I've decided to use custom template engine with Spring MVC framework.
my templates implemented in java and have method for rendering into String:
public String render(Map context);
how to configure spring to make them available in Controller beans as views, for example like:
ModelAndView modelAndView = new ModelAndView("activationPage"); // - view name which will actually be java class name reference.
modelAndView.addObject("validationResult", validationResult);
return modelAndView;
Model will be passed as context in code connecting spring and my template engine.
You need to implement org.springframework.web.servlet.View (which should be easy, you already have something very similar to the render method it needs), as well as org.springframework.web.servlet.ViewResolver, which maps the view names (e.g. "activationPage") on your custom views.
Once you have that, drop a bean of your ViewResolver class into the context, and (unless you've done something else that gets in the way) it should automatically be picked up by Spring and should just work. if you have other ViewResolvers already in there, they may get into a fight over who gets to resolve the view, in which case ask a new question.
Hi I am the author of Rythm template engine, about half year ago I am having the same requirement like you. What I did is to read the source code of Velocity and Freemarker view of SpringFramework. And then create the Rythm view for spring following their approach.
It's easy to follow something that is already there, and it makes your implementation in good quality to follow the official module. Good luck on you :-)
Related
I am currently working on a Spring Boot project and I am fairly new to template engines. This will also be my first own private project with Spring Boot.
I would like to know whether it is necessary to include a template engine, such as Thymeleaf, while developing a web application with Spring Boot. I'm using PostegreSQL for the database.
I read under another post that a template engine is not needed, if the backend framework uses JSON for data exchange, because template engines are for rendering retrieved data to HTML for the client. I retrieve JSON objects from the database, can I leave template engines out of my project then?
If any more details are needed, leave a comment below.
No they aren't necessary, in fact most new projects that require web-pages are using single page applications now like Angular, React, Vue, ... over thymeleaf or jsp.
Aside from that a Spring project doesn't always need web pages, for instance when you are just creating a REST API for other applications to call on, or when you are automating things like: a mail service / printing / ... You name it.
However, when you DO want a simple solution with some pages that aren't all that dynamic or complex, pivotal / VMware does recommend to use thymeleaf (over jsp and other solutions) because it integrates easily.
I read under another post that a template engine is not needed, if the backend framework uses JSON for data exchange, because template engines are for rendering retrieved data to HTML for the client. I retrieve JSON objects from the database, can I leave template engines out of my project then?
This is partly true. Yes, Thymeleaf and alike are mostly intended to render data to HTML. They can render any text data, including JSON, but there are tools better suited for the job. On other hand it does not matter how you store the data in your database or what database you are using. You can't just skip rendering (serializing) the response so it does not matter how you store it. What matters is what you want to return as response. For HTML Thymeleaf or even JSP are suitable, but for JSON you may want to use Jackson or Gson instead.
You didn't mentioned the technology you are going to use, so for my examples I'll assume you intend to use Spring Web MVC. Lets take a look at "traditional" controller:
#Controller
public class GreetingController {
#GetMapping("/greeting")
public ModelAndView greeting(#RequestParam(value = "name", defaultValue = "World") String name) {
return new ModelAndView("greeting", "greeting", new Greeting(name));
}
}
When you make GET request to "/greeting", Spring will call greeting and get the object it returns. In this case it contains the model (the data we want to render) and the view (the template file to use). Then it will try to find a view (something like greeting.html or greeting.jsp) and use template engine like Thymeleaf (or whatever else is configured) to render it (typically to HTML).
What if we want to return JSON instead? In this case we need to:
modify greeting to return Greeting instance instead of ModelAndView
Use RestController instead of Controller. This will tell Spring MVC that we want to directly serialize the object returned to JSON (or similar format) instead of using template to do that.
Here is the modified example:
#RestController
public class GreetingController {
#GetMapping("/greeting")
public Greeting greeting(#RequestParam(value = "name", defaultValue = "World") String name) {
return new Greeting(name);
}
}
Spring MVC still needs some help to serialize the Greeting instance to JSON. But if you use Spring Boot and the web starter, you don't have to worry about it. It will include Jackson for you.
