该程序应该工作的方式是servlet可以从后台获取一个javaDB . servlet从index.jsp获取一个关键字，并使用它来搜索数据库以获取与该关键字相关的信息 . 但是doGet方法甚至没有尝试在try / catch块中运行任何东西 . 我知道doGet方法正在运行，因为我已经尝试在那里加载测试代码并且它确实显示它，只是不会通过try / catch运行 .
DBConnector.java
package edu.uwf.cs.dsa;
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
*
* @author Bernd
*/
public class DBConnector extends HttpServlet {
private Context env;
@Override
public void init(ServletConfig config)
throws ServletException {
super.init(config);
try {
env = (Context) new InitialContext().lookup("java:comp/env");
} catch (NamingException e) {
throw new ServletException(e.getMessage());
}
}
private String getUrl() throws NamingException
{
return (String)env.lookup("jdbc:derby://localhost:1527/JA112");
}
private Connection getConnection()
throws NamingException, ServletException, ClassNotFoundException, SQLException
{
Class.forName((String)env.lookup("org.apache.derby.jdbc.EmbeddedDriver"));
return DriverManager.getConnection(getUrl());
}
private void getMovies(Connection conn, PrintWriter out) throws SQLException
{
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * from Student");
while (rs.next()) {
out.print(rs.getString(1)); out.println("
");
out.print(" " + rs.getString(2)); out.println("
");
out.print(" " + rs.getString(3)); out.println("
");
out.print(" " + rs.getString(4)); out.println("
");
out.println(" " + rs.getString(5)); out.println("
");
}
}
/**
* Processes requests for both HTTP
* <code>GET</code> and
* <code>POST</code> methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException, NamingException, ClassNotFoundException, SQLException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
Connection conn = getConnection();
// out.print("<html>\n <head>\n <body>\n<h1>test</h1>\n</body>\n</head>\n</html>");
try {
/* TODO output your page here. You may use following sample code. */
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet DBConnector</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Servlet DBConnector at " + request.getContextPath() + "</h1>");
out.println((String)env.lookup("driver"));
out.println("
");
out.println(getUrl());
out.println("
");
out.println(conn);
getMovies(conn,out);
out.println("
");
out.println("</body>");
out.println("</html>");
} finally {
out.close();
}
}
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP
* <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
processRequest(request, response);
} catch (Exception e) {
Logger.getLogger(DBConnector.class.getName()).log(Level.SEVERE, null, e);
}
}
/**
* Handles the HTTP
* <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
processRequest(request, response);
} catch (NamingException ex) {
Logger.getLogger(DBConnector.class.getName()).log(Level.SEVERE, null, ex);
} catch (ClassNotFoundException ex) {
Logger.getLogger(DBConnector.class.getName()).log(Level.SEVERE, null, ex);
} catch (SQLException ex) {
Logger.getLogger(DBConnector.class.getName()).log(Level.SEVERE, null, ex);
}
}
/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}
的index.jsp
<%--
Document : index
Created on : Nov 21, 2012, 9:20:16 PM
Author : Bernd
--%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<form method="GET" action="/DBServlet/DBConnector">
<h1>Movie Search</h1>
Enter Keyword <input type="text" name="keyword" id="keyword">
<input type="submit" value="submit" id="button">
</form>
</body>
</html>
1 回答
我最好的猜测是
env变量在正常测试中被初始化为null，你需要在processRequest()方法上添加catch块，这样就会明白这是错误，因为现在你只有finally块，所以异常它是隐藏的，不清楚的 .添加块并查看异常后，您需要检查您定义
java:comp/env的配置文件，可能是拼写错误或类似的东西可能导致真正的问题 .