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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 • 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 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> 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 Executing the datetime Web Application Figure 1: Executing the datetime Web Application 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> The JSF Container Rewrites the Requested Page Figure 2: The JSF Container Rewrites the Requested Page 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 The HTML Code That Is Generated by a JSF Page Figure 3: The HTML Code That Is Generated by a JSF Page 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 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 File datetime/WEB-INF/facesconfig.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> 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 A Simple JSF Program • #{dateTime.time} calls getTime of dateTime • The h:outputText tag converts the result of that method call to text 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 Steps for Deploying a JSF Application 1. Make a subdirectory with the name of your web application in the webapps directory of your Tomcat installation /usr/local/jakarta-tomcat/webapps/datetime or c:\Tomcat\webapps\datetime 2. Place the index.jsp file into that directory Continued Steps for Deploying a JSF Application 3. Create a subdirectory WEB-INF in your application directory /usr/local/jakarta-tomcat/webapps/datetime or c:\Tomcat\webapps\datetime\WEB-INF Steps for Deploying a JSF Application 4. Place faces-config.xml into the WEB-INF subdirectory 5. Place your Java classes (if any) inside WEB-INF/classes 6. Place the file web.xml inside the WEB-INF subdirectory 7. Start the web server 8. Point your browser to http://localhost:8080/datetime/index.faces The Directory Structure of the datetime Application Figure 4: The Directory Structure of the datetime Application The Java Studio Creator Tool Figure 5: The Java Studio Creator Tool 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> Self Check 1. 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.) 2. Does a Swing program automatically separate presentation and business logic? Answers 1. Place an image file, say clock.gif, into the datetime directory, and add a tag <img src="clock.gif"/> to the index.jsp file. 2. No–it is possible (and sadly common) for programmers to place the business logic into the frame and component classes of the user interface. 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 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 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 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, public Type getPropertyName() public void setPropertyName(Type newValue) • Exception: the accessor of a boolean property can use an is prefix public boolean isShopping() 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 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 JavaBeans Components • Many programmers follow the additional convention that the name of a bean class should end in Bean Continued 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 JavaBeans Components • This bean has two properties: creditCard and 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 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; } JavaBeans Components • To use a bean in a JSF page, define it in faces-config.xml <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> • Called a managed bean because the JSF container manages its lifetime Continued 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 JavaBeans Components • Access the bean properties in value bindings <h:outputText value="#{user.creditCard}"/> • Specify the name of the property, not the name of the get or set methods <h:inputText value="#{user.creditCard}"/> first calls getCreditCard When the user submits the form, the setCreditCard is called to store the edited property value 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 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: String[] ids = TimeZone.getAvailableIDs(); getTimeZone returns a TimeZone object for a given ID string: String id = "America/Los_Angeles"; TimeZone zone = TimeZone.getTimeZone(id); 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 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 The timezone Application Figure 6: The timezone Application File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 01: 02: 03: 04: 05: 06: 07: 08: 09: 10: 11: 12: 13: 14: 15: package bigjava; import java.text.DateFormat; import java.util.Date; import java.util.TimeZone; /** This bean formats the local time of day for a given date and city. */ public class TimeZoneBean { /** Initializes the formatter. */ Continued