How can I know the id of a JSF component so I can

2018-12-31 08:28发布

站内问答 / JavaScript
1501 6 4

Problem: Sometimes you will want to access a component from javascript with getElementById, but id's are generated dynamically in JSF, so you need a method of getting an objects id. I answer below on how you can do this.

Original Question: I want to use some code like below. How can I reference the inputText JSF component in my Javascript?

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core">
    <head>
       <title>Input Name Page</title>
        <script type="javascript" >
          function myFunc() {
            // how can I get the contents of the inputText component below          
            alert("Your email address is: " + document.getElementById("emailAddress").value);
          }
       </script>
    </head>
    <h:body>
        <f:view>
            <h:form>
                Please enter your email address:<br/>
                <h:inputText id="emailAddresses" value="#{emailAddresses.emailAddressesStr}"/>
                <h:commandButton onclick="myFunc()" action="results" value="Next"/>
            </h:form>
        </f:view>
    </h:body>
</html>

Update: this post Client Identifiers in JSF2.0 discusses using a technique like:

<script type="javascript" >
  function myFunc() {
    alert("Your email address is: " + document.getElementById("#{myInptTxtId.clientId}").value);
  }
</script>

<h:inputText id="myInptTxtId" value="backingBean.emailAddress"/>
<h:commandButton onclick="myFunc()" action="results" value="Next"/>

Suggesting that the attribute id on the inputText component creates an object that can be accessed with EL using #{myInptTxtId}, in the above example. The article goes on to state that JSF 2.0 adds the zero-argument getClientId() method to the UIComponent class. Thereby allowing the #{myInptTxtId.clientId} construct suggested above to get the actual generated id of the component.

Though in my tests this doesn't work. Can anyone else confirm/deny. The answers suggested below suffer from drawback that the above technique doesn't. So it would be good to know if the above technique actually works.

6条回答
还给你的自由
2楼-- · 2018-12-31 08:37

I know this is not the JSF way but if you want to avoid the ID pain you can set a special CSS class for the selector. Just make sure to use a good name so that when someone reads the class name it is clear that it was used for this purpose.

<h:inputText id="emailAddresses" class="emailAddressesForSelector"...

In your JavaScript:

jQuery('.emailAddressesForSelector');

Of course you would still have to manually manage class name uniqueness. I do think this is maintainable as long as you do not use this in reusable components. In that case you could generate the class names using a convention.

查看更多
0人赞 添加讨论(0) 举报
时光乱了年华
3楼-- · 2018-12-31 08:38

Id is dynamically generated, so you should define names for all parent elements to avoid j_id123-like ids.

Note that if you use jQuery to select element - than you should use double slash before colon:

    jQuery("my-form-id\\:my-text-input-block\\:my-input-id")

instead of:

    jQuery("my-form-id:my-text-input-block:my-input-id")

In case of Richfaces you can use el expression on jsf page:

    #{rich:element('native-jsf-input-id')}

to select javascript element, for example:

    #{rich:element('native-jsf-input-id')}.value = "Enter something here";
查看更多
0人赞 添加讨论(0) 举报
大哥的爱人
4楼-- · 2018-12-31 08:42

You need to use exactly the ID as JSF has assigned in the generated HTML output. Rightclick the page in your webbrowser and choose View Source. That's exactly the HTML code which JS sees (you know, JS runs in webbrowser and intercepts on HTML DOM tree).

Given a

<h:form>
    <h:inputText id="emailAddresses" ... />

It'll look something like this:

<form id="j_id0">
    <input type="text" id="j_id0:emailAddress" ... />

Where j_id0 is the generated ID of the generated HTML <form> element.

You'd rather give all JSF NamingContainer components a fixed id so that JSF don't autogenerate them. The <h:form> is one of them.

<h:form id="formId">
    <h:inputText id="emailAddresses" value="#{emailAddresses.emailAddressesStr}"/>

This way the form won't get an autogenerated ID like j_id0 and the input field will get a fixed ID of formId:emailAddress. You can then just reference it as such in JS.

var input = document.getElementById('formId:emailAddress');

From that point on you can continue using JS code as usual. E.g. getting value via input.value.

See also:

Update as per your update: you misunderstood the blog article. The special #{component} reference refers to the current component where the EL expression is been evaluated and this works only inside any of the attributes of the component itself. Whatever you want can also be achieved as follows:

var input = document.getElementById('#{emailAddress.clientId}');

with (note the binding to the view, you should absolutely not bind it to a bean)

<h:inputText binding="#{emailAddress}" />

but that's plain ugly. Better use the following approach wherein you pass the generated HTML DOM element as JavaScript this reference to the function

<h:inputText onclick="show(this)" />

with

function show(input) {
    alert(input.value);
}

If you're using jQuery, you can even go a step further by abstracting them using a style class as marker interface

<h:inputText styleClass="someMarkerClass" />

with

$(document).on("click", ".someMarkerClass", function() {
    var $input = $(this);
    alert($input.val());
});
查看更多
0人赞 添加讨论(0) 举报
不流泪的眼
5楼-- · 2018-12-31 08:45

You can view the HTML source when this is generated and see what the id is set to, so you can use that in your JavaScript. As it's in a form it is probably prepending the form id to it.

查看更多
0人赞 添加讨论(0) 举报
大哥的爱人
6楼-- · 2018-12-31 08:47

Answer: So this is the technique I'm happiest with. Doesn't require doing too much weird stuff to figure out the id of a component. Remember the whole point of this is so you can know the id of a component from anywhere on your page, not just from the actual component itself. This is key. I press a button, launch javascript function, and it should be able to access any other component, not just the one that launched it.

This solution doesn't require any 'right-click' and see what the id is. That type of solution is brittle, as the id is dynamically generated and if I change the page I'll have to go through that nonsense each time.

  1. Bind the component to a backing bean.

  2. Reference the bound component wherever you want.

So here is a sample of how that can be done.

Assumptions: I have an *.xhtml page (could be *.jsp) and I have defined a backing bean. I'm also using JSF 2.0.

*.xhtml page

<script>
  function myFunc() {
    var inputText = document.getElementById("#{backBean.emailAddyInputText.clientId}")                 
    alert("The email address is: " + inputText.value );
  }
</script>

<h:inputText binding="#{backBean.emailAddyInputText}"/>
<h:commandButton onclick="myFunc()" action="results" value="Next"/>

BackBean.java

UIInput emailAddyInputText;

Make sure to create your getter/setter for this property too.

查看更多
0人赞 添加讨论(0) 举报
刘海飞了
7楼-- · 2018-12-31 08:57 
<h:form  id="myform">
 <h:inputText  id="name" value="#{beanClass.name}" 
                a:placeholder="Enter Client Title"> </h:inputText>
</h:form>

This is a small example of jsf. Now I will write javascript code to get the value of the above jsf component:

    var x = document.getElementById('myform:name').value; //here x will be of string type

   var y= parseInt(x,10); //here we converted x into Integer type and can do the 
                           //arithmetic operations as well
查看更多
0人赞 添加讨论(0) 举报
登录 后发表回答
相关问题
查看全部
相关文章
查看全部
收藏的人(4)