java.lang.IllegalStateException：BindingResult和bean名称'user'的普通目标对象都不可用作请求属性 [英] java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'user' available as request attribute
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问题描述
这些天我开始学习Spring，Iam得到以下异常：我只是想从登录页面导航（稍后将使用DAO在db中插入opeartion）到某些index.jsp页面
I started learning Spring these days,Iam getting below exception: Iam just tring to navigate from login page (will do insert opeartion in db later using DAOs) to some index.jsp page
exception
org.apache.jasper.JasperException: An exception occurred processing JSP page /login.jsp at line 11
8: </head>
9: <body>
10: <form:form method="post" commandName="user" action="login">
11: <form:label path="uname" /> <form:input path="uname" />
12: <form:label path="password" /> <form:input path="password" />
13: <input type="submit" value="Submit" />
14: </form:form>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:521)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:424)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'user' available as request attribute
org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:141)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:179)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:199)
org.springframework.web.servlet.tags.form.LabelTag.autogenerateFor(LabelTag.java:130)
org.springframework.web.servlet.tags.form.LabelTag.resolveFor(LabelTag.java:120)
org.springframework.web.servlet.tags.form.LabelTag.writeTagContent(LabelTag.java:90)
org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:103)
org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80)
org.apache.jsp.login_jsp._jspx_meth_form_005flabel_005f0(login_jsp.java:157)
org.apache.jsp.login_jsp._jspx_meth_form_005fform_005f0(login_jsp.java:111)
org.apache.jsp.login_jsp._jspService(login_jsp.java:71)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
login.jsp
<%@page contentType="text/html" pageEncoding="UTF-8"%><%@ taglib
prefix="form" uri="http://www.springframework.org/tags/form"%>
<!DOCTsYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Login</title>
</head>
<body>
<form:form method="post" commandName="user" action="login">
<form:label path="uname" /> <form:input path="uname" />
<form:label path="password" /> <form:input path="password" />
<input type="submit" value="Submit" />
</form:form>
</body>
</html>
LoginController.java
package com.bts.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.SessionAttributes;
@Controller
@RequestMapping("/login")
@SessionAttributes("user")
public class LoginController {
@RequestMapping(method=RequestMethod.POST)
public String onSubmit(){
System.out.println("entered in submit methodd....");
return "index";
}
}
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"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
id="WebApp_ID" version="2.5">
<display-name>BugTrackingSystem</display-name>
<welcome-file-list>
<welcome-file>login.jsp</welcome-file>
</welcome-file-list>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/application-context.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
User.java
* 强文 *
package com.bts.vo;
import java.util.ArrayList;
import java.util.List;
public class User {
public User() {
countries = new ArrayList<String>();
countries.add("India");
countries.add("US");
}
private String uname;
private String password;
private List<String> countries;
public String getUname() {
return uname;
}
public void setUname(String uname) {
this.uname = uname;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public List<String> getCountries() {
return countries;
}
public void setCountries(List<String> countries) {
this.countries = countries;
}
}
应用程序上下文。 xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<import resource="dispatcher-servlet.xml"/>
<import resource="datasource.xml"/>
<import resource="hibernate-beans.xml"/>
</beans>
dispatcher-servlet.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<bean id="viewResolver"
class="org.springframework.web.servlet.view.InternalResourceViewResolver" p:order="1">
<property name="prefix">
<value>/WEB-INF/jsp/</value>
</property>
<property name="suffix">
<value>.jsp</value>
</property>
</bean>
<context:component-scan base-package="com.bts.controller" />
</beans>
请有人可以运行我的代码并为我提供解决方案.. :)
推荐答案
JSP中的表单标记正在尝试绑定到名为 user （由 commandName =user表示）但是这尚未作为控制器中的模型属性公开。
The form tag in your JSP is trying to bind to a bean named user (as denoted by commandName="user") but this hasn't been exposed as a model attribute in your controller.
尝试添加到您的控制器：
Try adding to your controller:
@ModelAttribute("user")
public User createModel() {
return new User();
}
因为你的控制器是用注释的@SessionAttributes（ user）模型将在第一次创建时存储在会话中。后续请求将从会话中提取模型。
Because your controller is annotated with @SessionAttributes("user") the model will be stored in session the first time it has been created. Subsequent requests will pull the model from session.
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