File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 16: 17: 18: 19: 20: 21: 22: 23: 24: 25: 26: 27: 28: 29: 30: public TimeZoneBean() { timeFormatter = DateFormat.getTimeInstance(); } /** Setter for city property. @param aCity the city for which to report the // local time */ public void setCity(String aCity) { city = aCity; zone = getTimeZone(city); } Continued File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 31: 32: 33: 34: 35: 36: 37: 38: 39: 40: 41: 42: 43: 44: 45: /** Getter for city property. @return the city for which to report the local time */ public String getCity() { return city; } /** Read-only time property. @return the formatted time */ public String getTime() { Continued File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 46: 47: 48: 49: 50: 51: 52: 53: 54: 55: 56: 57: 58: 59: if (zone == null) return "not available"; timeFormatter.setTimeZone(zone); Date time = new Date(); String timeString = timeFormatter.format(time); return timeString; } /** Looks up the time zone for a city @param aCity the city for which to find the time zone @return the time zone or null if no match is found */ private static TimeZone getTimeZone(String city) { Continued File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 60: 61: 62: 63: 64: 65: 66: 67: 68: 69: 70: 71: 72: 73: 74: String[] ids = TimeZone.getAvailableIDs(); for (int i = 0; i < ids.length; i++) if (timeZoneIDmatch(ids[i], city)) return TimeZone.getTimeZone(ids[i]); return null; } /** Checks whether a time zone ID matches a city @param id the time zone ID (e.g. "America/Los_Angeles") @param aCity the city to match (e.g. "Los Angeles") @return true if the ID and city match */ private static boolean timeZoneIDmatch(String id, // String city) { Continued File timezone/WEB-INF/classes/ bigjava/TimeZoneBean.java 75: 76: 77: 78: 79: 80: 81: 82: } String idCity = id.substring(id.indexOf('/') + 1); return idCity.replace('_', ' ').equals(city); } private DateFormat timeFormatter; private String city; private TimeZone zone; File timezone/WEB-INF/facesconfig.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> 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}"/> Continued 16: </p> 17: <p> File timezone/index.jsp 18: Set time zone: 19: <h:inputText value="#{zone.city}"/> 20: </p> 21: <p> 22: <h:commandButton value="Submit"/> 23: </p> 24: </h:form> 25: </body> 26: </f:view> 27: </html> 28: The Directory Structure of the timezone Application Figure 7: The Directory Structure of the timezone Application Self Check 3. Is the Random class a Java bean? 4. What work does the setCity method of the TimeZoneBean do besides setting the city instance field? 5. When you start the timezone application for the first time, why does the input field contain the string "Los Angeles"? Answers 3. Technically, yes. It has a default constructor. However, it has no methods whose name start with get or set, so it exposes no properties. 4. It sets the zone instance field to match the time zone of the city. 5. When the zone bean was constructed, its city property was set to "Los Angeles". When the input field is rendered, its default value is the current value of the city property. Session State and Cookies Figure 8: Viewing the Cookies in a Browser JSF Components • Each component has a value attribute to connect the component value with a bean property <h:inputSecret value="#{user.password}"/> • h:inputTextArea has attributes to specify the rows and columns <h:inputTextArea value="#{user.comment}" rows="10" cols="40"/> Continued JSF Components • Radio button and checkbox groups allow you to specify horizontal or vertical layout: <h:selectOneRadio value="#{burger.topping}" layout="lineDirection"> JSF Components: Button Groups and Menus • Require two properties: the collection of possible choices the actual choice • The value attribute specifies the actual choice to be displayed • The collection of possible choices is defined by a nested f:selectItems tag <h:selectOneRadio value="#{creditCard.expirationMonth}" layout="pageDirection"> <f:selectItems value="#{creditCard.monthChoices}"/> </h:selectOneRadio> Continued JSF Components: Button Groups and Menus • monthChoices must have a type that can describe a list of choices For example, Map The keys of the map are the labels The corresponding map values are the label values Example: Using a Map to Describe a List of Choices • To create the list of choices: public class CreditCardBean { . . . public Map<String, Integer> getMonthChoices() { Map<String, Integer> choices = new LinkedHashMap<String, Integer>(); choices.put("January", 1); choices.put("February", 2); . . . return choices; } } Continued Example: Using a Map to Describe a List of Choices • The type of the value property of the component must match the type of the map value For example, creditCard.expirationMonth must be an integer • If multiple selections