Spring MVC Tutorial

Spring MVC tutorial provides an elegant solution to use MVC in spring framework by the help of DispatcherServlet.

In Spring Web MVC, DispatcherServlet class works as the front controller. It is responsible to manage the flow of the spring mvc application.

The @Controller annotation is used to mark the class as the controller in Spring 3.

The @RequestMapping annotation is used to map the request url. It is applied on the method.

Understanding the flow of Spring Web MVC

As displayed in the figure, all the incoming request is intercepted by the DispatcherServlet that works as the front controller. The DispatcherServlet gets entry of handler mapping from the xml file and forwards the request to the controller. The controller returns an object of ModelAndView. The DispatcherServlet checks the entry of view resolver in the xml file and invokes the specified view component.

Spring MVC Hello World Example

In this application, I am creating most simple employee management application demo having only one feature i.e. list all available employees in system. Let’s note down the directory structure of this application.

pom.xml
Below pom.xml file contains dependencies for spring mvc and taglibs support for writing jsp files.

web.xml

This minimum web.xml file declares one servlet (i.e. dispatcher servlet) to receive all kind of requests. Dispatcher servlet here acts as front controller

    

spring-servlet.xml (You can have applicationContext.xml as well)

We are using annotated classes at request handler, service and dao layer so I have enabled annotation processing for all class files in base package “com.teachtojava.demo“.

   

EmployeeController.java

Annotation @RequestMapping at class level and method level determine the URL at which method will be invoked.

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.teachtojava.demo.service.EmployeeManager;

@Controller

@RequestMapping("/employee-module")

public class EmployeeController

{

    @Autowired

    EmployeeManager manager;

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

    public String getAllEmployees(Model model)

    {

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

        return "employeesListDisplay";

    }

}

EmployeeVO.java

This class act as model for MVC pattern.

package com.teachtojava.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;

    //Setters and Getters

    @Override

    public String toString() {

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

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

    }

}

EmployeeDAO.java

The classes at third tier in 3-tier architecture. Responsible for interacting with underlying DB storage.

import java.util.List;

import com.teachtojava.demo.model.EmployeeVO;

public interface EmployeeDAO

{

    public List getAllEmployees();

}

EmployeeDAOImpl.java

import java.util.ArrayList;

import java.util.List;

import org.springframework.stereotype.Repository;

import com.teachtojava.demo.model.EmployeeVO;

@Repository

public class EmployeeDAOImpl implements EmployeeDAO {

    public List getAllEmployees()

    {

        List employees = new ArrayList();

        

        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

The classes at second tier in 3-tier architecture. Responsible for interacting with DAO Layer.

import java.util.List;

import com.teachtojava.demo.model.EmployeeVO;

public interface EmployeeManager

{

    public List getAllEmployees();

}

EmployeeManagerImpl.java

import java.util.List;

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

import org.springframework.stereotype.Service;

import com.teachtojava.demo.dao.EmployeeDAO;

import com.teachtojava.demo.model.EmployeeVO;

@Service

public class EmployeeManagerImpl implements EmployeeManager {

     @Autowired

    EmployeeDAO dao;

    

    public List getAllEmployees()

    {

        return dao.getAllEmployees();

    }

}

employeesListDisplay.jsp

This jsp is used to display all the employees in system. It iterates the collection of employees in loop, and print their details in a table. This fits into view layer of MVC pattern.

Now deploy the application in your application server (i am using tomcat 7). And hit the URL “http://localhost:8080/springmvcexample/employee-module/getAllEmployees“. You will see below screen if you have configured everything correctly.