404和500错误解决方法

<error-page>
		<error-code>404</error-code>
		<location>/error/error_404.html</location>
	</error-page>
	<error-page>
		<error-code>500</error-code>
		<location>/error/error_500.html</location>
	</error-page>
	<error-page>
		<exception-type>java.lang.NullPointerException</exception-type>
		<location>/error/error_exceptionByNull.html</location>
	</error-page>