这是什么错误？

Question

type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Exception in JSP: /biyesheji/chakan1.jsp:8986:    ResultSet rs=null;
87:   
88:    String str=request.getParameter("id");
89:    byte b[]=str.getBytes("ISO-8859-1");
90:    str=new String(b);
91:    try{
92:      Class.forName("com.mysql.jdbc.Driver");
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:504)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.NullPointerException
org.apache.jsp.biyesheji.chakan1_jsp._jspService(chakan1_jsp.java:131)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.这到底什么错误？

Answer 1

88: String str=request.getParameter("id");
89: byte b[]=str.getBytes("ISO-8859-1");java.lang.NullPointerException
org.apache.jsp.biyesheji.chakan1_jsp._jspService(chakan1_jsp.java:131)这个str为null吧。参数没传过来？

Answer 2

以下是代码：
<%
  Connection conn=null;
  Statement stmt=null;
  ResultSet rs=null;
 
  String str=request.getParameter("id");
  byte b[]=str.getBytes("ISO-8859-1");
  str=new String(b);
  try{
    Class.forName("com.mysql.jdbc.Driver");
  }
  catch(ClassNotFoundException ce){
    out.println(ce.getMessage());
  }
  
  if(str==null)str="1";
  try{
    conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/job","root","123");
stmt=conn.createStatement();
rs=stmt.executeQuery("SELECT*FROM apply_inf where s_name='"+str+"'");

while(rs.next()){
   out.print("<br>姓名:"+rs.getString("s_name"));
   out.print("<br>性别:"+rs.getString("sex"));
   out.print("<br>专业:"+rs.getString("major"));
   out.print("<br>学历:"+rs.getString("edu_bg"));
   out.print("<br>应聘职位:"+rs.getString("apply_for"));
   out.print("<br>-------------------------------------------");
}
%>
            </p>
            <p align="justify">                  <span class="style5"><a href="shoucangjia.jsp">返回</a></span>
<%

 }
 catch(SQLException e){
    System.out.println(e.getMessage());
 }
 finally{
    stmt.close();
conn.close();
 }
 %>是id的没传过来吧    

Answer 3

byte b[]=str.getBytes("ISO-8859-1");
str如果为null，就会出错啊。很明显的问题。

Answer 4

把if(str==null)str="1";
放到byte b[]=str.getBytes("ISO-8859-1");的前一行即可。