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duminică, 28 iunie 2015

[OmniFaces utilities 2.2] Unmodifiable list with all child UIParameter components of the given parent component


Starting with version 2.2 - SNAPSHOT (FINAL) the
 Components#getParams() was fixed to take into account converter of ParamHolder.

[OmniFaces utilities] The getParams() method returns an unmodifiable list with all child UIParameter components (<f|o:param>) of the given parent component as a list of ParamHolder instances. Those with disabled=true and an empty name are skipped.

Method (left side uses org.omnifaces.component.SimpleParam from version 2.1, while right side uses SimpleParam from version 2.2):


Before seeing an example of using the Components#getParams(), is important to inspect the above source code and to notice that it relies on org.omnifaces.component.ParamHolder and org.omnifaces.component.SimpleParam. The ParamHolder is a simple interface that extends standard ValueHolder in order to provide:

-          a method for obtaining the parameter name associated with the parameter value
-          a method to return the original, unconverted value of the parameter
-          a method to return the converted value of the parameter (especially needed for <o:param>)

package org.omnifaces.component;

import javax.faces.application.Application;
import javax.faces.component.ValueHolder;
import javax.faces.convert.Converter;

import org.omnifaces.util.Faces;

public interface ParamHolder extends ValueHolder {

 // returns the name of the parameter
 public String getName();

 // returns the original, unconverted value of the parameter
 public Object getLocalValue();

 // returns the converted value of the parameter
 public Object getValue();

The SimpleParam provides a basic and default implementation of the ParamHolder interface. Ultimately, this class can be used as a simple key-value pair holder (parameter name-value) which uses an explicit/implicit JSF converter to convert the object value to string.

Now, let's suppose that we have the following simple form (notice that, for variety, the #{param['age']} is just a request parameters passed in the URL query string as ?age=24):

<h:form id="form">
 <h:commandButton id="submit" value="Send" action="#{myBean.sendAction()}">
  <f:param name="age" value="#{param['age']}"/>
  <f:param name="name" value="#{}"/>
  <o:param name="address" value="#{myBean.address}" converter="addressConverter"/>

Further, we can use the Components#getParams() utility to programmatically collect the UIParameters  (<f|o:param>) nested in the above <h:commandButton/>. This can be accomplish in different JSF artifacts; for example, in a bean (obviously, there are several ways to identify the parent UIComponent of the UIParameters that we want to collect - the UIComponent that should be passed to the #getParams() should be obtained in a convenient manner depending on your circumstances; below, we simply used the Components#findComponent() utility):

UIComponent uc = Components.findComponent("form:submit"); // see: Components#findComponent()
List<ParamHolder> params = Components.getParams(uc);

for (ParamHolder ph : params) {
    // the getName() will return the parameter name

    // starting with version 2.2 
    // getLocalValue() returns the unconverted value
       // getValue() returns the converted value (passed through getAsString())    

Note Don't worry about <o:param> with attached converter, OmniFaces 2.2 takes care of it. 

API 2.1 GH 2.1

By Anghel Leonard and Constantin Alin

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