Spring MVC Form Handling Example
With this tutorial we shall explain create and submit a form in Spring MVC. Spring MVC provides tags that are data binding-aware and allow us to handle form elements, compining JSP and Spring Web MVC. Each tag in Spring MVC provides support for the set of attributes of its corresponding HTML tag, thus making the tags familiar and intuitive to use.
In this example we shall make use of a textbox
, a password
, a checkbox
, a dropdown box
and a hidden value
, all tags provided by Spring MVC. They will be used as properties inside a class, which is the MVC model. There is also a validator for all these fields, and a view that contains a form with all these fields to fill and submit.
You may skip project creation and jump directly to the beginning of the example below.
Our preferred development environment is Eclipse. We are using Eclipse Juno (4.2) version, along with Maven Integration plugin version 3.1.0. You can download Eclipse from here and Maven Plugin for Eclipse from here. The installation of Maven plugin for Eclipse is out of the scope of this tutorial and will not be discussed. We are also using JDK 7_u_21. Tomcat 7 is the application server used.
Let’s begin,
1. Create a new Maven project
Go to File -> Project ->Maven -> Maven Project.
In the “Select project name and location” page of the wizard, make sure that “Create a simple project (skip archetype selection)” option is unchecked, hit “Next” to continue with default values.
Here the maven archetype for creating a web application must be added. Click on “Add Archetype” and add the archetype. Set the “Archetype Group Id” variable to "org.apache.maven.archetypes"
, the “Archetype artifact Id” variable to "maven-archetype-webapp"
and the “Archetype Version” to "1.0"
. Click on “OK” to continue.
In the “Enter an artifact id” page of the wizard, you can define the name and main package of your project. Set the “Group Id” variable to "com.javacodegeeks.snippets.enterprise"
and the “Artifact Id” variable to "springexample"
. The aforementioned selections compose the main project package as "com.javacodegeeks.snippets.enterprise.springexample"
and the project name as "springexample"
. Set the “Package” variable to "war"
, so that a war file will be created to be deployed to tomcat server. Hit “Finish” to exit the wizard and to create your project.
The Maven project structure is shown below:
- It consists of the following folders:
- /src/main/java folder, that contains source files for the dynamic content of the application,
- /src/test/java folder contains all source files for unit tests,
- /src/main/resources folder contains configurations files,
- /target folder contains the compiled and packaged deliverables,
- /src/main/resources/webapp/WEB-INF folder contains the deployment descriptors for the Web application ,
- the pom.xml is the project object model (POM) file. The single file that contains all project related configuration.
2. Add Spring-MVC dependencies
Add the dependencies in Maven’s pom.xml
file, by editing it at the “Pom.xml” page of the POM editor. The dependency needed for MVC is the spring-webmvc
package. The javax.validation
and the hibernate-validator
packages will be also used here for validation:
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.javacodegeeks.snippets.enterprise</groupId> <artifactId>springexample</artifactId> <packaging>war</packaging> <version>0.0.1-SNAPSHOT</version> <name>springexample Maven Webapp</name> <url>http://maven.apache.org</url> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>2.5</version> </dependency> <dependency> <groupId>javax.validation</groupId> <artifactId>validation-api</artifactId> <version>1.1.0.Final</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator</artifactId> <version>5.1.0.Final</version> </dependency> </dependencies> <build> <finalName>springexample</finalName> </build> <properties> <spring.version>3.2.9.RELEASE</spring.version> </properties> </project>
3. Create the model
Form.java
is the class that will be used as the model. It has properties for all the fields that will be used in the form, which are a textbox
, a password
, a checkbox
, a dropdown box
and a hidden value
. All fields must have getters and setters to be rendered in the view.
