ModelMap

Model is a class in the spring core package under com.springframework.ui and is used for transferring the data or attributes from our business logic to the rendering view pages. It is an extension of the Model interface, as it also implements the java.util.Map to provide a Map-like structure to access the attributed with the Key-Value pair fashion.

It is fully compatible with the Model objects and also has additional methods implemented from the Map interface.

Create a simple Controller named LoginController under the package src/main/java/com/example/springmodelsdemo/controller using the @Controller Annotation
Create a method to map it for login requests and pass a ModelMap object to it, so Spring will provide it for us.
addAttribute(String name, Object obj) is used to add the objects to the Model object.
Use the put(String name, Object obj) method to easily add attributes with the key-value pair fashion.
return the view so that the view will have access to this ModelMap object while rendering, as we have added the attributes the rendering view can use it to display the data from this model.

Java

// Controller layer for Login Page 
// Using ModelMap 
  
package com.example.springmodelsdemo.controller; 
  
import org.springframework.stereotype.Controller; 
import org.springframework.ui.Model; 
import org.springframework.ui.ModelMap; 
import org.springframework.web.bind.annotation.GetMapping; 
import org.springframework.web.bind.annotation.RequestParam; 
import org.springframework.web.servlet.ModelAndView; 
  
// A simple controller using spring 
// web annotations 
@Controller
public class LoginController { 
    
    // returning the login jsp 
    // for root of the webpage 
    @GetMapping("/")  
      public String home(){ 
        return "login.jsp"; 
    } 
  
    // mapping the /login request 
    // requestparam is used to get the value 
    // from get request parameters 
    @GetMapping("/login") 
    public String loginActionUsingModelMap( 
        @RequestParam("name") String name, 
        @RequestParam("password") String pass, 
        ModelMap model 
    ){ 
        
        model.addAttribute("userName", name); 
        
          // supports the use of put method 
          // from java.util.Map interface 
        model.put("password", pass); 
        return "result.jsp"; 
    } 
} 

Output:

output gif

Model, ModelMap, ModelAndView in Spring MVC

Spring is one of the most used Java-based frameworks for creating enterprise-grade applications in Java. In that Spring MVC was one of the popular projects under the Spring family of Java projects. In this article, we will explore how Model, ModelMap, and ModelAndView work in Spring MVC.

Spring MVC follows the Model-View-Controller (MVC) pattern to break down the application into three individual components called MVC. Model, ModelMap, and ModelAndView create a flow of data from the Model and View in the MVC pattern.

To reduce the configuration works we will be using Spring Boot to bootstrap the Spring project.

Prerequisite:

To continue with this article you should be comfortable with the following topics to easily understand and go through the article.

Java – Core and Advanced Java
Servlets & JSP’s
Spring & Spring MVC
Maven & Eclipse or IDE which supports Java

Initial Setup:

Go to the Spring Starter set webpage to create a simple spring boot app.
Enter your required group and artifactId for the project.
Add the below dependencies.
- Spring Web for creating the MVC application
- Spring Devtools to automatically reload the app after changes.

spring starter

Download the zip, extract it, and open the project in your favorite IDE.

Open the pom.xml to add the tomcat-jasper library to the dependency of your project
spring mvc can work with .jsp files as a response.

XML

<?xml version="1.0" encoding="UTF-8"?> 
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> 
  
<modelVersion>4.0.0</modelVersion> 
<parent> 
    <groupId>org.springframework.boot</groupId> 
    <artifactId>spring-boot-starter-parent</artifactId> 
    <version>3.2.0</version> 
    <relativePath /> <!-- lookup parent from repository -->
 </parent> 
    
 <groupId>com.example</groupId> 
 <artifactId>springmodelsdemo</artifactId> 
 <version>0.0.1-SNAPSHOT</version> 
 <name>springmodelsdemo</name> 
 <description>Demo project for spring model, modelmap, modelandview</description> 
 <properties> 
   <java.version>17</java.version> 
 </properties> 
    
<dependencies> 
    <dependency> 
      <groupId>org.springframework.boot</groupId> 
      <artifactId>spring-boot-starter-web</artifactId> 
    </dependency> 
    <dependency> 
        <groupId>org.apache.tomcat</groupId> 
        <artifactId>tomcat-jasper</artifactId> 
        <version>10.1.16</version> 
    </dependency> 
    <dependency> 
        <groupId>org.springframework.boot</groupId> 
        <artifactId>spring-boot-devtools</artifactId> 
        <scope>runtime</scope> 
        <optional>true</optional> 
    </dependency> 
    <dependency> 
        <groupId>org.springframework.boot</groupId> 
        <artifactId>spring-boot-starter-test</artifactId> 
        <scope>test</scope> 
    </dependency> 
</dependencies> 
  
 <build> 
    <plugins> 
      <plugin> 
        <groupId>org.springframework.boot</groupId> 
        <artifactId>spring-boot-maven-plugin</artifactId> 
      </plugin> 
    </plugins> 
 </build> 
  
</project> 

Create a web app folder under the src/main parent directory to store the .jsp and static resources for the project.
Add the below styles under the resources/static/css/ with the file name style.css

This file contains all the style related to web design to make the center-aligned.

CSS

* { 
    font-size: 20px; 
    font-family: Verdana; 
} 
  
.container { 
    min-height: 100vh; 
    display: flex; 
    justify-content: center; 
    align-items: center; 
    flex-direction: column; 
    display: flex; 
} 
  
.row { 
    margin: 1rem; 
} 
  
.btn { 
    padding: 8px; 
    border-radius: 5px; 
}

Create a login.jsp file under the web app folder to host a form to pass some data to the Spring MVC, add the below code.

This HTML file contains the frontend form with two input fields i.e. username, password

HTML

<%@ page language="java" contentType="text/html"%> 
    
<!DOCTYPE html> 
<head> 
    <title>Welcome</title> 
    <link rel="stylesheet" href="/css/style.css"> 
</head> 
<body> 
    <div class="container"> 
        <form action="login"> 
            <div class="row"> 
                <label for="name">Enter your username:</label> <input type="text"
                    id="name" name="name"> 
            </div> 
            <div class="row"> 
                <label for="pass">Enter your Password:</label> <input
                    type="password" id="pass" name="password"> 
            </div> 
            <div class="row"> 
                <button class="btn">Submit</button> 
            </div> 
        </form> 
    </div> 
</body> 
</html>

After that create a result.jsp file under the web app folder to show the view of the resultant data from Spring MVC.

This HTML code contains frontend display of username and password stored in the previous page.

HTML

<%@ page language="java" contentType="text/html"%> 
<!DOCTYPE html> 
  <head> 
    <title>Welcome</title> 
    <link rel="stylesheet" href="/css/style.css" /> 
  </head> 
  <body> 
      <div class="container"> 
          <div class="row">Your Username is: ${userName}</div> 
          <div class="row">Your Password is: ${password}</div> 
      </div> 
  </body> 
</html>

Now we have configured our project for the initial setup and can continue with the Model, ModelMap, and ModelAndView explanation.

Tags:

#Geeks Premier League 2023 #Java-Spring-MVC #Advance Java #Geeks Premier League #Java #Java

Model:

ModelAndView:

ModelMap

Java

Output:

Model, ModelMap, ModelAndView in Spring MVC

Prerequisite:

Initial Setup:

XML

CSS

HTML

HTML

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