Lecture 7 Web Services JAX-WS & JAX-RS

JEE - Web Services JAX-WS &
JAX-RS
Fahad R. Golra
ECE Paris Ecole d'Ingénieurs - FRANCE

Lecture 7 - Web Services JAX-
WS & JAX-RS
• JAX-WS - SOAP Web Services
• JAX-RS - RESTful Web Services
2 JEE - Web Services JAX-WS & JAX-RS

Web Services: Definition
• WW3C: “A software system designed to support
interoperable machine-to-machine interaction over a
network.”
• A Web service is a collection of functions that are
packaged as a single entity and published to the
network for use by other programs

Why Web Services ?
• Distributed architecture
• Interoperability
• Based on open standards
• Utilizes existing infrastructure
• Can be accessed from any programming language
• Based on internet Standards
• XML, XSD, http, etc.

Why Web Services ?
• Ease of use
• Easy to understand concepts
• Easy to implement
• Toolkits allow COM, JEE and CORBA components
to be exposed as Web Services

Java Web Services
• Improved since J2EE 1.4 and JAX-RPC
• JAX-B: standard XML Binding
• JAX-WS: improving on JAX-RPC using annotations
• JAX-RS: developed for Java EE 6, stateless service

Marshalling & Unmarshalling
Java
Object
Java
Object
Relational
Table
XML
Document
Object Relational Mapping Java/XML Binding

eXtensible Markup Language (XML)
• Hierarchical tag-based structure like HTML
• Language independent
• Architecture neutral
• Supports arbitrarily complex data formats
• Schema can be used to define document formats
• defined in xsd files

Web Service Implementation
• Write a POJO implementing the service
• Add @WebService annotation to the POJO Class
• Optionally, inject a WebServiceContext
• WebServiceContext allows a web service endpoint
implementation class to access message context and
security information relative to a request
• Deploy the application
• Let your clients access the WSDL

Basic Web Service Example
@WebService
public class BookCatalog {
@WebMethod
public List<String> getBooksCategory() {
List<String> bookCategory = new ArrayList<>();
bookCategory.add("Alpha");
bookCategory.add("Bravo");
bookCategory.add("Charlie");
return bookCategory;
}
}

Web Services Architecture
2. Request contract information
3. Retrieve WSDL definition
4. Exchange SOAP messages
1. Register contract information
Service
Consumer
Service
provider
WSDL
WSDL
• SOAP defines the communication mechanism
• UDDI defines the registry of interface definitions
• WSDL defines the actual interfaces
UDDI
Registry

Web Services Model
Stub
Request: SOAP
invoke
Response: SOAP
return
results
Service
Consumer
Service
provider
Server-Side
Code
Client
Code
SOAP runtime
Library
invoke
return
results
Network

Simple Object Access Protocol (SOAP)
• XML based protocol for
exchange of information
• defines encoding rules for
datatype instances
• RPC invocations
• Based on HTTP request-
response model
• Uses XML Schema
• Two different modes
• RPC
• Document
SOAP Envelope
<soap:Envelope
xmlns:soap=“http://…”>
</soap:Envelope>
SOAP Header
<soap:Header>
</soap:Header>
SOAP Body
<soap:Body>
</soap:Body>
Headers
XML Content
Optional SOAPFault

SOAP Example: Request
• Sample SOAP Message for our simple example
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/
envelope/">
<soap:Header/>
<soap:Body>
<ns2:getBooksCategory xmlns:ns2="http://jee.ece.com/"/>
</soap:Body>
</soap:Envelope>

SOAP Example: Response
• Sample SOAP response from our basic example
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope
xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<SOAP-ENV:Header/>
<soap:Body>
<ns2:getBooksCategoryResponse xmlns:ns2="http://jee.ece.com/">
<return>Alpha</return>
<return>Bravo</return>
<return>Charlie</return>
</ns2:getBooksCategoryResponse>
</soap:Body>
</soap:Envelope>
15

Universal Description, Discovery and
Integration (UDDI)
• An online XML based registry where services can be
• listed & registered
• discovered & located
• Platform-independent, open framework for integrating
business services
• Includes white, green and yellow pages for searching

Web Service Description Language
(WSDL)
• An interface definition language for Web Services
• Uses XML
• Describes the web service operation signatures
• Based on XML Schema
• Serves as a contract between the service providers
and the service consumers

Code First vs. Contract First
WSDL
JAVA
WSDL
JAVA
Code First Contract First

Code First
• Write your code
• Annotate your code
• Deploy it in a container that supports JAX-WS
• JAX-WS runtime (metro) will
• Generate WSDL
• Translate SOAP request to a Java method
invocation
• Translate method return into a SOAP response

Contract First
• Write your WSDL
• Generate an interface for each portType from the
WSDL using wsimport
• Create a class that implements each interface
• Deploy these Service Endpoint Implementation
classes to a JAX-WS container