Form.java
package com.javacodegeeks.snippets.enterprise.form.model; import java.util.List; public class Form { // textbox, password, // checkbox, dropdown, hidden value private String name; private String email; private String gender; private String password; private String passwordConf; private List<String> courses; private String tutor; private String hiddenMessage; public String getName() { return name; } public void setName(String name) { this.name = name; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getPasswordConf() { return passwordConf; } public void setPasswordConf(String passwordConf) { this.passwordConf = passwordConf; } public List<String> getCourses() { return courses; } public void setCourses(List<String> courses) { this.courses = courses; } public String getTutor() { return tutor; } public void setTutor(String tutor) { this.tutor = tutor; } public String getHiddenMessage() { return hiddenMessage; } public void setHiddenMessage(String hiddenMessage) { this.hiddenMessage = hiddenMessage; } }
4. Create a Validator
The validator is the class that will be used in the controller to check on the values of each field in the form. In order to create a validator class, we are making use of the API provided by Spring MVC. FormValidator.java
below implements the org.springframework.validation.Validator
, and overrides the two methods it provides.
The boolean supports(Class<?> paramClass)
method is used to check if the validator can validate instances of the paramClass
.
In the validate(Object obj, Errors errors)
method, an instance of the class is provided, and an Errors
object. The org.springframework.validation.ValidationUtils
is used here, since it offers validation API methods to check the fields of the object. All error messages are passed in the error
object. A properties
file with error messages is used here to pass various validation messages to the errors
object as shown below:
FormValidator.java
package com.javacodegeeks.snippets.enterprise.form.validator; import java.util.List; import org.springframework.validation.Errors; import org.springframework.validation.ValidationUtils; import org.springframework.validation.Validator; import com.javacodegeeks.snippets.enterprise.form.model.Form; public class FormValidator implements Validator { private static final String EMAIL_PATTERN = "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})quot;;
public boolean supports(Class<?> paramClass) {
return Form.class.equals(paramClass);
}public void validate(Object obj, Errors errors) {
Form form = (Form) obj;
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "name", "valid.name");
if(!form.getEmail().matches(EMAIL_PATTERN)) {
errors.rejectValue("email","valid.email");
}
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "gender", "valid.gender");
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "valid.password");
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "passwordConf", "valid.passwordConf");
if (!form.getPassword().equals(form.getPasswordConf())) {
errors.rejectValue("passwordConf", "valid.passwordConfDiff");
}
List<String> courses = form.getCourses();
if (courses == null || courses.size() < 2) {
errors.rejectValue("courses", "valid.courses");
}
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "tutor", "valid.tutor");
}
}
Thevalidation.properties
file below is the file that contains all the error messages.validation.properties
valid.name= Please type your name valid.gender = Please select your gender! valid.email=Please type a correct email valid.password=Please select a password valid.passwordConf=Please confirm your password valid.passwordConfDiff=Your password is different valid.courses = Please select at least two courses! valid.tutor=Please choose your tutor!5. Create the Controller
The
Controller
is where theDispatcherServlet
will delegate requests. The@Controller
annotation indicates that the class serves the role of a Controller. The@RequestMapping
annotation is used to map a URL to either an entire class or a particular handler method.A
org.springframework.validation.Validator
is injected here, via the@Autowired
annotation, also making use of the@Qualifier
annotation to specify that theFormValidator.java
implementation of theorg.springframework.validation.Validator
class is injected.The
@InitBinder
annotation ininitBinder(WebDataBinder binder)
method allows us to configure web data binding directly within the controller. With@InitBinder
we can initialize theWebDataBinder
, that is used for data binding from web request parameters to JavaBean objects. Here, theWebDataBinder
is where the validator is set.The Controller consists of two basic methods, a GET method, which is
String initForm(Model model)
and a POST method, which isString submitForm(Model model, @Validated Form form, BindingResult result)
. The first method creates and returns to the"form"
view a new instance of theForm.java
class. The second method also gets theModel
, and theForm
object created in the form.Form
is annotated with the@Validated
