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Chapter 27 JavaServer Pages and Servlets

Chapter 27 JavaServer Pages and Servlets. Chapter Goals. To implement dynamic web pages with JavaServer Faces (JSF) technology To learn the syntactical elements of JavaServer Faces To learn about navigation in JSF applications To build three-tier web applications. A Simple JSF Program.

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Chapter 27 JavaServer Pages and Servlets

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  1. Chapter 27JavaServerPages and Servlets

  2. Chapter Goals • To implement dynamic web pages with JavaServer Faces (JSF) technology • To learn the syntactical elements of JavaServer Faces • To learn about navigation in JSF applications • To build three-tier web applications

  3. A Simple JSF Program • JSF: Java Server Faces • To develop a JSF application, you need a web server that is integrated with a JSF container • A JSF page contains HTML and JSF tags • The user interface of a JSF application is described by a set of JSF pages

  4. A Simple JSF Program • Each JSF page has the following structure: <html> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> <f:view> <head> <title>Page title</title> </head> <body> <h:form> Page contents </h:form> </body> </f:view> </html>

  5. A Simple JSF Program • Previous structure has three parts: • taglib directives required to locate two JSF libraries • Tags from the core library have the prefix f: (such as f:view) • Tags from the HTML library have the prefix h: (such as h:form) • All JSF tags must be contained inside an f:view tag • The h:form tag encloses all user interface elements

  6. Executing the datetime Web Application Figure 1:Executing the datetime Web Application

  7. File datetime/index.jsp 01:<html> 02: <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> 03: <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> 04: 05: <f:view> 06: <head> 07: <title>The datetime application</title> 08: </head> 09: <body> 10: <h:form> 11: <p>Number of milliseconds since January 1, 1970: 12: <h:outputText value="#{dateTime.time}"/> 13: </p> 14: </h:form> 15: </body> 16: </f:view> 17:</html>

  8. The JSF Container Rewrites the Requested Page Figure 2:The JSF Container Rewrites the Requested Page

  9. A Simple JSF Program • Purpose of a JSF page is to generate an HTML page • Basic process: • HTML tags in the page are retained; they are the static part of the page • JSF tags are translated into HTML; translation is dynamic, it depends on the state of Java objects • The h: tags generate HTML • The f: describe structural information that the h: tags use • The taglib directives are stripped out

  10. The HTML Code That Is Generated by a JSF Page Figure 3:The HTML Code That Is Generated by a JSF Page

  11. A Simple JSF Program • The JSF container converts a JSF page to an HTML page, replacing JSF tags with text and HTML • In the example, the h:outputText tag has the value binding #{dateTime.time} • Value bindings link JSF pages with Java objects Continued

  12. A Simple JSF Program • The Java objects are defined in a configuration file • Named faces-config.xml • Placed in the WEB-INF subdirectory of the web application's base directory

  13. File datetime/WEB-INF/faces-config.xml 01:<?xml version="1.0"?>02: 03:<!DOCTYPE faces-config PUBLIC 04: "-//Sun Microsystems, Inc. //DTD JavaServer Faces Config 1.0//EN" 05: "http://java.sun.com/dtd/web-facesconfig_1_0.dtd"> 06: 07:<faces-config> 08: <managed-bean> 09: <managed-bean-name>dateTime</managed-bean-name> 10: <managed-bean-class>java.util.Date</managed-bean-class> 11: <managed-bean-scope>request</managed-bean-scope> 12: </managed-bean>13: </faces-config>

  14. A Simple JSF Program • This file defines an object dateTime with type java.util.Date • A new object is constructed with each "request" • Whenever a browser requests the page, • A new Date object is constructed, and • It is attached to the dateTime variable • The Date constructor constructs an object with the current time Continued

  15. A Simple JSF Program • #{dateTime.time} calls getTime of dateTime • The h:outputText tag converts the result of that method call to text

  16. Important Design Principle of the JSF Technology • JSF enables the separation of presentation and business logic • Presentation logic: the user interface of the web application • Business logic: the part of the application that is independent of the visual presentation • JSF pages define the presentation logic • Java objects define the business logic • The value bindings tie the two together

  17. Steps for Deploying a JSF Application • Make a subdirectory with the name of your web application in the webapps directory of your Tomcat installation or • Place the index.jsp file into that directory /usr/local/jakarta-tomcat/webapps/datetime c:\Tomcat\webapps\datetime Continued

  18. Steps for Deploying a JSF Application • Create a subdirectory WEB-INF in your application directory or /usr/local/jakarta-tomcat/webapps/datetime c:\Tomcat\webapps\datetime\WEB-INF

