请问为什么会报错？

[sunck]

--------------------------------------------------------------------------------

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /add_single_rule.jsp at line 45

42: <%!
43: public String UNI2GBK(String s) throws UnsupportedEncodingException{
44: String temp=s;
45: temp=new String(s.getBytes("ISO8859_1"),"GBK");
46: return temp;
47: }
48: public String GBK2UNI(String s) throws UnsupportedEncodingException{


Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:524)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:435)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


root cause

java.lang.NullPointerException
org.apache.jsp.add_005fsingle_005frule_jsp.UNI2GBK(add_005fsingle_005frule_jsp.java:15)
org.apache.jsp.add_005fsingle_005frule_jsp._jspService(add_005fsingle_005frule_jsp.java:126)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.


同样的代码在其他程序里，就没问题，不知道是不是jsp的问题，我使用的是myEclipse进行调试的

[kingssq]

temp=new String(s.getBytes("ISO8859_1"),"GBK");
改为temp=new String(s.getBytes("ISO8859-1"),"GBK");

[sunck]

发现原因了，原来是取出来的参数是null

[sunck]

发现是参数为空，导致