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Editorial Team
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Asked: 2026-05-21T21:51:33+00:00

I’m not sure how i should put this question cos’ there are couple of

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I’m not sure how i should put this question cos’ there are couple of files (.java, .xhtml, etc) involved. Anyway this programs involves couple of checkboxes (selectmanycheckbox) and others. There is a onchange=submit() on this selectmanycheckboxes.

Here’s what i noticed:

  1. The generated html for each of those checkboxes there is a onchange=submit(). Kind of funny that by checking a checkboxes, it is submitting the form everytime.

The real issue is when i check one of the checkboxes, there is an error exactly as printed.

======================================================================
java.lang.ClassCastException: [I cannot be cast to [Ljava.lang.Object;

Caused by:
java.lang.ClassCastException – [I cannot be cast to [Ljava.lang.Object;

I don’t understand the [I here. Any idea?

What i did after that was to remove all the checkboxes and submit the form. Still getting the same error.

Any idea?

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1 Answer

  1. Editorial Team

    The source code is available on their site. Your particular code is provided in javaee/ch04/select folder.

    The generated html for each of those checkboxes there is a onchange=submit(). Kind of funny that by checking a checkboxes, it is submitting the form everytime.

    It’s been set by the <h:selectManyCheckbox onchange="submit()" /> in the code example. The onchange attribute is indeed totally unnecessary. It’s likely an oversight of the author.

    The real issue is when i check one of the checkboxes, there is an error exactly as printed.

    java.lang.ClassCastException: [I cannot be cast to [Ljava.lang.Object;

    I don’t understand the [I here. Any idea?

    The [I is the signature of an int[] type. The exception is telling that an instance of int[] type cannot be cast to an instance of Object[]. This makes in turn no sense, it should work fine. This particular problem is caused by something else.

    What i did after that was to remove all the checkboxes and submit the form. Still getting the same error.

    The <h:selectManyMenu> in the code example is also bound to an int[] property.

    However removing them is not the right solution. It should work fine. Your problem is caused by something else deeper under the hoods. It’s likely a bug in the EL implementation used. What servletcontainer make/version are you using? What servlet API version is your web.xml declared to? Did you try upgrading the servletcontainer?

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