spring mvc rest

Building RESTful applications with

Spring MVC

Craig Walls

E-mail: [email protected] Blog: http://www.springinaction.com Twitter: @habuma Slides: http://www.slideshare.net/habuma

Who Am I?

Java, Spring, and OSGi fanaticPrincipal Consultant with Improving

AuthorXDoclet in Action (Manning)

Spring in Action (Manning)

Modular Java (Pragmatic Bookshelf)

E-mail: [email protected] Blog: http://www.springinaction.com Twitter: habuma

What REST is

Web Serviceswith URLs

NOT!!!


It’s about Resources

Things, not actions

Requests, not demands

Resources, not services

Transfer of state, not RPC


The Pillars of REST

Resources

URIs/URLs

HTTP Methods

Representations


The Pillars of REST

Resources

URIs/URLs

HTTP Methods

Representations

Produced as model data in Spring MVC Controllers

Supported in handler methods by @PathParam

@RequestMapping, HiddenHttpMethodFilter, <form:form>

Rendered by view resolversHTML, XML, JSON, RSS, Atom, PDF, Excel, etc.

Negotiated by ContentNegotiatingViewResolver


Identifying Resources


Demanding URLs

http://www.somestore.com/displayProduct?sku=1234

Direct ImperativeCommand

Resource identifier is pushed into

a query parameter

Not very cacheable orsearch engine friendly

Very service-y


Resourceful URLs

http://www.somestore.com/product/1234

We’re requestinga product’s info

Cacheable

The focus ison the product,not the action

This URL alsoidentifies a product(within a context)


Spring MVC overview


DispatcherServlet

In /WEB-INF/web.xml<servlet> <servlet-name>spitter</servlet-name> <servlet-class> org.springframework.web.servlet.DispatcherServlet </servlet-class> <load-on-startup>1</load-on-startup></servlet>

<servlet-mapping> <servlet-name>spitter</servlet-name> <url-pattern>/app/*</url-pattern></servlet-mapping>


ContextLoaderListener

<context-param> <param-name>contextConfigLocation</param-name> <param-value> /WEB-INF/spitter-security.xml classpath:service-context.xml classpath:persistence-context.xml classpath:dataSource-context.xml classpath:setup-context.xml </param-value></context-param>

<listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class></listener>

In /WEB-INF/web.xml


UrlRewriteFilter<filter> <filter-name>UrlRewriteFilter</filter-name> <filter-class> org.tuckey.web.filters.urlrewrite.UrlRewriteFilter </filter-class></filter><filter-mapping> <filter-name>UrlRewriteFilter</filter-name> <url-pattern>/*</url-pattern></filter-mapping>

In /WEB-INF/web.xml

<urlrewrite default-match-type="wildcard"> <rule> <from>/resources/**</from> <to>/resources/$1</to> </rule> <rule> <from>/**</from> <to>/app/$1</to> </rule> <outbound-rule> <from>/app/**</from> <to>/$1</to> </outbound-rule> </urlrewrite>

In /WEB-INF/urlrewrite.xml

/product/1234

/app/product/1234


Essential Configuration

Scan for controller (and other) components<context:component-scan base-package="com.habuma.sample.mvc" />

Resolve JSP views<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix" value="/WEB-INF/jsp/"/> <property name="suffix" value=".jsp"/></bean>

<mvc:annotation-driven/>

Handle annotation-driven request mappings


Use-case-based controllers

@Controllerpublic class DisplayProductController { @RequestMapping(value="/displayProduct.htm") public String showProductBySku(String sku, Map<String,Object> model) { Product product = // ... lookup product ... model.put("product", product); return "product"; } // ...}

VERB!!!

http://host/myApp/displayProduct.htm?sku=1234


Resource-oriented controller

@Controller@RequestMapping("/product")public class ProductController { @RequestMapping(value="/{sku}", method=GET) public String showProductBySku( @PathVariable String sku, Map<String,Object> model) { Product product = // ... lookup product ... model.put("product", product); return "product"; }}

Noun

http://host/myApp/product/1234

Verb


HTTP Methods

GET, DELETE, PUTIdempotent

Transfers state of resourcePOST

Not IdempotentSends data (not nec. state)


PUT vs. POST

PUTUsed to transfer state to server

Useful when the resource’s URL is knownPOST

Used to send data to serverUseful when the resource’s URL is unknown

or when transferring partial state


Handling DELETE

@Controller@RequestMapping("/product")public class ProductController {

...

@RequestMapping(value="/{sku}", method=DELETE) public String deleteProduct( @PathVariable String sku) { // ... delete product ... return "redirect:home"; }}



Handling PUT


...