  19. Steps for Deploying a JSF Application • Place faces-config.xml into the WEB-INF subdirectory • Place your Java classes (if any) inside WEB-INF/classes • Place the file web.xml inside the WEB-INF subdirectory • Start the web server • Point your browser to http://localhost:8080/datetime/index.faces

  20. The Directory Structure of the datetimeApplication Figure 4:The Directory Structure of the datetime Application

  21. The Java Studio Creator Tool Figure 5:The Java Studio Creator Tool

  22. File datetime/WEB-INF/web.xml 01:<?xml version="1.0"?> 02: 03:<!DOCTYPE web-app PUBLIC 04: "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" 05:"http://java.sun.com/dtd/web-app_2_3.dtd"> 06: 07:<web-app> 08: <servlet> 09: <servlet-name>Faces Servlet</servlet-name> 10: <servlet-class>javax.faces.webapp.FacesServlet </servlet-class> 11: <load-on-startup>1</load-on-startup> 12: </servlet> 13: 14: <servlet-mapping> 15: <servlet-name>Faces Servlet</servlet-name> 16: <url-pattern>*.faces</url-pattern> 17: </servlet-mapping> 18:</web-app>

  23. Self Check • What steps are required to add the image of a clock to the datetime application? (The clock doesn't have to show the correct time.) • Does a Swing program automatically separate presentation and business logic?

  24. Answers • Place an image file, say clock.gif, into the datetime directory, and add a tag <img src="clock.gif"/> to the index.jsp file. • No–it is possible (and sadly common) for programmers to place the business logic into the frame and component classes of the user interface.

  25. JavaBeans Components • Software component: • Encapsulates functionality • Can be plugged into a software system without programming • For example, the dateTime object • Unlike some programming languages, Java does have explicit support for components Continued

  26. JavaBeans Components • In Java, use a programming convention to implement components • A JavaBean is a Java class that follows this convention • A JavaBean exposes properties–values of the component that can be accessed without programming

  27. JavaBeans Components • JavaBean requirements: • Must have a public constructor with no parameters • Must have methods for accessing the component properties that follow the get/set naming convention

  28. JavaBeans Components • For example, to get or set the time of a Date object, must use getTime and setTime • For a property with name propertyName and type Type, • Exception: the accessor of a boolean property can use an is prefix public Type getPropertyName() public void setPropertyName(Type newValue) public boolean isShopping()

  29. JavaBeans Components • The name of a property starts with a lowercase letter • The corresponding methods have an uppercase letter (isShopping) • Exception: property names can be all capitals (e.g. ID or URL) • getID or setURL Continued

  30. JavaBeans Components • Read-only property: has only a get method • Write-only property: has only a set method • A JavaBean can have additional methods, but they are not connected with properties

  31. JavaBeans Components • Many programmers follow the additional convention that the name of a bean class should end in Bean Continued

  32. JavaBeans Components public class UserBean { // Required default constructor public UserBean() { . . . } // creditCard property public String getCreditCard() { . . . } public void setCreditCard(String newValue) { . . . } // shopping property public boolean isShopping() { . . . } public void setShopping(boolean newValue) { . . . } // Other methods . . . // Instance fields . . . } Continued

  33. JavaBeans Components • This bean has two properties: creditCardand shopping • Do not make any assumptions about the internal representation of properties • May have an instance field for every property: private String creditCard; private boolean shopping; Continued

  34. JavaBeans Components • Do not make any assumptions about the internal representation of properties • May store the credit card state in a database • get and set methods would contain database operations • May compute the property value: public boolean isShopping() { return shoppingCart != null; }

  35. JavaBeans Components • To use a bean in a JSF page, define it in faces-config.xml • Called a managed bean because the JSF container manages its lifetime <managed-bean> <managed-bean-name>user</managed-bean-name> <managed-bean-class>bigjava.UserBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> Continued

  36. JavaBeans Components • Session scope: the bean is available for multiple requests by the same browser • Application scope: the bean stays alive for the entire web application • It is shared among different users

  37. JavaBeans Components • Access the bean properties in value bindings • Specify the name of the property, not the name of the get or set methods • <h:inputText value="#{user.creditCard}"/> first callsgetCreditCard • When the user submits the form, the setCreditCard is called to store the edited property value <h:outputText value="#{user.creditCard}"/>

  38. JavaBeans Components: An Example • We want to display the current time, not the number of milliseconds since January 1, 1970 • Default time computation uses the time zone at the server location → not very useful • We will prompt for the city in which the user is located, and display the time in the user's time zone

