为啥 doGet 不运行 processRequest？
Posted
技术标签:
【中文标题】为啥 doGet 不运行 processRequest？【英文标题】：Why won't doGet run processRequest?为什么 doGet 不运行 processRequest？ 【发布时间】：2018-12-09 13:07:10 【问题描述】：程序应该工作的方式是后台有一个 javaDB，servlet 可以从中提取。 servlet 从 index.jsp 中获取关键字，并使用该关键字搜索 DB 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，因为我尝试在其中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("<br />");
out.print(" " + rs.getString(2)); out.println("<br />");
out.print(" " + rs.getString(3)); out.println("<br />");
out.print(" " + rs.getString(4)); out.println("<br />");
out.println(" " + rs.getString(5)); out.println("<br />");
/**
* 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("<br />");
out.println(getUrl());
out.println("<br />");
out.println(conn);
getMovies(conn,out);
out.println("<br />");
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>
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>
【问题讨论】：
DBConnector如何在web.xml中定义？
【参考方案1】：
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，这样就很清楚这是错误，现在你只有finally 块，所以 Exception 它是隐藏且不清楚的。
添加块并查看异常后，您需要检查定义 java:comp/env 的配置文件，可能是拼写错误或类似的东西会导致真正的问题。
【讨论】：
以上是关于为啥 doGet 不运行 processRequest？的主要内容，如果未能解决你的问题，请参考以下文章
找不到脚本函数 doget，但我没有在我的代码上使用 doGet
servlet的生命周期，啥情况下调用doGet()和doPost()?
Servlet doGet 在简单的 get 方法上返回 404？ [复制]
此 URL 不支持 HTTP 方法 GET，尽管它执行 doGet [重复]