Java Code Guru Ji (8920128728): Spring MVC Internationalization (i18n) and Localization (i10n) Example

Internationalization is the process of designing a software application so that it can potentially be adapted to various languages and regions without engineering changes. Localization is the process of adapting internationalized software for a specific region or language by adding locale-specific components and translating text [Wiki]. Spring framework is shipped with LocaleResolver to support the internationalization and thus localization as well. This tutorial will help you in learning how to add internationalization support in your spring mvc based web application.

Table of Contents

1) Adding locale specific message resources
2) Adding LocaleResolver configuration in spring context
3) JSP changes to display locale specific messages
4) Project Structure
5) Testing the Application
6) Other Project Files

Let’s start analyzing the changes which you will need to make for adding i18n support into your spring web application.

1) Adding locale specific message resources

If you want to support multiple locales, then first step is obliviously to have each locale specific properties file having texts in that locale specific language. In our example, I am supporting two locales. First is United States with language English, and second locale is Chinese.

messages.properties

lbl.Id=Employee Id

lbl.firstName=First Name

lbl.lastName=First Name

lbl.page=All Employees in System

messages_zh_CN.properties

lbl.Id=\u5458\u5DE5ID

lbl.firstName=\u540D\u5B57

lbl.lastName=\u59D3

lbl.page=\u7CFB\u7EDF\u4E2D\u7684\u6240\u6709\u5458\u5DE5

Notice the naming convention for these properties files. Locale specific files have locale short-code appended into their name.

2) Adding LocaleResolver configuration in spring context

To make Spring MVC application supports the internationalization, you will need to register two beans.

1. SessionLocaleResolver

SessionLocaleResolver resolves locales by inspecting a predefined attribute in a user’s session. If the session attribute doesn’t exist, this locale resolver determines the default locale from the accept-language HTTP header.

<bean id="localeResolver" class="org.springframework.web.servlet.i18n.SessionLocaleResolver">

    <property name="defaultLocale" value="en" />

</bean>

2. LocaleChangeInterceptor

LocaleChangeInterceptor interceptor detects if a special parameter is present in the current HTTP request. The parameter name can be customized with the paramName property of this interceptor. If such a parameter is present in the current request, this interceptor changes the user’s locale according to the parameter value.

<bean id="localeChangeInterceptor" class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">

    <property name="paramName" value="lang" />

</bean>

<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">

    <property name="interceptors">

        <list>

            <ref bean="localeChangeInterceptor" />

        </list>

    </property>

</bean>

The complete application context file for this application looks like this:

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xmlns:context="http://www.springframework.org/schema/context"

    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.howtodoinjava.demo" />

    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">

        <property name="prefix" value="/WEB-INF/views/" />

        <property name="suffix" value=".jsp" />

    </bean>

    <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">

        <property name="basename" value="messages" />

    </bean>

    <bean id="localeResolver" class="org.springframework.web.servlet.i18n.SessionLocaleResolver">

        <property name="defaultLocale" value="en" />

    </bean>

    <bean id="localeChangeInterceptor" class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">

        <property name="paramName" value="lang" />

    </bean>

    <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">

        <property name="interceptors">

            <list>

                <ref bean="localeChangeInterceptor" />

            </list>

        </property>

    </bean>

</beans>

3) JSP changes to display locale specific messages

Next step is to make view changes to support displaying locale specific text messages. This can be done using spring TLDs in below manner.

<%@ page contentType="text/html;charset=UTF-8" %>

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>

<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>

<html>

<head>

    <title>Spring MVC Hello World</title>

</head>

<body>

    <h2><spring:message code="lbl.page" text="All Employees in System" /></h2>

    <table border="1">

        <tr>

            <th><spring:message code="lbl.Id" text="Employee Id" /></th>

            <th><spring:message code="lbl.firstName" text="First Name" /></th>

            <th><spring:message code="lbl.lastName" text="Last Name" /></th>

        </tr>

        <c:forEach items="${employees}" var="employee">

            <tr>

                <td>${employee.id}</td>

                <td>${employee.firstName}</td>

                <td>${employee.lastName}</td>

            </tr>

        </c:forEach>

    </table>

</body>

</html>

4) Project Structure

The complete structure for this application is this:

5) Testing the Application

Hit the URL : http://localhost:8080/springmvcexample/employee-module/getAllEmployees

As you see that all labels are displayed in English language.

