}
// This method is private so it can be called only by other
// methods in SimpleProgram. Java is case sensitive so methods
// can have the same name differing only in case. Except for
// main this is not recommended, however.
private void Main(String[] args)
{
// Enclose the code in a try/catch block. If anything goes
// wrong the catch block will print a stack trace which
// includes class/method names and line numbers.
try
{
// Print the number of times this class is created
System.out.println("Parameter = " + ValuePassedOnConstructor);
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
Some AS/400 Specifics
The Integrated File System on the AS/400
To understand how Java programs are stored and run on the AS/400, a knowledge of the AS/400's integrated file system is helpful. The integrated file system, or IFS, is a part of the OS/400 operating system that supports stream I/O and storage management similar to Unix and PC operating systems. Key features of the IFS include a hierarchical directory structure and support for storing information in stream files. Benefits of the IFS include fast access to OS/400 data and efficient handling of stream data including images and audio. All Java programs and libraries that reside on the AS/400 are stored in the Integrated File System. Libraries and files are accessible via the QSYS.LIB directory. An example of a directory tree is shown below:
AS/400 Directory Tree Structure
- QSYS.LIB
- QOpenSys
- UserDir1
- file1
- file2
- userDir2
- file2
Java Programs on the AS/400
All Java Virtual Machines (JVM) convert from Java bytecodes to machine instructions. Most JVMs convert at run time. The bytecodes are converted to machine instructions but the machine instructions are not saved. The bytecodes must be converted every time the class is run. In order to make Java run faster on the AS/400, the class file can be converted once and the machine instructions saved for future use. The converted version is called an AS/400 Java Program. An AS/400 Java Program is a preverified, compiled version of a class file. The AS/400 command CRTJVAPGM creates the Java Program. The original bytecodes still exist in the IFS. In fact, the AS/400 Java Program isn't visible in IFS. Only commands like CRTJVAPGM, DSPJVAPGM and DLTJVAPGM allow you to interact with the Java Program. The AS/400 keeps track of the two versions (bytecodes and AS/400 machine instructions) and discards the AS/400 Java Program if the bytecodes are changed.
Exercise 1: Creating and Running the HelloWorld Application on Windows
What This Exercise Is About
In this exercise you will create a simple "Hello World" Java application on Windows 95.
What You Should Be Able To Do
At the end of this exercise, you should be able to:
- Enter Java source code
- Compile the Java source into a Java class file
- Run the Java program from the command line
- Know how to print text to the screen in a Java application
Introduction
Let's create your very first Java application. It's just a simple program that will print out the words "Exercise 1 -- Hello World".
Exercise Instructions
Open An Editor
- Open an MS-DOS prompt. (Press the Start button, follow the menu to Programs and choose MS-DOS prompt)
- Create a directory in which to place your work. Run the following command to create the directory.
mkdir c:\LABxxx
- Change to the directory you created in the previous step.
cd \LABxxx
- Open an editor to enter your Java source. The source file is named HelloWorld.java. This is done by using the following command. Alternatively, you can use Notepad instead of Edit.
edit HelloWorld.java
Enter And Compile The Source
Type in the follow following source code. Please note the punctuation as well as the capitalization. Both are very important elements of Java's syntax.
public class HelloWorld
{
public static void main(String[] args)
{
System.out.println("Exercise 1 -- Hello World!");
}
}
- Under the File pulldown menu, choose Save. Then under the File pulldown menu, choose Exit. You should be back at the MS-DOS command line.
- It's now time to compile your source code into Java bytecodes using the javac compiler. Issue the follow command at the MS-DOS prompt.
javac HelloWorld.java
- If the source code compiles successfully, you will be presented again with another MS-DOS prompt. If there are errors in your source code, they will be displayed.
- If you have any errors in your source code, re-edit the HelloWorld.java file to fix the errors. If you have an error, something was probably spelled incorrectly, capitalized incorrectly or punctuation was not quite right.
- After you compile with no errors, you will notice a new file exists in your directory called HelloWorld.class. Issue the 'dir' command to see it.
Run The HelloWorld Application
Once you are able to successfully compile HelloWorld.java, it is time to run the Application.
- At the MS-DOS prompt issue.
java HelloWorld
- You should now see the message
Exercise 1 -- Hello World!
(Leave the MS-DOS box open. You will use it in other exercises.)