@RequestMapping(value="/{sku}", method=PUT) public String saveProduct( @PathVariable String sku, Product product) { // ... save product ... return "redirect:/product/" + sku; }}



Handling POST


...

@RequestMapping(method=POST) public String setPrice(String sku, double price) { // ... update price ... return "redirect:/product/" + sku; }}

http://host/myApp/productFORM DATA: sku=1234

price=5.99


Using PUT/DELETE in formsMost browsers only support GET and POST

Spring’s <form:form> supports all

<form:form method="DELETE" action="http://host/myApp/product/1234">...</form:form>

<form method="POST" action="http://host/myApp/product/1234"> <input type="hidden" name="_method" value="DELETE">...</form>

Hidden method field


HiddenHttpMethodFilter<filter> <filter-name>httpMethodFilter</filter-name> <filter-class> org.springframework.web.filter.HiddenHttpMethodFilter </filter-class></filter>

<filter-mapping> <filter-name>httpMethodFilter</filter-name> <url-pattern>/*</url-pattern></filter-mapping>

POST_method=DELETE

DELETE

Hid

denH

ttpM

etho

dFilt

er


Data representation

Spring MVCViews

RSS/Atom

Excel

JSON

PDF


Negotiating Content

ContentNegotiating

ViewResolver

Request


Choosing a view

1. Determine the media type

HTTP Accept header

URL path extension/mediaTypes

format parameter

URL path extension/JAF

2. Find a view resolver thatserves that media type


ContentNegotiatingViewResolver

<bean class="org.springframework.web.servlet.view. ContentNegotiatingViewResolver"> <property name="mediaTypes"> <map> <entry key="htm" value="text/html"/> <entry key="json" value="application/json"/> </map> </property> <property name="defaultViews"> <list> <bean class="org.springframework.web.servlet.view.json. MappingJacksonJsonView" /> </list> </property></bean>

<bean id="spittles" class="com.habuma.spitter.mvc.view.SpittlesAtomView"/>


Spring’s new views

MappingJacksonJsonView

MarshallingView

AbstractAtomFeedView

AbstractRssFeedView


XML Marshalling View

<bean id="oxmMarshaller" class="org.springframework.oxm.xstream.XStreamMarshaller" />

<bean id="marshallingHttpMessageConverter" class="org.springframework.http.converter.xml. MarshallingHttpMessageConverter"> <property name="marshaller" ref="oxmMarshaller" /> <property name="unmarshaller" ref="oxmMarshaller" /></bean>


Sample RSS Viewpublic class SpittlesRssView extends AbstractRssFeedView {

@Override protected List<Item> buildFeedItems( Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {

@SuppressWarnings("unchecked") List<Spittle> spittles = (List<Spittle>) model.get("spittles"); List<Item> items = new ArrayList<Item>(); for (Spittle spittle : spittles) { Item item = new Item(); item.setTitle(spittle.getText()); item.setPubDate(spittle.getWhen()); item.setAuthor(spittle.getSpitter().getFullName()); items.add(item); } return items; }}


Sample Atom Viewpublic class SpittlesAtomView extends AbstractAtomFeedView {

@Override protected List<Entry> buildFeedEntries( Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception { @SuppressWarnings("unchecked") List<Spittle> spittles = (List<Spittle>) model.get("spittles"); List<Entry> entries = new ArrayList<Entry>(); for (Spittle spittle : spittles) { Entry entry = new Entry(); entry.setTitle(spittle.getText()); entry.setCreated(spittle.getWhen()); entry.setAuthors(asList(spittle.getSpitter().getFullName())); entries.add(entry); } return entries; }}


ETags

<filter> <filter-name>etagFilter</filter-name> <filter-class>org.springframework.web.filter.ShallowEtagHeaderFilter</filter-class></filter> <filter-mapping> <filter-name>etagFilter</filter-name> <servlet-name>spitter</servlet-name></filter-mapping>

Returns HTTP 304 if content is unmodifiedif-none-match

(MD5 Hash comparison)

Saves bandwidth


RestTemplate

<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">

RestTemplate rest = (RestTemplate) context.getBean("restTemplate");Map result = rest.getForObject( "http://localhost:8080/mugbooks/book/1.json", Map.class);

In Spring context: (or yes, it could just be new’d up in Java)

In Java:


Summary

•Spring provides a flexible web MVC framework

•Full support for REST as of Spring 3.0

•Can consume REST services via a template

Thank You

Don’t forget the evals!

spring mvc rest

Documents

product product

http methodsget

product return product

lookup product

products info http

habuma slides

pathvariable string

resources email