Spring 3.x - Spring MVC - Advanced topics

Spring MVC – Advanced topics
Guy Nir
January 2012

Spring MVC

Agenda
» Annotation driven controllers
» Arguments and return types
» Validation

Annotation driven
controllers


Annotation driven controllers
» @Controller
» @RequestMapping (class-level and method-level)
» @PathVariable (URI template)
» @ModelAttribute (method-level, argument-level)
» @CookieValue, @HeaderValue
» @DateTimeFormat
» @RequestBody
» @ResponseBody


@Controller
» Spring stereotype that identify a class as being a Spring
Bean.
» Has an optional ‘value’ property.
// Bean name is ‘loginController’
@Controller
public class LoginController {
}

// Bean name is ‘portal’.
@Controller(‚portal‛)
public class PortalController {
}


@RequestMapping
» Define URL mapping for a class and/or method.
// Controller root URL: http://host.com/portal
@Controller
@RequestMapping(‚/portal‛)
public class PortalController {

// Handle [GET] http://host.com/portal
@RequestMapping(method = RequestMethod.GET)
public String enterPortal() { ... }

// Handle [GET] http://host.com/portal/userProfile
@RequestMapping(‚/userProfile‛)
public String processUserProfileRequest() { ... }
}

» Support deterministic and Ant-style mapping


@RequestMapping
» Available properties:
 method – List of supported HTTP method (GET, POST, ...).
 produces/consumes – define expected content types.

GET http://google.com/ HTTP/1.1
Accept: text/html, application/xhtml+xml, */* HTTP
Accept-Language: he-IL request
Accept-Encoding: gzip, deflate

HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8 HTTP
Date: Sun, 29 Jan 2012 19:45:21 GMT response
Expires: Tue, 28 Feb 2012 19:45:21 GMT


@RequestMapping
@Controller
@RequestMapping(‚/portal‛)
public class UserInfoController {

@RequestMapping(value = ‚/userInfo/xml‚,
consumes = ‚application/json‛,
produces = ‚application/xml‛)
public UserInformation getUserInformationAsXML() { Requires message
}
converters

@RequestMapping(value = ‚/userInfo/yaml‚,
consumes = ‚application/json‛,
produces = ‚application/Json‛)
public UserInformation getUserInformationAsJSon() {
}
}


@RequestMapping
» Required parameters.
// URL must in a form of: http://host.com/?userId=...&username=admin
@RequestMapping(value = ‚/‚, params = { ‚userId‛, ‚username!=guest‛, ‚!password‛ })
public UserInformation getUserInformationAsXML() {
}

» Required headers
@RequestMapping(value = ‚/userInfo‚, headers = { ‚Accept-Language=he-IL‛ })
public UserInformation getUserInformationAsXML() {
} GET http://google.com/ HTTP/1.1
Accept-Language: he-IL
Accept-Encoding: gzip, deflate


URI templates (@PathVariable)
» Allow us to define part of the URI as a template token.
» Support regular expressions to narrow scope of values.
» Only for simple types, java.lang.String or Date variant.
» Throw TypeMismatchException on failure to convert.
// Handle ‘userId’ with positive numbers only (0 or greater).
@RequestMapping(‚/users/{userId:[0-9]+})
public void processUserRequest(@PathVariable(‚userId‛) int userId) { ... }

// Handle ‘userId’ with negative numbers only.
@RequestMapping(‚/users/{userId:-[0-9]+})
public void processUserRequest(@PathVariable(‚userId‛) int userId) { ... }


@ModelAttribute
» Define a new model attribute.
 Single attribute approach
 Multiple attributes approach
» Access existing model attribute.


@ModelAttribute
» Definition of a single model attribute
@Controller
public class PrepareFormController

@Override
public ModelAndView prepareForm() {
ModelAndView mav = new ModelAndView("details");
mav.addObject("userDetails", new UserDetails());

mav.addObject("months", createIntegerList(1, 12));
mav.addObject("years", createIntegerList(1940, 2011));
return mav;
}
}


@ModelAttribute
@Controller
public class PrepareFormController

@ModelAttribute("userDetails")
public UserDetails newUserDetails() {
return new UserDetails();
}

@ModelAttribute("months")
public int[] getMonthList() {
return new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
}
}


@ModelAttribute
@Controller
public class ValidateUserFormController

public String validateForm(HttpServletRequest request, HttpServletResponse ...) {
String firstName = request.getParameter(‚firstName‛);
String lastName = request.getParameter(‚lastName‛);

// ...
}
}


@ModelAttribute
@Controller
public class ValidateUserFormController

public String validateForm(@ModelAttribute("userDetails") UserDetails details) {
// ...
}

@ModelAttribute("userDetails")
public UserDetails getUserDetails(HttpServletRequest request) {
UserDetails user = new UserDetails();
user.setFirstName(request.getParameter("firstName"));
return user;
}
}


@ModelAttribute
public class UserFormControllerTest {

@Test
public void testValidateForm() {
UserFormController formController = new UserFormController();
UserDetails userDetails = new UserDetails();
// ...

