1. 環境
Myfaces1.4 + tomahawk-1.1.3 + tomcat5.x + JDK5
下載：http://myfaces.apache.org
2. 問題描述
假設場景，首先顯示用戶列表（用dataTable來實現列表顯示），然后可以點擊用戶的名字導航到用戶詳細信息頁面。
3. 嘗試實現以及出現的問題
UserInfo.java
package com.wide.jsf.model;
/**
* 用戶信息
*
* @author cydooo
*
*/
public class UserInfo {
private Long userId;
private String username;
private String userdesc;
public UserInfo() {
}
public UserInfo(Long userId, String username) {
this.userId = userId;
this.username = username;
}
public UserInfo(Long userId, String username, String userdesc) {
this(userId, username);
this.userdesc = userdesc;
}
//省略getter和setter
}
UserInfoAction.java
package com.wide.jsf.web;
import java.util.Arrays;
import java.util.List;
import javax.faces.context.FacesContext;
import com.wide.jsf.model.UserInfo;
public class UserInfoAction {
/*
* 用于顯示詳細信息
*/
private UserInfo userInfo;
/*
* 用于顯示用戶列表
*/
private List<UserInfo> userInfos;
public UserInfo getUserInfo() {
return userInfo;
}
public void setUserInfo(UserInfo userInfo) {
this.userInfo = userInfo;
}
public List<UserInfo> getUserInfos() {
return userInfos;
}
public void setUserInfos(List<UserInfo> userInfos) {
this.userInfos = userInfos;
}
public String listUser() {
userInfos = Arrays.asList(new UserInfo[] { new UserInfo(1L, "Tom"),new UserInfo(2L, "John"), new UserInfo(3L, "Lily") });
return "listUser";
}
public String showDetail() {
FacesContext context = FacesContext.getCurrentInstance();
Long userId = Long.parseLong((String) context.getExternalContext()
.getRequestParameterMap().get("userId"));
System.out.println("==>" + userId);
switch (userId.intValue()) {
case 1:
userInfo = new UserInfo(1L, "Tom", "I am Tom");
break;
case 2:
userInfo = new UserInfo(2L, "John", "I am John");
break;
case 3:
userInfo = new UserInfo(3L, "Lily", "I am Lily");
}
return "userdetail";
}
}
Backingbean和navigation的配置
<managed-bean>
<managed-bean-name>userInfoAction</managed-bean-name>
<managed-bean-class>
com.wide.jsf.web.UserInfoAction
</managed-bean-class>
<managed-bean-scope>request</managed-bean-scope>
</managed-bean>
<navigation-rule>
<from-view-id>/listUser.jsp</from-view-id>
<navigation-case>
<from-outcome>userdetail</from-outcome>
<to-view-id>/userdetail.jsp</to-view-id>
</navigation-case>
</navigation-rule>
<navigation-rule>
<from-view-id>/userdetail.jsp</from-view-id>
</navigation-rule>
Jsp頁面內容
A． listUser.jsp
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%>
<%@ page contentType="text/html; UTF-8" pageEncoding="UTF-8"%>
<f:view>
<html>
<head>
<title>userlist</title>
</head>
<body>
<h:form>
<h:dataTable var="user" value="#{userInfoAction.userInfos}">
<h:column>
<h:commandLink value="#{user.username}" action="#{userInfoAction.showDetail}">
<f:param value="#{user.userId}" name="userId"/>
</h:commandLink>
</h:column>
</h:dataTable>
</h:form>
</body>
</html>
</f:view>
B. userdetail.jsp
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%>
<%@ page contentType="text/html; UTF-8" pageEncoding="UTF-8"%>
<f:view>
<html>
<head>
<title>userDetail</title>
</head>
<body>
<h:form>
<h:outputText value="#{userInfoAction.userInfo.userdesc}"/>
</h:form>
</body>
</html>
</f:view>
編碼結束，啟動tomcat測試，進入userlist頁面之后，我們可以看到用戶列表，但點擊用戶查看詳細信息的時候，發現并沒有調用showDetail方法。
4. 解決辦法
A． 將<managed-bean-scope>request</managed-bean-scope>改為<managed-bean-scope>session</managed-bean-scope>。這是最簡單的做法，改了之后重起Tomcat之后馬上就看到效果了。但是很明顯的使用session scope不好，比如這個例子，用戶列表在當前seesion有效的情況下將一直保留，多窗口瀏覽器中也容易發生意想不到的問題。沒有必要不要用session。
B． 將用戶列表綁定到dataTable控件。
首先修改UserInfo類，讓他實現Serializable接口，其他代碼完全一樣，實現Serializable接口是必須的，否則會拋出java.io.NotSerializableException異常。
public class UserInfo implements Serializable{…}
UserInfoAction.java的修改
package com.wide.jsf.web;
import java.util.Arrays;
import java.util.List;
import javax.faces.component.html.HtmlDataTable;
import javax.faces.context.FacesContext;
import com.wide.jsf.model.UserInfo;
public class UserInfoAction {
/*
* 用于顯示詳細信息
*/
private UserInfo userInfo;
/*
* 綁定用戶列表
*/
private HtmlDataTable dataTable = new HtmlDataTable();
public UserInfo getUserInfo() {
return userInfo;
}
public void setUserInfo(UserInfo userInfo) {
this.userInfo = userInfo;
}
public String listUser() {
List<UserInfo> userInfos = Arrays.asList(new UserInfo[] { new UserInfo(1L, "Tom"),
new UserInfo(2L, "John"), new UserInfo(3L, "Lily") });
dataTable.setValue(userInfos);
return "listUser";
}
public String showDetail() {
FacesContext context = FacesContext.getCurrentInstance();
Long userId = Long.parseLong((String) context.getExternalContext()
.getRequestParameterMap().get("userId"));
System.out.println("==>" + userId);
switch (userId.intValue()) {
case 1:
userInfo = new UserInfo(1L, "Tom", "I am Tom");
break;
case 2:
userInfo = new UserInfo(2L, "John", "I am John");
break;
case 3:
userInfo = new UserInfo(3L, "Lily", "I am Lily");
}
return "userdetail";
}
public HtmlDataTable getDataTable() {
return dataTable;
}
public void setDataTable(HtmlDataTable dataTable) {
this.dataTable = dataTable;
}
}
listUser.jsp的修改
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%>
<%@ page contentType="text/html; UTF-8" pageEncoding="UTF-8"%>
<f:view>
<html>
<head>
<title>userlist</title>
</head>
<body>
<h:form>
<h:dataTable var="user" binding="#{userInfoAction.dataTable}">
<h:column>
<h:commandLink value="#{user.username}" action="#{userInfoAction.showDetail}">
<f:param value="#{user.userId}" name="userId"/>
</h:commandLink>
</h:column>
</h:dataTable>
</h:form>
</body>
</html>
</f:view>
重起Tomcat一切OK，不需要非得在session scope下了。
本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/pengrg166/archive/2007/01/22/1490174.aspx