Spring Mvc Rest

Building RESTful applications with Spring MVC Craig Walls

Who Am I? Java, Spring, and OSGi fanatic Principal Consultant with Improving Author XDoclet in Action (Manning) Spring in Action (Manning) Modular Java (Pragmatic Bookshelf) E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: @habuma Slides: http://www.slideshare.net/habuma

What REST is NOT!!! Web Services with URLs E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

It’s about Resources Things, not actions Requests, not demands Resources, not services Transfer of state, not RPC E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

The Pillars of REST Resources URIs/URLs HTTP Methods Representations E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

The Pillars of REST Resources Produced as model data in Spring MVC Controllers URIs/URLs Supported in handler methods by @PathParam HTTP Methods @RequestMapping, HiddenHttpMethodFilter, <form:form> Representations Rendered by view resolvers HTML, XML, JSON, RSS, Atom, PDF, Excel, etc. Negotiated by ContentNegotiatingViewResolver E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Identifying Resources E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Demanding URLs Direct Imperative Resource identifier Command is pushed into a query parameter http://www.somestore.com/displayProduct?sku=1234 Very service-y Not very cacheable or search engine friendly E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Resourceful URLs The focus is on the product, We’re requesting not the action a product’s info http://www.somestore.com/product/1234 Cacheable This URL also identifies a product (within a context) E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Spring MVC overview E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

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> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

ContextLoaderListener In /WEB-INF/web.xml <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> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

UrlRewriteFilter In /WEB-INF/web.xml <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/urlrewrite.xml <urlrewrite default-match-type="wildcard"> <rule> 1234 /pr oduct/ <from>/resources/**</from> <to>/resources/$1</to> /1234 </rule> uct /ap p/prod <rule> <from>/**</from> <to>/app/$1</to> </rule> <outbound-rule> <from>/app/**</from> <to>/$1</to> </outbound-rule> </urlrewrite> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

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> Handle annotation-driven request mappings <mvc:annotation-driven/> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Use-case-based controllers VERB!!! @Controller public 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"; } // ... } http://host/myApp/displayProduct.htm?sku=1234 E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Resource-oriented controller Noun @Controller Verb @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"; } } http://host/myApp/product/1234 E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

HTTP Methods GET, DELETE, PUT Idempotent Transfers state of resource POST Not Idempotent Sends data (not nec. state) E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

PUT vs. POST PUT Used to transfer state to server Useful when the resource’s URL is known POST Used to send data to server Useful when the resource’s URL is unknown or when transferring partial state E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Handling DELETE @Controller @RequestMapping("/product") public class ProductController { ... @RequestMapping(value="/{sku}", method=DELETE) public String deleteProduct( @PathVariable String sku) { // ... delete product ... return "redirect:home"; } } http://host/myApp/product/1234 E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Handling PUT @Controller @RequestMapping("/product") public class ProductController { ... @RequestMapping(value="/{sku}", method=PUT) public String saveProduct( @PathVariable String sku, Product product) { // ... save product ... return "redirect:/product/" + sku; } } http://host/myApp/product/1234 E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Handling POST @Controller @RequestMapping("/product") public class ProductController { ... @RequestMapping(method=POST) public String setPrice(String sku, double price) { // ... update price ... return "redirect:/product/" + sku; } } http://host/myApp/product FORM DATA: sku=1234 price=5.99 E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Using PUT/DELETE in forms Most browsers only support GET and POST Spring’s <form:form> supports all <form:form method="DELETE" action="http://host/myApp/product/1234"> ... </form:form> Hidden method ﬁeld <form method="POST" action="http://host/myApp/product/1234"> <input type="hidden" name="_method" value="DELETE"> ... </form> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

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> HiddenHttpMethodFilter POST DELETE _method=DELETE E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Data representation PDF RSS/Atom Spring MVC Views JSON Excel E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Negotiating Content Request Content Negotiating View Resolver E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Choosing a view 1. Determine the media type URL path extension/mediaTypes format parameter URL path extension/JAF HTTP Accept header 2. Find a view resolver that serves that media type E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

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"/> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Spring’s new views MappingJacksonJsonView MarshallingView AbstractAtomFeedView AbstractRssFeedView E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

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> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Sample RSS View public 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; } } E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Sample Atom View public 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; } } E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

ETags Returns HTTP 304 if content is unmodiﬁed if-none-match (MD5 Hash comparison) Saves bandwidth <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> E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

RestTemplate In Spring context: (or yes, it could just be new’d up in Java) <bean id="restTemplate" class="org.springframework.web.client.RestTemplate"> In Java: RestTemplate rest = (RestTemplate) context.getBean("restTemplate"); Map result = rest.getForObject( "http://localhost:8080/mugbooks/book/1.json", Map.class); E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Summary • Spring provides a ﬂexible web MVC framework • Full support for REST as of Spring 3.0 • Can consume REST services via a template E-mail: craig@habuma.com Blog: http://www.springinaction.com Twitter: habuma

Thank You Don’t forget the evals!

Spring Mvc Rest

by Craig Walls on Feb 21, 2010

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