web server programming 1. nuts and bolts. premises of course provides general introduction, no...
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Web Server Programming
1. Nuts and Bolts
Premises of Course
• Provides general introduction, no in-depth training• Assumes some HTML knowledge• Assumes some programming experience• Assumes some knowledge of object orientation• Only treats JAVA applications. Alternatives:
– Perl, (PHP)
– XML
Web Services
• Document level– XML + Style sheets– Client-side programming (javascript, applets)– Server-side programming:
• CGI
• JAVA servlets
• HTML++ / XML++ (SSI: php, asp, jsp)
• RPCs
Contents of this course
• Web technology: protocols & languages
• Web server: request handling, output generation, session & user management
• Server programming:– Java servlets– JSP
What This Course Is NOT About
• RPCs
• Use of XML for (enterprise) web services
• Layout & content management
• Use of external components (databases, etc.)
• Client based software (applets, etc.)
About the Web
• Reinier Post
JAVA Support
• Component based
• Platform independent
• Built-in security
• Software libraries for every application
Web Applications
• Cooperating parts:– (HTML) documents– Servlets– JSP pages– Applets (client side software)
• Common context– Properties (appl. param., configuration data)– Resources (shared data)
JAVA servlets
Alternative for CGI scripts:
• JAVA technology
• Servlet support integrated in server– JAVA threads: no independent process– Sharing of resources
• Protocol independent
• Security issues: JAVA sandbox
JSP Pages
• Based on HTML or XML
• Contain processing tags
• Use servlet classes
• Converted to servlet
What About Servlets?
• Standard for interfacing web client with web server.
• Set of JAVA packages (javax.servlet, javax.servlet.http)
• Way of interfacing clients with back-end services (JDBC servers, etc.)
• Way to implement proxies (e.g. for applets)
Servlet API
• Interface Servlet
• Interface ServletConfig
• Interface ServletContext
• Interface ServletRequest
• Interface ServletResponse
Interface Servlet
• Init()
• Service()
• Destroy()
• getServletConfig()
• getServletInfo()
Class HttpServlet
• Inherits from GenericServlet (impl. Servlet)• Additional methods:
– doGet()– doPost()– doHead()– doDelete()– doOptions()– doTrace()
Requests and Responses
• Interface HttpServletRequest– Request as stream
– HTTP headers
– Parameters
– Path info
• Interface HttpServletResponse– Output stream
– HTTP headers
– Cookies
Example: TestServlet.java
• Implements doGet() and doPost() using common (private) function doIt()
• Analyses client request and shows:– Servlet requested– Path info– Get and post parameters
public class TestServlet extends HttpServlet { private static final String CONTENT_TYPE = "text/html"; private PrintWriter out; //Initialize global variables public void init() throws ServletException { } //Process the HTTP Get request public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doIt(request, response); } //Process the HTTP Post request public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doIt(request, response); } private void doIt(HttpServletRequest req, HttpServletResponse res) throws
ServletException, IOException { res.setContentType(CONTENT_TYPE); out = res.getWriter(); out.println("<html>"); .. out.println("</html>"); } //Clean up resources public void destroy() { }}
Assignment
• Modify TestServlet to show the current date.
• Study the servlet API documentation.
• Modify TestServlet to show initial parameters, and provide some of those.