Spring 3.x - Spring MVC - Advanced topics

Spring MVC – Advanced topicsGuy Nir

January 2012

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» Annotation driven controllers» Arguments and return types» Validation

Agenda

Spring MVC

Annotation driven controllers

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

Annotation driven controllers

Spring MVC – Advanced topics

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» Spring stereotype that identify a class as being a Spring Bean.

» Has an optional ‘value’ property.

Annotation driven controllers@Controller


// Bean name is ‘loginController’@Controllerpublic class LoginController {}

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

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» Define URL mapping for a class and/or method.

» Support deterministic and Ant-style mapping

Annotation driven controllers@RequestMapping


// 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() { ... }}

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



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

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

HTTP request

HTTP response

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@Controller@RequestMapping(“/portal”)public class UserInfoController {

@RequestMapping(value = “/userInfo/xml“, consumes = “application/json”, produces = “application/xml”) public UserInformation getUserInformationAsXML() { }

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

Requires message converters

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» Required parameters.

» Required headers



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

@RequestMapping(value = “/userInfo“, headers = { “Accept-Language=he-IL” })public UserInformation getUserInformationAsXML() {} GET http://google.com/

HTTP/1.1Accept-Language: he-ILAccept-Encoding: gzip, deflate

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» 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.

Annotation driven controllersURI templates (@PathVariable)


// 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) { ... }

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» Define a new model attribute. Single attribute approach Multiple attributes approach

» Access existing model attribute.

Annotation driven controllers@ModelAttribute


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» Definition of a single model attribute



@Controllerpublic 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; }}

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@Controllerpublic 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 }; }}

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@Controllerpublic class ValidateUserFormController

@RequestMapping(method = RequestMethod.GET) public String validateForm(HttpServletRequest request, HttpServletResponse ...) { String firstName = request.getParameter(“firstName”); String lastName = request.getParameter(“lastName”);

// ... }}

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@Controllerpublic class ValidateUserFormController

@RequestMapping(method = RequestMethod.GET) 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; }}

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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); }}

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» Definition of a multiple model attribute



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

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

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

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» Session attribute binding



@Controller@SessionAttributes("userDetails");public class ValidateUserFormController {

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

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

values.

Annotation driven controllers@CookieValue, @HeaderValue


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» 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.

Annotation driven controllers@DateTimeFormat


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Annotation driven controllers@DateTimeFormat


@Controllerpublic class CheckDatesRangeController {

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

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» Provide access to HTTP request body.

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

Annotation driven controllers@RequestBody


@Controllerpublic class PersistCommentController {

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

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» Convert return value to HTTP response body.

Annotation driven controllers@ResponseBody


@Controllerpublic class FetchCommentController {

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

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

Arguments and returntypes

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Arguments and return types


@Controllerpublic class SomeController {

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

}

Return value

Arguments

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» 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

Arguments and return typesAllowed arguments


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» java.security.Principle» HttpEntity

Spring framework API» java.util.Map, Model, ModelMap

Allow access to the current model.» Errors, BindingResult

Arguments and return typesAllowed arguments


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» 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.

Arguments and return typesAllowed return types


Validation

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» 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


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ValidationDeclaring binding process


@Controllerpublic class ValidateFormController {

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

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@Controllerpublic class ValidateFormController {

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

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

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

 <form:errors path="firstName"/>

</form:form>

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» Spring framework support 3rd-party JSR-303 integration.

» Requires additional artifacts JSR-303 spec artifacts.» Requires RI (reference implementation)

e.g: Hibernate Validation

ValidationJSR-303 based validation


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ValidationJSR-303 based validation


@RequestMappingpublic 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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Spring 3.x - Spring MVC - Advanced topics

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