java.lang.IllegalStateException : Neither BindingResult nor plain target object for bean name 'login' available as request attribute

Question

理论上，单击提交后，应该调用登录方法并检查用户的用户名和密码是否匹配，并将其重定向到另一个 .jsp 页面，但是当我尝试加载 .jsp 页面时，出现以下错误.

我确定该错误与我的 .jsp 文件有关，但我不确定可能出了什么问题。

Jul 31, 2017 8:03:46 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [jsp] in context with path [/Atomicity] threw exception [An exception occurred processing JSP page [/login.jsp] at line [20]

17:                 class="register-form">
18:                 <table>
19:                     <tr>
20:                         <td><form:input path="username" /></td>
21:                         <td><form:errors path="username" /></td>
22:                     </tr>
23:                     <tr>


Stacktrace:] with root cause
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'login' available as request attribute
at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:144)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:168)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:188)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getName(AbstractDataBoundFormElementTag.java:154)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.autogenerateId(AbstractDataBoundFormElementTag.java:141)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.resolveId(AbstractDataBoundFormElementTag.java:132)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.writeDefaultAttributes(AbstractDataBoundFormElementTag.java:116)
at org.springframework.web.servlet.tags.form.AbstractHtmlElementTag.writeDefaultAttributes(AbstractHtmlElementTag.java:422)
at org.springframework.web.servlet.tags.form.InputTag.writeTagContent(InputTag.java:142)
at org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:84)
at org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80)
at org.apache.jsp.login_jsp._jspx_meth_form_005finput_005f0(login_jsp.java:298)
at org.apache.jsp.login_jsp._jspService(login_jsp.java:165)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:625)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:498)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:796)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1372)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)

[登录.jsp]

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<link rel="shortcut icon" href="favicon1.ico" />
<title>Login page</title>
<link rel="stylesheet" href="css/normalize.css" />
<link rel="stylesheet" href="css/mystyle.css" />
</head>
<body>
<img id="logoImg2" src="img/atomicitylogo.png" alt="atomicity logo">
<div class="login-page">
    <div class="form">
        <form:form action="login" method="POST" commandName="login"
            class="register-form">
            <table>
                <tr>
                    <td><form:input path="username" /></td>
                    <td><form:errors path="username" /></td>
                </tr>
                <tr>
                    <td><form:input path="password" /></td>
                    <td><form:errors path="password" /></td>
                </tr>
                <tr>
                    <td colspan="2"><input type="submit" value="Log In" />
                        <p class="message">
                </tr>
            </table>
            <p>
                Not registered? <a href="register.html">Create an account</a>
            </p>
        </form:form>
        </div>
    </div>
</body>
</html>

[LoginComponent.java]

package com.atomicity.components;

import javax.validation.constraints.NotNull;

import org.springframework.stereotype.Component;

@Component(value = "login")
public class LoginComponent {

@NotNull
private String username;
@NotNull
private String password;

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}
}

[LoginController.java]

package com.atomicity.controllers;

import javax.validation.Valid;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import com.atomicity.components.LoginComponent;
import com.atomicity.dao.UsersDAO;
import com.atomicity.domain.Users;

@Controller
public class LoginController {

@RequestMapping(value = "/loggingIn", method = RequestMethod.POST)
public String login(@Valid @ModelAttribute("login") LoginComponent login, BindingResult br, Model m) {
    ApplicationContext appCon = new ClassPathXmlApplicationContext("beans.xml");
    UsersDAO uDAO = (UsersDAO) appCon.getBean("usersDAO");
    Users user = uDAO.getUserByName(login.getUsername());

    if (user != null) {
        // Check if password is correct
        if (user.getPassword().equals(login.getPassword())) {
            m.addAttribute("firstname", user.getFirstName());
            m.addAttribute("lastname", user.getLastName());
            m.addAttribute("email", user.getEmail());
            m.addAttribute("username", login.getUsername());
            ((AbstractApplicationContext) appCon).close();
            return "account";
        } else {
            // Wrong Password
        }
    } else {
        // User/Password does not exists
    }
    ((AbstractApplicationContext) appCon).close();
    return null;
}
}

欢迎任何帮助。

[编辑]删除login.jsp中的表允许页面显示，所以我认为问题可能存在(或不存在)。

Answer 1

java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'login' available as request attribute

查看堆栈跟踪，它表明您尚未将登录对象传递给 View 。因此 JSP 无法正确呈现..

@GetMapping("/login")
public String login(Model m) {

    //Use model to expose the LoginComponent object
    m.addAttribute("login", new LoginComponent());
    return "login";
}

您可以在此处找到更详细的演练:https://spring.io/guides/gs/handling-form-submission/