Hints
- PCs use the backslash as the separator character.
- File name case is important. The case must match the class name (the "public class HelloWorld" statement in the file ) and must match when running the java and javac commands.
- The Java language is case sensitive so the program must be typed correctly.
- No file extension is entered when running the java command.
Exercise 2: Running the Hello World Application On the AS/400
What This Exercise Is About
This exercise will demonstrate the 'write once, run anywhere' ability of Java. In this exercise you will run the "Hello World" Java application on the AS/400.
What You Should Be Able To Do
At the end of this exercise, you should be able to:
- FTP files from the PC to the AS/400
- Run Java programs on the AS/400
Introduction
In the previous exercise you created a Java program and ran it on the PC. Now you will run the same program on the AS/400.
Exercise Instructions
Use the emulator to sign-on to the AS/400
To run a Java program on the AS/400 the program must be in the integrated file system (IFS) of the AS/400. Sign-on to the AS/400, then create a directory to store the Java program. Run the following two commands where Javaxx is your id:
MKDIR DIR('/LABxxxx')
MKDIR DIR('/LABxxx/Javaxx')
Go back to the MS-DOS prompt of exercise 1
You will now copy the Java program from the PC to the AS/400. Java programs are stored in .class files. You will FTP the file from the PC to the AS/400. (Another/better option would be to use a Client Access/400 network drive to copy the file. To keep it simple you will use FTP in this lab). From the DOS prompt, enter the following commands where system is the name of your AS/400 and Javaxx is your userid.
- ... Make sure you are in the directory containing the exercises (C:\LABxxx)
- ftp system
- ... Enter your userid and password when prompted
- cd /. You must cd to "/" to go to the root directory of IFS.
- cd /LABxxx/Javaxx
- put HelloWorld.java
- bin
- put HelloWorld.class
- quit
Return to the emulator
The Java program is now on the AS/400. Now use Java on the AS/400 to run the program. The first step is to tell Java the location of your program. Java uses the CLASSPATH environment variable to find Java programs. You will tell it to look in /LABxxx/Javaxx. CLASSPATH is case sensitive so make sure you type it in uppercase. As on the PC, you run a Java program with the java command.
From the AS/400 command prompt enter the following commands.
- ADDENVVAR CLASSPATH '/LABxxx/Javaxx'
- java HelloWorld
As in the last exercise, Exercise 1 -- Hello World should be displayed. Press F3 to exit the Java shell and return to an AS/400 command prompt.
(Leave the emulator open. You will use it in other exercises.)
Hints
- The AS/400 uses the forward slash as the separator character.
- When running ftp, you must do the "cd /". By default, the target is an AS/400 library. The "cd /" switches the target so it is now the IFS.
- When running ftp, you must do the "bin" to transfer in binary mode.
- CLASSPATH must be upper case.
- Java programs on the AS/400 run in a "Java Shell". You must exit the shell before running AS/400 commands.
Exercise 3: AS/400 Java Programs
What This Exercise Is About
Java class files contain bytecodes. All platforms that support Java must convert these bytecodes into machine instructions. The AS/400 has two ways of doing this -- interpreted (convert when the class file is run) and static (convert once and save the converted version). In this exercise you will examine the CRTJVAPGM, DSPJVAPGM and DLTJVAPGM commands on the AS/400. These commands deal with static conversion.
What You Should Be Able To Do
At the end of this exercise, you should be able to:
- Use CRTJVAPGM to make a Java program run faster
- Use DSPJVAPGM to analyze how a Java program was created
- Use DLTJVAPGM to delete the AS/400 Java program
Introduction
All Java Virtual Machines (JVM) convert from Java bytecodes to machine instructions. Most JVMs convert at run time. The bytecodes are converted to machine instructions but the machine instructions are not saved. The bytecodes must be converted every time the class is run. In order to make Java run faster on the AS/400, the class file can be converted once and the machine instructions saved for future use. The converted version is called an AS/400 Java Program. An AS/400 Java Program is a preverified, compiled version of a class file. The AS/400 command CRTJVAPGM creates the Java Program. The original bytecodes still exist in the IFS. In fact, the AS/400 Java Program isn't visible in IFS. Only commands like CRTJVAPGM, DSPJVAPGM and DLTJVAPGM allow you to interact with the Java Program. The AS/400 keeps track of the two versions (bytecodes and AS/400 machine instructions) and discards the AS/400 Java Program if the bytecodes are changed.