Spring i18n - En Locale — Spring i18n – En Locale

Hit the URL : http://localhost:8080/springmvcexample/employee-module/getAllEmployees?lang=zh_CN

Now, locale has been changed to chinese and all labels are displayed in chinese language.

Spring i18n - CN Locale — Spring i18n – CN Locale

6) Other Project Files

Let’s list down other files involved into this application.

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 Web MVC Hello World Application</display-name>

    <servlet>

        <servlet-name>spring</servlet-name>

            <servlet-class>

                org.springframework.web.servlet.DispatcherServlet

            </servlet-class>

        <load-on-startup>1</load-on-startup>

    </servlet>

    <servlet-mapping>

        <servlet-name>spring</servlet-name>

        <url-pattern>/</url-pattern>

    </servlet-mapping>

</web-app>

EmployeeController.java

package com.howtodoinjava.demo.controller;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import com.howtodoinjava.demo.service.EmployeeManager;

@Controller

@RequestMapping("/employee-module")

public class EmployeeController 

{

    @Autowired

    EmployeeManager manager;

    @RequestMapping(value="/getAllEmployees", method = RequestMethod.GET)

    public String welcome(Model model) 

    {

        model.addAttribute("employees",manager.getAllEmployees());

        return "employeesListDisplay";

    }

}

EmployeeDAO.java

package com.howtodoinjava.demo.dao;

import java.util.List;

import com.howtodoinjava.demo.model.EmployeeVO;

public interface EmployeeDAO 

{

    public List<EmployeeVO> getAllEmployees();

}

EmployeeDAOImpl.java

package com.howtodoinjava.demo.dao;

import java.util.ArrayList;

import java.util.List;

import org.springframework.stereotype.Repository;

import com.howtodoinjava.demo.model.EmployeeVO;

@Repository

public class EmployeeDAOImpl implements EmployeeDAO {

    public List<EmployeeVO> getAllEmployees() 

    {

        List<EmployeeVO> employees = new ArrayList<EmployeeVO>();

        EmployeeVO vo1 = new EmployeeVO();

        vo1.setId(1);

        vo1.setFirstName("Lokesh");

        vo1.setLastName("Gupta");

        employees.add(vo1);

        EmployeeVO vo2 = new EmployeeVO();

        vo2.setId(2);

        vo2.setFirstName("Raj");

        vo2.setLastName("Kishore");

        employees.add(vo2);

        return employees;

    }

}

EmployeeManager.java

import java.util.List;

import com.howtodoinjava.demo.model.EmployeeVO;

public interface EmployeeManager 

{

    public List<EmployeeVO> getAllEmployees();

}

EmployeeManagerImpl.java

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import com.howtodoinjava.demo.dao.EmployeeDAO;

import com.howtodoinjava.demo.model.EmployeeVO;

@Service

public class EmployeeManagerImpl implements EmployeeManager {

    @Autowired

    EmployeeDAO dao;

    public List<EmployeeVO> getAllEmployees() 

    {

        return dao.getAllEmployees();

    }

}

EmployeeVO.java

package com.howtodoinjava.demo.model;

import java.io.Serializable;

public class EmployeeVO implements Serializable 

{

    private static final long serialVersionUID = 1L;

    private Integer id;

    private String firstName;

    private String lastName;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    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;

    }

    @Override

    public String toString() {

        return "EmployeeVO [id=" + id + ", firstName=" + firstName

                + ", lastName=" + lastName + "]";

    }

}

Please let me know if any queries or thoughts.

Java Code Guru Ji (8920128728)

Saturday, April 18, 2020

Spring MVC Internationalization (i18n) and Localization (i10n) Example