我一直致力于简单的银行业项目，我处于初始阶段。我想要的是通过register.html将客户信息保存在数据库中 和RegisterServlet.java页面。但不幸的是，它停止使用错误StatndardWrapperValve调用错误（NullPointerException）。我一直试图从过去3天解决这个问题，但没有解决方案。我也包括我的GitHub链接GitHub Jdbc Banking Project Link，在jar文件中我只包含了ojdbc6。我的代码在try块行中打破（ps = con.prepareStatement（＆＃34;插入客户（名称，电子邮件，移动，城市，dob）值（？，？，？，？，？）＆＃34;） ;）我需要一些认真的帮助。
My pages
1. login.html
2. register.html
3. RegisterServlet.java
4. DBConnectionManager.java
5. web.xml
register.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<h3 align="center">Customer Registration Page</h3>
<form action="RegisterServletPath" method="post">
<table align="center">
<tr>
<td>Customer Name</td>
<td><input type="text" name="name"></td>
</tr>
<tr>
<td>Email</td>
<td><input type="text" name="email"></td>
</tr>
<tr>
<td>Mobile</td>
<td><input type="text" name="mobile"></td>
</tr>
<tr>
<td>City</td>
<td><input type="text" name="city"></td>
</tr>
<tr>
<td>DOB</td>
<td><input type="date" name="dob"></td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="Register"></td>
</tr>
</table>
</form>
</body>
</html>
RegisterServlet.java
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class RegisterServlet
*/
//@WebServlet("/RegisterServletPath")
@WebServlet(name="RegisterServlet", urlPatterns={"/RegisterServletPath"})
public class RegisterServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.getWriter().append("Served at: ").append(request.getContextPath());
System.out.println("Inide doGet method");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("Inside doPost method");
PrintWriter out = response.getWriter();
out.print("<html><h3>It is coming from RegisterServlet.java</h3></html>");
String name = request.getParameter("name");
String email = request.getParameter("email");
String mobile = request.getParameter("mobile");
String city = request.getParameter("city");
String dob = request.getParameter("dob");
/*write the logic for input validation*/
String errorMsg = null;
if(name == null || name.equals("")) {
errorMsg = "Name can't be empty";
}
if(email == null || email.equals("")) {
errorMsg = "Email can't be empty";
}
if(mobile == null || mobile.equals("")) {
errorMsg = "Mobile number can't be empty";
}
if(city == null || city.equals("")) {
errorMsg = "City name can't be empty";
}
if(dob == null || dob.equals("")) {
errorMsg = "Date of birth can't be empty";
}
System.out.println("Line 64");
//when the text field is not null, this code statement won't run
if(errorMsg != null) {
System.out.println("Line 67");
RequestDispatcher rd = getServletContext().getRequestDispatcher("/register.html");
PrintWriter out1 = response.getWriter();
out1.println("<font color=red>" +errorMsg+"</font>");
rd.include(request, response);
}
// System.out.println("Line 73");
else {
System.out.println("Line 73");
Connection con = (Connection)getServletContext().getAttribute("DBConnection");
PreparedStatement ps = null;
System.out.println("Line 79");
try{
System.out.println("Line 81");
ps = con.prepareStatement("insert into customers(name,email,mobile,city,dob) values (?,?,?,?,?)");
System.out.println("Line 82");
ps.setString(1, name);
ps.setString(2, email);
ps.setString(3, mobile);
ps.setString(4, city);
ps.setString(5, dob);
System.out.println("Line 87");
ps.execute();
//forward to login page to login
RequestDispatcher rd = getServletContext().getRequestDispatcher("/login.html");
PrintWriter out1 = response.getWriter();
out1.println("<font color=green>Registration Successful, please login.</font>");
rd.include(request, response);
}
catch(SQLException e) {
e.printStackTrace();
//logger.error("Database connection problem");
throw new ServletException("DB Connection Problem");
}
finally {
try {
ps.close();
}
catch(SQLException e) {
System.out.println("Inside second catch block");
//logger.error("SQLException is closing PreparedStatement");
}
}
}
//doGet(request, response);
}
}
DBConnectionManager.java
package com.banking.util;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
/*
* DBConnectionManager.java is a utility class for Oracle11g database connection and it has a method that
* returns connection object. We will use this class for database connection and then set the connection
* to servlet context attribute(web.xml) that other servlets can use.
