如何将变量的值从jsf的bean页面（即bean.java）移动到另一个Java类？
[英]how to move a variable's value from jsf's bean page (i.e, bean.java) to another java class?
问题描述
how to move a variable's value from jsf's bean page (ie, bean.java) to another java class? 
如何将变量的值从jsf的bean页面（即bean.java）移动到另一个Java类？ when i tried to do that, the value assinged to the variable in the second java class is NULL., 当我尝试执行此操作时，分配给第二个Java类中的变量的值为NULL。
I have used primefaces UI framework(something like jsf) and assigned every fields value in to a bean class. 我已经使用了primefaces UI框架（类似于jsf），并将每个字段值分配给了一个bean类。 the value assigned to every variable in bean class is proper. 分配给bean类中每个变量的值是正确的。 but when i tried to move those values to another .java file. 但是当我尝试将这些值移动到另一个.java文件时。 The scope of the variable dies, and the value is NULL. 变量的作用域消失，值为NULL。 Check out my codings.. 看看我的编码..
LOGIN.XHTML 登录XHTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:p="http://primefaces.prime.com.tr/ui">
<h:head></h:head>
<h:body>
<p:panel header="Login" style="">
<h:form>
<h:panelGrid columns="2" cellpadding="2">
<h:outputText value="Username"></h:outputText>
<p:inputText id="userName" value="#{loginBean.userName}"></p:inputText>
<h:outputText value="Password"></h:outputText>
<p:password id="password" value="#{loginBean.password}"></p:password>
<p:commandButton value="Sign in" ajax="false" actionListener="#{loginBean.forward}"></p:commandButton>
</h:panelGrid>
</h:form>
</p:panel>
</h:body>
</html>
loginBean.java loginBean.java
package bean;
import receive.*;
public class loginBean {
public String userName;
public String password;
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public void forward()
{
System.out.println(getUserName());
receiveclass r=new receiveclass();
r.dbc();
}
}
receiveclass.java receiveclass.java
package receive;
import bean.loginBean;
public class receiveclass {
loginBean lb=new loginBean();
public void dbc()
{
String s= lb.getUserName();
String p=lb.getPassword();
System.out.println(s);
System.out.println(p);
//System.out.println("hi");
}
}
output is, 输出是
if i give as admin, admin in text fields 如果我以管理员身份在文本字段中输入admin
i am receiving as 我收到
admin null null 管理员null null
2 个解决方案
解决方案1
1 已采纳 2011-10-14 14:24:05
You're manually creating the beans instead of letting JSF manage the beans. 您是在手动创建bean，而不是让JSF管理bean。 Manually created beans won't be used by JSF at all. 手动创建的bean完全不会被JSF使用。 You need to let JSF auto-create and manage those beans. 您需要让JSF自动创建和管理那些bean。 You can access other JSF managed beans by injecting it as @ManagedProperty : 您可以通过将其注入@ManagedProperty来访问其他JSF托管的bean：
In your particular case, the following should work: 在您的特定情况下，以下方法应该起作用：
@ManagedBean
@RequestScoped
public class LoginBean {
private String userName;
private String password;
@ManagedProperty
private ReceiveClass receiveClass;
public void forward() {
receiveClass.dbc(this);
}
// Add/generate getters and setters.
}
with 同
@ManagedBean
@SessionScoped
public class ReceiveClass {
public void dbc(LoginBean loginBean) {
System.out.println(loginBean.getUserName());
}
}
(Note that I fixed the code to adhere the Java Naming Conventions properly. Class names ought to start with uppercase) （请注意，我已修复代码以正确遵守Java命名约定 。类名应以大写字母开头）
See also: 也可以看看：
解决方案2
0 2011-10-14 11:41:30
in your receiveclass you create a completely new instance of loginBean. 在您的receiveclass中，您将创建一个全新的loginBean实例。 Values can only be null. 值只能为空。
I do it this way: I created a Java class in which I have static functions like this one 我这样做：我创建了一个Java类，其中有像这样的静态函数
public class JSFHelper
{
public static Object getMyObject(String objname, Class<?> classname )
{
FacesContext fCtx = FacesContext.getCurrentInstance();
ELContext elCtx = fCtx.getELContext();
ExpressionFactory ef = fCtx.getApplication().getExpressionFactory();
ValueExpression ve =
ef.createValueExpression(elCtx, "#{" + objname+ "}",classname);
return (Object) ve.getValue(elCtx);
}
}
If I need a value from another Bean it would look like this in your receiveclass: 如果我需要另一个Bean的值，则它在您的receiveclass中看起来像这样：
public class receiveclass
{
public void dbc()
{
loginBean lb=(loginBean)JSFHelper.getMyObject("loginBean",loginBean.class);
String s= lb.getUserName();
String p=lb.getPassword();
System.out.println(s);
System.out.println(p);
//System.out.println("hi");
}
}
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