org.apache.jasper.JasperException

exception org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.NullPointerException
java.io.Writer.<init>(Writer.java:70)
java.io.OutputStreamWriter.<init>(OutputStreamWriter.java:91)
com.ideas.bean.DealFile.writeCHStr(DealFile.java:230)
com.ideas.bean.DealFile.writeCHStr(DealFile.java:221)
com.ideas.bean.artBean.add(artBean.java:59)
org.apache.jsp.manage.art.list_jsp._jspService(list_jsp.java:166)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.到底出现了什么错误？？