initial page event

[Tugrul ...]

Hi all,
I want to, write some java code that must work while the page is loaded. For example, I want to populate the datatable in the page while the page is opening. I tried the setForm method of the page's backing bean but didnt work. The same code works if I put it under the same page's command button action. Then, I tried the constructor. The bean is in the request scope.
But in the constructor, I cant access the beans other objects. For example, there is a dataTable in the page and I want to populate it in the constructor. But when I access the dataTable object in the constructor, it gives nullPointerException in the runtime. (for ex: dataTable2.setBorder(1); throws exception in the constructor). The same code works if i put it under a command buttons action in the sam page..

I think, there must be a solution for initialization the page objects.
Thanks...

[Daniel Steel]

Dont do anything in the constructor try writing your logic in a separate method.

[Tugrul ...]

Logic and implementation is ready but cant find a suitable place to put.

[Rajeev Ravindran]

if you are using jsf-ibm.jar , prerender may be of some help

 <hx:scriptCollector id="scriptCollectorNewDeal" preRender="#{NewDeal.onPageLoadBegin}">   

Thanks,

[Tim Holloway]

"Tugrul ..."

Welcome to the JavaRanch. We don't have many rule around here, but we do ask that you make your display name conform to our Naming Standards. Please read them and adjust your display name accordingly. It helps us look more professional - even if we do have a moth-eaten mooose head as our logo.

There's limits to what you can overlap in a web app, whether you use JSF, raw servlets, or PERL CGI. One of those limits is that HTTP is a request/response protocol and not a client-server one, so the only way to get any overlap at all would be to spin off a worker thread that could be picked up on the next client request. An HTTP request isn't complete until the server-side code completes.

Also, as a general rule, backing beans in JSF should not talk directly to JSF objects. That is, you wouldn't normally make a bean that seeks out a datatable and stuff things into it. Instead you define the databable to reference the backing bean and have the datatable load itself from the backing bean - which it does automatically when you set the datatable's value attribute. This is a principle known as Inversion of Control (or IoC, for short).
[ March 21, 2006: Message edited by: Tim Holloway ]

[Steven Gray]

Hi Tim,
I have a question that is also related to page initialization.

I have a web site that is database driven. When a user logs in, their profile is looked up in a database and is used to determine the next page to be displayed. For example, an administrator might be taken to a page that allows them to run special admin reports. If a user is registering for a conference, the registration is customized based on the conference being registered for. If the user is registering for conference X, conference details are retrieved from the database before the registration page opens. When the user sees the registration page it might say:
National Association Of Space Engineers New Ideas Conference
May 3 - 7 2006
Registration begins April 1, 2006

I understand how a backing bean can be used to display these values, but when and how would these values be obtained?

Thanks In Advance
Steven

[Solmaz Anvar]

You can do this with a PhaseListener. Just regiser a
new listener for the RESTORE_VIEW phase, and
implement the beforePhase method; you can do this in
the backing bean's constructor, or somewhere elase.
This is pretty much the same as the Page_Load event
handler in .NET.
So far I have seen only examples which declare listeners in
faces-config.xml for the whole application (not per page).

Regards
Solmaz Anvar

[Steven Gray]

Thanks for all the help! I got the phase listener working. After the user logs in, they are displayed an instructions page (instructions.jsp) with a backing bean (InstructionPageBean.java). I have the backing bean coded to go out to the database and fetch the name of the image file to be displayed. Now my problem:

After logging in, the instructions page opens, but without displaying the image file.

    
<h:graphicImage rendered="true" value="#{instruction.imagePathTx}" />

If I click on the browser's refresh button, the image displays correctly. What am I doing wrong? Is InstructionPageBean's constructor getting called after the view is rendered for instrucions.jsp? Any help would be appreciated.

Here is the relevant code:

faces_config.xml - UserBean is a backing bean for the login screen (login.jsp).
InstructionPageBean is a backing bean for instructions.jsp.

    
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE faces-config PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN" "http://java.sun.com/dtd/web-facesconfig_1_1.dtd">
 