The AS/400 Java Program is created in one of two ways: by explicitly using the CRTJVAPGM command on a class/jar file, or when the file is first used. In this exercise we will look at some of the options of how AS/400 Java Programs are created.
DSPJVAPGM will display the attributes of a named class/jar file in IFS.
DLTJVAPGM will destroy the Java program that is associated with a class/jar file in IFS.
Exercise Instructions
CRTJVAPGM, DSPJVAPGM
We will work with the class files we created in the previous exercises.
- If not already signed on, sign on to the AS/400 and set up the CLASSPATH environment variable. Enter
ADDENVVAR ENVVAR(CLASSPATH) VALUE('/LABxxx/Javaxx')
- Change directory to the location of the class files. Enter
cd '/LABxxx/Javaxx'
- Now you will use the Java application HelloWorld you created in an earlier exercise. As was mentioned in the introduction, Java programs are created when a class file is used for the first time. Since you have already executed this Java application, there is already a Java program for the class file HelloWorld.class. Let's take a look at it. Enter
DSPJVAPGM CLSF(HelloWorld.class)
- Notice the various fields, most importantly the optimization field. Optimization level 10 is the default when a Java program is created. Let's make our Java program faster.
- Type CRTJVAPGM CLSF(HelloWorld.class) and hit F4 to prompt on it.
- Notice that optimization level 40 is the highest level available. Also note optimization level 10 or *INTERPRET is best when you are debugging your application. Optimization level 40 is best for speed.
- Notice that you may enable performance collection hooks. When you place these hooks into your Java programs, you can use the Performance Explorer to collect performance information on your Java applications.
- Enter 40 for the optimization level and press ENTER.
- Now rerun your HelloWorld application by entering
java HelloWorld Press F3 to exit the Java shell and return to an AS/400 command prompt.
- The first thing you probably will notice is that your Java application isn't running noticeably faster. Here's why. The class file HelloWorld.class is only one of many class files that are used when your Java application is run. The other class files are located in the jar file named classes.zip in the IFS directory /QIBM/ProdData/Java400/jdk11x/lib. Let's see what optimization level they are at. Run
DSPJVAPGM CLSF('/QIBM/ProdData/Java400/jdk11x/lib/classes.zip')
DLTJVAPGM
When you delete a class file from IFS, if there was a Java program associated with the class file, it will be deleted as well. But what if you want to save the class file and only get rid of the Java program associated with it? To do this, there is the DLTJVAPGM command. Let's try it out now on your HelloWorld application. Run
DLTJVAPGM CLSF('HelloWorld.class')
Your Java program should now be deleted. Let's use DPSJVAPGM to double check. Issue
DSPJVAPGM CLSF('HelloWorld.class')
The next time HelloWorld is run, a new Java Program will be created and saved at optimization 10.
Exercise 4: Create Your Own Home Page
What This Exercise Is About
Before we are able to create any Java Applets, you will need a home page on which to place them. In this lab you will create an HTML document for the Java Applets that you will create and reuse in the next exercises.
What You Should Be Able To Do
At the end of this exercise, you should be able to create a Web page using Netscape.
Introduction
World Wide Web pages are written using a language called HyperText Markup Language, better know as HTML. Learning HTML is comparable to learning another programming language. Thankfully HTML editors have entered in the market in recent years. These editors allow you to create your very own home page without having to learn any HTML. Composing a home page becomes as easy as writing a letter in your favorite word processor.
Exercise Instructions
Start Netscape and Composer
- Double Click on the Netscape Communicator icon that is located on your desktop.
- From the Communicator pulldown menu in Netscape choose the Composer menu item.
- You are now ready to start creating your own home page. Pictured is the Netscape Composer.
Adding Text To Your Web Page
- Let's put a title on this web page. We'll want to put this in a bigger headline font. Select Heading 1 in the leftmost drop down list box (Hint: It's located right under the icon labeled "New").
- Type "My Home Page" in the editor and hit ENTER.
Adding A Link In Your Web Page To Another Web Page
- Now we will make a link to the AS/400 Home Page. Press the Link button from the toolbar.
- Fill in the dialog as pictured and click on "OK"
Now your web page should look something like this:
Saving Your Web Page
Last you need to save your home page since it will be used in the next exercise.
