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Creating the Web Tier: JavaServer Pages

Creating the Web Tier: JavaServer Pages. Objectives. After completing this lesson, you should be able to do the following: Compare servlets and JavaServer Pages (JSP) Build a simple JSP Describe the JSP life cycle List the basic JSP elements

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Creating the Web Tier: JavaServer Pages

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  1. Creating the Web Tier: JavaServer Pages

  2. Objectives • After completing this lesson, you should be able to do the following: • Compare servlets and JavaServer Pages (JSP) • Build a simple JSP • Describe the JSP life cycle • List the basic JSP elements • Develop JSPs with declarations, expressions, and scriptlets • List implicit objects • Use JavaBeans with JSP

  3. JavaServer Pages Connects to Request JSP Database Client Generates Dynamic content Response EJB

  4. Comparing Servlets and JSPs • JavaServer Pages: • Are HTML pages with embedded Java code or they can be pure XML • Generate dynamic content • Separate static and dynamic content • Servlets: • Are Java programs with embedded HTML • Generate dynamic content • Do not separate static and dynamic content

  5. Invoking JSPs HTML Invoke JSP Servlet JSP

  6. The Date JSP <%@ page contentType="text/html;charset=WINDOWS-1252"%> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=WINDOWS-1252"> <title> Show Date </title> </head> <body> <h2> The current time is: </h2> <p> <%= new java.util.Date() %> </p> </body> </html>

  7. The Date Servlet ...public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType(CONTENT_TYPE); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<head><title>Show Date</title></head><body><h2>The current time is:</h2><p>"); out.println(new java.util.Date()); out.println("</body></html>"); out.close(); }...

  8. Automated JSP Features • A JSP is automatically converted into a servlet the first time it is invoked: • Java source files are generated. • Java class files are generated. • The Java Just-In-Time compiler can be used. • A JSP can contain extensible components: • Tags: Libraries such as OC4J JSP (OJSP) or custom-developed tags. • JavaBeans (Beans are reused and their properties are automatically introspected.)

  9. JSP Life Cycle J2EE container Yes Firsttime OC4J 1 Create servlet date.java http://host/date.jsp No 2 Compile servlet date.class 3 Servlet life cycle

  10. Basic JSP Elements • A JSP contains three main elements: • Text elements • Directives • Scripting elements • Declarations • Expressions • Scriptlets

  11. Declarations • Are used to define methods or variables • Begin with the sequence <%! • End with the sequence %> • Are inserted into the body of the servlet class during translation • Are used in conjunction with expressions or scriptlets <%! private int i=3; %> <%! private String a="Hello", b=" World"; %>

  12. Expressions • Begin with the sequence <%= • Contain Java expressions that are evaluated and inserted into the servlet’s output • End with the sequence %> • Do not end with a semicolon <%= i+1 %> <%= a + b %> <%= new java.util.Date() %> 1 2

  13. Scriptlets • Begin with the sequence <% • Contain a block of Java code that is executed every time a request is made • End with the sequence %> <% if (i<3) out.print("i<3"); if (i==3) out.print("i==3"); else out.print("i>3");%>

  14. Implicit Objects • There are eight implicit objects, also known as predefined variables, in JSP: • request • response • session • out • application • config • pageContext • page

  15. Example

  16. Directives • Are used to set global values such as class declaration, method implementations, and so on • Begin with the sequence <%@ • End with the sequence %> • Are of the following types: • page • include • taglib

  17. include: Example

  18. page Directive • You can define the following attributes by using the page directive: • import • contentType • isThreadSafe • session • buffer • autoflush • extends • info • errorPage • isErrorPage • language

  19. JSP and JavaBeans package lesson08; import java.lang.*; import java.util.*; public class LuckyNumberBean { private int luckyNum; public LuckyNumberBean() { luckyNum = (int) (1000 * Math.random()); } public int getLuckyNum() { return luckyNum; } public void setLuckyNum(int luckyNum) { this.luckyNum = luckyNum; } }

  20. Using JavaBeans with JSP • Accessing JavaBeans with the <jsp:useBean> tag: <jsp:useBean id="myBean" scope="session" class="lesson08.LuckyNumberBean" />

  21. scope Attribute of <jsp:useBean> Tag Client Request Response Request Response Forward Page 1 Page 3 Page 2 page scope page scope page scope request scope request scope session scope

  22. Accessing and Setting Bean Property • Accessing bean property: • Setting bean property: <jsp:getProperty name="myBean" property=“luckyNum" /> <jsp:setProperty name="myBean" property=“luckyNum" value="10" />

  23. JSP XML Document • Contains <jsp:root> as its root element • Includes only XML syntax and does not include the traditional JSP tags • Can be processed directly by the JSP container • Can be used with XML development tools

  24. Traditional Syntax Versus XML Syntax • Traditional: XML: • No root element • page directive<%@ page %> • Declaration tag<%! %> • Expression tag<%= expression %> • Scriptlet<% %> • <jsp:root> is the root element • <jsp:directive.page /> • <jsp:declaration></jsp:declaration> • <jsp:expression></jsp:expression> • <jsp:scriptlet></jsp:scriptlet>

  25. JDeveloper and JSPs • Use the JSP Wizard in JDeveloper to create JSPs containing skeleton code. • The structure pane helps to ensure that the JSP and HTML tags are properly formatted. • Tag Insight automatically inserts end tags after starting a scriptlet. • JSP code is automatically created and recompiled. • JDeveloper increases productivity while debugging JSPs: • Automatically includes source Java files such as your JavaBean source • Enables you to set breakpoints and watch expressions in JSPs

  26. Creating JSPs Visually

  27. JSP Tag Insight

  28. Summary • In this lesson, you should have learned how to: • Differentiate between servlets and JSPs • Build a simple JSP • Describe the JSP life cycle • Use JSP elements and implicit objects • Develop JSPs with declarations, expressions, and scriptlets • Use JavaBeans with JSP

  29. Practices 8-1, 8-2, and 8-3: Overview • These practices cover the following topics: • Creating a JSP that counts the occurrence of each character in a given string • Using JavaBean to calculate an equal discount on the total amount of purchase • Creating a JSP that displays product_id, product_name, and price in the form of a table

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