RPC over XML. Web services with Java. How to install it? Reference implementation. Setting the environment variables. Preparing the system

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Web services with Java

Distributed Systems SS03

RPC over XML

• Layered architecture based on TCP

• Bottommost layer is HTTP

• SOAP (XML) sits above it

• LOT of W3C standards and W3C drafts

describe it.

Reference implementation

• Sun JWSDK (Java Web Services Development

kit )

• Enables to test the newest technology for free

• Contains Tomcat (Apache-based webserver), Ant

(make utility) and several example applications

and JAX-RPC ( we will use this component),

JAXM (the message-based middleware).

• Installation and maintenance is quite hard! (About

6000 files in the tree, 60 MB disk-space required)

• Works under Windows and Linux (everything is

written in Java)

How to install it?

• Install J2SE 1.3.1 or better 1.4.x!

• Start the JWSDP installer!

• Follow the instructions to replace some

older files in the J2SE library tree

• Set the PATH variables

• Experiment with it!

Setting the environment variables

• Set JAVA_HOME to the J2SE‘s root

• Set TOMCAT_HOME and CATALINA_HOME

to the JWSDP‘s root

• Put the „bin“ directories into the search PATH

(don‘t forget to include ant‘s bin directory )

– PATH to JWSDP‘s Ant‘s bin directory should be at the

beginning! Otherwise things won‘t work

• Most problems with J2EE/JWSDP are caused by

wrong PATH and variable settings

Preparing the system

• Create a file, called build.properties in your

home-directory

– ~ on Unices

– C:\Dokumente und Einstellungen\yourName on

Windows systems

– It should contain the following 2 lines:

– username=your TOMCAT user name

– password=your TOMCAT password

– Look at the tomcat-users.xml file if you have forgotten

your user name and password

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Starting/Stopping Tomcat

• $JWSDP_HOME/bin/startup.sh

• Install your web applications

• (Write them if necessary)

• You can access the Tomcat server on the

port 8080

– http://localhost :8080/yourApplication

• $JWSDP_HOME/bin/shutdown .sh

How to develop a web service

with JAX-RPC?

• Write only 2 classes. One class exposes the service

method signature, the other class should provide

implementation of the service

• Define an XML configuration file that contain

instructions to generate client-side and server-side

stubs required by JAX-RPC (necessary for the

Java-to-WSDL mapping tool)

• Define a web.xml file that specifies the

deployment descriptor for deployment in an

application server

• That‘s all! – and install („deploy“) them!

Our sample web service – the

interface

• The interface defining the service should

extend java.rmi.Remote

• Every method should throw a

java.rmi.RemoteException

• No constant declaration is allowed

• Only SOAP-able data types are supported

• We will see the SOAP-able

Primitive data types in JAX-RPC

• JAX-RPC uses the following type-mapping

– Boolean -> xsd:boolean

– Byte -> xsd:byte

– Double -> xsd:double

– Float -> xsd:float

– Integer (int) -> xsd:int

– Long -> xsd:long

– Short -> xsd:short

Supported Java standard-classes

• BigDecimal -> xsd:decimal

• BigInteger -> xsd:integer

• Calendat -> xsd:dateTime

• Date -> xsd:dateTime [broken]

• GregorianCalendar -> xsd:dateTime

• String -> xsd:string

• JWSDP supports more data types that can be used only

if all involved parties are using Java (Vector, Stack,

HashTable, etc.)

