java 将一个页面传递到 JSF-2.0 中的另一个页面的参数？
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Parameter passing one page to another page in JSF-2.0?
提问by Zaw Than oo
I would like to pass a parameter from one page to another.
我想将参数从一个页面传递到另一个页面。
Each page will have a ViewScopedJSF Backing Bean.
每个页面都有一个ViewScopedJSF Backing Bean。
Although, I try to use <f:param>I get the following error:
when I click <h:commandLink>will navigate to another page.
虽然，我尝试使用时<f:param>出现以下错误：单击时<h:commandLink>将导航到另一个页面。
ERROR :
错误 ：
] Root cause of ServletException.
com.sun.faces.mgbean.ManagedBeanCreationException: Unable to create managed bean ReservationActionBean. The following problems were found:
- The scope of the object referenced by expression #{param.resvDataModel}, request, is shorter than the referring managed beans (ReservationActionBean) scope of view
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:265)
at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:244)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:116)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
.........
page1.xhtml
页面1.xhtml
<p:panelGrid style="margin-top:-1px;" id="dashboard">
<ui:repeat value="#{DashBoard.dayList}" var="day">
<p:row>
<p:column style="background:#C1CDCD;width:100px;">
<h:outputText value="#{day}" style="color:#333333;font-size:13px;">
<f:convertDateTime type="date" pattern="EEE, yyyy-MM-dd"/>
</h:outputText>
</p:column>
<ui:repeat value="#{DashBoard.timeSlot}" var="timeSlot">
<p:column style="background:#C1CDCD;text-align: center;">
<h:outputText value="#{timeSlot}" style="font-size:12px;"/>
</p:column>
</ui:repeat>
</p:row>
<ui:repeat value="#{DashBoard.resourceList}" var="res">
<p:row>
<p:column>
<h:outputText value="#{res.name}" style="font-size:12px;"/>
</p:column>
<ui:repeat value="#{DashBoard.getResvDataModelList(day, res)}" var="model">
<p:column style="background:#{model.colour};" colspan="#{model.section}">
<h:commandLink action="reservation" style="display:block;width:#{model.section * 50}px;height:20px;">
<f:param name="model" value="#{ReservationActionBean.resvDataModel}"/>
<!--h:outputText value="#{model.user}"rendered="#{model.resource.name == res.name ? true : false}"style="font-size:12px;"/-->
</h:commandLink>
</p:column>
</ui:repeat>
</p:row>
</ui:repeat>
</ui:repeat>
</p:panelGrid>
page2.xtml
page2.xml
<h:form id="reservationEntryFrom">
<f:metadata>
<f:viewParam name="resvDataModel" value="#{ReservationActionBean.resvDataModel}"/>
</f:metadata>
<!-- other -->
</h:form>
DashBoard.java
仪表盘.java
@ManagedBean(name = "DashBoard")
@ViewScoped
public class DashBoard extends BaseBean {
public List<ResvDataModel> getResvDataModelList(
Date date, MeetingRoom meetingRoom) {
// do operation
}
}
ReservationActionBean.java
预订ActionBean.java
@ManagedBean(name="ReservationActionBean")
@ViewScoped
public class ReservationActionBean extends BaseBean {
@ManagedProperty("#{param.resvDataModel}")
private ResvDataModel resvDataModel;
//other operations
}
ResvDataModel.java
ResvDataModel.java
public class ResvDataModel {
// attribute, getter and sertter
@Override
public boolean equals(Object object) {
return EqualsBuilder.reflectionEquals(this, object);
}
@Override
public int hashCode() {
return HashCodeBuilder.reflectionHashCode(this);
}
}
回答by BalusC
The @ManagedPropertyis invoked only once during bean's construction. Imagine that the bean is in session scope and the managed property references a request scoped variable (e.g. a request parameter), then only the parameter of the very first request would be set and it would never be updated with changed request parameter values in subsequent requests afterthe session bean construction. This is considered undesired behaviour. Hence @ManagedPropertycannot reference something which has a narrower scope than the @ManagedBeanitself.
该@ManagedPropertybean的施工过程中被调用一次。假设 bean 在会话范围内并且托管属性引用请求范围变量（例如请求参数），那么只会设置第一个请求的参数，并且在后续请求中永远不会使用更改的请求参数值更新它在会话 bean 构建之后。这被认为是不受欢迎的行为。因此@ManagedProperty不能引用范围比它@ManagedBean本身更窄的东西。
In this particular case, you need <f:viewParam>instead. Put the following in page2.xhtml:
在这种特殊情况下，您需要<f:viewParam>改为。将以下内容放入page2.xhtml：
<f:metadata>
<f:viewParam name="resvDataModel" value="#{ReservationActionBean.resvDataModel}" />
</f:metadata>
See also:
也可以看看：
However, there's another problem with this approach. You're passing non-Stringobject along as a request parameter. The value would be only com.example.ResvDataModel@hashcode(or whatever the toString()method of your ResvDataModelclass returns). This information is insufficient to reconstruct exactly the desired ResvDataModelinstance.
但是，这种方法还有另一个问题。您将非String对象作为请求参数传递。该值将仅为com.example.ResvDataModel@hashcode（或toString()您的ResvDataModel类返回的任何方法）。此信息不足以准确地重建所需的ResvDataModel实例。
You need to pass some unique identifier or action parameter value along instead of a whole complex Java object which can't be uniquely represented as a String.
您需要传递一些唯一标识符或操作参数值，而不是传递不能唯一表示为String.
