MVC Applications
There are two types of MVC Applications:
- Web Servlet Based on Servlets,Uses Servlets, Filters, Listeners
- Web Reactive Non-blocking approach, Supports reactive programming
To use an War the Application class must extend from SpringBootServletInitializer.
@RequestMapping
Annotation @RequestMapping is used to map requests to controllers method.
There are also HTTP method specific shortcut variants of @RequestMapping:
@GetMapping@PostMapping@PutMapping@DeleteMapping@PatchMapping
Examples:
@RequestMapping(value = "/ex/foos", headers = "key=val", method = GET)
@RequestMapping(
value = "/ex/foos",
headers = { "key1=val1", "key2=val2" }, method = GET)
@RequestMapping(
value = "/ex/foos",
method = GET,
headers = "Accept=application/json")
@RequestMapping(
value = "/ex/foos",
method = GET,
produces = { "application/json", "application/xml" }
)
@GetMapping(path = "/pets/{petId}", params = "myParam=myValue")
public void findPet(@PathVariable String petId) {
// ...
}
@RequestMapping(
value = { "/ex/advanced/bars", "/ex/advanced/foos" },
method = GET)
@ResponseBody
public String getFoosOrBarsByPath() {
return "Advanced - Get some Foos or Bars";
}
@RequestMapping(
value = "/ex/foos/multiple",
method = { RequestMethod.PUT, RequestMethod.POST }
)
@ResponseBody
public String putAndPostFoos() {
return "Advanced - PUT and POST within single method";
}References:
https://docs.spring.io/spring-framework/reference/web/webflux/controller/ann-requestmapping.html
https://www.baeldung.com/spring-requestmapping
@RequestParam
Annotation that reads values from query string.
Examples:
@GetMapping("/api/foos")
@ResponseBody
public String getFoos(@RequestParam String id) {
return "ID: " + id;
}
@RequestMapping(value = "/ex/bars", method = GET)
@ResponseBody
public String getBarBySimplePathWithRequestParam(
@RequestParam("id") long id) {
return "Get a specific Bar with id=" + id;
}
@RequestMapping(value = "/ex/bars", params = "id", method = GET)
@ResponseBody
public String getBarBySimplePathWithExplicitRequestParam(
@RequestParam("id") long id) {
return "Get a specific Bar with id=" + id;
}
@RequestMapping(
value = "/ex/bars",
params = { "id", "second" },
method = GET)
@ResponseBody
public String getBarBySimplePathWithExplicitRequestParams(
@RequestParam("id") long id) {
return "Narrow Get a specific Bar with id=" + id;
}@RequestHeader
Annotation can be used to read values from headers.
Examples:
@GetMapping("/greeting")
public ResponseEntity<String> greeting(@RequestHeader(HttpHeaders.ACCEPT_LANGUAGE) String language) {
// code that uses the language variable
return new ResponseEntity<String>(greeting, HttpStatus.OK);
}
@GetMapping("/double")
public ResponseEntity<String> doubleNumber(@RequestHeader("my-number") int myNumber) {
return new ResponseEntity<String>(String.format("%d * 2 = %d",
myNumber, (myNumber * 2)), HttpStatus.OK);
}
@GetMapping("/listHeaders")
public ResponseEntity<String> listAllHeaders(
@RequestHeader Map<String, String> headers) {
headers.forEach((key, value) -> {
LOG.info(String.format("Header '%s' = %s", key, value));
});
return new ResponseEntity<String>(
String.format("Listed %d headers", headers.size()), HttpStatus.OK);
}
@GetMapping("/nonRequiredHeader")
public ResponseEntity<String> evaluateNonRequiredHeader(
@RequestHeader(value = "optional-header", required = false) String optionalHeader) {
return new ResponseEntity<String>(String.format(
"Was the optional header present? %s!",
(optionalHeader == null ? "No" : "Yes")),HttpStatus.OK);
}
@GetMapping("/default")
public ResponseEntity<String> evaluateDefaultHeaderValue(
@RequestHeader(value = "optional-header", defaultValue = "3600") int optionalHeader) {
return new ResponseEntity<String>(
String.format("Optional Header is %d", optionalHeader), HttpStatus.OK);
}
References:
https://www.baeldung.com/spring-rest-http-headers
@PathVariable
To get values from query strings.
Examples:
@GetMapping("/api/employees/{id}")
@ResponseBody
public String getEmployeesById(@PathVariable String id) {
return "ID: " + id;
}
@GetMapping("/api/employeeswithvariable/{id}")
@ResponseBody
public String getEmployeesByIdWithVariableName(@PathVariable("id") String employeeId) {
return "ID: " + employeeId;
}
@GetMapping("/api/employees/{id}/{name}")
@ResponseBody
public String getEmployeesByIdAndName(@PathVariable String id, @PathVariable String name) {
return "ID: " + id + ", name: " + name;
}
@RequestMapping(value = "/ex/foos/{id}", method = GET)
@ResponseBody
public String getFoosBySimplePathWithPathVariable(
@PathVariable("id") long id) {
return "Get a specific Foo with id=" + id;
}
@RequestMapping(value = "/ex/foos/{id}", method = GET)
@ResponseBody
public String getFoosBySimplePathWithPathVariable(
@PathVariable String id) {
return "Get a specific Foo with id=" + id;
}
@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;
}
@RequestMapping(value = "/ex/bars/{numericId:[\\d]+}", method = GET)
@ResponseBody
public String getBarsBySimplePathWithPathVariable(
@PathVariable long numericId) {
return "Get a specific Bar with id=" + numericId;
}@ResponseStatus
Sets the status of an HTTP response.
@ResponseStatus(HttpStatus.BAD_REQUEST, reason = "Some parameters are invalid")
void onIllegalArgumentException(IllegalArgumentException exception) {}@RequestBody and @ResponseBody
@RequestBody annotation maps the HttpRequest body to a transfer or domain object, enabling automatic deserialization.
@ResponseBody annotation tells a controller that the object returned is automatically serialized into JSON and passed back into the HttpResponse object.
Examples:
@PostMapping("/request")
public ResponseEntity postController(
@RequestBody LoginForm loginForm) {
exampleService.fakeAuthenticate(loginForm);
return ResponseEntity.ok(HttpStatus.OK);
}@Controller
@RequestMapping("/post")
public class ExamplePostController {
@Autowired
ExampleService exampleService;
@PostMapping("/response")
@ResponseBody
public ResponseTransfer postResponseController(
@RequestBody LoginForm loginForm) {
return new ResponseTransfer("Thanks For Posting!!!");
}
}ResponseBody
@RestController annotation incorporates @Controller and @ResponseBody, assuming that Rest response data is returned. @ResponseBody disables the View handling system.
Spring will automatically inject argument in the method endpoint: HttpServletRequest, HttpSession, Principal, Locale.
Method examples:
Message converters
Response message format can be leverage with ResponseEntity by setting headers or content type.
