f:param does not work with p:commandLink or h:commandLink on query string

Question

f:param works great with h:link, but not with p:commandLink or h:commandLink.

For example, I have two pages test_first.xhtml and test_second.xhtml, and a backing java bean TestBean.java.

I start running test_first.xhtml.

If I click link1, which is a h:link, the page will redirect to test_second.xhtml. With the help of f:param, the address bar of the browser will show .../test_second.xhtml?id=1. On that page, testBean.userId gets printed.

If I click link2 or link3, the page redirects to test_second.xhtml. However, the address bar only shows .../test_second.xhtml, there is NO ?id=#! And testBean.userId does not get printed on that page.

How can I make commandLink work with f:param? Sometimes I want the link not to redirect to another page but to call some methods of bean depending on the data.

test_first.xhtml:

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:p="http://primefaces.org/ui">
<h:head/>
<h:body>
<h:form>
    <h:link value="link1" outcome="test_second" >
        <f:param name="id" value="1"/>
    </h:link>
    <br/><br/>
    <h:commandLink value="link2" action="test_second?faces-redirect=true" >
        <f:param name="id" value="2" />
    </h:commandLink>
    <br/><br/>
    <p:commandLink value="link3" action="test_second?faces-redirect=true">
        <f:param name="id" value="3" />
    </p:commandLink>
    <br/><br/>
</h:form>
</h:body>
</html>

test_second.xhtml:

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:p="http://primefaces.org/ui">
<f:metadata>
    <f:viewParam name="id" value="#{testBean.userId}" />
</f:metadata>
<h:head/>
<h:body>
<h:form>
    This is the second page.
    <h:outputText value="Selected id is #{testBean.userId}" />
    <h:commandButton value="Print page id" action="#{testBean.print()}" />
</h:form>
</h:body>
</html>

TestBean.java

@ManagedBean
@SessionScoped
public class TestBean implements Serializable{
    private Integer userId;

    public void print() {
        System.out.println(userId);
    }

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }
}

Related: http://stackoverflow.com/questions/4317684/when-should-i-use-houtputlink-instead-of-hcommandlink/4317723#4317723 — BalusC, Aug 21 '13 at 12:33

score 8 · Accepted Answer · edited Oct 06 '14 at 07:50

You misinterpreted the meaning of those two tags, namely <h:link> and <h:commandLink>, therefore, you also misinterpreted the meaning of <f:param> attached to either of the two. In anycase it is worthwhile to always read the documentation before asking the questions to get more insight.

<h:link> renders an HTML "a" anchor element. The value of the component is rendered as the anchor text and the outcome of the component is used to determine the target URL rendered in the "href" attribute. Any child UIParameter components are appended to the String to be output as the value of the "href" attribute as query parameters before rendering...

<h:commandLink> render an HTML "a" anchor element that acts like a form submit button* when clicked ... if the disabled attribute is not present, or its value is false. It renders "#" as the value of the "href" attribute, renders the current value of the component as the link text if it is specified and *renders JavaScript that is functionally equivalent to the following as the value of the "onclick" attribute:
document.forms['CLIENT_ID']['hiddenFieldName'].value='CLIENT_ID';    
document.forms['CLIENT_ID']['PARAM1_NAME'].value='PARAM1_VALUE'; 
document.forms['CLIENT_ID']['PARAM2_NAME'].value='PARAM2_VALUE'; return false;
document.forms['CLIENT_ID'].submit()" 
where hiddenFieldName is as described above, CLIENT_ID is the clientId of the UICommand component, PARAM_NAME and PARAM_VALUE are the names and values, respectively, of any nested UIParameter children.

In other words, within <h:link> tag nested <f:param> will end up as a query parameter of the generated URL, while within <h:commandLink> tag nested <f:param> will end up as a request parameter with a given value.

While the first one is clear, the second one deserves a better elaboration. To understand what it does, consider that if we abstract away from the details <h:commandLink> sends a POST request and attaches all nested <f:param> tags as request parameters. But it is up to you how you will handle them, as navigation is entirely in your hands.

So, the first option is to set a hardcoded action attribute, which use case is dubious, like in action="second-page", in which way you didn't pass any query parameter at all. What will be done is POSTing to the same view and forwarding to the second without undertaking any action. Quite a dumb action.

The second option is to specify an action method, like in action="#{bean.action}". In this case you must handle navigation in the provided action method, i.e. return null/void from the method for a postback, or return a navigation case outcome as a string to make a forward to the specified view. As for the request parameters that you passed with <f:param> they will be available with standard JSF means like @ManagedProperty("#{param.name}") on a request-scoped bean, or by calling ExternalContext#getRequestParameterMap() in any-scoped bean, for example, in action method, like in String param = externalContext.getRequestParameterMap().get("name"). So now you have your parameter in action method that you're free to use how you like, just adhere to a set of rules that exist for URLs.

Two things left worth mentioning. Remember that request parameters passed with calling the command link will be available only within that same request, as you might expect it to survive a faces-redirect=true that basically fires another request. The other option is to specify includeviewparams=true to pass through the paramaters of the current view, if that's desired, as mentioned in the other answer.

fischermatte · Answer 2 · 2013-08-21T06:13:00.083

2

You could do it by concatenating the parameters with & directly at the action attribute:

<p:commandLink value="link3" action="test_second?faces-redirect=true&id=3"/>

Update 1

You might also consider to add &includeViewParams=true. This way view parameters of your target navigation will be included automatically.

edited Aug 21 '13 at 06:13

answered Aug 21 '13 at 05:58

fischermatte

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f:param does not work with p:commandLink or h:commandLink on query string

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