- Click on Save from the Toolbar. Save your page to directory C:\LABxxx (the same directory where you placed your HelloWorld Java code from Exercise 1).
- Name your HTML file HomePage and click on the Save button.
- Next you will be presented with a dialog to give your page a title. Click on OK again.
Exercise 5: Creating The Hello World Applet
What This Exercise Is About
Applets are Java programs that are dynamically downloaded over the World Wide Web and run in your browser. In this exercise you will create a very simple Hello World Applet and place it on the home page you created in the previous exercise.
What You Should Be Able To Do
At the end of this exercise, you should be able to:
- Create an Applet
- Compile an Applet with javac
- Add an Applet inside of an existing HTML page
- Test a Web Page with an Applet
Introduction
The source code to create an Applet is very similar to the HelloWorld application that you created earlier. When you create a Java Applet, you must extend the java.applet.Applet class. This means you are going to use the java.applet.Applet class as a reusable part and extend it to do what you want. In this case you will make it print out the word "Hello World" in the browser.
Create The HelloWorldApplet Source File
- Open an MS-DOS prompt. (Press the Start button, follow the menu to Programs and choose MS-DOS prompt) or use the MS-DOS prompt from the previous exercise.
- If you opened a new prompt, change directory to the directory that holds the exercises. Enter
cd \LABxxx
- Open the MS-DOS editor to create a new piece of Java source named HelloWorldApplet.java. This is done by using the following command.
edit HelloWorldApplet.java
Enter And Compile The Source
Type the following source code. Please note the punctuation as well as the capitalization.
import java.awt.Graphics;
public class HelloWorldApplet extends java.applet.Applet
public void paint(Graphics g)
{
g.drawString("Applet -- Hello World!",5 ,25);
}
}
- Under the File pulldown menu, choose Save. Then under the File pulldown menu, choose Exit. You should be back at the MS-DOS command line.
- It's now time to compile your source code into Java bytecodes using the javac compiler. Issue the following command at the MS-DOS prompt:
javac HelloWorldApplet.java
- If the source code compiles successfully, you will be presented again with the MS-DOS prompt. If there are errors in your source code, they will be displayed.
- If you have any errors in your source code, re-edit the HelloWorldApplet.java file to fix the errors. If you have an error, something was probably spelled incorrectly, capitalized incorrectly or punctuation was not quite right.
- After you successfully compile the source file, you will notice a new file your directory called HelloWorldApplet.class. Issue the 'dir' command to see it.
Insert The HelloWorldApplet Into Your Home Page
- Start Netscape.
- From the Communicator pulldown menu click on the Composer menu item.
- In the Netscape Composer window, from the File pulldown menu click on the Open Page... menu item. Click on the Choose File... button. Select the home page you created in the previous exercise. It should be C:\LABxxx\HomePage. Click on the Open button once you have selected the file. Lastly click on the Open button in the Open Page dialog. Your home page should appear in the editor.
- Pick a location where you would like the Applet to appear on your home page. (Below the link to the AS/400 home page would be a good spot). Click once to place the cursor in the location you have chosen.
- From the Insert pulldown menu click on the HTML Tag... menu item. For the tag enter
<applet code="HelloWorldApplet.class" width=300 height=300>
- Click OK.
- You just entered the applet tag, now you must end the tag. The cursor should be at the end of the box. From the Insert pulldown menu click on the HTML Tag... menu item. For the tag enter
</applet>
- Click OK.
- Your HTML document should now look like this picture.
Test The HelloWorldApplet
- From the File pulldown menu click on the Browse Page menu item. You will be prompted if you would like to save your changes. Click on yes.
- A new Netscape window should appear with your home page in it. After a moment the HelloWorldApplet should start up and display its message.
Exercise 6: Creating The Hello World Servlet
What This Exercise Is About
Servlets are Java programs that run inside Java-enabled web servers. Servlets provide a middle-tier of communication between a browser application and a host's protected resources. The servlet accepts requests from the browser client, processes the requests (which may involve host database updates) and then sends HTML responses back to the client. In this exercise you will create a very simple Hello World servlet and run it from an AS/400 web server.
