Restful Application Development

Transcription

1 Restful Application Development

2 Instructor Welcome Currently a consultant in my own business and splitting my time between training and consulting. Rob Gance Assist clients to incorporate Web 2.0 technologies and solutions to enhance collaboration and rich application development. Proponent of developing standards-based solutions and layered semantic architectures. Introduced developers within Yahoo to the Yahoo User Interface (YUI) Library. Have extensive experience with Prototype, jquery, ExtJS, and Dojo as well. Authored numerous Web 2.0-based courses, including those on developing Rich Internet Applications.

3 Rest Architectures Today's Agenda Advantages of REST Java Solutions using REST Java-based REST Frameworks Implementing with REST Creating and Manipulating REST-based Services Binding Web Services with the Front-End

4 REST Architectures

5 RESTful Web Services REST Representational State Transfer A distributed architecture often associated with Service-Oriented Architectures A set of principals that define how resources are accessed and manipulated

6 Motivations for REST REST is a data-centric view of services Follows the intended vision for the way information should be exchanged on the web Semantic use of HTTP methods Ease of use in RIAs, front-end architectures Lends itself toward "Web 2.0" implementations Plays well with browsers

7 Resistance to REST SOA (SOAP, WSDL, etc.) has huge industry backing Pushed heavily by large IT companies How can REST cover all of the complexities of "real" applications?

8 Naming Resources REST uses globally unique identifiers URI Resource Examples of Resources: Blog entries Queries Calculations Published Documents or Files

9 Examples of using URLs

10 REST URLs vs. Query Strings Careful, not all URLs are RESTful: Doesn't map nicely to all the rest actions An update would require changing the URL Works best best as as a noun

11 REST Verbs There are four HTTP behaviors associated with REST actions GET DELETE PUT POST

12 GET The GET operation performs a read GET It is considered a "safe" operation Nothing on the server-side changes GET can return complete representations or partial ones Makes it suitable for query operations

13 DELETE DELETE removes a resource DELETE It is not commonly implemented for all resources DELETE Some clients, such such as as Flex Flex and and Silverlight, cannot properly handle DELETE and and PUT PUT operations This could have disastrous effects if allowed

14 PUT PUT replaces or creates a specified resource Similar to a DB insert or delete and then insert While POST is often used to create server-side resources, strictly speaking, a PUT operation is most suited for this task

15 POST POST can be used to create or modify a resource Semantically, using a POST to retrieve a resource's state is not correct POST should generally be used to update the state of a resource

16 Example Representation A blog entry Blog Entry Title DateCreated Username Comments Client { "title" : "The London Eye", "created" : "17-Feb-09", "user" : "Ed Rice" }

17 Java and REST Java has defined JAX-RS (JSR 311) as the Java API for RESTful Web Services 1.0 release, Sept Available separately now (via Jersey) Will become incorporated into Java EE 6

18 A Survey of REST Implementations A number of Java-based REST-oriented frameworks exist: Jersey Restlets RESTEasy CXF

19 Apache Project CXF An open source Enterprise Service Bus Supports other transports such as SOAP, CORBA, XML over HTTP Its JAX-RS implementation can be used separately from the bus Integration with Spring JSON binding Full WS-* stack support

20 RESTEasy JBoss Implementation for JAX-RS Has built-in client-side framework Embeddable server for unit testing Support for Spring, Comet

21 Restlets Oldest of frameworks compared No support for annotations

22 Jersey JAX-RS Reference Implementation A few JARs to deploy into any servlet container Jersey 1.02 implements JAX-RS 1.0

23 Beginning with Jersey To begin using Jersey, drop the following JARs into your web application These are found in the Jersey distribution's lib directory asm-3.1.jar jersey-core jar jersey-server jar jsr311-api-1.0.jar

24 Create the Web App Create a typical web application Our Our REST-based resource Web Web app app config file file

25 Configure the Jersey Servlet A Servlet will be used to intercept requests web.xml <servlet> <servlet-name>jerseyservlet</servlet-name> <servlet-class> com.sun.jersey.spi.container.servlet. ServletContainer </servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>jerseyservlet</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping>

26 Create the Resource The following resource was created next package com.rest.demo; import javax.ws.rs.get; import javax.ws.rs.path; import javax.ws.rs.produces; JAX-RS public class public String getmessage() { return "This is is your typical hello world app!"; } }

27 Test It Out! That's it! Deploy the app and test it out! Browse to the following URL: This is your typical hello world app!

28 Round Two In this example we'll map to a list of Country resources Since no no specific country indicated, refers to to all all countries

29 The Resource specified in public class classcountryresource { in @Produces("text/json") public String getcountries() { String retval = "{'countries' : [ "; "; for for (int (inti = 0; 0; i < ApplicationData.countries.size(); i++) i++) { // // iterate over over the the countries, // // build build JSON JSON output manually } retval += += " ]}"; ]}"; Developer return retval; must still still define } what is is returned from methods }

30 The Results {'countries' : [ 'United States', 'Afghanistan', 'Argentina', 'Australia', 'Belgium', 'Brazil', 'Bulgaria', 'Cambodia', 'Canada', 'Cuba', 'Denmark', 'England', 'France' ]} ]} The The representation is is rendered in in JSON format

31 Okay, now what? So far, we've introduced REST using JAX- RS and the RI called Jersey Next we'll add: Support for JSON output Support for other REST actions (PUT, DELETE, POST) Specify URLs for nested resources A Rich Ajax-based Front-End

32 Implementing with REST

33 Nested Path Parameters Let's add the ability to select individual countries Recall the URL: GET Our solution requires a new path level and therefore a new Java resource CountryDetailsResource

34 public class classcountrydetailsresource { Support for for @Produces("text/plain") public String getcountry(@pathparam("name") String name) name) { for for (Country country : ApplicationData.countries) { if if (country.getname().equalsignorecase(name)) return country.tostring(); } return new newcountry().tostring(); // // empty empty object } }

35 JAX-RS Annotations The following is a list of some of the more common annotations in the @Consumes

36 Jersey and JSON Jersey supports the ability to convert Java objects to JSON using JAXB First some minor configuration additions: Add the jersey-json jar archive to the project's /WEB-INF/lib directory

37 Binding JSON = "message") public class classmessagejson { } private String msg msg = "This "This is is the the default @Produces("application/json") public MessageJSON getmessage(@queryparam("msg") String msg) msg) { } this.msg = msg; msg; return this; this; GET msg=sample%20message

38 Using Other REST Actions POST Operation can be used to update country data DELETE could be used to remove a country PUT could be used to create/add a country

39 Creating a Client Front-End In the following example we'll add Ajax capability and RIA components using a JavaScript Library called ExtJS Other Libraries are possible: YUI, Dojo, jquery, Prototype Let's break it down...

40 The Front End Environment The Front End Uses ExtJS Components

41 Summary In Today's Session we: Explored REST principles Discussed Various Java-based REST Frameworks Examined JAX-RS and Jersey Created an Ajax-based REST-oriented application using a JS Library, JAX-RS, and Jersey