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Mastering Servlets and JSP: A Comprehensive Guide

Dive into Servlets and JavaServer Pages (JSP) with this detailed guide. Learn the basics, handling form data, HTTP request headers, CGI variables, generating server responses, managing cookies, and more. Get ready to enhance your web development skills!

nayda-cobb
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Mastering Servlets and JSP: A Comprehensive Guide

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  1. Chapter 1: Overview of Servlets and JavaSerevr Pages

  2. What Are Servlets: Replacement for CGI • Basic operations: receive, process, send • Advantages over CGI and other techniques: • Efficient • Convenient • Powerful • Portable • Secure • Inexpensive

  3. What is JavaServer Pages (JSP): Enables you to mix static HTML with dynamically generated content. • Advantages of JSP Versus: • ASP: Dynamic part is written in JAVA • PHP: Extensive library for Networking, DB, distributed Objects • Pure Servlets: Easier to develop specially if the pages are almost static ones. • SSI: More powerful set of tools • JavaScript: Access DB and networking • Static HTML: You know • Installing s/w: Available In Windows machine Stright107.

  4. Chapter 2: First Servlets

  5. Basic Servlet structure: ServletTemplate.java • Simple Servlet generating plain text: HelloWorld.java • A Servlet that generates HTML: HelloWWW.java (Always set Content type first) • Packaging Servlets: HelloWWW2.java • Simple HTML-Building Utilities: ServletUtilities.java &HelloWWW3.java

  6. The Servlet life cycle: • The init() method: With/Without parameters • The service() method: support HEAD, OPTIONS, and TRACE requests. Call doGet, doPost, doXxx • Implementing the SingleThreadModel • The destroy() method: performs cleaning up • Using Initialization Parameters: ShowMessage.java • Using Modification Date: LotteryNumbers.java • Debugging Servlets: log, command windows, stop/start, look and request/response data • Sending HTTP request: WebClient.java

  7. Chapter 3: Reading Form Data

  8. Reading Form Data: methods getParameter(“name”), getParameterValues(“name”), getParameterNames() • Example: ThreeParams.java and .html • Using GET and POST: ShowParametersGetForm.htm, ShowParametersPostForm.htm, & ShowParameters.java • A resume posting service: SubmitResume.htm & SubmitResume.java • Filtering HTML specific characters: BadCodeServlet.java, FilteredCodeServlet.java

  9. Chapter 4: Handling HTTP Request Headers

  10. The request object has a number of methods to enable you to access all the headers of an HTTP request • getHeader(), getContentLength(), getContentType(), getHeadersName(), etc. • Other methods such as getMethod(), getProtocol(), etc. can access info into the request line • Example: ShowRequestHeaders.java

  11. HTTP 1.1 request headers are case insensitive and include: • Accept (MIME type) • Accept-Encoding, Accept-Language, Accept-Charset • Authorization • Connection • Content-Length • Content-type • From (Email address of the sender- Only sent by web Spiders) • Host, User-Agent, Via, ……etc

  12. Sending compressed web pages: EncodedPage.java • Restricting access to Web page: ProtectedPage.java and PasswordBuilder.java

  13. Chapter 5: Accessing the Standard CGI Variables

  14. The standard CGI variables can be accessed using servlets but in many cases we really do not want to do so. • Examples: CONTENT_LENGTH, DOCUMENT_ROOT, QUERY_STRING, ETC. • Program example: ShowCGIVariables.java

  15. Chapter 6: Generating the Server Response: HTTP Status Codes

  16. The status code is usually returned using response.setStatus(int code) • There are two other methods sendError(int code, String message) & sendRedirect(String URL) • Generally, there is five categories • 100-199: Informational • 200-299: Request success • 300-399: Files moved (usually indicates a location header) • 400-499: Client error • 500-599: Server error

  17. Example: Front end to various search engines • Files: SearchEngines.java, SearchSpec.java, SearchEngines.html

  18. Chapter 7: Generating the Server Response: HTTP Response Headers

  19. Any permitted header can be set by using the method setHeader(String header name, String value); • In Servlets 2.2 setHeader() replace existing ones so you can use addHeader() to add new entries of an already existed header • Convenient methods setContentType(), setContentLength(), addCookie(), sendRedirect() • Some common headers: Connection, Content-Language, Content-Type, Content-Length, Location, Refresh { response.setHeader(“Refresh”, “5”); }

  20. Persistent Servlet and auto-reloading • Handling multiple simultaneous connections: • Maintaining state between requests or even among various servlets in the same engine using the ServletContext object (getServletContext()) • Code: PrimeNumbers.java, PrimeList.java, Primes.java • Persistent HTTP connections: PersistentConnection.java & ImageRetriever.java • Generating Gif Images: ShadwedText.java & MessageImage.java

  21. Chapter 8: Handling Cookies

  22. Steps: • Create a cookie: new Cookie(name. value) • Access attributes: cookie.setXxx(), cookie.getXxx() • Insert it into response header: addCookie(cookie) • Get all cookies: request.getCookies(), returns array of cookies objects • Use getName() and getValue() methods of cookie • Examples: setCookies.java & ShowCookies.java • Customized search engine: CustomizedSearchEngine.java & SearchEngineFrontEnd.java

  23. Chapter 10: JSP Scripting Elements

  24. A very attractive alternative to Servlets specially if the page is mostly static with few dynamic parts • Advantages: Widely supported & using JAVA!!! • The JSP page is automatically converted to normal Servlet! • Three types of JSP constructs • Scripting elements: Java code that will become part of the resultant Servlet • Directives: Control the overall Servlet structure • Actions: Specifying components that control JSP engine

  25. Scripting Elements: • Expressions: <%= expression %> • Scriptlets: <% code %> {inserted into _jspService method called by the service method} • Declaration: <%! Code %> {code inserted outside any existing method • Expressions example: Expressions.jsp • Scriptlets: in many situations you need more complex behavior than what simple expressions can do • Example: BGColor.jsp

  26. JSP Directives: Contain code that will be inserted in the main body of the resultant Servlet. Ex <%! String str=“str” %> • They are normally used in conjunction with Expressions • Example: AccessCounts.jsp • Predefines Variables: Simplify JSP code • request: The request object!! • response: The response object!! • out: An object of type JSPWriter which is a child of PrintWriter • application: The ServletContext object

  27. Chapter 11: JSP Page Directive

  28. There are three types of directives: • page: import classes, select parent, set content type • include: Insert a file in the Servlet class during JSP file translation • taglib: allow you to define custom markup tags • The page directives has a number of case-sensitive attributes. • General form: <%@ page attr=“value”%> • The “import” attribute, ex ImportAttribute.jsp • The “contentType” attribue: ex ContentType.jsp to return text/plain. Ex, Excel.jsp to return Excel spread sheet using tabs & ApplesAndOranges.jsp using tables.

  29. The “isThreadSafe” attribute: default is true otherwise specify false for the SingleThreadModel • The “buffer” & “autoflush” attributes • The “errorPage” and “isErrorPage” attributes: ex ComputeSpeed.jsp & SpeedError.jsp

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