<faces-config>
<application>
<message-bundle>com.tec.TecResources</message-bundle>
</application>
<navigation-rule>
<from-view-id>/login.jsp</from-view-id>
<navigation-case>
<from-outcome>loginFailure</from-outcome>
<to-view-id>/login.jsp</to-view-id>
</navigation-case>
<navigation-case>
<from-outcome>loginSuccessAdmin</from-outcome>
<to-view-id>/rptadmin.jsp</to-view-id>
</navigation-case>
<navigation-case>
<from-outcome>loginSuccessInstructions</from-outcome>
<to-view-id>/instructions.jsp</to-view-id>
</navigation-case>
</navigation-rule>
<navigation-rule>
<from-view-id>/rptadmin.jsp</from-view-id>
</navigation-rule>
<managed-bean>
<managed-bean-name>user</managed-bean-name>
<managed-bean-class>com.tec.UserBean</managed-bean-class>
<managed-bean-scope>session</managed-bean-scope>
<managed-property>
<property-name>password</property-name>
<property-class>java.lang.String</property-class>
<null-value />
</managed-property>
<managed-property>
<property-name>userId</property-name>
<property-class>java.lang.Integer</property-class>
<null-value />
</managed-property>
<managed-property>
<property-name>userType</property-name>
<property-class>java.lang.String</property-class>
<null-value />
</managed-property>
<managed-property>
<property-name>cnfncCd</property-name>
<property-class>java.lang.String</property-class>
<null-value />
</managed-property>
<managed-property>
<property-name>phaseNb</property-name>
<property-class>java.lang.Integer</property-class>
<null-value />
</managed-property>
<managed-property>
<property-name>name</property-name>
<property-class>java.lang.String</property-class>
<null-value />
</managed-property>
</managed-bean>
<managed-bean>
<managed-bean-name>instruction</managed-bean-name>
<managed-bean-class>com.tec.InstructionPageBean</managed-bean-class>
<managed-bean-scope>session</managed-bean-scope>
</managed-bean>
<navigation-rule>
<from-view-id>/instructions.jsp</from-view-id>
</navigation-rule>
</faces-config>

UserBean.java

    
/**
 * 
 */
package com.tec;
 
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
 
import javax.faces.application.FacesMessage;
import javax.faces.context.FacesContext;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;
 
 
/**
 * @author Steven Gray
 *
 */
public class UserBean {
private Integer phaseNb;
private Integer userId;
private String cnfncCd;
private String cnfncGroupCd = "A";
private String name;
private String password;
private String userType;
private boolean loggedIn = false;
private Logger logger = Logger.getLogger("com.tec");

public Integer getPhaseNb() {return phaseNb;}
public void setPhaseNb(Integer newValue) {phaseNb = newValue;}
 
public Integer getUserId() {return userId;}
public void setUserId(Integer newValue) {userId = newValue;}

public String getCnfncCd() {return cnfncCd;}
public void setCnfncCd(String newValue) {cnfncCd = newValue;}
 
public String getCnfncGroupCd() {return cnfncGroupCd;}
public void setCnfncGroupCd(String newValue) {cnfncGroupCd = newValue;}

public String getName() {return name;}
public void setName(String newValue) {name = newValue;}
 

public String getPassword() {return password;}
public void setPassword(String newValue) {password = newValue;}
 
public String getUserType() {return userType;}
public void setUserType(String newValue) {userType = newValue;}

public String login(){
try {
doLogin();
}
catch (SQLException ex) {
logger.log(Level.SEVERE,"loginAction", ex);
return "internalError";
}
catch (NamingException ex){
logger.log(Level.SEVERE,"loginAction", ex);
return "internalError";
}
if (loggedIn) {
if (userType.equalsIgnoreCase("A")) {
return "loginSuccessAdmin";
}
else return "loginSuccessInstructions";
}
else {
        FacesContext facesContext = FacesContext.getCurrentInstance(); 
        FacesMessage facesMessage = new FacesMessage("You have entered an invalid user name and/or password"); 
        facesMessage.setSeverity(FacesMessage.SEVERITY_ERROR);
        facesContext.addMessage("loginForm", facesMessage);
return "loginFailure";
}
}

public String logout() {
loggedIn = false;
return "login";
}
public void doLogin() throws SQLException, NamingException {
Context ctx = new InitialContext();
if (ctx == null) throw new NamingException("No initial context");

DataSource ds = (DataSource) ctx.lookup("java:/comp/env/jdbc/DefaultDS");
 
if (ds == null) throw new SQLException("No data source");
 
Connection conn = ds.getConnection();
if (conn == null) throw new SQLException("No connection");

try {
PreparedStatement passwordQuery = conn.prepareStatement(
      "SELECT tec_users.userid, "+
                   "tec_users.cnfnc_cd, "+
                   "tec_users.host_visitor_fg, "+
                   "conference_phase.phase_nb "+
             "FROM tec_users,  "+
                  "conference_phase "+
            "WHERE ( tec_users.username_tx = ? ) "+
              "AND ( tec_users.password_tx = ? ) "+
        "AND ( tec_users.cnfnc_cd = conference_phase.cnfnc_cd ) "+
        "AND ( tec_users.actv_fg = 'Y' ) ");
passwordQuery.setString(1,name);
passwordQuery.setString(2,password);
ResultSet result = passwordQuery.executeQuery();
if (!result.next()) return;
loggedIn = true;
userId = result.getInt(1);
cnfncCd = result.getString(2);
userType = result.getString(3);
phaseNb = result.getInt(4);


}
finally {
conn.close();
}
}


 
}

InstructionPageBean.java

    
/**
 * 
 */
package com.tec;
 
import javax.faces.event.PhaseEvent;
import javax.faces.event.PhaseId;
import javax.faces.event.PhaseListener;
import javax.faces.lifecycle.LifecycleFactory;
import javax.faces.lifecycle.Lifecycle;
import javax.faces.FactoryFinder;
import javax.faces.context.FacesContext;
import javax.naming.*;
import java.sql.*;
import javax.sql.DataSource;
 