are allowed, the type of the value property must be a list or array of matching types Common JSF Components Self Check 6. Which JSF components can be used to give a user a choice between "AM/PM" and "military" time? 7. How would you supply a set of choices for a credit card expiration year to a h:selectOneMenu component? Answers 6. h:selectOneRadio, h:selectOneMenu, or h:selectOneCheckbox Answers 7. You would need a bean with a property such as the following: public Map<String, Integer> getYearChoices() { Map<String, Integer> choices = new TreeMap<String, Integer>(); choices.put("2003", 2003); choices.put("2004", 2004); . . . return choices; } Then supply a tag <f:selectItems value="#{creditCard.yearChoices}"/> Navigation Between Pages • Consider an enhancement of our timezone program • We start with a page that prompts the user to enter the name of a city • When the user clicks "Submit" a new page appears Continued Navigation Between Pages • Next page is either the page with the time display or an error page if no time zone is available • The JSF container needs to determine which page to show next Navigating Between Pages Figure 9: Navigating Between Pages Navigation Between Pages • Each button has an outcome, a string used to look up the next page • Generally, next page may depend on the result of some computation • We need different outcomes depending on the city entered Continued Navigation Between Pages • Specify a method binding as the action attribute: <h:commandButton value="Submit" action="#{zone.addCity}"/> • A method binding consists of the name of a bean and the name of a method Navigation Between Pages • When the form is submitted, the JSF engine calls zone.addCity() public class TimeZoneBean { . . . public String addCity() { if (zone == null) return "unavailable"; // Add the city . . . return "available"; } Continued Navigation Between Pages • If next page doesn't depend on a computation, you set the action attribute of the button to a fixed outcome string <h:commandButton value="Back" action="back"/> Navigation Between Pages • faces-config.xml contains a navigation rule that maps outcome strings to pages: <faces-config> <navigation-rule> <navigation-case> <from-outcome>available</from-outcome> <to-view-id>/next.jsp</to-view-id> </navigation-case> <navigation-case> <from-outcome>unavailable</from-outcome> <to-view-id>/error.jsp</to-view-id> </navigation-case> <navigation-case> <from-outcome>back</from-outcome> <to-view-id>/index.jsp</to-view-id> </navigation-case> </navigation-rule> . . . </faces-config> Continued Navigation Between Pages • Current page is redisplayed when The button has no action attribute, or The action outcome is not listed in the navigation rules Self Check 8. What tag would you need to add to error.jsp so that the user can click on a button labeled "Help" and see help.jsp? What other changes do you need to make to the web application? 9. Which page would be displayed if the addCity method returned null? Answers 8. Add the tag <h:commandButton value="Help" action="help"/> to error.jsp, and add a navigation rule to faces-config.xml: <navigation-case> <from-outcome>help</from-outcome> <to-view-id>/help.jsp</to-view-id> </navigation-case> 9. The current page would be redisplayed. A Three-Tier Application • A three-tier application has separate tiers for presentation, business logic, and data storage The presentation tier: the web browser The "business logic" tier: the JSF container, the JSF pages, and the JavaBeans The storage tier: the database Three-Tier Architecture Figure 10: Three-Tier Architecture Two-Tier Client-Server Architecture Figure 10: Two-Tier Client-Server Architecture A Three-Tier Application • A Three-Tier Application • If business logic changes In a two-tier application, new client program must be distributed over all desktops In a three-tier application, server code is updated, while presentation tier remains unchanged • Simpler to manage A Three-Tier Application • We will have a single database table, CityZone, with city and time zone names • If the TimeZoneBean can't find the city among the standard time zone IDs, it makes a query: SELECT Zone FROM CityZone WHERE City = the requested city • If there is a matching entry in the database, that time zone is returned File multizone/misc/CityZone.sql\ 1: CREATE TABLE CityZone (City TEXT, Zone TEXT) 2: INSERT INTO CityZone VALUES ('San Francisco', 'America/Los Angeles') 3: INSERT INTO CityZone VALUES ('Kaoshiung', 'Asia/Taipei') 4: SELECT * FROM CityZone The cityZone Table Figure 12: The cityZone Table A Three-Tier Application • To query the database, the bean needs a Connection object • With Tomcat, specify the database configuration in conf/server.xml Locate the element <Host name="localhost" . . . > Immediately after, add the configuration information found on the next slide