In this example, we will learn how to create a dropdown box in Spring MVC using Springs tag library. We will use the <form:select> and <form:options> for creating a drop-down. Here we will create a simple Spring MVC form with a country dropdown and we will add validation support to check if it is not empty.

In Spring MVC we will use <form:select> and <form:options> tag to render a dropdown

 <form:select path="country">
     <form:option value="" label="...." />
     <form:options items="${countryList}"/>
 </form:select>

Which produces the below HTML code.

 <select id="country" name="country">
     <option value="">....</option>
     <option value="India">India</option>
     <option value="Australia">Australia</option>
     <option value="England">England</option>
 </select>

Folder Structure :

1. Create a Dynamic Web Project SpringMVCFormHandling and create a package for our src files “com.javainterviewpoint“
2. Place the Spring 3 jar files under WEB-INF/Lib 

   commons-logging-1.1.1.jar
   log4j-1.2.16.jar
   slf4j-api-1.7.5.jar
   slf4j-log4j12-1.7.5.jar
   hibernate-validator-4.2.0.Final.jar
   spring-aspects-3.2.4.RELEASE.jar
   spring-beans-3.2.4.RELEASE.jar
   spring-context-3.2.4.RELEASE.jar
   spring-core-3.2.4.RELEASE.jar
   spring-expression-3.2.4.RELEASE.jar
   spring-web-3.2.4.RELEASE.jar
   spring-webmvc-3.2.4.RELEASE.jar
   validation-api-1.1.0.Final.jar
   jstl-1.1.2.jar

3. Create the Java classes MVC_Controller.java and RegistrationBean.java under com.javainterviewpoint folder.
4. Place the SpringConfig-servlet.xml and web.xml  under the WEB-INF directory
5. View files SpringMVC_DropDownExample.jsp and dropdown_Success.jsp are put under the sub directory under WEB-INF/Jsp

Controller

Dropdown_Controller.java

• The DispatcherServlet mapping which we make in the web.xml will delegate the all the request to our Dropdown_Controller as we have annotated it with @Controller annotation.
• We use the @RequestMapping annotation to map each of the requests which we get to individual methods. Our controller has three methods getCountry(),initializeForm() and  processForm(). 
• The getCountry() method returns a list of country which will be used by view for populating the country dropdown.
• The initializeForm() will take the user to the “SpringMVC_DropdownExample” which is our view component with form backing object DropdownBean.
•  The processForm() method will get called when the user submits the form. The DropdownBean object “db”  will be validated as we have annotated it with @Valid annotationand the validation results will be added to the BindingResult. Based on the result we will re-direct the user back to the “SpringMVC_DropdownExample” or “dropdown_Success” page.

package com.javainterviewpoint;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.validation.Valid;

import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class Dropdown_Controller 
{
	ModelAndView mav = null;
	@ModelAttribute("countryList")
	public List getCountry()
	{
		List countryList = new ArrayList();
		countryList.add("India");
		countryList.add("Australia");
		countryList.add("England");
		return countryList;
	}
	
	@RequestMapping("/DropdownExample")
	public String dispForm(Map model)
	{
		DropdownBean db = new DropdownBean();
		model.put("db",db);
		return "SpringMVC_DropdownExample";
		
	}
	@RequestMapping("/processCountry")
	public String processForm(@Valid @ModelAttribute("db") DropdownBean db1,BindingResult result)
	{
		if(result.hasErrors())
		{
			System.out.println("Validation Failed");
			return "SpringMVC_DropdownExample";
		}
		else
		{
			System.out.println("Validated Successfully");
			return "dropdown_Success";
		}
	}
}

Model

DropdownBean.java

Here DropdownBean act as a Model which has a country property. We have added the annotation @NotEmpty to validate if the user has selected a value in the dropdown. The custom validation messages are added in the props.properties file.

package com.javainterviewpoint;


import org.hibernate.validator.constraints.NotEmpty;

public class DropdownBean 
{
	@NotEmpty
	String country;

	public String getCountry() {
		return country;
	}

	public void setCountry(String country) {
		this.country = country;
	}
	
}

View

SpringMVC_DropdownExample.jsp

Our view component has a dropdown field generated using the Spring form tag library. The dropdown gets its value from our controller class. @ModelAttribute(“countryList”) of our controller will be called and it will return a list of Country when <form:options items=”${countryList}”/>  is called.<form:errors> tag displays the error message which occurs during the validation

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
 pageEncoding="ISO-8859-1"%>
 <%@ taglib uri="http://www.springframework.org/tags/form" prefix="form" %>
<!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>Insert title here</title>
<style>
.error {
 color: #ff0000;
}
 
.commonerrorblock {
 color: #000;
 background-color: #ffEEEE;
 border: 3px solid #ff0000;
 
}
</style>
</head>
<body>
 <form:form method="post" action="processCountry" commandName="db">
 <form:errors path="*" element="div" cssClass="commonerrorblock"/>
 <table>
 <tr>
 <td>Country</td>
 <td>
 <form:select path="country">
 <form:option value="" label="...." />
 <form:options items="${countryList}"/>
 </form:select>
 </td>
 <td>
 <form:errors path="country" cssClass="error"/>
 </td>
 </tr>
 <tr>
 <td></td><td><input type="submit"></td>
 </tr>
 </table>
 </form:form>
</body>
</html>

props.properties

NotEmpty.db.country = Please select a Country!!

dropdown_Success.jsp

<%@ 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>Insert title here</title>
</head>
<body>
 Country Selected : ${db.country}
</body>
</html>

Configurations

web.xml

The web.xml has everything about the application that a server needs to know, which is placed under the WEB-INF directory. <servlet-name> contains the name of the SpringConfiguration, when the DispatcherServlet is initialized the framework will try to load a configuration file “[servlet-name]-servlet.xml” under the WEB-INF directory.

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<?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>SpringMVCFormHandling</display-name>
	<welcome-file-list>
		<welcome-file>index.html</welcome-file>
		<welcome-file>index.htm</welcome-file>
		<welcome-file>index.jsp</welcome-file>
		<welcome-file>default.html</welcome-file>
		<welcome-file>default.htm</welcome-file>
		<welcome-file>default.jsp</welcome-file>
	</welcome-file-list>
	<servlet>
		<servlet-name>SpringConfig</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>SpringConfig</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
</web-app>

SpringConfig-servlet.xml

• The SpringConfig-servlet.xml is also placed under the WEB-INF directory.
• <context:component-scan> will let the Spring Container to search for all the annotation under the package “com.javainteriviewpoint”. 
• <mvc:annotation-driven/> annotation will activate the @Controller, @RequestMapping, @Validetc annotations.
• The view is resolved through “org.springframework.web.servlet.view.InternalResourceViewResolver” which searches for the jsp files under the /WEB-INF/Jsp/ directory.
• Resource Bundle is accessed through the “org.springframework.context.support.ResourceBundleMessageSource”  through its property “basename” which has the value “props”, and hence our property file should “props.properties”

<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">

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

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

	<bean id="messageSource"
		class="org.springframework.context.support.ResourceBundleMessageSource">
		<property name="basename" value="props"></property>
	</bean>
</beans>

Lets run our application

Now lets run our application, do a clean build and deploy the application in the Server

Hit on the url “http://localhost:8080/SpringMVCFormHandling/DropdownExample”

Submit the form without selecting a value in the dropdown.

Upon successful validation, success page will be returned

[출처] http://www.javainterviewpoint.com/spring-mvc-dropdown-box-example/