java - BindingResult 和 bean 名称的普通目标对象都不能作为请求属性

Question

URL(在浏览器中尝试):ip:port/Spring3MVC/studentRegistration.jsp

如果我从 form:input 中删除所有输入，则表示没有错误。我针对同一问题尝试了此处提供的其他解决方案，但没有用。请帮助缩小问题范围。提前致谢。

异常跟踪:

SEVERE: Neither BindingResult nor plain target object for bean name 'student' available as request attribute
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'student' available as request attribute
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:141)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:174)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:194)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getName(AbstractDataBoundFormElementTag.java:160)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.autogenerateId(AbstractDataBoundFormElementTag.java:147)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.resolveId(AbstractDataBoundFormElementTag.java:138)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.writeDefaultAttributes(AbstractDataBoundFormElementTag.java:122)
    at org.springframework.web.servlet.tags.form.AbstractHtmlElementTag.writeDefaultAttributes(AbstractHtmlElementTag.java:409)
    at org.springframework.web.servlet.tags.form.InputTag.writeTagContent(InputTag.java:140)
    at org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:102)
    at org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:79)
    at org.apache.jsp.studentRegistration_jsp._jspx_meth_form_005finput_005f0(studentRegistration_jsp.java:144)
    at org.apache.jsp.studentRegistration_jsp._jspx_meth_form_005fform_005f0(studentRegistration_jsp.java:99)
    at org.apache.jsp.studentRegistration_jsp._jspService(studentRegistration_jsp.java:63)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)

Controller :

@Controller
public class HelloWorldController {
    List<Student> students = new ArrayList<Student>();
    @RequestMapping(method = RequestMethod.GET,value="/addStudent")
    public String addStudent(Model model,@ModelAttribute("student") Student student)
    {
        students.add(student);
        model.addAttribute("student", student);
        return "studentAddedOk";
    }
}

studentRegistration.jsp

<%@ page contentType="text/html"  %>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form"%>

<form:form commandName = "student" modelAttribute = "student" action="addStudent">
    <form:input path="name"/>
    <form:input path="age"/>
    <form:input path="qualification"/>
    <input type="submit" value="submit"/>
</form:form>

spring3-context.xml

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop-3.0.xsd ">

    <bean id="student" class="spring.beans.Student" />

</beans> 

spring3-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    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">


    <context:component-scan base-package="spring.controller" />

    <bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>

    <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" />
    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />

</beans>

Student.java

package spring.beans;
public class Student {
    private String name;
    private String age;
    private String qualification;
    // getters and setters
}

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">

    <servlet>
        <servlet-name>spring3</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>spring3</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    <context-param>
     <param-name>contextConfigLocation</param-name>
     <param-value>/WEB-INF/spring3-context.xml</param-value>
    </context-param>
    <listener>
    <listener-class>
     org.springframework.web.context.ContextLoaderListener
    </listener-class>
    </listener>
</web-app>

Answer 1

在 Controller 中，您需要添加 student 对象作为 model 的 attribute:

model.addAttribute("student", new Student());

在您调用学生 View 的 Controller 中。喜欢

@RequestMapping(value = "/", method = RequestMethod.GET) 
public String displayStudent( Model model) { 
 model.addAttribute("student", new Student()); 
 return "student"; 
} 

如果上述操作已经完成，并且您还没有发布代码，请尝试从表单标记中删除 commandName 属性，modelAttribute 属性就足够了