I configured a Basic Spring Boot app containing Hibernate. However, no page is being rendered.
I have places my pages in src/main/resources/templates/ and content(CSS and JS) in src/main/resources/static/
I have added Thymeleaf through Maven and written a basic controller to render my page -
#RestController
#RequestMapping("/testui")
public class GreetingController {
#RequestMapping("/greeting")
public String greeting(#RequestParam(value="name", required=false, defaultValue="World") String name, Model model) {
model.addAttribute("name", name);
return "greeting";
}
}
Instead of rendering a page with my name, it is rendering the string - "greeting"
I have placed the greeting.html in templates file. What are the changes in application.properties I need to make to render pages (what keys and values must I give?)
Update - I somehow do not have the webapp folder. Added that. Created a folder called jsp and added a simple page. Referenced it - didnt work
Why is it not working?
Because you are using #RestController. #RestController is used to create API controllers which serve JSON/XML, whereas #Controller is used to create controllers which serve web content such as HTML.
Proposed solution
Replace #RestController with #Controller. For further details, please see the official Getting Started guide of Spring.
You've added #RestController on the Controller class, which means that you want all values returned by the controller methods to be considered as response body (that's the equivalent of annotating all controller methods with #ResponseBody).
Remove that annotation from the class and replace it with #Controller and you should get the expected result.
Related
How can I get Spring Boot and Thymeleaf to automatically find and map template files to be processed when accessed by the browser?
src/main/resources/templates/index.xhtml
src/main/resources/templates/bar.xhtml
src/main/resources/application.properties contains spring.thymeleaf.suffix=.xhtml
FooController.java contains #RequestMapping("/foo") and a #PostMapping method that returns bar
If I enter http://localhost:8080/ in the browser, Thymeleaf processes and displays the index.xhtml page with no extra configuration needed. But http://localhost:8080/index, http://localhost:8080/index.xhtml, and http://localhost:8080/index.html all result in 404 Not Found.
My index view does a POST to foo; FooController is activated and returns bar; and Thymeleaf processes and shows bar.xhtml, even though bar.xhtml isn't mapped anywhere in the configuration. Yet accessing http://localhost:8080/bar, http://localhost:8080/bar.xhtml, and http://localhost:8080/bar.html in a browser all result in 404 Not Found.
Why does GET http://localhost:8080/ process the index.xhtml template, but GET http://localhost:8080/index does not?
How can Thymleaf use bar as a view, but I cannot access http://localhost:8080/bar directly?
How can I configure Thymeleaf so that I can add src/main/resources/templates/example.xhtml and have it processed automatically as a template that I can access via http://localhost:8080/example in the browser, with no explicit configuration specifically for the example.xhtml file?
If I absolutely have to configure controllers (see my answer below), is there a way that I can at least do this in some declarative file, outside of my code?
As noted in Spring in Action, Fifth Edition, I can do something like this in a #Configuration class that implements WebMvcConfigurer
#Override
public void addViewControllers(final ViewControllerRegistry registry) {
registry.addViewController("/bar");
}
That will allow me to process bar.xhtml automatically. (I presume there is some default configuration registry.addViewController("/").setViewName("index"), which is why my index.xhtml file is getting processed by accessing the root path.
And I can even use the following to automatically pick up any template:
#Override
public void addViewControllers(final ViewControllerRegistry registry) {
registry.addViewController("/**");
}
Unfortunately this removes the mapping from / to /index, and also prevents accessing any static resources from src/main/resources. I'm not sure how to tell Thymeleaf to use a template if it can, and fall back to a static file if not.
How can I keep links in my UI templates (e.g. Thymeleaf templates) in sync with the corresponding request mappings in my Spring application?
I've seen that e.g. the Play framework uses the #router-Object within its templates. How is it solved by Spring?
One example:
Spring Controller - simple
#Controller
public class UserController {
#GetMapping("/users/{username}")
public String getUser(#PathParam String username) {
// do some stuff....
return "user";
}
}
HTML-Page
<body>
User details
</body>
Now I want to change "/users" to "/accounts". I'm pretty sure that I've got to update every html page by hand to update the link. Is there an easier solution for this?
As far as I know, there is no simple way to do this with built-in tools from Spring. However, I don't think that this would be too hard to build. You would need the following:
A YAML file with all of your URL templates defined
A Properties Spring bean that contains your URL mappings (read from the YAML file)
All of your #RequestMapping annotations would have to be prop values; i.e.
#GetMapping("${urls.users.byUsername}")
A custom tag that knows about the Properties bean and can create URLs from the templates that were defined in your YAML file.
