我一直试图从我的jsp表单调用servlet，到目前为止，它一直失败。它重定向到servlet的processRequest（）并引发java.lang.NullPointerException：
13-May-2019 18:33:30.193 SEVERE [http-nio-8084-exec-252] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [index] in context with path [/RoyalAwards] threw exception
java.lang.NullPointerException
at index.doPost(index.java:85)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:217)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
13-May-2019 18:44:38.618 SEVERE [http-nio-8084-exec-252] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [index] in context with path [/RoyalAwards] threw exception
java.lang.NullPointerException
at index.doPost(index.java:85)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:217)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
我尝试使用action =“ $ {pageContext.request.contextPath} / index”，
我尝试确保表单按钮具有method =“ post”，
我尝试确保使用request.getParameter（）引用正确的名称，
我试图寻找要删除的jsp-api-*。jar文件（在我的项目中不存在），
我尝试检查点击错误，并突出显示了if（password.equals（password_confirmation））{
jsp形式：
<form action="${pageContext.request.contextPath}/index" method="post" data-remote="true" accept-charset="UTF-8">
<input type="radio" name="reg_type" value="sme" checked> SME <br>
<input type="radio" name="reg_type" value="freelancer"> Freelancer <br>
<input id="id" class="form-control" type="text" placeholder="Identification Nmber" name="id">
<input id="email" class="form-control" type="text" placeholder="Email" name="email">
<input id="password" class="form-control" type="password" placeholder="Password" name="password">
<input id="password_confirmation" class="form-control" type="password" placeholder="Repeat Password" name="password_confirmation">
<input class="btn btn-default btn-register" type="submit" value="Create account" name="submit">
</form>
servlet：
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
String password = request.getParameter("password");
String password_confirmation = request.getParameter("password_confirmation");
String reg_type = request.getParameter("reg_type");
String id = request.getParameter("id");
String email = request.getParameter("email");
boolean check = false;
if(password.equals(password_confirmation)){
try{
UserDAO udao = new UserDAO();
check = udao.registerUser(id, email, password);
} catch(Exception e){
System.out.println(password);
System.out.println(password_confirmation);
System.out.println(reg_type);
System.out.println(id);
System.out.println(email);
System.out.println(check);
e.printStackTrace();
}
if(reg_type.equals("sme")){
if (check) {
//response.sendRedirect("http://localhost:8084/RoyalAwards/sme reg/SME Application Form.jsp/#email="+email);
RequestDispatcher view = request.getRequestDispatcher("/sme reg/SME Application Form.jsp/#email="+email);
view.forward(request, response);
}else{
//else
}
}else{
if (check) {
//response.sendRedirect("http://localhost:8084/RoyalAwards/freelancer reg/Freelancer Application Form.jsp/#email="+email);
RequestDispatcher view = request.getRequestDispatcher("/freelancer reg/Freelancer Application Form.jsp/#email="+email);
view.forward(request, response);
}else{
}
}
}else{
// error
}
}
数据库方法：
public boolean registerUser(String identificationNumber, String email, String password) throws Exception {
boolean check = false;
try {
String query = "insert into userinfo values('"+identificationNumber+"', '"+email+"', '"+password+"', 'pending')";
PreparedStatement preparedStmt = con.prepareStatement(query);
check = preparedStmt.execute();
con.close();
return check;
}catch(Exception e) {
System.out.println(e.getLocalizedMessage());
throw e;
}
}
数据库连接字符串：
public UserDAO() throws Exception {
try{
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/pb","root","");
stmt = con.createStatement();
}catch(Exception e){
System.out.println(e.getLocalizedMessage());
throw e;
}
}
成功后，我希望Web应用程序将数据插入数据库并重定向到另一个注册页面。