@modelattribute是最重要的Spring MVC注释之一。

@ModelAttribute用于将请求参数与Model对象绑定。
让我们说你有10个请求参数，可以将它们包装到模型对象并将其传递给handler方法。

有两种方法可以创建模型对象。

• 对象已存在于会话或者ModelMap对象中。
• 使用@ModelAttribute注释注释另一种方法并创建模型对象。在实际处理程序调用之前将调用此方法。

例子：

以下是创建Spring MVC ModelAttribute示例的步骤。

1)使用名为"springmvcmodelattributexample"的Eclipse中的Maven创建动态Web项目

Maven依赖项

2)我们需要在类路径中添加Hymanson Json实用程序。

<dependency>
            <groupId>com.fasterxml.Hymanson.core</groupId>
            <artifactId>Hymanson-databind</artifactId>
             <version>2.4.1</version>
 </dependency>

Spring将Hymanson2jsonmessageConverter自动加载到其应用程序上下文中。
每当我们使用Accep Headers ="Accept = Application/JSON"时请求资源作为JSON，那么Hymanson2jsonMessageConverter就会进入图片并将资源转换为JSON格式。

现在更改pom.xml如下：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>com.igi.theitroad</groupId>
  <artifactId>SpringRestfulWebServicesWithJSONExample</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>SpringRestfulWebServicesWithJSONExample 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>javax.servlet</groupId>
   <artifactId>javax.servlet-api</artifactId>
   <version>3.1.0</version>
  </dependency>
 
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-core</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-webmvc</artifactId>
   <version>${spring.version}</version>
  </dependency>
   <dependency>
            <groupId>com.fasterxml.Hymanson.core</groupId>
            <artifactId>Hymanson-databind</artifactId>
             <version>2.4.1</version>
        </dependency>
 </dependencies>
 <build>
  <finalName>SpringRestfulWebServicesWithJSONExample</finalName>
 
  <plugins>
   <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.1</version>
    <configuration>
     <source>${jdk.version}</source>
     <target>${jdk.version}</target>
    </configuration>
   </plugin>
  </plugins>
 
 </build>
 <properties>
  <spring.version>4.2.1.RELEASE</spring.version>
  <jdk.version>1.7</jdk.version>
 </properties>
</project>

Spring应用程序配置：

3)更改Web.xml如下：

<?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"
 version="3.0">
 <display-name>Archetype Created Web Application</display-name>
  <welcome-file-list>  
   <welcome-file>index.jsp</welcome-file>  
 
  </welcome-file-list>
 <servlet>
 <servlet-name>springrest</servlet-name>
 <servlet-class>
  org.springframework.web.servlet.DispatcherServlet
 </servlet-class>
 <load-on-startup>1</load-on-startup>
</servlet>
 
<servlet-mapping>
 <servlet-name>springrest</servlet-name>
 <url-pattern>/</url-pattern>
</servlet-mapping>
 
</web-app>

4)在/Web-Inf /文件夹中创建名为springrest-servlet.xml的XML文件。
请更改上下文：组件扫描如果要使用不同的套装来搜索控制器。
请参阅Spring MVC Hello World示例以获取更多的理解。

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:context="http://www.springframework.org/schema/context"
 xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 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="org.igi.theitroad.controller" 
 <bean
  class="org.springframework.web.servlet.view.InternalResourceViewResolver">
  <property name="prefix">
   <value>/WEB-INF/</value>
  </property>
  <property name="suffix">
   <value>.jsp</value>
  </property>
 </bean>
 <mvc:default-servlet-handler
</beans>

创建bean类

5)在org.igi.theitroad.Bean中创建bean名称"country.java"。

package org.igi.theitroad.bean;
 
public class Country{
 
 String countryName; 
 long population;
 
 public Country() {
  super();
 }
 public Country(String countryName,long population) {
  super();
  this.countryName = countryName;
  this.population=population;
 }
 public String getCountryName() {
  return countryName;
 }
 public void setCountryName(String countryName) {
  this.countryName = countryName;
 }
 public long getPopulation() {
  return population;
 }
 public void setPopulation(long population) {
  this.population = population;
 } 
 
}

创建控制器

6)在Package org.igi.theitroad.Controller中创建名为"CountryController.java"的控制器

package org.igi.theitroad.controller;
 
import org.igi.theitroad.bean.Country;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
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.bind.annotation.RequestParam;
 
@Controller
public class CountryController {
 
 @ModelAttribute
 public Country getCountry(@RequestParam String countryName, @RequestParam  long population)
 {
  Country country=new Country();
  country.setCountryName(countryName);
  country.setPopulation(population);
  return country;
 }
 @RequestMapping(value = "/addCountry", method = RequestMethod.POST)
 public String addCountry(@ModelAttribute Country country,ModelMap model) {
  model.addAttribute("countryName", country.getCountryName());
  model.addAttribute("population", country.getPopulation());
  return "countryDetails";
 }
}

Create view

修改下面的index.jsp a s

<head>
<style>
           
.blue-button{
 background: #25A6E1;
 filter: progid: DXImageTransform.Microsoft.gradient( startColorstr='#25A6E1',endColorstr='#188BC0',GradientType=0);
 padding:3px 5px;
 color:#fff;
 font-family:'Helvetica Neue',sans-serif;
 font-size:12px;
 border-radius:2px;
 -moz-border-radius:2px;
 -webkit-border-radius:4px;
 border:1px solid #1A87B9
}     
table {
  font-family: "Helvetica Neue", Helvetica, sans-serif;
   width: 50%;
}
th {
  background: SteelBlue;
  color: white;
}
 td,th{
                border: 1px solid gray;
                width: 25%;
                text-align: left;
                padding: 5px 10px;
            }
</style>
</head>
<body>
<form action="addCountry" method="post">
 
<table>
  <tr>
   <th colspan="2">Add Country</th>
  </tr>
  <tr>
   <td>Country</td>
   <td><input type="text" name=countryName></td>
  </tr>
  <tr>
   <td>Population</td>
   <td><input type="text" name=population>
  </td></tr>
  <tr>
   <td colspan="2"><input type="submit"
    class="blue-button" </td>
  </tr>
 </table>
 
</form>
</body>

在/web-inf /文件夹中创建countrydetails.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>Country Details</title>
</head>
<body>
  Added country :
 <h3>Country Name: {countryName}</h3>
 <h3>Population : ${population}</h3>
 </body> 
</html>

7)这是时候做Maven建造了。

右键单击项目 - >运行AS - > Maven Build

8)将目标作为清洁安装(下面给出)，然后单击运行

运行应用程序

9)右键单击项目 - >在服务器上运行AS - >运行

选择Apache Tomcat，然后单击"完成"

10)单击"提交"按钮时，我们将看到以下屏幕。