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将 SQL 查询结果传递到 ArrayList<Object> , 返回列表到 servlet

[英]Passing SQL query results into ArrayList<Object>, returning list to servlet

 原文  2022-07-19 14:28:31  4   1    java/ html/ sql/ arraylist/ servlets

问题描述

我正在尝试重构我的代码，这样做我试图将 SQL 查询留给一个类。 我正在尝试将参数从 html 表单传递给 servlet，然后将这些参数传递给 ApplicationDao 在其方法参数中，它（应该）以用户对象数组列表的形式返回结果集。 当我通过电子邮件时，它说未找到列，但是当我在 servlet 中执行完全相同的操作时，我正在重构结果很好。 显然，由于该问题，数组列表将长度 0 传递回来！

我真的很困惑我做错了什么，任何建议都将不胜感激！

数据库结构

登录 HTML 表单

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Log In: Canadian Voting Portal</title>
<link rel="stylesheet" type="text/css" href="style2.css">
</head>
<body id="logInPage">
<div class="LogInContainer1">
<img src="images/CanadaLogo.jpg" width="150px" height="70px">
<h1 id="LogInHeading">Voting Portal Website & Access</h1>

<div class="LogInContainer2">

<div class="LogContainer3">
<form method="post" action="testServlet">
<label class="logInLabel" id="emailLabel" for="email">Email:</label>
<input class="logInInput" type="text" id="userEmail" name="email">
<br>
<label class="logInLabel" id="passwordLabel" for="password">Password:</label>
<input class="logInInput" type="text" id="userPassword" name="password">
<br>
<button id="logInButton" type="submit">LOG IN</button>
</form>
<p id="createParagraph">Don't have an account? Create one <a id="createLink" href="http://localhost:8080/CapstoneProject/CreateAccountServlet">here.</a> Forgot log-in information? Start the reset process of your account <a id="resetLink" href="http://localhost:8080/CapstoneProject/ResetPasswordServlet">here.</a></p>
</div>

</div>

</div>
</body>
</html>

应用程序

public class ApplicationDao {

    

    public ArrayList<User> userLogIn(String email, String password){

        
        ArrayList<User> users = new ArrayList<User>();
        
        try{
            
            
        
            
            String sql="SELECT * FROM `user` WHERE email = ? and password = ?" ;
            
            Connection connection =DBConnection.getConnectionToDatabase();
            java.sql.PreparedStatement statement;
            
            statement = connection.prepareStatement(sql);
            statement.setString(1,email);
            statement.setString(2,password);
            
            
            ResultSet set = statement.executeQuery();
            
            if(set.next()){         
            
                User user = new User();
                
                user.setEmail(set.getString(email));
                user.setPassword(password);
                user.setDateOfBirth("DOB");
                user.setFirstName("firstName");
                user.setLastName("lastName");
                
                set.close();
                statement.close();
                
                users.add(user);
            }

        }
        catch(SQLException exception){
            exception.printStackTrace();
        }
        return users;
        
        }

    }

测试服务器

@WebServlet("/testServlet" )
public class testServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    //List<User> users = new ArrayList<User>();

    public testServlet() {
        super();
    }
   
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
    
    }
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException{
        
        String email = request.getParameter("email");
        String password = request.getParameter("password");
        PrintWriter writer = response.getWriter();
        ApplicationDao dao = new ApplicationDao();
        ArrayList<User> user = dao.userLogIn(email,password);
        
        String DOB = user.get(0).getDateOfBirth();
        
        
        
        
        writer.write(email + DOB);
    }}

CONSOLE（从 servlet 传递参数时）

MySQL JDBC Driver Registered!
Connection made to DB!
java.sql.SQLException: Column 'caytegibbons@gmail.com' not found.
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63)
    at com.mysql.cj.jdbc.result.ResultSetImpl.findColumn(ResultSetImpl.java:584)
    at com.mysql.cj.jdbc.result.ResultSetImpl.getString(ResultSetImpl.java:896)
    at dao.ApplicationDao.userLogIn(ApplicationDao.java:45)
    at servlets.testServlet.doPost(testServlet.java:51)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)
Jul. 19, 2022 10:16:10 A.M. org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [servlets.testServlet] in context with path [/CapstoneProject] threw exception
java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
    at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
    at java.base/java.util.Objects.checkIndex(Objects.java:372)
    at java.base/java.util.ArrayList.get(ArrayList.java:459)
    at servlets.testServlet.doPost(testServlet.java:53)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)

CONSOLE（硬编码参数时）

1 个解决方案

解决方案1
 1 已采纳  2022-07-19 15:06:46

错误在ApplicationDao的第 45 行，查看堆栈跟踪：

    at dao.ApplicationDao.userLogIn(ApplicationDao.java:45)

我假设它是这一行：

user.setEmail(set.getString(email));

您将电子邮件变量作为列名传递。 它应该是：

user.setEmail(set.getString("email"));

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