无法检索从控制器发送到spring mvc中的值

Question

I am new to Spring MVC. 我是Spring MVC的新手。 I am writing a simple maven web project to display a hello world on view when it is invoked. 我正在编写一个简单的maven web项目，以便在调用时在视图上显示hello world。 In addition to this I am using apache tomcat 7. 除此之外，我使用的是apache tomcat 7。
I am following this 我跟着这个
The Controller is getting invoked and I am able to set and print the modelmap. 控制器被调用，我可以设置和打印模型图。

pom.xml 的pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>springmvc</groupId>
<artifactId>demo</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>demo Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>3.8.1</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>4.3.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>


</dependencies>
<build>
    <finalName>demo</finalName>
</build>

web.xml web.xml中

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
 <servlet>
        <servlet-name>HelloWeb</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>HelloWeb</servlet-name>
        <url-pattern>*.action</url-pattern>
    </servlet-mapping>

</web-app>

HelloWeb-servlet.xml 的HelloWeb-servlet.xml中

<?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:mvc="http://www.springframework.org/schema/mvc"
    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 http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <mvc:annotation-driven />
    <context:component-scan base-package="com.tutorialpoint" />

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

</beans>

HelloController 为HelloController

package com.tutorialpoint;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
@RequestMapping("/hello")
public class HelloController {

    public HelloController(){
        System.out.println("hiii");
    }

    @RequestMapping(method  = RequestMethod.GET)
    public String printHello(Model model){

        System.out.println("this is controller");
        model.addAttribute("testvalue", "Hello World!!");
        System.out.println(model.toString());

        return "output";
    }
}

Output.jsp output.jsp的

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Output</title>
</head>
<body>
    <p>This is output jsp page  message is </p> ${testvalue}
</body>
</html>

But on resulting view(output.jsp) I am unable to fetch the value. 但是在结果视图（output.jsp）上，我无法获取该值。 I tried 我试过了

using spring core tag in jsp 在jsp中使用spring core标签
using the c:out tag 使用c：out标签
putting maven dependency for jstl 把maven依赖放在jstl上

Thanks in advance. 提前致谢。

Edit - adding output.jsp screen shot 编辑 - 添加output.jsp屏幕截图

Answer 1

If you want to use EL you need to declare your deployment descriptor (web.xml) as Servlet 2.4 or higher. 如果要使用EL，则需要将部署描述符（web.xml）声明为Servlet 2.4或更高版本。 As you use Tomcat 7 which supports Servlet 3.0 I'd recommend you to use that version. 当您使用支持Servlet 3.0的Tomcat 7时，我建议您使用该版本。

You can achieve it by changing your opening bracket in web.xml to this: 您可以通过将web.xml中的左括号更改为：

<web-app version="3.0"
  xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="
    http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">

If that hasn't resolved your problem try to include below directive in your view: 如果这还没有解决您的问题，请尝试在您的视图中包含以下指令：

<%@ page isELIgnored="false" %>

Hope it helped. 希望它有所帮助。

Answer 2

Here the problem is with the web.xml header 这里的问题是web.xml标题

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

Change it to the following. 将其更改为以下内容。

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

You don't need to add <%@ page isELIgnored="false" %> to every page instead change the web.xml header once. 您不需要将<%@ page isELIgnored="false" %>到每个页面，而是更改web.xml标头一次。

Answer 3

It will not work, as you are modifying the modal in controller and then moving to new view altogether which will have its own model . 它将无法工作，因为您正在修改控制器中的modal ，然后完全移动到具有自己的model新view 。 Hence any change you do will be nullified . 因此，您所做的任何更改都将nullified 。

I would recommend you to use flash attribute facility of Spring MVC by adding RedirectAttributes in your controller method as follows, 我建议您通过在控制器方法中添加RedirectAttributes来使用Spring MVC的flash attribute工具，如下所示，

 @RequestMapping(method  = RequestMethod.GET)
    public String printHello(Model model, RedirectAttributes redir){

        System.out.println("this is controller");
       // model.addAttribute("testvalue", "Hello World!!");
        redir.addFlashAttribute("testvalue", "Hello World!!");
        System.out.println(model.toString());

        return "redirect:/output";
    }

Or Create a new ModelAndView and return it, 或者创建一个新的ModelAndView并将其返回，

 @RequestMapping(method  = RequestMethod.GET)
    public ModelAndView printHello(Model model){

        ModelAndView model= new ModelAndView("output");
        System.out.println("this is controller");
        model.addAttribute("testvalue", "Hello World!!");
        System.out.println(model.toString());

        return model;
    }

无法检索从控制器发送到spring mvc中的值

问题描述

3 个解决方案

解决方案1
4 已采纳 2016-12-20 09:09:35

解决方案2
3 2016-12-20 09:39:15

解决方案3
2 2016-12-20 09:08:11

无法检索从控制器发送到spring mvc中的值

问题描述

3 个解决方案

解决方案1 4 已采纳 2016-12-20 09:09:35

解决方案2 3 2016-12-20 09:39:15

解决方案3 2 2016-12-20 09:08:11

解决方案1
4 已采纳 2016-12-20 09:09:35

解决方案2
3 2016-12-20 09:39:15

解决方案3
2 2016-12-20 09:08:11