• Arrays of supported JAX-RPC types are also supported

Supported application classes

• Other, programmer defined classes are also

supported. They must adhere to some conventions

– They must have a public default constructor

– It must not implement the java.rmi.Remote interface

– Ist fields must be supported JAX-RPC types

– A public field cannot be final or transient

– A non-public field may have corresponding getter and

setter methods (JavaBeans coding convention)

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Hello web service description

• The world‘s simplest distributed greeting

serviceJ

• Its input is a name (String)

• The result is a greeting in String form

• Implemented as a JAX-RPC web service

endpoint

The hello web service interface

package hello;

import java.rmi.Remote;

import java.rmi.RemoteException;

public interface HelloIF extends Remote {

public String sayHello(String s)

throws RemoteException;

}

A sample XML configuration file

for the hello service

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

<configuration

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

</configuration>

This file (config.xml) will be used to generate cliens/server

stubs/skeletons with the wscompile utility.

hello – implementation class

package hello ;

public class HelloImpl implements HelloIF {

public String message = "Hello ";

public String sayHello(String s) { return message + s;

} }

Using wscompile(.sh/.bat) to

generate client stubs

• The hard way ....

~/jwsdp -1.1/jaxrpc- 1.0.3/bin/wscompile.sh -gen:client - d build/client/ hello –classpath

build/shared config.xml

– And then execute deployment, etc. etc. with the

manager login of your Tomcat server!

• The easy way:

– Download ds2003webservices.tar from the course page – Modify the war-path (use your directory instead of /home /itec/csb) – Start the command „kompajl“ to compile everything

– Start the command „ant run“ to execute the client

– If the paths are set correctly , the program will be deployed and run!

A client application of the service

import javax.xml.rpc.Stub; import java.util .Date; public class HelloClient {

public static void main(String[] args) { try {

Stub stub = createProxy (); HelloIF hello = ( HelloIF)stub ; System.out.println(hello.sayHello("Duke!")); } catch (Exception ex) {ex.printStackTrace();} }

private static Stub createProxy() {

return (Stub)(new MyHello _Impl(). // for JWSDP

getHelloIFPort()); //see jaxrpc -ri.xml!

} }

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Client stub name

• The name of the client stub is not standardized

• JWSDP uses the file jaxrpc-ri.xml when contructing

the client stub

• Look at it! Here is an excerpt:

<endpointMapping

endpointName="MyHello"

• That ‘s why wscopile and we used MyHello for the

stub‘s classname.

• wscompile creates client stubs based on their WSDL

description („downloaded“ from the Tomcat server)

Implementation-specific parts

• The file config.xml is used by JWSDP only

• jaxrpc-ri.xml too

• Stub and tie (server skeleton ) class names

• The tools (wscompile,wsdeploy,deploytool)

• Support for collections as parameters and return

values

• (Using JAX- RPC with J2EE is not the same as

with JWSDP)

• We use the latest version (1.1) of JWSDP

Common errors

• The paths are not set

• An older version of „ant“ is in the PATH before a

newer one

• Tomcat is not running during compilation time

(remember: WSDL descriptions stored in WAR

files are accessed during compilation)

• HTTP -specific response codes:

– 404: resource unavailable

– 401: password required (does the file named

build.properties contain the right password?)

SOAP on the wire – request hdr

localhost.37408 > localhost.http-alt:

POST /hello-jaxrpc/hello HTTP/1.1 Content-Type: text/xml; charset="utf-8" Content-Length:477

SOAPAction : ""

User-Agent:Java/1.4.1_02 Host: localhost:8080

Accept: text/html, image/gif, image/jpeg , *; q=2, */*; q=2

Connection : keep -alive

SOAP on the wire – request body

<?xml.version="1.0" encoding ="UTF-8"?> <env:Envelope xmlns:env="http:// schemas.xmlsoap.org/soap/envelop e/" xmlns:xsd="http:// www.w3.org/2001/XMLSchema" xmlns:xsi="http:// www.w3.org/2001/XMLSchema-instance" xmlns:enc="http:// schemas.xmlsoap.org/soap/encoding/ " xmlns:ns0="http:// com.test/wsdl/MyHello" env:encodingStyle="http:// schemas.xmlsoap.org/soap/e ncoding/"> <env:Body><ns0:sayHello ><String_1 xsi:type="xsd:string">Duke!</String_1> </ns0: sayHello ></env:Body></ env:Envelope >

