关闭浏览器报 getOutputStream() has already been called for this response

纠结了很久的错误;

点击发送请求页面，在请求未返回前关闭页面报错：

java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:611)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)

处理：需要在web.xml添加【503】错误配置，并在【503】错误页面添加

out.clear();
out = pageContext.pushBody();