Sample Servlets

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Here are some sample servlets that run with the Java^TM Web Server^TM:

Simple
Snoop
Cookie Counter
Phone
Protected Servlet
Date
Hello World
Certificate Authority (requires Navigator client)

Note: If you're reading this on the java.sun.com site, none of the links on this page will work. To see what these servlets do, download a copy of the Java Web Server (with documentation), run it, and enter a URL of the form:

  http://server_host_name/system/doc/servlets/sample.html

Simple Servlet

This servlet outputs a simple HTML page. It illustrates the core concepts behind HTTP servlets.

Try it, Source

Snoop Servlet

This servlet displays the arguments it receives:

The URL it thinks was used to invoke it.
Any initialization parameters passed to the servlet.
All the data made available to it through standard servlet request methods, including any parameters.
When used over HTTPS, it shows the SSL cipher suite used, as well as any X509 certificate chain presented by the client.

Try it, Source

Cookie Counter Servlet

This servlet uses cookies to maintain a persistent counter. It shows:

How to use the sun.servlet.util.Cookie programming interface to get and set cookies.
Using servlet initialization parameters to make different instances of the same servlet class behave differently.
Explicit buffering of servlet response data to ensure that HTTP connections use "keep alive".

Try it, Source

Phone Servlet

This servlet loads a list of phone numbers from a file specified as an initialization parameter. On request, it will return a particular person's phone number if their name is specified in the query string. Otherwise, it will return the entire list.

Try it, Source

Protected Servlet

This servlet simply outputs an html page. To demonstrate the basic authentication scheme, this servlet is protected by an ACL (user jeeves and password jeeves).

Try it, Source

Date Servlet

This servlet outputs the current date and time in plain text format, suitable for embedding in an existing HTML document as a server-side include.

Try it, Server Side Include Example, Source

Hello World Servlet

This is another simple servlet which outputs a simple html document. It is used in the servlet tutorial. However, it is not loaded by default when Java Web Server starts up. To load it, do the following:

1. Save this page in your browser.

2. Go to the URL http://<server:9090>.

3. Log in to the Administration Tool with admin/admin as the username/password.

4. Once logged on, select Web Page Service -> Manage -> Servlets -> (Servlets) Add.

5. Enter "hello" as the Servlet Name.

6. Enter "HelloWorldServlet" as the Class Name.

7. Press the Add Button.

8. Return to this page.

Then the servlet can be accessed by the URL http://<server>/servlet/hello

See the tutorial, Try it, Source

Certificate Authority Servlet

This servlet is a relatively advanced example, showing:

The use of HTML forms with the POST method.
Use of the ServletUnavailable exception for reporting fatal initialization time errors.
Dynamic generation of non-HTML data by a servlet.
Some relatively complex parsing for the form parameters.
Integration with the KEYGEN extension in Netscape Navigator.
How to use the sun.security.x509 package in JDK^TM 1.1 (being augmented by public Java APIs in a later version of the JDK) to create and sign public key certificates.
Some of the basic functionality of a Certificate Authority, such as VeriSign.

The POST method is used both because a relatively large amount of data is sent to this servlet, and because the GET method is inappropriate for this kind of application. That is, applications that involve servers storing data (in this case, the generated certificate) can't safely be repeated, and GET methods are supposed to be safely repeatable.

This servlet illustrates the kind of significant web-based services that can be hosted using servlets to update shared data. The class which implements the servlet will be the gateway into the service, and it will interact with other servlets and subsystems to do the bulk of the work requested through the servlet.

Try it, Source

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