  39. JavaBeans Components: An Example • Java library contains a TimeZone class • A time zone is identified by a string such as "America/Los_Angeles" or "Asia/Tokyo" • getAvailableIDs returns a string array containing all IDs: • getTimeZone returns a TimeZone object for a given ID string: String[] ids = TimeZone.getAvailableIDs(); String id = "America/Los_Angeles"; TimeZone zone = TimeZone.getTimeZone(id);

  40. JavaBeans Components: An Example • Use a DateFormat object to get a time string: DateFormat timeFormatter = DateFormat.getTimeInstance(); timeFormatter.setTimeZone(zone); Date now = new Date(); // Suppose the server is in New York, and it's noon there System.out.println(timeFormatter.format(now)); // Prints 9:00:00 AM

  41. JavaBeans Components: An Example • Interaction with user: • The user will simply enter the city name • The time zone bean will replace the spaces in the name with underscores • Then, check if that string appears at the end of one of the valid time zone IDs

  42. The timezone Application Figure 6:The timezone Application

  43. File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 01:package bigjava; 02: 03:import java.text.DateFormat; 04:import java.util.Date; 05:import java.util.TimeZone; 06: 07: /** 08: This bean formats the local time of day for a given date 09: and city. 10: */ 11:public class TimeZoneBean 12:{ 13: /** 14: Initializes the formatter. 15: */ Continued

  44. File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 16:public TimeZoneBean() 17: { 18: timeFormatter = DateFormat.getTimeInstance(); 19: } 20: 21: /** 22: Setter for city property. 23: @param aCity the city for which to report the // local time 24: */ 25:public void setCity(String aCity) 26: { 27: city = aCity; 28: zone = getTimeZone(city); 29: } 30: Continued

  45. File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 31: /** 32: Getter for city property. 33: @return the city for which to report the local time 34: */ 35: public String getCity() 36: { 37:return city; 38: } 39: 40: /** 41: Read-only time property. 42: @return the formatted time 43: */ 44:public String getTime() 45: { Continued

  46. File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 46:if (zone == null) return"not available"; 47: timeFormatter.setTimeZone(zone); 48: Date time = new Date(); 49: String timeString = timeFormatter.format(time); 50:return timeString; 51: } 52: 53: /** 54: Looks up the time zone for a city 55: @param aCity the city for which to find the time zone 56: @return the time zone or null if no match is found 57: */ 58:private static TimeZone getTimeZone(String city) 59: { Continued

  47. File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 60: String[] ids = TimeZone.getAvailableIDs(); 61:for (int i = 0; i < ids.length; i++) 62:if (timeZoneIDmatch(ids[i], city)) 63:return TimeZone.getTimeZone(ids[i]); 64:return null; 65: } 66: 67: /** 68: Checks whether a time zone ID matches a city 69: @param id the time zone ID (e.g. "America/Los_Angeles") 70: @param aCity the city to match (e.g. "Los Angeles") 71: @return true if the ID and city match 72: */ 73:private static boolean timeZoneIDmatch(String id, // String city) 74: { Continued

  48. File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 75: String idCity = id.substring(id.indexOf('/') + 1); 76:return idCity.replace('_', ' ').equals(city); 77: } 78: 79:private DateFormat timeFormatter; 80:private String city; 81:private TimeZone zone; 82:}

  49. File timezone/WEB-INF/faces-config.xml 01:<?xml version="1.0"?> 02: 03:<!DOCTYPE faces-config PUBLIC 04: "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.0//EN" 05: "http://java.sun.com/dtd/web-facesconfig_1_0.dtd"> 06: 07:<faces-config> 08: <managed-bean> 09: <managed-bean-name>zone</managed-bean-name> 10: <managed-bean-class>bigjava.TimeZoneBean< /managed-bean-class> 11: <managed-bean-scope>session</managed-bean-scope> 12: <managed-property> 13: <property-name>city</property-name> 14: <value>Los Angeles</value> 15: </managed-property> 16: </managed-bean> 17:</faces-config>

  50. File timezone/index.jsp 01:<html> 02: <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> 03: <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> 04: 05: <f:view> 06: <head> 07: <title>The timezone application</title> 08: </head> 09: <body> 10: <h:form> 11: <p> 12: The current date and time in 13: <h:outputText value="#{zone.city}"/> 14: is: 15: <h:outputText value="#{zone.time}"/> 16: </p> 17: <p> Continued

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