JAX-WS Usage
• Building and using a web service
• write & compile the endpoint implementation class
• package as war archive & deploy it
• Code the client class
• Use “wsimport” tool to generate and compile the web
service artefacts needed to connect to the service
• Compile and run the client class

Service Endpoint Implementation
• Annotations come with attributes
• e.g. @WebService has following attributes
• endpointInterface
• name
• portName
• serviceName
• targetNamespace
• wsdlLocation

Using annotation attributes
• Web Services work on the idea of Interfaces
• A change of interface will loose all the clients that
connect to your service.
• It is a bad idea to directly annotate the class
without concretising the interface
• Interface can be concretised (locked) by
• the use of proper annotation attributes
• moving the annotations to an interface that is
implemented by the class

Annotations in Web Services
• Web Services Metadata Annotations
• @WebService
• @WebMethod
• @OneWay
• @WebParam
• @WebResult
• JAX-WS Annotations
• @RequestWrapper
• @ResponseWrapper
• @WebEndpoint
• @WebFault
• @WebServiceClient
• @WebServiceRef

Example with annotations
@WebService(name = "EceBookCatalog",
portName = "EceBookCatalogPort",
serviceName = "BookCatalogueService",
targetNamespace = "http://www.example.com")
@SOAPBinding(style = SOAPBinding.Style.DOCUMENT,
use = SOAPBinding.Use.LITERAL,
parameterStyle = SOAPBinding.ParameterStyle.WRAPPED)
public class BookCatalog2 {
BookServiceBusiness bookService = new BookServiceBusiness();
……….
@WebMethod(action = "fetch_books", operationName = "fetchBooks")
@WebResult(name = "bookList")
public List<String> getBook(@WebParam(name = "categoryName") String Category) {
return bookService.getBooks(Category);
}
………..
}
25

Coding the client
• Use “wsimport” tool to generate service artefacts
• Copy them to your client project
• Create an object of the service
• Retrieve a proxy to the service, also known as port.
• The service operations can be called through this
port.

wsimport tool
• wsimport tool is used for client side generation from
the WSDL
• Syntax
wsimport [options] <wsdl location>
• Options
• -d <directory> : generate out files location
• -s <directory> : source files location
• -keep : Keep generated files

Client Side Generated Files
• BookCatalogService.java
Service factory
• BookCatalog.java
Service Endpoint Interface
• GetBookCategory.java
Custom data type for request
• GetBookCategoryResponse.java
Custom data type for response
• ObjectFactory.java
JAXB XML Registry
• package-info.java
Holder for JAXB package annotations

Client for our Example
public class BookCustomer {
public static void main(String[] args) {
List<String> bookCategories;
BookCatalogService service = new BookCatalogService();
BookCatalog port = service.getBookCatalogPort();
bookCategories = port.getBooksCategory();
for (String category : bookCategories) {
System.out.println("Book category: " + category);
}
}
}
29

Java Architecture for XML Binding
(JAXB)
• JAX-WS delegates the mapping of the Java language
data types to JAXB API.
• JAXB converts XML schemas (and data types) to Java
and vice versa
• XML schema described by WSDL is translated to Java
and vice versa, by JAXB

Schema Type vs. Data Type
XML Schema Type Java Data Type
xsd:string java.lang.String
xsd:integer java.math.BigInteger
xsd:int int
xsd:long long
xsd:short short
xsd:decimal java.math.BigDecimal
xsd:float float

RESTful Web Services
• REpresentational State Transfer (REST)
• No specification for RESTful web
services
• An approach presented by Roy Fielding
in his doctoral thesis

Coming from SOAP
• No Standard Protocol
• XML, JSON, Text or any other format
• No Service Definition
• No WSDL
• WADL, but not used commonly
• Better implementations should not use any

Inspiration from HTTP
• Resource based URI
• Methods: GET, POST, PUT, DELETE
• Metadata (header)
• Status Codes
• Content Type

Principles of REST
• Give everything an ID
• Standard set of methods
• Link things together
• Multiple representations
• Stateless communications

Resource based URI
• Treat each dynamic page as a static resource
• www.facebook.com/user1
• www.facebook.com/{userid}
• Resource relations
• www.example.com/tutorials/{tutorialid}/sections{sectionid}
• Collection URIs
• www.example.com/tutorials/{tutorialid}/sections
• URI Filters
• www.example.com/tutorials/{tutorialid}/sections?
offset=5&limit=3

Resource based URI
• Resource == Java class
• POJO
• No required interfaces
• ID provided by @Path annotation
• Value is relative URI, base URI is provided by
deployment context or parent resource
• Embedded parameters for non-fixed parts of the URI
• Annotate class or “sub-resource locator” method

Resource based URI
@Path("orders/{order_id}")
public class OrderResource {
@GET
@Path("customer")
CustomerResource
getCustomer(@PathParam(“order_id”) int id) {...}
}

