Setup Spring Boot in Maven Project in Eclipse Part 2

Posted Jul 16, 2021

By Harshit Yadav

5 min read

1. Clean

Clean the Server Instance

2. pom.xml

Go to the File pom.xml of the project and add the following dependencies below the existing “junit” dependency already created when creating a maven , to add more dependencies or latest dependencies go toMVNRepository, search for the dependency you want to add it will give yout snippet to add that dependency

Link :https://mvnrepository.com/

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-webmvc</artifactId>

<version>5.3.8</version>

</dependency>

<dependency>

<groupId>javax.servlet</groupId>

<artifactId>javax.servlet-api</artifactId>

<version>4.0.1</version>

<scope>provided</scope>

</dependency>

<dependency>

<groupId>javax.servlet</groupId>

<artifactId>jstl</artifactId>

<version>1.2</version>

</dependency>

3. home.jsp

In the created project go to directory

/<Project Name >/src/main/webapp/WEB-INF

and rename the existing index.jsp-> home.jsp with the following code replacing the default hello world template

<!Doctype html PUBLIC >

<html>

<head>

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1" isELIgnored="false"%>

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />

<title>Spring MVC Page</title>

</head>

<body>

<h1>Welcome to Spring MVC !</h1>

<span>Using programmatic application context and controllers</span>

</body>

</html>

4. Create New Class

Create a new class that will specify the application context of this app this is going to be a java class in the java folder at the following location and create a new java class named “ ApplicationContextConfiguration”

<projectname>/main/java

Application Context

Spring configuration file which holds the Bean definition for our spring app

This is the file that hold the bean definition for our spring app
These are property that apply as a whole and are not specific to Spring MVC
We are defining these file pro grammatically then creating it using XML configuration

5. Import Libraries

Add the following libraries to the package

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.servlet.mvc.Controller;

import org.springframework.web.servlet.view.InternalResourceViewResolver;

so that it looks like this

6. @Configuration

Any programmatic configuration in java has to be annotated with @Configuration , annotation

It is part of Core spring framework
This indicates that this class has the BEAN methods
The Spring framework will look for classes tagged with
“@” and pick up the bean defination from this class

7. Specifying the Bean

The Bean specified is “viewResolver”
View resolver can be thought of as logical mapping from view names to specific kind of view this allows to render views without being tied to specific view technology
By Always specifying views within the app with their logical names rather then physical implementation allows us to decouple app from how views are actually implemented

@Bean(name="viewResolver")

Any time there is need for viewResolver within our application this internal resource viewResolver is what will be injected into that object.

Mapping a logical view to actual view is role of view resolver

viewResolver.setPrefix("/");

The directory corresponds to root director that is “ WEB-INF” folder

viewResolver.setSuffix(".jsp");

Suffix for all views pages

the whole class will look like this:

8. MessageDisplayController Class

Create the class same way as created in the previous step just this time name the class as the “ MessageDisplayController”

This is going to be MessageControl object that will handle the incoming web request from our web application users , access the model update the model state if needed and respond with corresponding view

Setup the libraries within the controller

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.ModelAndView;

import org.springframework.web.servlet.mvc.Controller;

Have this controller implement Controller Interface is an explicit specification

public class MessageDisplayController implements Controller {}

Any class implementing this interface should be able to handle http web request in a thread safe manner
Notice the input arguments are http servlet request and http servlet response
View simply return the model to be rendered using the

return new ModelAndView(“home”);

The ModelAndView in MVC contain the model map as well as a view
The name of the view is simply “home”
This model will be recieved by the dispatcher servlet to be rendered

@Override

public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception

{

return new ModelAndView("home");

}

9. Setting Controller Bean

Next in the ApplicationContextConfiguration.java class add the following bean

@Bean(name="/")

public Controller getMessageDisplayController()

{

return new MessageDisplayController();

}

Returns the object of the controller interface instantiated
/ corresponds the the root of the web application
This is the handler mapping
Any request made to the root of the web application , will be given to this controller to handle that request

10. Setup the WebServletConfiguration

Create Another Class in the java/main folder name WebServletConfiguration

And add in the following libraries

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.ServletRegistration;

import org.springframework.web.WebApplicationInitializer;

import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;

import org.springframework.web.servlet.DispatcherServlet;

These libraries are spring specific not Spring MVC specific
This is the class we are going to use programatically configure the servlet

add the following inheritance

implements WebApplicationInitializer

It allows to configure server context programmatically
Any implementation of this web application initializer interface is automatically detected by the spring servlet container
It will be included as the bootstrap process for the servlet container

@Override

public void onStartup(ServletContext ctx) throws ServletException {

AnnotationConfigWebApplicationContext appContext = new AnnotationConfigWebApplicationContext();

appContext.register(ApplicationContextConfiguration.class);

ServletRegistration.Dynamic servlet = ctx.addServlet("dispatcher", new DispatcherServlet(appContext));

servlet.setLoadOnStartup(1);

servlet.addMapping("/");

}

onStartup is part of webInitializer startup interface
Servlet context will be inject into the spring
On startup of the application register the context of the application
In Spring MVC Application we need to explicitly register the dispatcher servlet

The code for this class will look like this

public class WebServletConfiguration  implements WebApplicationInitializer{

@Override

public void onStartup(ServletContext ctx) throws ServletException {

AnnotationConfigWebApplicationContext appContext = new AnnotationConfigWebApplicationContext();

appContext.register(ApplicationContextConfiguration.class);

ServletRegistration.Dynamic servlet = ctx.addServlet("dispatcher", new DispatcherServlet(appContext));

servlet.setLoadOnStartup(1);

servlet.addMapping("/");

}

}

11. Now to Build the Application

12 . Update Maven Project

Clean Server
Run Maven Build
Refresh and check “Target” Folder to see the new Build files created
Lookout for .war file
Under controller folder there will be .class folder for every file in the project
Can Also Clean Eclipse Cache from top bar » project » clean
Run the Server , on tomacat

Reference

Original Medium article

Spring Boot

This post is licensed under CC BY 4.0 by the author.