<style>
/* Changing the layout to use less space for mobiles */
@media screen and (max-device-width: 480px), screen and (-webkit-min-device-pixel-ratio: 2) {
    #email-body { min-width: 30em !important; }
    #email-page { padding: 8px !important; }
    #email-banner { padding: 8px 8px 0 8px !important; }
    #email-avatar { margin: 1px 8px 8px 0 !important; padding: 0 !important; }
    #email-fields { padding: 0 8px 8px 8px !important; }
    #email-gutter { width: 0 !important; }
}
</style>
<div id="email-body">
<table id="email-wrap" align="center" border="0" cellpadding="0" cellspacing="0" style="background-color:#f0f0f0;color:#000000;width:100%;">
    <tr valign="top">
        <td id="email-page" style="padding:16px !important;">
            <table align="center" border="0" cellpadding="0" cellspacing="0" style="background-color:#ffffff;border:1px solid #bbbbbb;color:#000000;width:100%;">
                <tr valign="top">
                    <td bgcolor="#3e4c4e" style="background-color:#3e4c4e;color:#ffffff;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;line-height:1;"><img src="https://www.jboss.org/dms/hibernate/images/jira/jiraheader_hibernate.png" alt="" style="vertical-align:top;" /></td>
                </tr><tr valign="top">
    <td id="email-banner" style="padding:32px 32px 0 32px;">
        
                
        
        
            <table align="left" border="0" cellpadding="0" cellspacing="0" width="100%" style="width:100%;">
    <tr valign="top">
        <td style="color:#505050;font-family:Arial,FreeSans,Helvetica,sans-serif;padding:0;">
                                        <img id="email-avatar" src="https://hibernate.onjira.com/secure/useravatar?avatarId=10162" alt="" height="48" width="48" border="0" align="left" style="padding:0;margin: 0 16px 16px 0;" />
                        <div id="email-action" style="padding: 0 0 8px 0;font-size:12px;line-height:18px;">
                                    <a class="user-hover" rel="pekarna" id="email_pekarna" href="https://hibernate.onjira.com/secure/ViewProfile.jspa?name=pekarna" style="color:#6c797f;">Ondra Žižka</a>
     created <img src="https://hibernate.onjira.com/images/icons/improvement.gif" height="16" width="16" border="0" align="absmiddle" alt="Improvement"> <a style='color:#6c797f;text-decoration:none;' href='https://hibernate.onjira.com/browse/HHH-7955'>HHH-7955</a>
            </div>
                        <div id="email-summary" style="font-size:16px;line-height:20px;padding:2px 0 16px 0;">
                <a style='color:#6c797f;text-decoration:none;' href='https://hibernate.onjira.com/browse/HHH-7955'><strong>UX improvement: Check for inconsistency between declared and actual class to prevent &quot;IllegalArgumentException: object is not an instance of declaring class&quot;</strong></a>
            </div>
                    </td>
    </tr>
</table>
    </td>
</tr>
<tr valign="top">
    <td id="email-fields" style="padding:0 32px 32px 32px;">
        <table border="0" cellpadding="0" cellspacing="0" style="padding:0;text-align:left;width:100%;" width="100%">
            <tr valign="top">
                <td id="email-gutter" style="width:64px;white-space:nowrap;"></td>
                <td>
                    <table border="0" cellpadding="0" cellspacing="0" width="100%">
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    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 10px 10px 0;white-space:nowrap;">
        <strong style="font-weight:normal;color:#505050;">Issue Type:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
                <img src="https://hibernate.onjira.com/images/icons/improvement.gif" height="16" width="16" border="0" align="absmiddle" alt="Improvement">        Improvement
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    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 10px 10px 0;white-space:nowrap;">
        <strong style="font-weight:normal;color:#505050;">Affects Versions:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
                    4.1.6            </td>
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        <strong style="font-weight:normal;color:#505050;">Assignee:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
                    Unassigned            </td>
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    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 10px 10px 0;white-space:nowrap;">
        <strong style="font-weight:normal;color:#505050;">Components:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
                    core            </td>
</tr>
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    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 10px 10px 0;white-space:nowrap;">
        <strong style="font-weight:normal;color:#505050;">Created:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
        28/Jan/13 9:47 PM
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        <strong style="font-weight:normal;color:#505050;">Description:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
        <p style='margin-top:0;margin-bottom:10px;'>I was getting `IllegalArgumentException: object is not an instance of declaring class`.</p>

<p style='margin-top:0;margin-bottom:10px;'>It turned to be a mapping error (as usually).<br/>
But the message I was getting was a bit confusing:</p>

<blockquote>
<p style='margin-top:0;margin-bottom:10px;'>org.hibernate.PropertyAccessException: IllegalArgumentException occurred calling getter of org.jboss.essc.web.model.ProductCustomField.id</p></blockquote>

<p style='margin-top:0;margin-bottom:10px;'>It had nothing to do with the id property. It was due to wrong type in <br/>
`@MapKeyClass(FooBar.class)`.</p>

<p style='margin-top:0;margin-bottom:10px;'>What made it really tricky was that when reading, this didn't matter (probably not used?); only when writing back to DB, `id` was inspected in a call to `ForeignKeys.isTransient()`.</p>

<p style='margin-top:0;margin-bottom:10px;'>I can see a nice point 4 levels back in the call stack where it could be nice to check/warn if (or at least `assert` that) the entity and expected entity type are the same:</p>

<p style='margin-top:0;margin-bottom:10px;'>In `MapType.replaceElements()`</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java"><span class="code-object">Object</span> key = cp.getIndexType().replace( me.getKey(), <span class="code-keyword">null</span>, session, owner, copyCache );</pre>
</div></div>
<p style='margin-top:0;margin-bottom:10px;'>`cp.indexType.associatedEntityName` knows that `me.getKey()` type doesn't match.</p>

<p style='margin-top:0;margin-bottom:10px;'>So perhaps `replace()` could check?</p>

<p style='margin-top:0;margin-bottom:10px;'>And in general, in places where user-specified classes are used, Hibernate could check for such errors, it would make it much easier to debug such errors.<br/>
@MapKeyClass(ProductCustomField.class)</p>
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    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 10px 10px 0;white-space:nowrap;">
        <strong style="font-weight:normal;color:#505050;">Project:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
        <a style="color:#6c797f;" href="https://hibernate.onjira.com/browse/HHH">Hibernate ORM</a>
    </td>
</tr>                                                <tr valign="top">
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 10px 10px 0;white-space:nowrap;">
        <strong style="font-weight:normal;color:#505050;">Priority:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
                <img src="https://hibernate.onjira.com/images/icons/priority_minor.gif" height="16" width="16" border="0" align="absmiddle" alt="Minor">        Minor
    </td>
</tr>                        <tr valign="top">
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 10px 10px 0;white-space:nowrap;">
        <strong style="font-weight:normal;color:#505050;">Reporter:</strong>
    </td>
    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
                                        <a class="user-hover" rel="pekarna" id="email_pekarna" href="https://hibernate.onjira.com/secure/ViewProfile.jspa?name=pekarna" style="color:#6c797f;">Ondra Žižka</a>
                </td>
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                </td>
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