Stateless
• A RESTFul application does not maintain sessions/
conversations on the server
• Doesn’t mean an application can’t have state
• REST mandates
• That state be converted to resource state
• Conversational state be held on client and transferred
with each request
• Sessions are not linkable
• You can’t link a reference to a service that requires a
session

Standard Set of Methods
Method Purpose
GET Read, possibly cached
POST Update or create without a known Id
PUT Update or create with a known Id
DELETE Remove

Behavior of Methods
• Predictable behavior
• GET - readonly and idempotent. Never changes the
state of the resource
• PUT - an idempotent insert or update of a resource.
Idempotent because it is repeatable without side
effects.
• DELETE - resource removal and idempotent.
• POST - non-idempotent, “anything goes” operation

JAX-RS Annotations
• @Path
• Defines URI mappings and templates
• @ProduceMime, @ConsumeMime
• What MIME types does the resource produce and
consume
• @GET, @POST, @DELETE, @PUT, @HEADER
• Identifies which HTTP method the Java method is
interested in

JAX-RS Annotations
• @PathParam
• Allows you to extract URI parameters/named URI
template segments
• @QueryParam
• Access to specific parameter URI query string
• @HeaderParam
• Access to a specific HTTP Header
• @CookieParam
• Access to a specific cookie value
• @MatrixParam
• Access to a specific matrix parameter

Hello Example
package com.ece.jee;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
@Path("/app")
public class SayHello {
@GET
@Produces(MediaType.TEXT_HTML)
@Path("/hello")
public String sayHello() {
return "<h1> Hello Dude !!! </h1>";
}
}

Multiple Representations
• Offer data in a variety of formats
• XML (Type safety advantage)
• JSON (easy to parse with JavaScript clients)
• (X)HTML (Ideal for clients like browsers for human readable
documents
• Support content negotiation
• Accept header
GET /foo
Accept: application/json
• URI-based
GET /foo.json

Accept: application/xml 
Accept: application/json;q=1.0, text/plain;q=0.5,
application/xml;q=0.5,
@GET
@Produces({"application/xml","application/json"})
Order getOrder(@PathParam("order_id") String id) { ...
}
@GET
@Produces("text/plain")

Content Negotiation: Accept Header
Accept: application/xml 
Accept: application/json;q=1.0, text/plain;q=0.5,
application/xml;q=0.5,
@GET
@Produces({"application/xml","application/json"})
Order getOrder(@PathParam("order_id") String id) {
...
}
@GET
@Produces("text/plain")
String getOrder2(@PathParam("order_id") String id) {
...
}
47

Content Negotiation: URL Based
@Path("/orders") 
public class OrderResource {
@Path("{orderId}.xml") 
@Produces(“application/xml”) 
@GET 
public Order getOrderInXML(@PathParam("orderId") String orderId) { ... 
}
@Path("{orderId}.json") 
@Produces(“application/json”) 
@GET 
public Order getOrderInJSON(@PathParam("orderId") String orderId) {
... }
}
48

Configuration in Wildfly
• Resteasy is the JBoss Implementation of JAX-RS API
• Bundled with wildfly server
• Specify Servlet mapping as per specification
OR
• Create a class
@ApplicationPath("/version")
public class MyApplication extends Application {
}
49

JAX-RS summary
• Java API for building RESTful Web Services
• POJO based
• Annotation-driven
• Server-side API
• HTTP-centric

Jersey Client Side API
• Consume HTTP-based RESTful Services
• Easy-to-use
• Better than HttpURLConnection
• Reuses JAX-RS API
• Resources and URI are first-class citizens
• Not part of JAX-RS yet
• com.sun.jersey.api.client

Jersey Client Side API - Code Sample
Client client = Client.create(); 
WebResource resource = client.resource(“...”);
//curl http://example.com/base
String s = resource.get(String.class);
//curl -HAccept:text/plain http://example.com/base
String s = resource.accept(“text/plain”).get(String.class);

JAX-RS Wildfly Client-side API
public class HelloClient {
private Client client;
private WebTarget target;
public HelloClient() {
this.client = ClientBuilder.newClient();
this.target = this.client
.target("http://localhost:8080/Rest/version/app/hello");
}
public void asyncInvocation() throws InterruptedException {
this.target.request("text/html").async()
.get(new InvocationCallback<String>() {
public void completed(String response) {
System.out.println("--" + response);
}
public void failed(Throwable throwab) {
}
});
Thread.sleep(2000);

Rest Client Wildfly: Hello Example
public class HelloClient {
private Client client;
private WebTarget target;
public HelloClient() {
this.client = ClientBuilder.newClient();
this.target = this.client
.target("http://localhost:8080/Rest/version/app/hello");
}
public void asyncInvocation() throws InterruptedException {
this.target.request("text/html").async()
.get(new InvocationCallback<String>() {
public void completed(String response) {
System.out.println("--" + response);
}
public void failed(Throwable throwab) {
}
});
Thread.sleep(2000);
}
}
54

Lecture 7 Web Services JAX-WS & JAX-RS

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