尝试使用表达式而不是scriptlet:

Try using an expression, instead of a scriptlet:

<%= request.getSession().getAttribute("currentUser"); %>

您的代码片段将执行，但是没有任何输出.表达式的结果会自动写入输出中.

Your scriplet will execute, but nothing is output. The result of an expression is automtically written to the output.