我创建了这个用作货币转换的 servlet。它可以转换三种货币（SAR、USD、Euro）。我有访问表，其中包含要读取转换值的字段。如何将此 servlet 转换为 JSP？..
public class cur_exchange extends HttpServlet {
String from = "";
String to = "";
double amount = 0.0;
String message = "";
double total = 0.0;
@Override
public void init() {
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
System.out.println("JDBC driver loaded");
}
catch (ClassNotFoundException e) {
System.out.println(e.toString());
}
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
display_form(false, request, response, false);
}
@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
from = request.getParameter("from");
to = request.getParameter("to");
boolean error = false;
try
{
amount = Double.parseDouble(request.getParameter("amount").toString());
}
catch (Exception e) {
message = "Error: Please Type Valid Number To Convert";
error = true;
}
if(from.equals(to))
{
total = amount;
display_form(true, request, response, false);
}
else
{
try {
Connection con = DriverManager.getConnection("jdbc:odbc:MS Access Database");
System.out.println("got connection");
Statement s = con.createStatement();
String sql = "SELECT RATE FROM EXCHANGE_RATE WHERE FROM_CUR='"+from+"' AND TO_CUR='"+to+"'";
ResultSet rs = s.executeQuery(sql);
if (rs.next()) {
total = amount * Double.parseDouble(rs.getString(1));
}
else
{
s = con.createStatement();
sql = "SELECT RATE FROM EXCHANGE_RATE WHERE FROM_CUR='"+to+"' AND TO_CUR='"+from+"'";
rs = s.executeQuery(sql);
if (rs.next())
{
total = amount / Double.parseDouble(rs.getString(1));
}
}
}
catch (SQLException e) {
message = "Error." + e.toString();
error = true;
}
catch (Exception e) {
message = "Error." + e.toString();
error = true;
}
rs.close();
s.close();
con.close();
if (error)
display_form(true , request, response, true);
else
display_form(true, request, response, false);
}
}
public void display_form(boolean populated, HttpServletRequest request, HttpServletResponse response, boolean error) throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head>");
out.println("</head>");
out.println("<body>");
out.println("<CENTER>");
if (error)
out.println("<h3 style='color:red'>"+message+"</h3><br /><br />");
out.println("<h1 style='text-decoration:underline'>Currency Converter</h1>");
out.println("<form action='cur_exchange.java' method='post'>");
out.println("<br /><br /><label>From:");
out.println("<select name='from'>");
if (populated)
{
if (from.equals("SAR"))
{
out.println("<option selected='selected'>SAR</option>");
}
else
{
out.println("<option>SAR</option>");
}
if (from.equals("$"))
{
out.println("<option selected='selected'>$</option>");
}
else
{
out.println("<option>$</option>");
}
if (from.equals("EURO"))
{
out.println("<option selected='selected'>EURO</option>");
}
else
{
out.println("<option>EURO</option>");
}
}
else
{
out.println("<option>SAR</option>");
out.println("<option>$</option>");
out.println("<option>EURO</option>");
}
out.println("</select></label>");
out.println("<br /><br /><label>To:");
out.println("<select name='to'>");
if (populated)
{
if (to.equals("SAR"))
{
out.println("<option selected='selected'>SAR</option>");
}
else
{
out.println("<option>SAR</option>");
}
if (to.equals("$"))
{
out.println("<option selected='selected'>$</option>");
}
else
{
out.println("<option>$</option>");
}
if (to.equals("EURO"))
{
out.println("<option selected='selected'>EURO</option>");
}
else
{
out.println("<option>EURO</option>");
}
}
else
{
out.println("<option>SAR</option>");
out.println("<option>$</option>");
out.println("<option>EURO</option>");
}
out.println("</select></label><br />");
if(populated)
{
out.println("<br /><label>Amount: <input name='amount' type='text' size='25' maxlength='30' id='amount' value='"+amount+"' /></label><br />");
}
else
{
out.println("<br /><label>Amount: <input name='amount' type='text' size='25' maxlength='30' id='amount' /></label><br />");
}
if(populated)
{
out.println("<br /><label>Result: <input name='result' type='text' size='25' maxlength='30' id='result' disabled='disabled' value='"+total+"'/></label><br />");
}
else
{
out.println("<br /><label>Result: <input name='result' type='text' size='25' maxlength='30' id='result' disabled='disabled' /></label><br />");
}
out.println("<br /><input type='submit' value='Convert'/>");
out.println("</form>");
out.println("</CENTER>");
out.println("</body>");
out.println("</html>");
}
}