Lecture 10: Web Services. Outline Overview of Web Services Create a Web Service with Sun J2EE...

Lecture 10:Web Services

Outline

• Overview of Web Services

• Create a Web Service with Sun J2EE (JAX-RPC)

What is a Web Service?• A web service is a network accessible interface to

application programs, built using standard Internet technologies.

• Clients of web services do NOT need to know how it is implemented.

Application

client

Application

programNetwork Web

Service

Web Service Architecture

Service provider

Service broker Service requestor

publish(WSDL)

find(UDDI)

bind(SOAP)

"server"

"client""naming service"

Web Service Technology Stack

Discovery

Description

Packaging

Transport

Network

shopping web service?

WSDL URIsWeb ServiceClient

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

SOAP pkg response ProxyProxy

Client Proxy = Stub, Server Proxy = Tie

publish WSDL URIs

Step 1. Write Web Service Method

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

publish WSDL URIs

Step 2. Describe Web Service using WSDL

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

WSDL can be automatically generated

publish WSDL URIs

Step 3. Deploy Service at Server

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

Tie will be created, service location stored in WSDL

publish WSDL URIs

Step 4. Publish Service

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

Client can locate the service querying UDDI

publish WSDL URIs

Step 5. Generate Client Proxy

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

publish WSDL URIs

Stubs can be generated from WSDL automatically

Step 6. Write Client to Invoke Proxy

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

publish

Step 7. Execute Client

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDLSOAP pkg request

SOAP pkg responseProxyProxy

publish

Client invokes service (almost) like a local method

JAX-RPC

• JAX-RPC = Java Web Services Architecture

• Sun's solution for writing Web Services and Web Service clients

• Example: "HelloWorld" Service

Step 1. Write Web Service Method

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

publish WSDL URIs

Service Interface

package iis;

import java.rmi.Remote;

import java.rmi.RemoteException;

public interface HelloIF extends Remote {

public String sayHello(String s) throws RemoteException;

Web Service Interface derived from class Remote

Methods required to throw RemoteException

Service Implementation

package iis;

public class HelloImpl implements HelloIF

{ public String message ="Hello"; public String sayHello(String s)

throws RemoteException { return message + s; }

Compile the classes: javac HelloIF.java HelloImpl.java

Step 2. Describe Web Service using WSDL

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

WSDL can be automatically generated

publish WSDL URIs

Configuration File

• All relevant information on Web Service

<?xml version="1.0" encoding="UTF-8"?>

<configuration

xmlns="http://java.sun.com/xml/ns/jax-rpc/ri/config">

<service

name="HelloWorldService"

targetNamespace="http://lsirwww.epfl.ch/"

typeNamespace="http://lsirwww.epfl.ch/"

packageName="iis">

</service>

</configuration>

Generate WSDL

• Automatically derived from Interface and Configuration Filewscompile -define -mapping build/mapping.xml -d build -nd build -classpath build config.xml

• Deploytool will need information from mapping.xml

Structure of WSDL<?xml version="1.0">

<schema> definition of parameter data types in XML Schema (optional)

</schema></types> <message name="HelloIF_sayHello">

definition of a message (request, reply)</message> <portType name="HelloIF">

<operation name="sayHello">definition of an operation (request – reply pair)

</operation></portType> <binding name="HelloIfBinding" type="HelloIF">

definition of a protocol binding (typically SOAP)</binding><service name="HelloWorldService">

<port name="StockQuotePort">definition of a port (an Internet address)

</port></service></definitions>

abstract concrete

Messages

Provides message names and passing of parameters

</operation></portType>

Define message sequences corresponding to a service invocation

Protocol Binding

<binding name="HelloIFBinding" type="tns:HelloIF"> <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="rpc"/> <operation name="sayHello"> <soap:operation soapAction=""/> <input> <soap:body encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"

use="encoded" namespace="http://lsirwww.epfl.ch/"/></input>

<output> <soap:body encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"

use="encoded" namespace="http://lsirwww.epfl.ch/"/> </output> </operation></binding>

Implement abstract messages according to SOAP protocol

Sample Soap Message

<?xml version='1.0' ?> <env:Envelope xmlns:env="http://www.w3.org/2002/12/soap-envelope"> <env:Header> <m:HelloIF_sayHello xmlns:m="http://lsirwww.epfl.ch/" env:role="http://www.w3.org/2002/12/soap-envelope/role/next" env:mustUnderstand="true"> </m:HelloIF_sayHello> </env:Header> <env:Body> <p:String_1 xmlns:p="http://lsirwww.epfl.ch/">

Hello World!</p:String_1>

</env:Body> </env:Envelope>

SOAP client SOAP serverRequest message

Response message

Service Access

<service name="HelloWorldService"> <port name="HelloIFPort"

binding="HelloIFBinding"> <soap:address location="REPLACE_WITH_ACTUAL_URL"/>

</port></service>

Location not known before deployment

Step 3. Deploy Service at Server

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

Tie will be created, service location stored in WSDL

publish WSDL URIs

Deploy Service

• Web service tie is implemented as servlet

• Servlet is a Java application that can interact with Web Server (also JSPs are implemented as servlets!)

• Tie automatically generated at deployment

WAR file and Context Root

WAR file is archive collecting all needed files (like JAR)

Contect Root is location on Web Server

Provide WSDL File

As generated before

Provide Service Implementation

Note: WSDL does not know about the implementation!

Service Access

Note: Multiple Ports may have been provided in WSDL!

WSDL after Deployment

<service name="HelloWorldService"> <port name="HelloIFPort" binding="tns:HelloIFBinding"> <soap:address location=

"http://lsir-cis-pcx:8009/hello/helloService"/> </port></service>

This can be published via UDDI

Step 4. Publish Service

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

Client can locate the service querying UDDI

publish WSDL URIs

Step 5. Generate Client Proxy

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

publish WSDL URIs

Generate Stubs

• Client Configuration File<configuration

xmlns="http://java.sun.com/xml/ns/jax-rpc/ri/config">

</configuration>

• Automatically created using WSDL and client configuration file

wscompile -gen:client -d build -classpath build

config-client.xml

Step 6. Write Client to Invoke Proxy

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDL

SOAP pkg request

publish

Client Application

package iis;

import javax.xml.rpc.Stub;

public class HelloClient {

private String endpointAddress;

public static void main(String[] args) {

Stub stub = createProxy();

stub._setProperty (javax.xml.rpc.Stub.ENDPOINT_ADDRESS_PROPERTY, args[0]);

HelloIF hello = (HelloIF)stub;

System.out.println(hello.sayHello(args[1]));

} catch (Exception ex) {

ex.printStackTrace();

see next slide

WS address

parameter

Creating Proxy (Stub)

private static Stub createProxy() {

return (Stub) (new HelloWorldService_Impl().getHelloIFPort());}

attaching _Impl to the service name is an implementation-specific naming convention

Compiling and Packaging

compile javac –classpath system_jars:server_class_files:

stub_class_files HelloClient.java

package jar cvf hello-client.jar

all_client_class_files:all_server_class_files

Note: in the exercise the commands are automated by using the asant scripting utility provided by Sun J2EE

Step 7. Execute Client

Discovery

Description

Packaging

Transport

Network

Web Service

ProxyProxy

WSDLWSDLSOAP pkg request

SOAP pkg responseProxyProxy

publish

Client invokes service (almost) like a local method

Invoke Client

java –classpath hello-client.jar:jwsdp-jars hello.HelloClient

"Hello World!"

Generated at Server – Displayed at Client

Lecture 10: Web Services. Outline Overview of Web Services Create a Web Service with Sun J2EE...

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