Table of Contents
1. Overview
In this article, we’ll look at the use of the core org.springframework.ui.Model, org.springframework.ui.ModelMap and org.springframework.web.servlet.ModelAndView provided by Spring MVC.
2. Maven Dependencies
Let’s start with the spring-context dependency in our pom.xml file:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.2.2.RELEASE</version>
</dependency>
The latest version of spring-context dependency can be found here.
For the ModelAndView, the spring-web dependency is required:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>5.2.2.RELEASE</version>
</dependency>
The latest versions of spring-web dependency can be found here.
And, if we use Thymeleaf as our view, we should add this dependency to pom.xml:
<dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf-spring5</artifactId>
<version>3.0.11.RELEASE</version>
</dependency>
The latest version of Thymeleaf dependency can be found here.
3. Model
Let’s start with the most basic concept here – the Model.
Simply put, the model can supply attributes used for rendering views.
To provide a view with usable data, we simply add this data to its Model object. Additionally, maps with attributes can be merged with Model instances:
@GetMapping("/showViewPage")
public String passParametersWithModel(Model model) {
Map<String, String> map = new HashMap<>();
map.put("spring", "mvc");
model.addAttribute("message", "VietMX");
model.mergeAttributes(map);
return "viewPage";
}
4. ModelMap
Just like the Model interface above, ModelMap is also used to pass values to render a view.
The advantage of ModelMap is it gives us the ability to pass a collection of values and treat these values as if they were within a Map:
@GetMapping("/printViewPage")
public String passParametersWithModelMap(ModelMap map) {
map.addAttribute("welcomeMessage", "welcome");
map.addAttribute("message", "VietMX");
return "viewPage";
}
5. ModelAndView
The final interface to pass values to a view is the ModelAndView.
This interface allows us to pass all the information required by Spring MVC in one return:
@GetMapping("/goToViewPage")
public ModelAndView passParametersWithModelAndView() {
ModelAndView modelAndView = new ModelAndView("viewPage");
modelAndView.addObject("message", "VietMX");
return modelAndView;
}
6. The View
All the data, we place within these models, is used by a view – in general, a templated view to render the web page.
If we have a Thymeleaf template file targeted by our controller’s methods as their view. A parameter passed through the model will be accessible from within the thymeleaf HTML code:
<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<title>Title</title>
</head>
<body>
<div>Web Application. Passed parameter : th:text="${message}"</div>
</body>
</html>
The parameter passed here is used through the syntax ${message}, which is known as a placeholder. The Thymeleaf template engine will replace this placeholder with an actual value from an attribute of the same name passed through the model.
7. Conclusion
In this quick tutorial, we’ve discussed three core concepts in Spring MVC – the Model, the ModelMap and the ModelAndView. We also had a look at examples of how the view can make use of these values.
As always, the implementation of all these examples and code snippets can be found over on Github.