You need to place the JDBC driver file into common/lib Restart server after changing the configuration file A Three-Tier Application <DefaultContext> <Resource name="jdbc/mydb" auth="Container" type="javax.sql.DataSource"/> <ResourceParams name="jdbc/mydb"> <parameter> <name>factory</name> <value>org.apache.commons.dbcp. BasicDataSourceFactory</value> </parameter> <parameter> <name>driverClassName</name> <value>driver class</value> </parameter> <parameter> <name>url</name> <value>database URL</value> </parameter> Continued A Three-Tier Application <parameter> <name>username</name> <value>database user name</value> </parameter> <parameter> <name>password</name> <value>database user password</value> </parameter> </ResourceParams> </DefaultContext> A Three-Tier Application • To obtain a database connection, first look up the data source that was configured in the JSF container: InitialContext ctx = new InitialContext(); DataSource source = (DataSource) ctx.lookup("java:comp/env/jdbc/mydb"); Connection conn = source.getConnection(); try { Use the connection } finally { conn.close(); } Continued A Three-Tier Application • JSF containers such as Tomcat manage a pool of database connections Pooling avoids the overhead of creating new database connections Pooling is completely automatic A Three-Tier Application • Enhanced TimeZoneBean so that it manages a list of cities • Can add cities to the list and remove a selected city Continued A Three-Tier Application Figure 13: The multizone Application Shows a List of Cities The Directory Structure of the multizone Application Figure 14: The Directory Structure of the multizone Application File multizone/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 multizone application</title> 08: </head> 09: <body> 10: <h:form> 11: <p> 12: Enter city: 13: <h:inputText value="#{zone.city}"/> 14: </p> Continued 15: <p> File multizone/index.jsp 16: 17: 18: 19: 20: 21: <h:commandButton value="Submit" action="#{zone.addCity}"/> </p> </h:form> </body> </f:view> </html> File multizone/next.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 multizone application</title> 08: </head> 09: <body> 10: <h:form> 11: <p> 12: <h:selectOneRadio value="#{zone.cityToRemove}" 13: layout="pageDirection"> 14: <f:selectItems value= "#{zone.citiesAndTimes}"/> 15: </h:selectOneRadio> Continued File multizone/next.jsp 16: 17: 18: 19: 20: 21: 22: 23: 24: </p> <p> <h:commandButton value= "Remove selected" action ="#{zone.removeCity}"/> <h:commandButton value= "Add another" action="back"/> </p> </h:form> </body> </f:view> </html> File multizone/error.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 multizone application</title> 08: </head> 09: <body> 10: <h:form> 11: <p> 12: Sorry, no information is available for 13: <h:outputText value="#{zone.city}"/> 14: </p> 15: <p> Continued File multizone/error.jsp 16: <h:commandButton value="Back" action="back"/> 17: </p> 18: </h:form> 19: </body> 20: </f:view> 21: </html> File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 001: 002: 003: 004: 005: 006: 007: 008: 009: 010: 011: 012: 013: 014: 015: 016: package bigjava; import import import import import import import import import import import import import import java.sql.Connection; java.sql.PreparedStatement; java.sql.ResultSet; java.sql.SQLException; java.text.DateFormat; java.util.ArrayList; java.util.Date; java.util.Map; java.util.TimeZone; java.util.TreeMap; java.util.logging.Logger; javax.naming.InitialContext; javax.naming.NamingException; javax.sql.DataSource; Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 017: 018: 019: 020: 021: 022: 023: 024: 025: 026: 027: 028: 029: 030: 031: 032: /** This bean formats the local time of day for a given date and city. */ public class TimeZoneBean { /** Initializes the formatter. */ public TimeZoneBean() { timeFormatter = DateFormat.getTimeInstance(); cities = new ArrayList<String>(); } Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 033: 034: 035: 036: 037: 038: 039: 040: 041: 042: 043: 044: 045: 046: 047: 048: /** Setter for city property. @param aCity the city to add to the list of cities */ public void setCity(String aCity) { city = aCity; zone = getTimeZone(city); } /** Getter for city property. @return the city to add to the list of cities */ public String getCity() { Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 049: 050: 051: 052: 053: 054: 055: 056: 057: 058: 059: 060: 061: 062: 063: 064: return city; } /** Setter for the cityToRemove property @param aCity the city to remove */ public void setCityToRemove(String aCity) { cityToRemove = aCity; } /** Getter for the cityToRemove property. @return the empty string */ Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 065: 066: 067: 068: 069: 070: 071: 072: 073: 074: 075: 076: 077: 078: 079: public String getCityToRemove() { return cityToRemove; } /** Read-only