/**
 * @author stegra
 * 
 */
public class InstructionPageBean {
private boolean pageLoaded = false;
 
// Variables for dynamically setting text and images based on
// conference.
private String imagePathTx = null;
private int width = 0;
private int height = 0;
private String webCaption = null;
private String nextPage = null;

private Connection conn = null;
 
String cnfncCd;
 
String cnfncGroupCd;
 
java.sql.Statement stmt = null;
 
java.sql.PreparedStatement pstmt = null;
 
ResultSet rs = null;
 
/**
 * Constructor
 */
public InstructionPageBean() 
{
LifecycleFactory lifecycleFactory = (LifecycleFactory) 
    FactoryFinder.getFactory(FactoryFinder.LIFECYCLE_FACTORY);
Lifecycle lifecycle = lifecycleFactory
.getLifecycle(LifecycleFactory.DEFAULT_LIFECYCLE);
lifecycle.addPhaseListener(new PhaseListener() {
public void beforePhase(PhaseEvent event) {
if (!pageLoaded) 
{
try
{
loadPage();
}
catch (Exception ex)
{
System.out.println("Unhandled Exception: " + ex.toString());
}

}
 
}
 
public void afterPhase(PhaseEvent event) {
 
}
 
public PhaseId getPhaseId() {
return PhaseId.RESTORE_VIEW;
}
}
 
);
}// End constructor

public String getImagePathTx() {return imagePathTx;}
public void setImagePathTx(String newValue) {imagePathTx = newValue;}
public int getHeight() {return height;}
public void setHeight(int newValue) {height = newValue;}
public int getWidth() {return width;}
public void setWidth(int newValue) {width = newValue;}
 
 
public void loadPage() throws Exception{
String sql = null;
InitialContext ctx = null;
 
try {
FacesContext fc = FacesContext.getCurrentInstance();
UserBean user = (UserBean) fc.getApplication().createValueBinding("#{user}").getValue(fc); 
ctx = new InitialContext();
Context envCtx = (Context) ctx.lookup("java:comp/env");
DataSource ds = (DataSource) envCtx.lookup("jdbc/DefaultDS");
conn = ds.getConnection();
stmt = conn.createStatement();
cnfncCd = user.getCnfncCd();
cnfncGroupCd = user.getCnfncGroupCd();
sql = "SELECT web_image.image_path_tx, "
+ "web_image.width, "
+ "web_image.height "
+ "FROM web_image, "
+ "conference_phase "
+ "WHERE ( web_image.cnfnc_cd = '"
+ cnfncCd
+ "' ) AND "
+ "( web_image.cnfnc_group_cd = '"
+ cnfncGroupCd
+ "' ) AND "
+ "( web_image.web_page = 'instructions.jsp' ) AND "
+ "( web_image.host_visitor_fg = 'A' ) AND "
+ "( web_image.cnfnc_cd = conference_phase.cnfnc_cd ) AND "
+ "( web_image.cnfnc_group_cd = conference_phase.cnfnc_group_cd ) AND "
+ "( web_image.phase_nb = conference_phase.phase_nb ) ";
 
rs = stmt.executeQuery(sql);
if (!conn.isClosed()) {
while (rs.next()) {
imagePathTx = rs.getString("image_path_tx");
width = rs.getInt("width");
height = rs.getInt("height");
}// while (rs.next())
} else {
throw new Exception("Connection from DataSource is closed!");
}
 
pageLoaded = true;
}// try
catch (NamingException ex)
{
System.out.println("Naming Exception: " + ex.toString());
}
catch (SQLException ex)
{
System.out.println("SQL Exception: " + ex.toString());
}
catch (Exception ex) 
{
throw ex;
} finally 
{
try {
if (stmt != null)
stmt.close();
if (pstmt != null)
stmt.close();
if (conn != null)
conn.close();
if (ctx != null)
ctx.close();
} catch (Exception ex) {
// do nothing
}
}//Finally
 
}//loadPage
 
}//InstructionPageBean

instructions.jsp

    
<%@ page language="java" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%>
 
<%String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<f:view>
<f:loadBundle basename="com.tec.TecResources" var="bundle" />
<head>
<base href="<%=basePath%>">
 
<title><h :-o	 utputText value="#{bundle.instruction_page_title}" /></title>
 
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
 
<body>
<h:form id="instructionForm" rendered="true">
<h :-P	 anelGrid rendered="true" id="instructionHeader" columns="2">
<h:graphicImage rendered="true" value="#{instruction.imagePathTx}" />
</h :-P	 anelGrid>
</h:form>
</body>
</f:view>
</html>

[ March 30, 2006: Message edited by: Steven Gray ]
[ March 30, 2006: Message edited by: Steven Gray ]