What You Should Be Able To Do
At the end of this exercise, you should be able to:
- Create a servlet
- Compile a servlet with javac
- Understand how to put the servlet on the AS/400 web server
- Test the servlet from a web browser
Introduction
The source code to create a servlet uses the Java Servlet API. The Servlet API is a Standard Extension to Java that provides the classes used in servlet development. All servlets implement the Servlet interface within the Java Servlet API. You will use the javax.servlet.http.HttpServlet class as a reusable part and extend it to implement your servlet. The HttpServlet class is a common protocol used between browsers and servlets. In this case you will make the HttpServlet class print out "Hello World" in the browser.
Create The HelloWorldServlet Source File
- Open an MS-DOS prompt. (Press the Start button, follow the menu to Programs and choose MS-DOS prompt) or use the MS-DOS prompt from the previous exercise.
- If you opened a new prompt, change directory to the directory that holds the exercises. Enter
cd \LABxxx
- Open the MS-DOS editor to create a new piece of Java source named HelloWorldServlet.java. This is done by using the following command.
edit HelloWorldServlet.java
Enter And Compile The Source
Type the following source code. Please note the punctuation as well as the capitalization.
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorldServlet extends HttpServlet
{
public void doGet (HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
{
PrintWriter out;
res.setContentType("text/html");
out=res.getWriter();
out.println("<html>");
out.println("<head><title>Hello World Servlet</title></head>");
out.println("<body>");
out.println("<h1>Hello World</h1>");
out.println("</body></html>");
}
}
- Under the File pulldown menu, choose Save. Then under the File pulldown menu, choose exit. You should be back at the MS-DOS command line.
- It's now time to compile your source code into Java bytecodes using the javac compiler. Issue the following command at the MS-DOS prompt:
javac HelloWorldServlet.java
- If the source code compiles successfully, you will be presented again with the MS-DOS prompt. If there are errors in your source code, they will be displayed.
- If you have any errors in your source code, re-edit the HelloWorldServlet.java file to fix the errors. If you have an error, something was probably spelled incorrectly, capitalized incorrectly or punctuation was not quite right.
- After you successfully compile the source file, you will notice a new file your directory called HelloWorldServlet.class. Issue the 'dir' command to see it .
Place the HelloWorldServlet onto the IBM Web Sphere web server.
Only one version of the HelloWorldServlet.class file is needed on the web server. A copy of the servlet you just created has already been put on the web server and is ready for your use. The servlet has been stored on the AS/400 in the following IFS directory:
/QIBM/ProdData/IBMWebAS/Servlets/HelloWorldServlet.class
This directory stores servlets in use on the AS/400 system by the IBM Web Sphere web server.
Please do not copy your version of the HelloWorldServlet to the AS/400 web server.
Run the HelloWorldServlet
To run the HelloWorldServlet you need to call it from your web browser.
- Double click on the Netscape Communicator icon that is located on your desktop.
- Enter the URL location of your servlet. Into the Location: box enter:
http://system/servlet/HelloWorldServlet
- This causes the servlet to run. The Hello World message should be displayed in your browser.
Bonus Lab 1: QShell
What This Exercise Is About
Introduce you to QShell on the AS/400.
What You Should Be Able To Do
At the end of this exercise, you should be able to use QShell to compile and run Java programs.
Introduction
The 'command line' way to run Java programs in Windows is via the MS-DOS prompt. In Unix, the typescript window is used to run command line programs. The home for Java programs on the AS/400 is the Java shell. In previous labs you ran Java programs on the AS/400 via the AS/400 Java command. You may have noticed that while running the program you are switched to the Java shell. You pressed F3 to exit the shell and return to the AS/400 command prompt. Another way to get into this Java shell is by running QShell. QShell is a full function shell environment, but for the purpose of this lab it is simply a convenient place to run Java programs.
Using QShell
From the AS/400 command prompt, enter QSH. This starts the shell interpreter. If you are used to Windows or Unix, the shell has a more familiar look and feel. Do the following from the shell:
- Set up the CLASSPATH environment variable. Enter
export CLASSPATH=/LABxxx/Javaxx
- Change directory to the directory containing your lab exercises. Enter
cd /LABxxx/Javaxx
- Display the contents of the directory. Notice by default the shell uses Unix commands. Enter
ls
- Run one of your Java programs. Enter
java HelloWorld
- You can also compile inside the shell Enter
javac HelloWorld.java
- Press F3 when you are ready to exit the shell.