Spring @ModelAttribute Annotation with Example





Hey guys in this post we will discuss Spring @ModelAttribute annotation with example.

Overview


@ModelAttribute annotation refers to the Model object in MVC. We can pass @ModelAttribute annotation to method arguments or we can even annotate a method as well.

Passing @ModelAttribute to method argument indicates that the value should bind to the method argument.

public String processForm(@ModelAttribute("person") Person person){
    person.getStuff();
}

Assume that we have a form that is backed by the Person object, when the user submits the form, the values should bind to the method argument with the help of @ModelAttribute annotation.

By annotating @ModelAttribute annotation to method defines the object, which will automatically be added to the Model, and later we can use the Model object inside the view template.

@ModelAttribute("person")
public Person getPerson(){
    return new Person();
}

Here the above method will allow access to the Person object in our View since it gets automatically gets added to the Models by Spring.

Methods annotated with @ModelAttribute are invoked PRIOR TO every @RequestMapping method that is invoked in the same controller class. This is generally used for populating read-only components for a form – eg the values for a select list.

Watch the video


Example on @ModelAttribute


The best way to understand @ModelAttribute annotation is by looking at the example

Create spring boot project


There are many different ways to create a spring boot application, you can follow the below articles to create one –

>> Create spring boot application using Spring initializer
>> Create spring boot application in Spring tool suite [STS]
>> Create spring boot application in IntelliJ IDEA

Add maven dependencies


Open pom.xml and add the following dependencies –

<?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>2.4.3</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>in.bushansirgur</groupId>
	<artifactId>modelattribute</artifactId>
	<version>v1</version>
	<name>modelattribute</name>
	<description>Spring boot model attribute annotation</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-thymeleaf</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</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>

The spring-boot-starter-thymeleaf is a starter for building MVC web applications using Thymeleaf views.




spring-boot-starter-web dependency for building web applications using Spring MVC. It uses the tomcat as the default embedded container. spring-boot-devtools dependency for automatic reloads or live reload of applications.

Create an entity class


Create Customer.java inside the in.bushansirgur.springboot.entity package and add the following content

package in.bushansirgur.springboot.entity;

public class Customer {
	
	private String name;
	
	private Long age;
	
	private String location;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Long getAge() {
		return age;
	}

	public void setAge(Long age) {
		this.age = age;
	}

	public String getLocation() {
		return location;
	}

	public void setLocation(String location) {
		this.location = location;
	}

	@Override
	public String toString() {
		return "Customer [name=" + name + ", age=" + age + ", location=" + location + "]";
	}

	public Customer(String name, Long age, String location) {
		super();
		this.name = name;
		this.age = age;
		this.location = location;
	}
	
}
package in.bushansirgur.springboot.entity;

public class Customer {
	
	private String name;
	
	private Long age;
	
	private String location;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Long getAge() {
		return age;
	}

	public void setAge(Long age) {
		this.age = age;
	}

	public String getLocation() {
		return location;
	}

	public void setLocation(String location) {
		this.location = location;
	}

	@Override
	public String toString() {
		return "Customer [name=" + name + ", age=" + age + ", location=" + location + "]";
	}

	public Customer(String name, Long age, String location) {
		super();
		this.name = name;
		this.age = age;
		this.location = location;
	}
	
}

This is just a plain old java class that has private fields, setters, getters and constructors.

Create a Rest controller


Create CustomerController.java inside the in.bushansirgur.springboot.controller package and add the following content

package in.bushansirgur.springboot.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;

import in.bushansirgur.springboot.entity.Customer;

@Controller
public class CustomerController {
	
	@GetMapping("/customer")
	public String getCustomer () {
		return "customer";
	}
	
	@ModelAttribute("customer")
	public Customer customer() {
		return new Customer("Bushan", 28L, "India");
	}
}

We are annotating @ModelAttribute annotation to customer() method which will return the Customer object. @ModelAttribute methods in a controller are invoked before @RequestMapping methods, within the same controller.

Create a view template


Create customer.html inside the templates folder of src/main/resources and add the following content

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<p th:text="'My name is '+${customer.name}+'. I am '+${customer.age}+' years old and I am living in '+${customer.location}"></p>
</body>
</html>

Run the app


Run the application using the below maven command –

mvn spring-boot:run

Open the browser and enter the following URL

  • http://localhost:8080/customer

Screenshot-2021-03-09-at-7-19-21-PM



About the author

Bushan Sirgur

Hey guys, I am Bushan Sirgur from Banglore, India. Currently, I am working as an Associate project in an IT company.

View all posts

Leave a Reply

Your email address will not be published. Required fields are marked *