Spring MVC – Spring Blog

Table of Contents

Request Mapping

https://docs.spring.io/spring-framework/reference/web/webflux/controller/ann-requestmapping.html

@RequestMapping, annotation 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";
}

https://www.baeldung.com/spring-requestmapping

RequestParam

Annotation to read values from query string.

@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

@RequestHeader annotation can be used to read values from headers.

@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);
}

https://www.baeldung.com/spring-rest-http-headers

@PathVariable

To get values from query strings.

@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

To set 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.

@PostMapping("/request")
public ResponseEntity postController(
  @RequestBody LoginForm loginForm) {
 
    exampleService.fakeAuthenticate(loginForm);
    return ResponseEntity.ok(HttpStatus.OK);
}

@ResponseBody annotation tells a controller that the object returned is automatically serialized into JSON and passed back into the HttpResponse object.

@Controller
@RequestMapping("/post")
public class ExamplePostController {

    @Autowired
    ExampleService exampleService;

    @PostMapping("/response")
    @ResponseBody
    public ResponseTransfer postResponseController(
      @RequestBody LoginForm loginForm) {
        return new ResponseTransfer("Thanks For Posting!!!");
     }
}

MVC annotations

Name	Description
@Model	Interface, holder for model attributes
@ModelMap	Class, in ModelMap attibute key can be omitted and the value of the attribute will be use to generate the key.
@ModelAndView	ModelAndView it’s a container for both View object and ModelMap

@ModelAttribute

Annotation that binds a method parameter or method return method to a named model attribute.

Method level

The purpose of the method is to add one or more model attributes. This methods can’t be directly mapped to requests. Spring MVC will always make a call to this method before any request handler controllers.

@ModelAttribute
public void addAttributes(Model model) {
    model.addAttribute("msg", "Welcome to the Netherlands!");
}

Method argument

The argument will be retrieved from the model

@RequestMapping(value = "/addEmployee", method = RequestMethod.POST)
public String submit(@ModelAttribute("employee") Employee employee) {
    // Code that uses the employee object

    return "employeeView";
}

https://www.baeldung.com/spring-mvc-and-the-modelattribute-annotation

Resources

https://www.baeldung.com/spring-mvc-model-model-map-model-view