How to pass a parameter into rendered attribute?

问题

I try to pass a parameter into method admin like this:

<p:toolbarGroup align="right" rendered="#{loginBean.admin('dataread'}">
                            <h:form>
                                <p:commandButton value="manage users" ajax="false"
                                                 icon="ui-icon-document" action="/admin/manageUsers.xhtml?faces-redirect=true"/>
                            </h:form>
                        </p:toolbarGroup>

the code in my managed Bean is like that

public boolean isAdmin(String role){
          FacesContext facesContext = FacesContext.getCurrentInstance();
          HttpServletRequest request = (HttpServletRequest) FacesContext.getCurrentInstance().getExternalContext().getRequest();
          return request.isUserInRole("admin");                
          }

回答1:

rendered="#{loginBean.admin('dataread'}"

You've there with the missing ) an EL syntax error which causes the value not being recognized as an EL expression and is thus treated as a plain vanilla string which would in the rendered attribute thus default to boolean true. Also, when specifying action expressions like #{bean.method()} instead of value expressions like #{bean.property}, you should specify the full method name, thus isAdmin() instead of admin().

All with all, this should do:

rendered="#{loginBean.isAdmin('dataread')}"

Unrelated to the concrete problem, the HttpServletRequest is already available in the EL scope by #{request}, so this should also do without the need for backing bean boilerplate:

rendered="#{request.isUserInRole('admin')}"

回答2:

Correct syntax:

rendered="#{loginBean.isAdmin('dataread')}">

instead of

rendered="#{loginBean.admin('dataread'}"

Make sure your EL supports such feature:

 <dependency>
      <groupId>org.glassfish.web</groupId>
      <artifactId>el-impl</artifactId>
      <version>2.2</version>
 </dependency>

Look for more information containing tutorials on passing parameters in JSF:

How to pass parameters in method expression – JSF 2.0
4 ways to pass parameter from JSF page to backing bean

来源：https://stackoverflow.com/questions/10726462/how-to-pass-a-parameter-into-rendered-attribute

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