问题
I'd like to know if there's a way to bind the returned value of a method into a JSF component. I'll explain myself better. Let's say I have a class like this:
public class Document {
private List<Attachment> attachments;
//getter and setter here
}
this class is exposed to jsf through a registered managed bean in a property called currentDocument, and used in a jsf this way
<h:outputText value="#{myManagedBean.currentDocument.attachment.size}" />
This isn't correct, I know. But what is the correct way to do this? Am I supposed to create an attribute on the Document class, let's say numberOfAttachments, and bind to that, or there's a way to bind directly on a method's return value?
回答1:
If you're running an EL 2.2 capable container (Tomcat 7, Glassfish 3, JBoss AS 6 or newer, all implementing Servlet 3.0), or are using JBoss EL, then you should be able to invoke non-getter methods by EL:
<h:outputText value="#{myManagedBean.currentDocument.attachment.size()}" />
An alternative is to use JSTL fn:length():
<html xmlns:fn="http://java.sun.com/jsp/jstl/functions" ...>
...
<h:outputText value="#{fn:length(myManagedBean.currentDocument.attachment)}" />
If none of that is possible for you for some reason, then your best bet is to create an EL function yourself
<h:outputText value="#{my:size(myManagedBean.currentDocument.attachment)}" />
or to add an extra getter method to #{myManagedBean} which returns exactly that.
<h:outputText value="#{myManagedBean.currentDocumentAttachmentSize}" />
See also:
- Invoke direct methods or methods with arguments / variables / parameters in EL
来源：https://stackoverflow.com/questions/7120526/how-to-display-value-of-listsize-in-jsf-el