This
is continuation to my previous posts. In my previous post, I explained how
spring binds the request parameters to a java model object using
@ModelAttribute annotation.
But
in some cases, user may enter wrong inputs. For example, you developed a
registration form, where you are expecting below information.
Information
|
Type
|
userName
|
String
|
age
|
int
|
hobbies
|
Collection
|
If
user enter age as ‘Twenty Five’, where you are expecting an integer. Spring
throws an exception.
As
you see above registration form, I given ‘Twenty Five’ as the value for the
field ‘Age’. When I click on submit button, I got below exception.
As
you see above error page, I do not get any meaningful error message. To solve
this problem, spring provides 'BindingResult' interface.
BindingResult
interface
General
interface that represents binding results. If any error occurs, at the time of
binding the request parameters to java model object, we can use this interface
to retrieve the number of errors, error messages.
@RequestMapping("/registerMe")
public
ModelAndView getHelloMessage(@ModelAttribute("studentInfo") Student
student, BindingResult bindingResult) {
if (bindingResult.hasErrors()) {
ModelAndView modelAndView =
new ModelAndView("registration");
return modelAndView;
}
.....
.....
.....
}
As
you see above snippet, I am using bindingResult.hasErrors() method to check
whether there is any errors.
you
can use the <form:errors /> tag to
render those field error messages in an HTML page.
Example
<form:errors
path="studentInfo.*" />
Above
tag displays the error message, if the binding of the request parameters to the
studentInfo object is not successful.
Find
the below working application.
HelloWorldController.java
package com.sample.myApp.controllers; 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; import com.sample.myApp.model.Student; @Controller public class HelloWorldController { @RequestMapping("/registration") public String getRegistrationpage() { return "registration"; } @RequestMapping("/registerMe") public ModelAndView getHelloMessage(@ModelAttribute("studentInfo") Student student, BindingResult bindingResult) { if (bindingResult.hasErrors()) { ModelAndView modelAndView = new ModelAndView("registration"); return modelAndView; } ModelAndView modelAndView = new ModelAndView("welcome"); modelAndView.addObject("message", "Dear User, your details are registered"); return modelAndView; } }
Student.java
package com.sample.myApp.model; import java.util.List; public class Student { private String userName; private int age; private List<String> hobbies; public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public List<String> getHobbies() { return hobbies; } public void setHobbies(List<String> hobbies) { this.hobbies = hobbies; } }
Create
registration.jsp, welcome.jsp files under WEB-INF/jsp folder.
registration.jsp
<%@taglib prefix="form" uri="http://www.springframework.org/tags/form"%> <html> <head> <title>User Information Page</title> </head> <body> <h2 style="color:red;"><form:errors path="studentInfo.*" /></h2> <form method="post" action="/springdemo/registerMe" id="f1"> <table> <tr> <td>User Name :</td> <td><input type="text" name="userName" value="" /></td> </tr> <tr> <td>Age :</td> <td><input type="text" name="age" value="" /></td> </tr> <tr> <td>Hobbies :</td> <td><select multiple name="hobbies"> <option value="cricket">Cricket</option> <option value="chess">Chess</option> <option value="football">Football</option> <option value="tennis">Tennis</option> </select></td> </tr> <tr> <td><input type="submit" name="submit" value="submit" style="font-size: 18px;" /></td> </tr> </table> </form> </body> </html>
welcome.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>Hello World Spring Web MVC</title> </head> <body> <h1>${message}</h1> <h3> User Name : ${studentInfo.userName} <br /> Age : ${studentInfo.age} <br /> Hobbies: ${studentInfo.hobbies} </h3> </body> </html>
Create
web.xml, HelloWorld-servlet.xml files under WEB-INF folder.
web.xml
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>Spring MVC Hello WorldApplication</display-name> <servlet> <servlet-name>HelloWorld</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>HelloWorld</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> </web-app>
HelloWorld-servlet.xml
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" 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"> <context:component-scan base-package="com.sample.myApp" /> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix" value="/WEB-INF/jsp/" /> <property name="suffix" value=".jsp" /> </bean> </beans>
Create
index.jsp file under webapp folder.
index.jsp
<%@taglib prefix="form" uri="http://www.springframework.org/tags/form"%> <html> <head> <title>Welcome Page</title> </head> <body> <h1>Hello World</h1> </body> </html>
Project
structure looks like below.
Run
the application on server.
I
entered ‘Twenty Five’ in the Age field, When I click on submit button, it shows
the error information.
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