citiesAndTimes property. @return a map containing the cities and // formatted times */ public Map<String, String> getCitiesAndTimes() { Date time = new Date(); Map<String, String> result = new TreeMap<String, String>(); for (int i = 0; i < cities.size(); i++) Continued { File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 080: 081: 082: 083: 084: 085: 086: 087: 088: 089: 090: 091: 092: 093: 094: 095: 096: String city = cities.get(i); String label = city + ": "; TimeZone zone = getTimeZone(city); if (zone != null) { timeFormatter.setTimeZone(zone); String timeString = timeFormatter.format(time); label = label + timeString; } else label = label + "unavailable"; result.put(label, city); } return result; } Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 097: 098: 099: 100: 101: 102: 103: 104: 105: 106: 107: 108: 109: 110: /** Action for adding a city. @return "available" if time zone information is // available for the city, "unavailable" otherwise */ public String addCity() { if (zone == null) return "unavailable"; cities.add(city); cityToRemove = city; city = ""; return "available"; } Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 111: 112: 113: 114: 115: 116: 117: 118: 119: 120: 121: 122: 123: 124: 125: 126: /** Action for removing a city. @return null if there are more cities to remove, // "back" otherwise */ public String removeCity() { cities.remove(cityToRemove); if (cities.size() > 0) return null; else return "back"; } /** Looks up the time zone for a city @param aCity the city for which to find the time zone @return the time zone or null if no match is found Continued */ File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 127: 128: 129: 130: 131: 132: 133: 134: 135: 136: 137: 138: 139: 140: 141: 142: private static TimeZone getTimeZone(String city) { String[] ids = TimeZone.getAvailableIDs(); for (int i = 0; i < ids.length; i++) if (timeZoneIDmatch(ids[i], city)) return TimeZone.getTimeZone(ids[i]); try { String id = getZoneNameFromDB(city); if (id != null) return TimeZone.getTimeZone(id); } catch (Exception exception) { Logger.global.info("Caught in TimeZone.getTimeZone: " + exception); } Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 143: 144: 145: 146: 147: 148: 149: 150: 151: 152: 153: 154: 155: 156: 157: 158: return null; } private static String getZoneNameFromDB(String city) throws NamingException, SQLException { InitialContext ctx = new InitialContext(); DataSource source = (DataSource) ctx.lookup("java:comp/env/jdbc/mydb"); Connection conn = source.getConnection(); try { PreparedStatement stat = conn.prepareStatement( "SELECT Zone FROM CityZone WHERE City=?"); stat.setString(1, city); ResultSet result = stat.executeQuery(); Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 159: 160: 161: 162: 163: 164: 165: 166: 167: 168: 169: 170: 171: 172: 173: 174: 175: if (result.next()) return result.getString(1); else return null; } finally { conn.close(); } } /** Checks whether a time zone ID matches a city @param id the time zone ID (e.g. "America/Los_Angeles") @param aCity the city to match (e.g. "Los Angeles") @return true if the ID and city match */ Continued File multizone/WEB-INF/classes/ bigjava/TimeZoneBean.java 176: 177: 178: 179: 180: 181: 182: 183: 184: 185: 186: 187: } private static boolean timeZoneIDmatch(String id, String city) { String idCity = id.substring(id.indexOf('/') + 1); return idCity.replace('_', ' ').equals(city); } private private private private private DateFormat timeFormatter; ArrayList<String> cities; String city; TimeZone zone; String cityToRemove; File multizone/WEB-INF/facesconfig.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: <navigation-rule> 09: <navigation-case> 10: <from-outcome>available</from-outcome> 11: <to-view-id>/next.jsp</to-view-id> 12: </navigation-case> 13: <navigation-case> 14: <from-outcome>unavailable</from-outcome> 15: <to-view-id>/error.jsp</to-view-id> Continued 16: </navigation-case> File multizone/WEB-INF/facesconfig.xml 17: 18: 19: 20: 21: 22: 23: 24: <navigation-case> <from-outcome>back</from-outcome> <to-view-id>/index.jsp</to-view-id> </navigation-case> </navigation-rule> <managed-bean> <managed-bean-name>zone</managed-bean-name> <managed-bean-class>bigjava.TimeZoneBean </managed-bean-class> 25: <managed-bean-scope>session</managed-bean-scope> 26: </managed-bean> 27: </faces-config> Self Check 10. Why don't we just keep a database connection as an instance field in the TimeZoneBean? 11. Why does the removeCity method of the TimeZoneBean return null or "back", depending on the size of the cities field? Answers 10. Then the database connection would be kept open for the entire session. 11. As long as there are cities, the next.jsp page is redisplayed. If all cities are removed, it is pointless to display the next.jsp page, so the application navigates to the index.jsp page.