In JSP you can use the following:
<jsp-config>
<jsp-property-group>
<url-pattern>*.jsp</url-pattern>
<scripting-invalid>true</scripting-invalid> <!-- 1 -->
<page-encoding>UTF-8</page-encoding> <!-- 2 -->
</jsp-property-group>
<jsp-property-group>
<url-pattern>*.tag</url-pattern>
<page-encoding>UTF-8</page-encoding>
</jsp-property-group>
</jsp-config>
Is there a custom tag equivalent to set the encoding directive for all custom tags created using a *.tag file?
You can define JSP configuration parameters in deployment descriptor but tags declared in TLD (tag library decriptor). TLD have no encoding parameter and Deployment Descriptor have no such option for <taglib>
element that means that you cant.