// Simple way to test a method.
String viewName = formController.validateForm(userDetails);

Assert.assertEquals("OK", viewName);
}
}


@ModelAttribute
» Definition of a multiple model attribute
public int[] getMonthList() {
return new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
}

public int[] getYears() {
return new int[] { 1940, 1941, ... };
}

@ModelAttribute
public void populateAllAttributes(Model model, HttpServletRequest ...) {
model.addAttribute(‚years", new int[] { ... });
model.addAttribute(‚months", new int[] { ... });


@ModelAttribute
» Session attribute binding
@Controller
@SessionAttributes("userDetails");
public class ValidateUserFormController {

// UserDetails instance is extracted from the session.
public String validateForm(@ModelAttribute("userDetails") UserDetails details) {
// ...
}
}


@CookieValue, @HeaderValue
» @CookieValue provide access to client-side cookies.
» @HeaderValue provide access to HTTP request header
values.


@DateTimeFormat
» Allow conversion of a string to date-class type.
 long/java.lang.Long,
 java.util.Date, java.sql.Date,
java.util.Calendar,
 Joda time
» Applies to @RequstParam and @PathVariable
» Support various conventions.


@DateTimeFormat

@Controller
public class CheckDatesRangeController {

// http://host.com/checkDate?birthDate=1975/02/31
@RequestMapping
public String checkDateRange(
@RequestParam("birthdate")
@DateTimeFormat(pattren = "yyyy/mm/dd") Date birthDate) {
// ...
}
}


@RequestBody
» Provide access to HTTP request body.
@Controller
public class PersistCommentController {

@RequestMapping(method = RequestMethod.POST)
public String checkDateRange(@RequestBody String contents) {
// ...
}
}

» Also supported:
 Byte array, Form, javax.xml.transform.Source


@ResponseBody
» Convert return value to HTTP response body.
@Controller
public class FetchCommentController {

@RequestMapping
@ResponseBody
public String fetchComment(@RequestMapping (‚commentId") int commentId) {
// ...
}

@RequestMapping
@ResponseBody
public byte[] fetchAsBinary(@RequestMapping (‚commentId") int commentId) {
// ...
}
}

Arguments and return
types


Arguments and return types

@Controller
public class SomeController {

@RequestMapping
public String someMethod(...) { ... }

}

Return Arguments
value


Allowed arguments
» HttpServletRequest, HttpServletResponse, HttpSession
 Servlet API
» WebRequest, NativeWebRequest
 Spring framework API
» java.util.Locale
» java.io.InputStream, java.io.Reader
» java.io.OutputStream, java.io.Writer


Allowed arguments
» java.security.Principle
» HttpEntity
 Spring framework API
» java.util.Map, Model, ModelMap
 Allow access to the current model.
» Errors, BindingResult


Allowed return types
» ModelAndView, Model, java.util.Map, View
» String
 Represents a view name, if not specified otherwise.
» void
» HttpEntity<?>, ResponseEntity<?>
» Any other type that has a conversion.


Validation
» Allow us to validate form in a discipline manner.
» Provide a convenient and consistent way to validate
input.
» Support JSR-303 (not covered by this presentation).


Validation
Declaring binding process

@Controller
public class ValidateFormController {

@RequestMapping
public String validateForm(UserDetails details, Errors errors) {
if (details.getFirstName() == null) {
errors.rejectValue("firstName", null, "Missing first name.");
}
}
}


Validation

@Controller
public class ValidateFormController {

@RequestMapping
public String validateForm(UserDetails details, Errors errors) {
ValidationUtils.rejectIfEmpty(errors,
"firstName",
null,
"Missing first name.");
}
}

Validation

<form:form action="form/validate.do" method="POST" modelAttribute="userDetails">


First name: <form:input path="firstName" />


<form:errors path="firstName"/>

</form:form>


Validation
JSR-303 based validation
» Spring framework support 3rd-party JSR-303
integration.
» Requires additional artifacts JSR-303 spec artifacts.
» Requires RI (reference implementation)
 e.g: Hibernate Validation


Validation
JSR-303 based validation
@RequestMapping
public String validateForm(@Valid UserDetails details, Errors errors) { ... }

public class UserDetails {

@NotNull // JSR-303 annotation.
private String firstName;

@Size(min = 2, max = 64) // JSR-303 annotations.
private String lastName;

@Min(1) @Max(12) // JSR-303 annotations.
private int birthMonth;
}

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