In a typical Spring MVC application, @Controller classes are responsible for preparing a model map with data and selecting a view to be rendered. This model map allows for the complete abstraction of the view technology and, in the case of Thymeleaf, it is transformed into a Thymeleaf VariablesMap object that makes all the defined variables available to expressions executed in templates.
Spring model attributes
Spring MVC calls the pieces of data that can be accessed during the execution of views model attributes. The equivalent term in Thymeleaf language is context variables. There are several ways of adding model attributes to a view in Spring MVC. Below you will find some common cases: Add attribute to Model via its `addAttribute` method:
@RequestMapping(value = "message", method = RequestMethod.GET)
public String messages(Model model) {
model.addAttribute("messages", messageRepository.findAll());
return "message/list";
}Return `ModelAndView` with model attributes included:
@RequestMapping(value = "message", method = RequestMethod.GET)
public ModelAndView messages() {
ModelAndView mav = new ModelAndView("message/list");
mav.addObject("messages", messageRepository.findAll());
return mav;
}Expose common attributes via methods annotated with `@ModelAttribute`:
@ModelAttribute("messages")
public List<Message> messages() {
return messageRepository.findAll();
}As you may have noticed, in all the above cases the `messages` attribute is added to the model and it will be available in Thymeleaf views.
In Thymeleaf, these model attributes can be accessed with the following syntax: `${attributeName}` which is a Spring EL expression.
You can access model attributes in views with Thymeleaf as follows:
<tr th:each="message : ${messages}">
<td th:text="${message.id}">1</td>
<td><a href="#" th:text="${message.title}">Title ...</a></td>
<td th:text="${message.text}">Text ...</td>
</tr>Request parameters
Request parameters can be easily accessed in Thymeleaf views. Request parameters are passed from the client to server like:
https://example.com/query?q=Thymeleaf+Is+Great!
Let’s assume we have a `@Controller` that sends a redirect with a request parameter:
@Controller
public class SomeController {
@RequestMapping("/")
public String redirect() {
return "redirect:/query?q=Thymeleaf Is Great!";
}
}In order to access the `q` parameter you can use the `param.` prefix:
<p th:text="${param.q[0]}" th:unless="${param.q == null}">Test</p>Two things are important to notice in the above example:
- `${param.q != null}` checks if the parameter `q` is set
- Parameters are always string arrays, as they can be multivalued (e.g. `https://example.com/query?q=Thymeleaf%20Is%20Great!&q=Really%3F)
Another way to access request parameters is by using the special object `#httpServletRequest` that gives you direct access to the `javax.servlet.http.HttpServletRequest` object:
<p th:text="${#httpServletRequest.getParameter('q')}" th:unless="${#httpServletRequest.getParameter('q') == null}">Test</p>Session attributes
In the below example we add `mySessionAttribute` to session:
@RequestMapping({"/"})
String index(HttpSession session) {
session.setAttribute("mySessionAttribute", "someValue");
return "index";
}Similarly to the request parameters, session attributes can be access by using the `session.` prefix:
<div th:text="${session.mySessionAttribute}">[...]</div>Or by using `#httpSession`, that gives you direct access to the `javax.servlet.http.HttpSession` object.
ServletContext attributes, Spring beans
The full version of this article, that I wrote for thymeleaf.org, with a great help of Daniel Fernández, can be found here: http://www.thymeleaf.org/springmvcaccessdata.html
| Reference: | Spring MVC and Thymeleaf: how to acess data from templates from our JCG partner Rafal Borowiec at the Codeleak.pl blog. |