Since REST based controller methods only return objects ( not views ) to the client based on the request, how can I show view to my user ? Or maybe better question what is a good way to combine spring-mvc web app with REST, so my user always get the answer, not in just ( for example ) JSON format, but also with the view ?
So far as I understood, REST based controller would be perfectly fitting to the mobile app ( for example twitter ), where views are handled inside the app and the only thing server has to worry about is to pass the right object to the right request. But what about the web app ?
I might be wrong in several things ( correct me if I am ), since I am trying to understand REST and I am still learning.
To simplify things - you basically have two options:
1) Build Spring MVC application.
2) Build REST backend application.
In case of first option - within your application you will have both backend and frontend (MVC part).
In case of second option you build only backend application and expose it through REST API. In most cases, you will need to build another application - REST client for your application. This is more flexible application because it gives you opportunity to access your backend application from various clients - for example, you can have Android, IOS applications, you can have web application implemented using Angular etc...
Please note, that thins are not so simple, you can within one application have both REST backend and REST client etc... This is just very very simplified in order that you get some general picture. Hope this clarified a little things.
There is some additional clarification related to REST and views worth learning. From your question, I can see that you mean "view" in a sense of UI(user interface) and typical MVC usage. But "view" can mean different things in a different contexts.
So:
JSON can be considered as a view for data
JSON is a representation of the resource, just like HTML is
JSON doesn't have style (unless you are not using a browser
extension, which most the users are not using)
The browser is recognizing HTML as a markup language and applying a
style to it
Both are media types
Both JSON and HTML are data formats
Both can be transferred over the wire
This method returns a view
#RequestMapping("/home")
String home(Model model) {
return "home"; // resources\templates\home.html
}
This method Returns String
#RequestMapping(value = "/home")
#ResponseBody
public String home() {
return "Success";
}
If you annotate a method with #ResponseBody, Spring will use a json mapper to generate the response. Instead of annotating every method with #ResponseBody you can annotate your class with #RestController.
If you want to return a view, you need to annotate the class with #Controller instead of #RestController and configure a viewresolver. Bij default spring will use thymeleaf as a viewresolver if you have spring-web as a dependency on the classpath. The return type of the method is a String that references the template to be rendered. The templates are stored in src/main/resources/templates.
You can find a guide on the spring website: https://spring.io/guides/gs/serving-web-content/
I am pretty new to Spring Boot, and I saw that if I start a Spring Boot project and put an index.html file in the folder src/main/resources/static, then when I open my browser and go to address "localhost:8080", I'll see this file displayed in the browser.
Now, I have another html file (let's call it 'hello.html'), and I also placed it in src/main/resources/static. I wrote the following code:
#Configuration
#Controller
#EnableAutoConfiguration
#ComponentScan
public class TopicController {
#RequestMapping("/hello")
public String hello() {
return "hello.html";
}
}
As you can understand, I want that when I go to localhost:8000/hello, I'll see the display of 'hello.html' file.
However, I get the following error in the console:
javax.servlet.ServletException: Circular view path [hello.html]: would
dispatch back to the current handler URL [/hello.html] again. Check your
ViewResolver setup! (Hint: This may be the result of an unspecified
view, due to default view name generation.)
Do you know what I can do so I can get the hello.html file in the browser for accessing "localhost:8080/hello" ?
I just started studying Spring, and I'm so confused.
I just created a new 'Spring Legacy Project' at STS. HomeController and home.jsp are there.
When I run it on server, it comes through the HomeController first, and arrives to home.jsp.
#RequestMapping(value = "/", method = RequestMethod.GET)
public String home(Locale locale, Model model) {
return "home";
}
What makes my project go through the HomeController at the beginning? Should I look at any xml file?
What does value="/" mean in #RequestMapping?
At the home.jsp, I made a button to go 'result.jsp'. From the 'result.jsp' I want to go back to home.jsp. but it doesn't work. What should I do?
<input type="button" value="뒤로 " onclick="javascript:location.href='/views/home.jsp'">
Why isn't this button working? Those two JSP files are in same place.
Your app is deployed to some app server, such as tomcat. The request <app server>/<context root> is handled by the app server to the .war with the appropriate context root, e.g. to your app. Your app uses Spring MVC, so it is Spring's RequestMappingHandlerMapping bean from your .war file that initially handles the request and finds your method that will handle this request. It does so by comparing the path in the request with the value of each method annotated with #RequestMapping.
The annotation #RequestMapping(value="/") of your home() method means that request <app server>/<context root> will be handled by your 'home()' method.
Any request from your JSP will go back to the Spring MVC that will try to map it to the appropriate controller method, i.e. to the method annotated by #RequestMapping with the appropriate path relative to the context root. So if your result.jsp just links to "/", it should bring you to the home() method and then to the home.jsp.