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?
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
Related
Mojara 2.1.21
I've updated my question based on comments. I have two situation where a component is bound to server session bean. (Additional links with information: Binding attribute causes duplicate component ID found in the view and https://stackoverflow.com/a/12512672/2692917)
Version 1:
single.xhtml:
<h:outputText value=... binding="#{mysessionbean.out}" />
java:
#SessionScoped #Named public class Mysessionbean {
UIOutput out;
//getter and setter ....
}
Version 2:
template.xhtml:
<h:outputText value=... binding="#{mysessionbean.out}"
view1.xhtml:
<ui:composition template="template.xhtml" />
view2.xhtml:
<ui:composition template="template.xhtml" />
java:
#SessionScoped #Named public class Mysessionbean {
UIOutput out;
//getter and setter ....
}
Version 1 is ok. (At least I've not encounter any errors so far). But in version 2 the duplicate id error is occured if I navigate from one page to another. Why does it happen ?
Is it safe to use (request-scoped) component (in version 1) with session scoped binding ?
Are there another use cases to consider ?
Edit:
Functional requirement 1:
I want to use Primefaces datatable in a view. I need some info from this datatable. (Such as selected row or row index). So binding the datatable helps me to retrieve this info.
Functional requirement 2:
Components binding in composite components. They will be bound to session scoped bean. (And used mainly on one page, but what if I used it on another page ?
Requirements 3
The situation as in "Version 2". Template with primefaces menu and session scoped binding. For this I've used the EL-Binding.
In JSF 2.x, unless you want to manipulate components programmatically (which is at its own also rather fishy), there is no sensible real world use case to bind components to a backing bean. For sure not if they are further not been used in the backing bean itself, or if it are solely their attributes which are been flattened out.
As to the functional requirement of getting the current row of the data table, there are much better ways listed here, How can I pass selected row to commandLink inside dataTable?, for example if your environment supports EL 2.2:
<h:dataTable value="#{bean.items}" var="item">
<h:column>
<h:commandLink value="Foo" action="#{bean.foo(item)}" />
The two last requirements are totally unclear. At least, if you're doing something like:
<x:someComponent binding="#{bean.someComponent}" />
with in bean
someComponent.setSomeAttribute(someAttribute);
someComponent.setOtherAttribute(otherAttribute);
then you should instead be doing
<x:someComponent someAttribute="#{bean.someAttribute}" otherAttribute="#{bean.otherAttribute}" />
Or, if you intend to be able to use the component somewhere else in the view like so
<h:inputText ... required="#{not empty param[bean.save.clientId]}" />
...
<h:commandButton binding="#{bean.save}" ... />
and the instance is further nowhere been used in the bean, then just get rid of the unnecessary property altogether:
<h:inputText ... required="#{not empty param[save.clientId]}" />
...
<h:commandButton binding="#{save}" ... />
If there is really, really no way for some unclear reason, then split all request scoped properties of the session scoped bean out into a separate request scoped bean which you in turn bind to form actions. The session scoped one can just be injected as a #ManagedProperty of the request scoped one.
See also:
Binding attribute causes duplicate component ID found in the view
How does the 'binding' attribute work in JSF? When and how should it be used?
We ran into a similar problem and I just want to share our solution:
Problem:
In a view there was a (extended largely customized) datatable.
<x:dataTable binding="#{bean.someSomeDataTable}" />
After navigating to another page and back we wanted the datatable to have the exact same state. Previously we solved that by binding the datatable to to backing bean. This worked fine with JSPs. With Facelets we could not do that (Duplicate ID errors). So we used the binding, but only saved/restored the state of the datatable component.
public HtmlDataTable getSomeDataTable()
{
HtmlDataTable htmlDataTable = new HtmlDataTable();
if (tableState != null)
htmlDataTable.restoreState(FacesContext.getCurrentInstance(), tableState);
return htmlDataTable;
}
public void setSomeDataTable(HtmlDataTable table)
{
tableState = table.saveState(FacesContext.getCurrentInstance());
}
Project uses Spring Webflow and JSF (PrimeFaces). I have a p:commandButton with f:attribute
<p:commandButton disabled="#{editGroupMode=='edit'}" action="edit_article_group" actionListener="#{articleGroupManager.setSelectedRow}" ajax="false" value="Edit">
<f:attribute name="selectedIndex" value="${rowIndex}" />
</p:commandButton>
Backend code (Spring injected bean):
#Service("articleGroupManager")
public class ArticleGroupManagerImpl implements ArticleGroupManager{
public void setSelectedRow(ActionEvent event) {
String selectedIndex = (String)event.getComponent().getAttributes().get("selectedIndex");
if (selectedIndex == null) {
return;
}
}
}
The attribute "selectedIndex" is always null. Anybody knows what happened here? Thank you.
The variable name "rowIndex" suggests that you've declared this inside an iterating component, such as <p:dataTable>.
This is then indeed not going to work. There's physically only one JSF component in the component tree which is reused multiple times during generating HTML output. The <f:attribute> is evaluated at the moment when the component is created (which happens only once, long before iteration!), not when the component generates HTML based on the currently iterated row. It would indeed always be null.
There are several ways to achieve your concrete functional requirement anyway. The most sane approach would be to just pass it as method argument:
<p:commandButton value="Edit"
action="edit_article_group"
actionListener="#{articleGroupManager.setSelectedRow(rowIndex)}"
ajax="false" disabled="#{editGroupMode=='edit'}" />
with
public void setSelectedRow(Integer rowIndex) {
// ...
}
See also:
JSTL in JSF2 Facelets... makes sense?
