重定向异常： Cannot call sendRedirect() after the response has been committed

异常：threw exception [Request processing failed; nested exception is java.lang.IllegalStateException: Cannot call sendRedirect() after the response has been committed] with root cause

java.lang.IllegalStateException: Cannot call sendRedirect() after the response has been committed

原因：

response重定向后没有return，后续程序继续运行，重新提交了请求，所以报错，

当根据条件，进行转发或者重定向时对应转发或者重定向语句后面紧跟return;或者return null;