not able to see spring mvc validation error messages - spring

Question

I am new to spring MVC. To practice out my skills I made a sample form whose elements gets populated through respective controller. Now to check the validation part, I used all methodologies through annotations i.e. #NotNull, #Size, #Valid, #ModelAttribute, and BindingResult object. Below are the files I am using. I was following every necessary aspect, but don't know why am I not able to see RED colored validation messages.
Student class
package com.sikka.springmvcworking.custombeans;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
public class Student {
private String firstName;
#NotNull
#Size(min=1,message="is required")
private String lastName;
private String country;
private String course;
private String[] knownOs;
private String[] coutries;
private Map<String,String> countryMap;
private Map<String,String> courseMap;
private Map<String,String> kosMap;
public Student() {
}
public Student(String firstName, String lastName, String country, String course, String[] knownOs, String[] coutries,
Map<String, String> countryMap, Map<String, String> courseMap, Map<String, String> kosMap) {
this.firstName = firstName;
this.lastName = lastName;
this.country = country;
this.course = course;
this.knownOs = knownOs;
this.coutries = coutries;
this.countryMap = countryMap;
this.courseMap = courseMap;
this.kosMap = kosMap;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public Map<String, String> getCountryMap() {
return countryMap;
}
public void setCountryMap(Map<String, String> countryMap) {
this.countryMap = countryMap;
}
public String getCourse() {
return course;
}
public void setCourse(String course) {
this.course = course;
}
public String[] getKnownOs() {
return knownOs;
}
public void setKnownOs(String[] knownOs) {
this.knownOs = knownOs;
}
public String[] getCoutries() {
return coutries;
}
public void setCoutries(String[] coutries) {
this.coutries = coutries;
}
public Map<String, String> getCourseMap() {
return courseMap;
}
public void setCourseMap(Map<String, String> courseMap) {
this.courseMap = courseMap;
}
public Map<String, String> getKosMap() {
return kosMap;
}
public void setKosMap(Map<String, String> kosMap) {
this.kosMap = kosMap;
}
}
Student Controller class
package com.sikka.springmvcworking.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import java.util.*;
import javax.validation.Valid;
import com.sikka.springmvcworking.custombeans.Student;
#Controller
#RequestMapping("stu")
public class StudentController {
#RequestMapping("studentForm")
public String getStudentForm(Model model) {
Student student = new Student();
Map<String,String> countryMap = new LinkedHashMap<String,String>();
countryMap.put("IN", "INDIA");
countryMap.put("BR", "BRAZIL");
countryMap.put("MX", "MEXICO");
student.setCountryMap(countryMap);
Map<String,String> courseMap = new LinkedHashMap<String,String>();
courseMap.put("java", "JAVA");
courseMap.put(".net", ".NET");
courseMap.put("php", "PHP");
courseMap.put("andr", "ANDROID");
student.setCourseMap(courseMap);
Map<String,String> kosMap = new LinkedHashMap<String,String>();
kosMap.put("win", "WINDOWS");
kosMap.put("lnx", "LINUX");
kosMap.put("mac", "MACINTOSH");
student.setKosMap(kosMap);
model.addAttribute("student", student);
System.out.println("inside STUDENT-FORM");
return "STUDENT-FORM";
}
#RequestMapping("processStudent")
public String outputStudent(#Valid #ModelAttribute("student") Student student, BindingResult bindingResult) {
if(bindingResult.hasErrors()) {
return "redirect:studentForm";
}
return "VIEW-STUDENT";
}
}
Student Form JSP
<%# page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%# taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%# taglib prefix = "c" uri = "http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<style>
.error {color: red;}
</style>
</head>
<body>
<form:form action="processStudent" modelAttribute="student">
FirstName : <form:input type="text" path="firstName" placeholder="enter your first name"/><br>
LastName : <form:input type="text" path="lastName" placeholder="enter your last name"/>
<form:errors path="lastName" cssClass="error"/><br>
select country : <form:select path="coutries">
<form:options items="${student.countryMap}"/>
</form:select><br>
select course : <form:radiobuttons path="course" items="${student.courseMap}"/><br>
known OS(s) : <form:checkboxes items="${student.kosMap}" path="knownOs"/><br>
<input type="submit" value="submit">
</form:form>
</body>
</html>
Student Submit/View Jsp
<%# page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%# taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%# taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<br>
Student Name : ${student.firstName} ${student.lastName} <br>
Student visited countries:<br>
<c:forEach var="t" items="${student.coutries}">
<li> ${t} </li>
</c:forEach><br>
Known OS by student : <br>
<c:forEach var="t" items="${student.knownOs}">
<li> ${t} </li>
</c:forEach><br>
Student course : ${student.course}<br>
</body>
</html>
Every time to try lastName validation, I am leaving it blank. I am being redirected to same Student Form but with no error messages.
Is there any way to show validation error message in this jsp form.

Answer 1

I changed my Student Controller class to below code. Basically I used RedirectAttributes in my processStudent mapping. I also separate out the spring form element making maps to different methods. In studentForm I checked if student already exist (due to after validation process in processStudent mapping). Please see code:
Student-Controller class
package com.sikka.springmvcworking.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;
import java.util.*;
import javax.validation.Valid;
import com.sikka.springmvcworking.custombeans.Student;
#Controller
#RequestMapping("stu")
public class StudentController {
#RequestMapping("studentForm")
public String getStudentForm(Model model) {
Student student = new Student();
student.setCountryMap(getCountryMap());
student.setCourseMap(getCourseMap());
student.setKosMap(getKosMap());
if (!model.containsAttribute("student")) {
System.out.println("student not there");
model.addAttribute("student",student);
}
else {
System.out.println("student already there");
}
return "STUDENT-FORM";
}
#RequestMapping("processStudent")
public String outputStudent(#Valid #ModelAttribute("student") Student student, BindingResult bindingResult,RedirectAttributes attr) {
if(bindingResult.hasErrors()) {
attr.addFlashAttribute("org.springframework.validation.BindingResult.student", bindingResult);
student.setCountryMap(getCountryMap());
student.setCourseMap(getCourseMap());
student.setKosMap(getKosMap());
attr.addFlashAttribute("student", student);
return "redirect:studentForm";
}
return "VIEW-STUDENT";
}
private Map<String,String> getCountryMap(){
Map<String,String> countryMap = new LinkedHashMap<String,String>();
countryMap.put("IN", "INDIA");
countryMap.put("BR", "BRAZIL");
countryMap.put("MX", "MEXICO");
return countryMap;
}
private Map<String,String> getCourseMap(){
Map<String,String> courseMap = new LinkedHashMap<String,String>();
courseMap.put("java", "JAVA");
courseMap.put(".net", ".NET");
courseMap.put("php", "PHP");
courseMap.put("andr", "ANDROID");
return courseMap;
}
private Map<String,String> getKosMap(){
Map<String,String> kosMap = new LinkedHashMap<String,String>();
kosMap.put("win", "WINDOWS");
kosMap.put("lnx", "LINUX");
kosMap.put("mac", "MACINTOSH");
return kosMap;
}
}
Above approach solved my problem. I am not an expert in spring. Anyone out here can explain more deeply.