This is in no way exhaustive answer. As a matter of fact it skips a lot of details, but I hope nevertheless it is useful one. If you want to create REST API using JSON, this Building a RESTful Web Service guide is a good place to start. If you follow the Starting with Spring Initializr steps you'll get a project setup with only what is needed (well maybe with a bit extra but I would not worry too much about it).
Does anyone have an example of the new abstract method CreateContainerExtension that is in Prism.Wpf 7.1.0.172-pre? We are using the common service locator and have essentially bypassed IOC in Prism because we need to resolve things before the Bootstrapper has run.
You should remember that Prism is open source and the source code is in itself a form of documentation.
If you're using the classic Bootstrapper, you'll notice that it has been deprecated in favor of PrismApplication. Since your question is extremely vague as to what container you're even trying to use, it's impossible to tell exactly which Container Extension to use, but I will provide an example using Unity for your reference.
Whether you look at the UnityBootstraper or the Unity PrismApplication, you'll see that it simply returns an instance of the UnityContainerExtension.
protected override IContainerExtension CreateContainerExtension()
{
return new UnityContainerExtension();
}
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 provide a highly customisable application to my clients which is working totally by itself. But If one my client wants to overwrite any Controller, I want to replace my implementation by theirs. However just overwriting the controller causes an ambiguous definition of mappings.
I have been using Component Scanning to load beans.
The potential solutions came to my mind are:
Using component scanner with excluding by a custom filter? (This seems not so easy)
Using a xxxxPostProcessor to remove some beans? (How?)
Any help?
If I got your Question properly,
You can differ implementation by changing URL to particular Implementation name
Say Telecom is interface and AirtelImpl and RelianceImpl are Controllers then
Your request mapping
#RequestMapping(value= "/airtel/doBilling")
#RequestMapping(value= "/reliance/doBilling")
In this way, Implementation flow will differ.
I have followed these steps:
Created a custom annotation: #Devoted
Created a custom ImportBeanDefinitionRegistrar. Iterated already registered bean definitions to find out `#Devoted #Controller's and removed them.
Based on a request I will provide implementation details.
I am trying to put a "Contract" on a method call. My web application is in Spring 3.
Is writing customs Annotations the right way to go. If so, any pointers( I didn't find anything in spring reference docs).
Should I use tools like "Modern Jass", JML ...? Again any pointers will be useful.
Thanks
Using Spring EL and Spring security could get you most of the way. Spring security defines the #PreAuthorize annotation which is fired before method invocation and allows you to use Spring 3's new expression engine, such as:
#PreAuthorize("#customerId > 0")
public Customer getCustomer(int customerId) { .. }
or far more advanced rules like the following which ensures that the passed user does not have role ADMIN.
#PreAuthorize("#user.role != T(com.company.Role).ADMIN)")
public void saveUser(User user) { .. }
You can also provide default values for your contract with the #Value annotation
public Customer getCustomer(#Value("#{434}") int customerId) { .. }
You can even reference system properties in your value expressions.
Setting up Spring security for this purpose is not to hard as you can just create a UserDetailsService that grants some default role to all users. Alternatively you could make you own custom Spring aspect and then let this use the SpelExpressionParser to check method values.
if you don't mind writing some parts of your Java web application in Groovy (which is possible with Spring) I would suggest using GContracts.
GContracts is a Design by Contract (tm) library entirely written in Java - without any dependencies to other libraries - and has full support for class invariants, pre- and postconditions and inheritance of those assertions.
Contracts for Java which is based on Modern Jass is one way to write contracts.
http://code.google.com/p/cofoja/
As per the writing of this reply, this is pretty basic. Hopefully this will improve as we go on.
I didn't find an ideal solution to this, interestingly it is a planned feature for the Spring framework (2.0 implemented patch):
http://jira.springframework.org/browse/SPR-2698
The best thing I suggest to use JSR 303 which is for bean validation. AFAIK there are two implementations for this:
Agimatec Validations
Hibernate Validator
There's a guide here for integrating it into Spring, I haven't followed it through but it looks ok:
http://blog.jteam.nl/2009/08/04/bean-validation-integrating-jsr-303-with-spring/
I personally recommend C4J for 2 reasons:
It has Eclipse plugin so you don't need to manually configure it.
The documentation is written in a clear, structured format so you can easily use it.
Her's the link to C4J