JavaServer Pages (tm) Web Development Kit

Frequently Asked Questions

This document lists some frequently asked questions about the JavaServer(TM) Web Development Kit (JSWDK). Separate documents are available on the component technologies (Servlets and JSP) at java.sun.com:

JSP FAQ
Information on Servlets

What environment variables do I need to set to use the JSWDK?

You need a correct version of the JDK in the CLASSPATH variable. (For Unix, JDK 1.1.x or 1.2. For Windows, JDK 1.2.)

If you are using JDK 1.2, you also need to do one of the following:

Set JAVA_HOME to the JDK directory.
Put tools.jar in the CLASSPATH variable.

All other necessary classes and jar files are managed by the startserver script or batch file.

Where are the classes for JSPs and Servlets?
The files are as follows:

webserver.jar -- class files for the Servlet Engine
lib/jspengine.jar -- class files for the JSP Engine
lib/servlet.jar -- public APIs for Servlets
lib/xml.jar -- classes for parsing XML documents

Can I combine these classes with other webservers?

The JSP engine uses only the public portion of the Java Servlet 2.1 API. In theory, it could run on other Servlet engines that support the Servlet 2.1 API. Sun has not tested this release on any Servlet engine other than the one in the JSWDK.

Where do I put my JSP sources and beans?

If you are testing JSP pages without creating a separate web application, you can use the default "Example" application. If you are creating a new web application, refer to the question on installing a new web application in this FAQ.

To use the default "Example" application:

Put all of your JSP source files in /examples/jsp, either directly or in their own subdirectory.
Put all of your Beans (class files) under /examples/WEB-INF/jsp/beans. The startserver script automatically adds these classes to CLASSPATH at runtime.
If your server is already running, stop and restart it.
Invoke your JSP pages using http://locahost:8080/examples/jsp/yours.jsp

What is a web application?

A web application is a collection of resources that is mapped to a specific Uniform Resource Identifier (URI) prefix. These resources may include JSP pages, Servlets, HTML files, and images.

For example, all of the resources related to baseball can be assembled into a "baseball" directory. All requests starting with "/baseball" could then be mapped to this application.

How do I install a new web application?

Create a directory for the web application. In the following examples, we will call this WEBAPP. The directory could have the same structure as the Examples directory, with subdirectories for jsp, servlets, WEB-INF, and images, if appropriate. One way to do this is to copy the Examples directory and then edit the files as necessary.
Add a new application to the JSWDK by editing the file webserver.xml in the root JSWDK directory.

For example, to create a baseball application, you would make the following additions to the file (at the appropriate location):

    <WebApplication id="baseball0" mapping="/baseball" docBase="baseball="/>

How do I install Servlets within my web application?

Use the following procedure, substituting your application directory for WEBAPP:

Compile the Servlet and determine which web application context you will add it to.
Add the Servlet class file to the WEBAPP/WEB-INF/servlets directory.
Activate the newly installed Servlet by registering (adding) the servlet in the WEBAPP/WEB_INF/servlets.properties file. See the Examples/WEB-INF/servlets file for an example.
Optionally, you can map the Servlet to URI requests relative to the context in which the Servlet is located by adding an entry in the WEBAPP/WEB-INF/mappings.properties file. See the Examples/WEB-INF/mappings.properties file for an example.
Restart the server.

Access the Servlet using the following method, where WEBAPP is the web application URI name, and SERVLET_NAME is the base name of the servlet:

    http://localhost:8080/WEBAPP/servlet/SERVLET-NAME

If you have associated a URI path mapping to your servlet, you can access it as follows, where EXTENSION is a file time extension and MAP-PATH is an associated URI MAP path:

    http://localhost:8080/WEBAPP/foo.EXTENSION

                 --- or ---  

    http://localhost:8080/WEBAPP/MAP-PATH

How do I install JSP pages and Java Beans in a web application?

Put the JSP source files in any directory under your application directory (/WEBAPP in the examples above).
Make sure that the compiled beans are in the CLASSPATH. This can be done either by setting the CLASSPATH manually or by editing the startserver script.
Edit the file WEBAPP/WEB-INF/mappings.properties and the file WEBAPP/WEB-INF/servlets.properties to map ".jsp" in the URI to the JSP Servlet which will process the jsp file. (See the property files in /examples/WEB-INF/ for an example. Your mapping should be similar.)
Finally, restart the server.

You can invoke your new JSP page using a URI similar to the following:

    http://localhost:8080/WEBAPP/yourfile.jsp

How are the URIs mapped at the server?

The web-server matches the beginning of the requested URI with the prefixes of all contexts (web-applications). If no context matches, it uses the default context instead.

How do you pass data from a Servlet to a JSP page?

See the JSP examples included with the JSWDK for samples of passing data from a Servlet to a JSP page, and from a JSP page to a Servlet.

What do the different init parameters mean?

keepgenerated:: Indicates whether or not to keep the generated Java file. The options are true or false. Setting this to true retains the generated files. Setting it to false deletes these files after compilation.
scratchDir:: This sets the location for the work directory, which will be created for storing all generated code. This can be set to any directory. The work directory will be created under the DocBase.
largeFile:: True or false. Set this to true for large files. When this value is true, all static HTML is stored in a separate data file.
sendErrToClient:: True or false. If this parameter is set to true, all compilation/parsing errors will be sent as part of the response to the client.
ieClassId:: This parameter is used to activate the IE plug-in. The default value is set for IE 4 and 5. If the classID for IE changes in the future, this parameter will be helpful.

What does a 404 error mean?

It means the server was not able to locate the resource you requested. This may be due to one of two reasons:

The URL you entered was wrong or had a typo.
The URL could not be resolved with the current "docBase." If you are running your own web applications, please read the questions related to installing your own web application.

What does a 505 error mean?

A 505 error represents an "internal server error" encountered while processing your request. To find out more about the error, study the trace at the server window.

These errors can occur when translating JSP source to a Servlet. Translation-time errors typically occur because of a syntax error in the JSP file or in the generated Java file. Use the error message at the server window for debugging.

Errors can also occur at request time. Again, refer to the server-side trace for information about the specific problem or exception.