How can I pass selected row to commandLink inside dataTable?
Unrelated to the concrete problem, I'd in this particular case have used just a GET link with a request parameter to make the request idempotent (bookmarkable, re-executable without impact in server side, searchbot-crawlable, etc). See also Communication in JSF 2.0 - Processing GET request parameters.
I'm working with LastFM api, let's say I have a class called Artist which I call in this dataTable:
<h:dataTable var="artist" value="#{personEAO.topArtists}" >
<h:column>Artist : #{artist.name} </h:column>
</h:dataTable>
Artit have a field which refers to his picture :
artist.getImageURL(ImageSize.LARGE)
Which works fine, but how do I call this method in my jsf page using dataTable ?
I searched around for Javadocs, but I couldn't find them anywhere. The answer depends on what kind of constant ImageSize.LARGE is.
If ImageSize is an enum, just do:
<h:graphicImage value="#{artist.getImageURL('LARGE')}" />
But if it isn't and is thus a public static constant, then one of the ways is to wrap it in some helper bean which returns exactly that:
<h:graphicImage value="#{artist.getImageURL(someHelperBean.ImageSize_LARGE)}" />
I of course assume that your environment supports EL 2.2.
Is it possible to call bean methods & directly pass parameters to them from the view instead of requiring to first set the bean properties and then call methods without arguments using the commandButton or similar ?
I have a list of items with each item having a list of actions. To reduce the state, I am using a single primefaces remoteCommand, in place of several commandButton(s). On getting a action trigger from the view, I would call the remoteCommand from javascript but since the remoteCommand is one but used for multiple items thus I need to pass the id of the item as well. I am wondering if there is a way to pass the id of the item to the bean method directly as an argument instead of first setting it as a bean property ? Is there any way to do so ?
Actually I am looking at a better way to deal with multiple commandButtons on a page when there's a long list of items on the page.
Suggestions ? Thanks.
Using JSF 2.1.6 Mojarra with Primefaces 3.0RC1
Passing method arguments is supported since EL 2.2 which is part of Servlet 3.0. So if your webapp runs on a Servlet 3.0 compatible container (Tomcat 7, Glassfish 3, etc) with a web.xml declared conform Servlet 3.0 spec (which is likely true as you're using JSF 2.1 which in turn implicitly requires Servlet 3.0), then you will be able to pass method arguments to bean action methods in the following form:
<h:commandButton value="Submit" action="#{bean.submit(item.id)}" />
with
public void submit(Long id) {
// ...
}
You can even pass fullworthy objects along like as:
<h:commandButton value="Submit" action="#{bean.submit(item)}" />
with
public void submit(Item item) {
// ...
}
If you were targeting a Servlet 2.5 container, then you could achieve the same by replacing the EL implementation by for example JBoss EL which supports the same construct. See also Invoke direct methods or methods with arguments / variables / parameters in EL.
Yes, it is.
<h:commandButton action="#{bean.method(object)}" />
See this http://www.mkyong.com/jsf2/4-ways-to-pass-parameter-from-jsf-page-to-backing-bean/
You can call ManagedBean methods with arguments like this.
<h:commandButton actionListener="#{stateBean.delete(row.stateID)}"
value="Delete" id="btnDeleteS">
<f:ajax event="action" execute="#form" render="#form"/>
</h:commandButton>
The corresponding ManagedBean would be like this.
#ManagedBean
#RequestScoped
public class StateBean
{
#EJB
private RemoteInterface obj=null;
public void delete(String stateID)
{
//Code stuff here.
}
}
You can also directly set the value of ManagedBean properties using <f:setPropertyActionListener></f:setPropertyActionListener> like this.
<h:commandButton value="Delete" id="btnDeleteS">
<f:setPropertyActionListener target="#{stateBean.someProperty}"
value="#{someValue}"/>
<f:ajax event="action" execute="#form" render="#form"/>
</h:commandButton>
I can't get method calls with parameters to work in JSF 2.0 (MyFaces) and Tomcat 6.
This is how I try it:
<f:selectItems var="item" value="#{bla.someList}
itemValue="#{item.value1}"
itemLabel="#{item.value2}">
<f:param name="param1" value="0" />
</f:selectItems>
I can't define the method like this, right? And why not?
getSomeList(int a)
So this is what I tried:
getSomeList() {
Integer a = Integer.parseInt(FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("param1"));
return doSomething(a);
}
And this is what I get:
java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Integer.java:417)
I would be very grateful if someone helped me out. Thanks!
UPDATE: Ah, it worked with #{bla.getSomeList(0)}!
I can't define the method like this, right?
getSomeList(int a)
No.
And why not?
Because you're using old Tomcat 6 which doesn't support EL 2.2 where this feature was introduced.
And this is what I get:
java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Integer.java:417)
Because there it is null. The <f:param> works in links/buttons only, not on plain components.
In order to get method calls in EL to work, you need to upgrade to a Servlet 3.0 / EL 2.2 capable container like Tomcat 7, or to replace Tomcat 6's default EL 2.1 implementation by one which supports parameterized method calls. For detail see this answer. Once done that, you can use
<f:selectItems value="#{bla.getSomeList(0)}" ... />
An alternative is to replace List by Map, which can be a custom implementation which does (lazy) loading on get() method.
public Map<String, List<Something>> getSomeMap() {
return someCustomLazyLoadingMap;
}
with
<f:selectItems value="#{bla.someMap.keyName}" ... />
Try using
<f:selectItems var="item" value="#{bla.someList(0)} itemValue="#{item.value1}" itemLabel="#{item.value2}"/>
This works for some implementations of JSF.