With custom tags, including the JSTL, the tag attributes are defined in the TLD. Remember? This is the TLD from the custom <my:advice> tag from the last chapter:

<tag>
    <description>random advice</description>
    <name>advice</name>
    <tag-class>foo.AdvisorTagHandler</tag-class>
    <body-content>empty</body-content>

    <attribute>
        <name>user</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
</tag>

So, these are the things the developer who is using a tag needs to know. What’s the attribute name? Is it optional or required? Can it be an expression, or must it be only a String literal?

But while you do specify custom tag attributes in a TLD, you do NOT specify tag file attributes in a TLD!

That means we still have a problem—how does the page developer know what attributes the tag accepts and/or requires? Turn the page...