這裏是Eclipse
簡單登錄Servlet
的代碼,它從現有的數據庫表中檢查用戶名和密碼,並在存在或發送到登錄頁面時將其帶到主頁。當我在服務器上運行它並將信息放入登錄頁面時,它顯示以下錯誤。你能幫忙嗎?謝謝。ClassNotFoundException的無法訪問的catch塊。這個例外永遠不會從try語句主體中拋出
1.錯誤解決
root cause
java.lang.Error: Unresolved compilation problem:
Unreachable catch block for ClassNotFoundException. This exception is never thrown from the try statement body
com.loginapps.servlets.LoginServlet.doGet(LoginServlet.java:90)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
編碼
package com.loginapps.servlets;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.PreparedStatement;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/*** Servlet implementation class LoginServlet* @param <con>*/
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
Connection con;
PreparedStatement pst;
public void init(ServletConfig config) throws ServletException {
String dname = config.getInitParameter("drivername");
String uname = config.getInitParameter("username");
System.out.println(dname);
System.out.println(uname);
try{
Class.forName(dname);
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/logindb",uname,"");
}
catch(SQLException e){
e.printStackTrace();
}
catch(ClassNotFoundException e){
e.printStackTrace();
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
HttpSession session = request.getSession();
String uname = request.getParameter("txtuname");
String pwd = request.getParameter("txtpwd");
session.setAttribute("username",uname);
try {
pst = con.prepareStatement("select * from users where username = ? and password = ?");
pst.setString(1,uname);
pst.setString(2,pwd);
ResultSet rs = pst.executeQuery();
if(rs.next()){
response.sendRedirect("home.jsp");
}
else {
response.sendRedirect("login.html");
}
}
catch(SQLException e){
e.printStackTrace();
}
catch(ClassNotFoundException e){
e.printStackTrace();
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
你有tomcat(??)lib目錄下的mysql jar嗎? –
,你可以發佈你的'web.xml' \ – emotionlessbananas
是的。我在WebInf/lib forder中有mysql jar。這裏是web.xml文件。謝謝。 – Nikil