Setup Spring Boot in Maven Project in Eclipse Part 2

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 to MVNRepository , 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
@Overridepublic 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
@Overridepublic 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{@Overridepublic 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 <applicationName>.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

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