* */
public class DBConnectionManager {
private Connection connection;
public DBConnectionManager(String dbURL, String username, String password) throws
ClassNotFoundException, SQLException {
Class.forName("oracle.jdbc.driver.OracleDriver");
this.connection = DriverManager.getConnection(dbURL,username,password);
}
public Connection getConnection() {
return this.connection;
}
}
的web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>JDBC Banking Project</display-name>
<welcome-file-list>
<welcome-file>register.html</welcome-file>
</welcome-file-list>
<context-param>
<param-name>username</param-name>
<param-value>system</param-value>
</context-param>
<context-param>
<param-name>password</param-name>
<param-value>123456</param-value>
</context-param>
<context-param>
<param-name>dbURL</param-name>
<param-value>jdbc:oracle:thin:@localhost:1521:xe</param-value>
</context-param>
</web-app>
错误控制台
May 03, 2017 1:02:28 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:Hello World' did not find a matching property.
May 03, 2017 1:02:28 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:JDBC Banking Project' did not find a matching property.
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server version: Apache Tomcat/7.0.69
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server built: Apr 11 2016 07:57:09 UTC
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server number: 7.0.69.0
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Name: Windows 8.1
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Version: 6.3
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Architecture: amd64
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Java Home: C:\Program Files\Java\jre7
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Version: 1.7.0_79-b15
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Vendor: Oracle Corporation
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_BASE: D:\Eclipse Workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_HOME: C:\Program Files\Apache Software Foundation\Tomcat 7.0
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.base=D:\Eclipse Workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.home=C:\Program Files\Apache Software Foundation\Tomcat 7.0
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dwtp.deploy=D:\Eclipse Workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.endorsed.dirs=C:\Program Files\Apache Software Foundation\Tomcat 7.0\endorsed
May 03, 2017 1:02:28 PM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dfile.encoding=Cp1252
May 03, 2017 1:02:28 PM org.apache.catalina.core.AprLifecycleListener lifecycleEvent
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: C:\Program Files\Java\jre7\bin;C:\WINDOWS\Sun\Java\bin;C:\WINDOWS\system32;C:\WINDOWS;D:\app\Shital\product\11.2.0\dbhome_1\bin;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\Intel\OpenCL SDK\2.0\bin\x86;C:\Program Files (x86)\Intel\OpenCL SDK\2.0\bin\x64;C:\Program Files\Intel\WiFi\bin\;C:\Program Files\Common Files\Intel\WirelessCommon\;C:\Program Files (x86)\QuickTime Alternative\QTSystem;C:\Program Files\Java\jdk1.7.0_79\bin;C:\Program Files\Java\jdk1.7.0_79\jre\lib;.
May 03, 2017 1:02:29 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-bio-8080"]
May 03, 2017 1:02:29 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-bio-8009"]
May 03, 2017 1:02:29 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 924 ms
May 03, 2017 1:02:29 PM org.apache.catalina.core.StandardService startInternal
INFO: Starting service Catalina
May 03, 2017 1:02:29 PM org.apache.catalina.core.StandardEngine startInternal
INFO: Starting Servlet Engine: Apache Tomcat/7.0.69
May 03, 2017 1:02:29 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["http-bio-8080"]
May 03, 2017 1:02:29 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["ajp-bio-8009"]
May 03, 2017 1:02:29 PM org.apache.catalina.startup.Catalina start
INFO: Server startup in 907 ms
Inside doPost method
Line 64
Line 67
Inside doPost method
Line 64
Line 73
Line 79
Line 81
May 03, 2017 1:03:03 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [RegisterServlet] in context with path [/JDBC_Banking_Project] threw exception
java.lang.NullPointerException at RegisterServlet.doPost(RegisterServlet.java:110)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:436)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
答案 0 :(得分：0)
我无法在项目的任何地方看到您在Servlet上下文中设置连接，不确定您是否已发布完整的源代码。
Connection con = (Connection)getServletContext().getAttribute("DBConnection");
下面抛出NullPointerException
ps = con.prepareStatement("insert into customers(name,email,mobile,city,dob) values (?,?,?,?,?)");
无法在SQLException的catch子句中捕获。 在最后阻止它尝试关闭连接时。抛出NullPointerException。