annotation, which allows the form object to be validated with the validator.BindingResult
is where all validation errors are automatically passed, so it can be used to decide the next navigation step. If there are no errors, the validation is successful, so the method returns the String representation of thesuccessForm.jsp
page, and the form object is passed at theModel
. Otherwise, the returned String is the String representation of theform.jsp
page, which also has the error messages, as will be shown below.The
private void initModelList(Model model)
method is used to initialize all lists that are passed to the model for the tags that use options, such as thecheckbox
and thedropdown box
. So every time the form is rendered these lists are not null. If the lists are not initialized, then the iteration over the items of the lists leads to aNullPointerException
.FormController.java
package com.javacodegeeks.snippets.enterprise.form; import java.util.ArrayList; import java.util.List; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.stereotype.Controller; import org.springframework.ui.Model; import org.springframework.validation.BindingResult; import org.springframework.validation.Validator; import org.springframework.validation.annotation.Validated; import org.springframework.web.bind.WebDataBinder; import org.springframework.web.bind.annotation.InitBinder; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import com.javacodegeeks.snippets.enterprise.form.model.Form; @Controller @RequestMapping("/form.htm") public class FormController { @Autowired @Qualifier("formValidator") private Validator validator; @InitBinder private void initBinder(WebDataBinder binder) { binder.setValidator(validator); } @RequestMapping(method = RequestMethod.GET) public String initForm(Model model) { Form form = new Form(); form.setHiddenMessage("JavaCodeGeek"); model.addAttribute("form", form); initModelList(model); return "form"; } @RequestMapping(method = RequestMethod.POST) public String submitForm(Model model, @Validated Form form, BindingResult result) { model.addAttribute("form", form); String returnVal = "successForm"; if(result.hasErrors()) { initModelList(model); returnVal = "form"; } else { model.addAttribute("form", form); } return returnVal; } private void initModelList(Model model) { List<String> courses = new ArrayList<String>(); courses.add("Maths"); courses.add("Physics"); courses.add("Geometry"); courses.add("Algebra"); courses.add("Painting"); model.addAttribute("courses", courses); List<String> genders = new ArrayList<String>(); genders.add("Male"); genders.add("Female"); model.addAttribute("genders", genders); List<String> tutors = new ArrayList<String>(); tutors.add("Mrs Smith"); tutors.add("Mr Johnson"); tutors.add("Mr Clarks"); model.addAttribute("tutors", tutors); model.addAttribute("genders", genders); } }6. Create the view with a form
The view below is a simple example of how to create a form. It is a simple html view consisting of the
head
andbody
html tags.In order to create a form in Spring MVC, we make use of the
form:form
tag. Itsmethod
property is set to POST, and thecommandName
property is set to the name of the backing bean that is binded to the Model, which is theForm.java
class.The
form:input
tag is used to create the textbox, with itspath
property set to the field binded to it. Theform:password
tag is used to create the password field. Theform:checkboxes
tag has another property to configure, appart from thepath
property. It also provides theitems
property, where the list of the items to be displayed is set.In order to create a
hidden value
, we are using the simpleinput
tag, withname
property set to thehiddenMessage
, which is the field bound to it. Its type parameter is set tohidden
, so this component is not visible in the view. It also has avalue
parameter set to a String message.The
form:errors
tag defines where the error message of the specified field will be displayed in the view. Finally, theinput
tag, withtype
property set tosubmit
is used for the submit button.form.jsp
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%> <html> <head> <title>Spring MVC form submission</title> </head> <body> <h2>Fill your form!</h2> <form:form method="POST" commandName="form"> <table> <tr> <td>Enter your name:</td> <td><form:input path="name" /></td> <td><form:errors path="name" cssStyle="color: #ff0000;"/></td> </tr> <tr> <td>Enter your mail:</td> <td><form:input path="email" /></td> <td><form:errors path="email" cssStyle="color: #ff0000;" /></td> </tr> <tr> <td>Enter your gender</td> <td><form:checkboxes path="gender" items="${genders}" /></td> <td><form:errors path="gender" cssStyle="color: #ff0000;"/></td> </tr> <tr> <td>Enter a password:</td> <td><form:password path="password" showPassword="true"/></td> <td><form:errors path="password" cssStyle="color: #ff0000;"/></td> <tr> <td>Confirm your password:</td> <td><form:password path="passwordConf" showPassword="true"/></td> <td><form:errors path="passwordConf" cssStyle="color: #ff0000;"/></td> </tr> <tr> <td>Choose the courses you like:</td> <td><form:checkboxes path="courses" items="${courses}" /></td> <td><form:errors path="courses" cssStyle="color: #ff0000;"/></td> </tr> <tr> <td>Please select your tutor:</td> <td><form:select path="tutor"> <form:option value="" label="...." /> <form:options items="${tutors}" /> </form:select> </td> <td><form:errors path="tutor" cssStyle="color: #ff0000;" /></td> </tr> <tr> <form:hidden path="hiddenMessage"/> </tr> <tr> <td><input type="submit" name="submit" value="Submit"></td> </tr> <tr> </table> </form:form> </body> </html>Below is the page that will be rendered when the validation of the form succeeds:
successForm.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%> <html> <head> <title>Spring MVC form submission</title> </head> <body> Dear ${form.name}, <br> Your mail is ${form.email} <br> You chose the courses below: <br> <c:forEach var="course" items="${form.courses}"> <c:out value="${course}"/><br> </c:forEach> <br> ${form.tutor} will be your tutor! <br> Your hidden nickname is ${form.hiddenMessage} </body> </html>7. Configure the application
The files that we must configure in the application are the
web.xml
file and themvc-dispatcher-servlet.xml
file.The
web.xml
file is the file that defines everything about the application that a server needs to know. It is placed in the/WEB-INF/
directory of the application. The<servlet>
element declares theDispatcherServlet
. When theDispatcherServlet
is initialized, the framework will try to load the application context from a file named[servlet-name]-servlet.xml
located in/WEB-INF/
directory. So, we have created themvc-dispatcher-servlet.xml
file, that will be explained below. The<servlet-mapping>
element ofweb.xml
file specifies what URLs will be handled by theDispatcherServlet
.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_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>Archetype Created Web Application</display-name> <servlet> <servlet-name>mvc-dispatcher</servlet-name> <servlet-class> org.springframework.web.servlet.DispatcherServlet </servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>mvc-dispatcher</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> </web-app>
Themvc-dispatcher-servlet.xml
file is also placed inWebContent/WEB-INF
directory. Theorg.springframework.web.servlet.view.InternalResourceViewResolver
bean is used as internal resource views resolver, meaning that it will find thejsp
andhtml
files in theWebContent/WEB-INF/
folder. We can also set properties such asprefix
orsuffix
to the view name to generate the final view page URL. This is the file where all beans created, such as Controllers are placed and defined.The
<context:component-scan>
tag is used, so that the Spring container will search for all annotated classes under thecom.javacodegeeks.snippets.enterprise
package. The<mvc:annotation-driven>
tag is used, so that the container searches for annotated classes, to resolve MVC. TheFormValidator.java
class is also defined here as a bean, with an id.Finally, the
ResourceBundleMessageSource
is used, to provide access to resource bundles using specified basenames. Itsbasename
property is set tovalidation
, thus pointing to the properties file that holds the validation messages.mvc-dispatcher-servlet.xml
<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.javacodegeeks.snippets.enterprise" /> <mvc:annotation-driven /> <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource"> <property name="basename" value="validation" /> </bean> <bean id="formValidator" class="com.javacodegeeks.snippets.enterprise.form.validator.FormValidator" /> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix"> <value>/WEB-INF/</value> </property> <property name="suffix"> <value>.jsp</value> </property> </bean> </beans>8. Run the application
Now, let's run the application. We first build the project with Maven. All we have to do is right click on the project and select -> Run As: Maven build. The goal must be set to package. The
.war
file produced must be placed inwebapps
folder of tomcat. Then, we can start the server.Hit on:
http://localhost:8080/springexample/form.htm
So, here is our form. Press the submit button before having entered any values:
As a result all validation messages are rendered. Now, press different passwords and a wrong email and press the submit button again:
Again, there are validation messages. Now complete your form correctly and press on submit button:
There you go, your form is correctly submitted!
9. Download the Eclipse Project
This was an example of how handle a form in Spring MVC.
Download
You can download the full source code of this example here:SpringMVCFormHandling
This example is not very useful when the page tags are mixed in with the code.
Most of the “code” in FormValidator.java isn’t code, but text.
I’ve seen this on other pages, but this is one of the worst one so far.
I think these things wouldn’t happen so much if the pages were reviewed.