Front Controller :
the concept of the Front Controller in the typical Spring Model View Controller architecture
At a very high level, here are the main responsibilities we're looking at:
- Intercepts incoming requests
- Converts the payload of the request to the internal structure of the data
- Sends the data to Model for further processing
- Gets processed data from the Model and advances that data to the View for rendering
- DispatcherServlet plays the role of the Front Controller in the architecture.
- The diagram is applicable both to typical MVC controllers as well as RESTful controllers
- MVC applications are not service-oriented hence there is a View Resolver that renders final views based on data received from a Controller
- RESTful applications are designed to be service-oriented and return raw data (JSON/XML typically). Since these applications do not do any view rendering, there are no View Resolvers – the Controller is generally expected to send data directly via the HTTP response
MVC Controller :
@Controller@RequestMapping(value="Test")public class TestController{.....}
Rest Controller :
Maven Dependencies : spring-web, spring-webmvc, jackson-databind
Maven Dependencies : spring-web, spring-webmvc, jackson-databind
@Controllerpublic class TestController{@GetMapping(value = "/student/{studentId}")public @ResponseBody Student getTestData(@PathVariable Integer studentId) {Student student = new Student();student.setName("Peter");student.setId(studentId);return student;}}
@ResponseBody annotation on the method – which instructs Spring to bypass the view resolver and essentially write out the output directly to the body of the HTTP response.
Spring Boot - @RestController
@RestControllerpublic class RestAnnotatedController {@GetMapping(value = "/annotated/student/{studentId}")public Student getData(@PathVariable Integer studentId) {Student student = new Student();student.setName("Peter");student.setId(studentId);return student;}}
@RestController annotation from Spring Boot is basically a quick shortcut that saves us from always having to define @ResponseBody. Help by pass view rendering stage and directly writing response to HTTP response body
@RequestMapping
the annotation is used to map web requests to Spring Controller methods
Example 1 : Request Mapping with by path and HTTP method
@RequestMapping(value = "/ex/foos", method = POST)@ResponseBodypublic String postFoos() {return "Post some Foos";}
Example 2 : Request Mapping and HTTP header
@RequestMapping(value = "/ex/foos",headers = { "key1=val1", "key2=val2" }, method = GET)@ResponseBodypublic String getFoosWithHeaders() {return "Get some Foos with Header";}
Example 3 : Mapping media types produced and consumed by controller
@RequestMapping(value="/method6",produces={"application/json","application/xml"},consumes="text/html")@ResponseBodypublic String method6(){return "method6";}
Above method can consume message only with Content-Type as text/html and is able to produce messages of type application/json and application/xml.
Example 4 : Request Mapping with Path Variable
@RequestMapping(value = "/ex/foos/{fooid}/bar/{barid}", method = GET)
@ResponseBody
public String getFoosBySimplePathWithPathVariables(@PathVariable long fooid, @PathVariable long barid) {return "Get a specific Bar with id=" + barid +" from a Foo with id=" + fooid;}
Example 5 : Request Mapping with Request Parameters
@RequestMapping(value = "/ex/bars", method = GET)@ResponseBodypublic String getBarBySimplePathWithRequestParam( @RequestParam("id") long id) {return "Get a specific Bar with id=" + id;}
http://localhost:8080/spring-rest/ex/bars?id=100
Example 6 : Request Mapping with Fallback
@RequestMapping(value = "*",method = { RequestMethod.GET, RequestMethod.POST ... })@ResponseBodypublic String allFallback() {return "Fallback for All Requests";}
@RequestMapping New Shortcut Annotations
- @GetMapping
- @PostMapping
- @PutMapping
- @DeleteMapping
- @PatchMapping
