Spring 4 / 既不是 BindingResult 也不是普通目标对象

Question

我知道有人以不同的方式提出和回答了这个问题，但是 Spring 一切都不一样了。

我是 Spring 4 - MVS 的新手，只想创建我的第一个 MVC - HelloWorld 实现并遇到错误

java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'command' available as request attribute org.springframework.web.servlet.support.BindStatus.(BindStatus.java:141) org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.get

我的 web.xml 看起来像这样：

原型创建的 Web 应用程序你好世界 org.springframework.web.servlet.DispatcherServlet 1个你好世界 / 上下文配置位置 /WEB-INF/HelloWorld-servlet.xml org.springframework.web.context.ContextLoaderListener 我的 HelloWorld-servlet.xml 是这样的：

<context:component-scan base-package="com.programcreek.helloworld.controller" />

<bean
    class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix">
        <value>/</value>
    </property>
    <property name="suffix">
        <value>.jsp</value>
    </property>
</bean>

我的 student.jsp 看起来像这样：

     <%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<html>
<head>
    <title>Spring MVC Form Handling</title>
</head>
<body>

<h2>2 Student Information 2</h2>


<form:form method="POST" action="/HelloWorld/addStudent" >
   <table>
    <tr>
        <td><form:label path="name">Name</form:label></td>
        <td><form:input path="name" /></td>
    </tr>
    <tr>
        <td><form:label path="age">Age</form:label></td>
        <td><form:input path="age" /></td>
    </tr>
    <tr>
        <td><form:label path="id">id</form:label></td>
        <td><form:input path="id" /></td>
    </tr>
    <tr>
        <td colspan="2">
            <input type="submit" value="Submit"/>
        </td>
    </tr>
</table>  
</form:form>
</body>
</html>

和我的 StudentController.java 如下：

package com.programcreek.helloworld.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
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 org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("/")
public class StudentController {

   @RequestMapping(value = "/student", method = RequestMethod.GET)
   public ModelAndView student() {

      return new ModelAndView("student", "command2", new Student());
   }



   @RequestMapping(value = "/addStudent", method = RequestMethod.POST)
   public String addStudent(@ModelAttribute("HelloWorld")Student student, 
   ModelMap model) {

       System.out.println("Controller2");
      model.addAttribute("name", student.getName());
      model.addAttribute("age", student.getAge());
      model.addAttribute("id", student.getId());

      return "result";
   }
}

我总是阅读大量示例并将示例代码转移到我的eclipse中进行尝试，但是对于这个学生的案例，它是从一个旧示例（Spring 2.4）中提取的。

感谢您帮我解决问题。（我知道 spring-文档）

Answer 1

I have executed your code on my system

you are returning from your controller class

return new ModelAndView("student", "command2", new Student());

so you have map "command2" with the commandName in the form of student.jsp

commandName="command2" in your student.jsp like below

<form:form method="POST" commandName="command2" action="/HelloWorld/addStudent" >

full source code of your project :

student.java

package com.programcreek.helloworld.controller;

public class Student {
       private Integer age;
       private String name="";
       private Integer id;
       public Student(){

       }
       public void setAge(Integer age) {
          this.age = age;
       }
       public Integer getAge() {
          return age;
       }

       public void setName(String name) {
          this.name = name;
       }
       public String getName() {
          return name;
       }

       public void setId(Integer id) {
          this.id = id;
       }
       public Integer getId() {
          return id;
       }
    }

StudentController.java

package com.programcreek.helloworld.controller;

    import org.springframework.stereotype.Controller;
    import org.springframework.ui.ModelMap;
    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 org.springframework.web.servlet.ModelAndView;

    @Controller
    @RequestMapping("/")
    public class StudentController {

        @RequestMapping(value = "/student", method = RequestMethod.GET)
           public ModelAndView student() {

              return new ModelAndView("student", "command2", new Student());
           }



           @RequestMapping(value = "/addStudent", method = RequestMethod.POST)
           public ModelAndView addStudent(@ModelAttribute("HelloWorld")Student student) {
               ModelAndView modelAndView = new ModelAndView();

               System.out.println("Controller2");
               modelAndView.addObject("name", student.getName());
               modelAndView.addObject("age", student.getAge());
               modelAndView.addObject("id", student.getId());
               modelAndView.setViewName("result");


              return modelAndView;
           }
        }

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">



    <servlet>
        <servlet-name>DefaultServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>DefaultServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>


</web-app>

DefaultServlet-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:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="com.programcreek.helloworld.controller" />
    <!-- <context:component-scan base-package="com.packt.webstore.domain.repository.impl" />
    <context:component-scan base-package="com.packt.webstore.service.impl" /> -->

    <bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>


</beans>

student.jsp

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

<html>
<head>
    <title>Spring MVC Form Handling</title>
</head>
<body>

<h2>2 Student Information 2</h2>


<form:form method="POST" commandName="command2" action="addStudent" >
   <table>
    <tr>
        <td><form:label path="name">Name</form:label></td>
        <td><form:input path="name" /></td>
    </tr>
    <tr>
        <td><form:label path="age">Age</form:label></td>
        <td><form:input path="age" /></td>
    </tr>
    <tr>
        <td><form:label path="id">id</form:label></td>
        <td><form:input path="id" /></td>
    </tr>
    <tr>
        <td colspan="2">
            <input type="submit" value="Submit"/>
        </td>
    </tr>
</table>  
</form:form>
</body>
</html>

directory structure:

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Spring 4 / 既不是 BindingResult 也不是普通目标对象

Spring 4 / Neither BindingResult nor plain target object

java

spring-mvc

spring-4