Question

我正在阅读一篇教程，试图用MySql构建一个非常简单的Web应用程序。我的IDE是NetBeans 8.0。使用我的index.jsp欢迎文件，用户应该能够在文本字段中输入查询，然后结果表将显示在下面。或者，将显示说明该语句会影响多少行的文本。当我单击“执行”按钮时，没有任何反应。

我已将MySQL驱动程序添加到我的库中，并在“服务”选项卡中注册了MySQL服务器。

我能够使用Netbeans的“执行命令”执行查询，但我的Java Servlet似乎没有做任何事情。

我的servlet：

    package com.test;

import com.john.utils.SQLUtil;
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 javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 *
 * @author me
 */
public class SqlServlet extends HttpServlet {

    /**
     * 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 {
        String sqlStatement = request.getParameter("sqlStatement");
        String sqlResult = "";
        try
        {
            // load DB driver 
            Class.forName("com.mysql.jdbc.Driver");

            // get connection
            String dbURL = "jdbc:mysql://localhost:3306/tester";
            String username = "root";
            String password = "broken1";
            Connection connection = DriverManager.getConnection(dbURL, username, password);

            // create statement
            Statement statement = connection.createStatement();

            // parse SQL string
            sqlStatement = sqlStatement.trim();
            if(sqlStatement.length() >= 6)
            {
                String sqlType = sqlStatement.substring(0, 6);
                if(sqlType.equalsIgnoreCase("select"))
                {
                    ResultSet resultSet = statement.executeQuery(sqlStatement);
                    sqlResult = SQLUtil.getHtmlTable(resultSet);
                    resultSet.close();
                } else {
                    int i = statement.executeUpdate(sqlStatement);
                    if(i == 0) {
                        sqlResult = "<p>The statement executed successfully.</p>";
                    } else {
                        sqlResult = "<p>The statement executed successfully.</p>"
                        + i + " row (s) affected.</p>";
                    }
                }
            }
            statement.close();
            connection.close();
        } catch (ClassNotFoundException e){
            sqlResult = "<p>Error loading th edatabase driver: </br>"
                        + e.getMessage() + "</p>";
        } catch (SQLException e){
            sqlResult = "<p>Error executing the SQL statement: <br>"
                     + e.getMessage() + "</p>";
        }

        HttpSession session = request.getSession();
        session.setAttribute("sqlResult", sqlResult);
        session.setAttribute("sqlStatement", sqlStatement);

        String url = "/index.jsp";
        getServletContext()
                    .getRequestDispatcher(url)
                    .forward(request, response);

    }

    // <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 {
        processRequest(request, response);
    }

    /**
     * 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 {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

我的JSP：

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Query Master</title>
    </head>
    <body>
        <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
        <c:if test="${sqlStatement == null}">
            <c:set var="sqlStatement" value="select * from user" />
        </c:if>

        <h1>Input a SQL Statement</h1>

        <form action="SqlServlet" method="POST">
            <textarea name="sqlStatement" cols="60" rows="8">${sqlStatement}</textarea>
            <input type="submit" value="Execute"
        </form>

            <p>SQL Results</p>
        ${sqlResult}

    </body>
</html>

Answer 1

您忘记在sql查询中包含架构。写下你的查询：

SELECT * FROM Tester.User

还要尝试在输出窗口中查看Netbeans中的服务器日志。通常你可以找到他们的错误。

Servlet没有连接到MySQL或doPost（）无法正常工作

1 个答案: