Servlet RunTime Error
Buck Turgidson
Example code from a book that I purchased works fine, but a class I've
written doesn't, so that exonerates the software, and implicates the
programmer. My class compiles OK. I can't make heads or tails of the
error. Any clues here?
Win 98 Error:
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[04/04/2000 19:48:31:850 EDT] java.lang.InstantiationException: Mortgage
_
at java.lang.Class.newInstance0(Native Method)
_
at java.lang.Class.newInstance(Class.java, Compiled Code)
_
at
org.apache.jserv.JServServletManager.load_init(JServServletManager._
at
org.apache.jserv.JServServletManager.loadServlet(JServServletManage_
at
org.apache.jserv.JServConnection.processRequest(JServConnection.jav_
at org.apache.jserv.JServConnection.run(JServConnection.java:188)
_
at java.lang.Thread.run(Thread.java:479)
_
Linux Error
---------------
[Tue Apr 4 18:33:58 2000] [notice] suEXEC mechanism enabled (wrapper:
/usr/sbi)
java.lang.NoSuchMethodError
at org.apache.jserv.JServServletManager.load_init(Compiled Code)
at org.apache.jserv.JServServletManager.loadServlet(Compiled Code)
at org.apache.jserv.JServConnection.processRequest(Compiled Code)
at org.apache.jserv.JServConnection.run(Compiled Code)
at java.lang.Thread.run(Compiled Code)
Java Code
---------------
import java.io.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Mortgage extends HttpServlet {
double prin;
double rate;
double payment;
int term;
Mortgage(double p,double r,int t) {
this.prin = p;
this.rate = r;
this.term = t;
this.payment=round2d(calcpayment());
}
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
double pp = Double.valueOf(req.getParameter("prin")).doubleValue();
double rr = Double.valueOf(req.getParameter("rate")).doubleValue();
int tt = Integer.parseInt(req.getParameter("term"));
Mortgage m = new Mortgage(pp,rr,tt);
m.amortize();
}
double calcpayment(){
double tmp;
double monthly_interest = ((rate / 12.0) / 100.0);
tmp = 1.0 - java.lang.Math.pow((monthly_interest + 1.0),
(double)(-term));
return(monthly_interest * prin / tmp);
}
void amortize(){
double applied_prin;
double interest_paid;
int i;
System.out.println("<HTML>");
System.out.println("<HEAD><TITLE>Loan Amortization by Java
Servlets</TITLE></HEAD>");
System.out.println("<BODY>");
System.out.println("\nMonth # Balance Prin Paid Int Paid
Total Payment\n\n");
for(i=1; i <= term; i++) {
interest_paid = round2d(((rate / 12.0) / 100.0) * prin);
applied_prin = round2d(payment - interest_paid);
printform(i,prin, applied_prin, interest_paid, payment);
prin = round2d(prin - applied_prin);
}
System.out.println("</BODY></HTML>");
}
void printform(int i,double prin, double applied_prin, double
interest_paid, double payment) {
String s = new String();
DecimalFormat df = new
DecimalFormat("0,000,000,000.00;0,000,000,000.00CR");
DecimalFormat nf = new DecimalFormat("0000");
System.out.println( ltrim(nf.format(i))
+ ltrim(df.format(prin))
+ ltrim(df.format(applied_prin))
+ ltrim(df.format(interest_paid))
+ ltrim(df.format(payment))
);
}
String ltrim(String formatStr) {
StringBuffer s = new StringBuffer(formatStr);
for(int i=0;i<s.length();i++)
if(s.charAt(i) == '0' || s.charAt(i) == ',')
s.setCharAt(i, ' ');
else
break;
return(String.valueOf(s));
}
double round2d(double round_in){
return (java.lang.Math.floor(round_in * 100. + .5) / 100);
}
}
Krishna
You have provided a overloaded constructor for your servlet. The servlet
container which is reponsible for loading servlets doesn't know anything about
your constructor. It searches for the default no argument constructor and hence
it is not able to create the new instance. To make your class work, create a no
arg constructor and call super or remove your overloaded constructor and do all
the required operations from the doGet method. Hope this helps.
regards,
Krishna.