SOAP on the wire – reply hdr

localhost.http-alt > localhost.37408

HTTP/1.1 200 OK

Content-Type: text/xml; charset="utf-8"

SOAPAction: ""

Transfer-Encoding: chunked

Date: Sun, 01 Jun 2003 16:39:54 GMT

Server: Apache Coyote HTTP/1.1 Connector

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SOAP on the wire - reply body

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

<env :Envelope

xmlns:env="http://schemas .xmlsoap. org /soap/ envelope/" xmlns:xsd="http://www.w3. org /2001/ XMLSchema "

xmlns:xsi="http://www.w3. org /2001/ XMLSchema -instance" xmlns:enc="http://schemas .xmlsoap. org /soap/ encoding/" xmlns:ns0="http://com.test/wsdl /MyHello"

env: encodingStyle="http://schemas. xmlsoap.org/ soap /enco ding /">

<result xsi:type ="xsd: string ">Hello Duke!</ result> </ns0:sayHelloResponse ></ env :Body></env: Envelope>

And where are WSDL&UDDI?

• WSDL descriptions are automagically

generated by the wscompile tool in JWSDP

• They are stored in .war files (WEB

application archives)

• Take a look at the file hello-jaxrpc.war

– Unzip it

– Look for WEB-INF/MyHello .wsdl

• See the next 3 slides about the generated WSDL file

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

targetNamespace="http://com.test/wsdl/MyHello" xmlns:tns="http://com.test/wsdl/MyHello" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:xsd="http://www.w3.org/2001/ XMLSchema" xmlns:soap ="http://schemas.xmlsoap .org/wsdl/soa p/">

<outputmessage="tns:HelloIF_sayHelloResponse"/> </operation></portType > <binding name="HelloIFBinding" type="tns:HelloIF"> <operation name="sayHello"> <input> <soap:body encodingStyle="http:// schemas.xmlsoap.org/soap / encoding/" use="encoded" namespace="http://com.test/wsdl/MyHello"/></inp ut> <output> <soap:body encodingStyle="http:// schemas.xmlsoap.org/soap / encoding/" use="encoded" namespace="http://com.test/wsdl/MyHello"/></out put> <soap:operation soapAction=""/></operation> <soap:binding transport="http://schemas.xmlsoap.org/soap/http " style="rpc"/></binding>

<service name="MyHello">

<port name="HelloIFPort"

binding="tns:HelloIFBinding">

<soap:address

location="REPLACE_WITH_ACTUAL_URL"/></p

ort></service></definitions>

The UDDI

• Role of UDDI: stores links to WSDL

descriptions of web services

• UDDI registry is not part of JWSDP

• A registry browser and registry access

library are part of JWSDP

– See JAXR!

• Register your service if it works well at

well-known UDDI-Servers

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Well-known UDDI servers

• http://www-3.ibm.com/services/uddi

• https://uddi.ibm.com/

• https://uddi.ibm.com/ubr/registry.html

• http://uddi.microsoft.com

• A test server: http://test.uddi.microsoft.com

– Use only if a service will be added „soon“ into a the

public registry

• Other test server – this from IBM:

https://uddi.ibm.com/testregistry/publish

Registering your service@UDDI

• Open the start page of one of the UDDI servers, log in and

choose „Publish“

• Press „ Add a new Business“ and insert your (company‘s)

name and other details

• Add „Business Locators“ to it (categorize!)

• Press „ Continue“ and then „Save“

• Press „ Add a new Service“ and insert Name, Description,

Access Point, Locator

• Press „ Add a new Technical Model“ (also known as

tModel). Add the same information as above. The

„Overview URL“ will be the URL of yur WSDL

description

UDDI – Service Inquiry

• There are two ways to do this :

– Using inquiry API-s

• https://www-3.ibm.com/services/uddi/testregistry/inquiryapi

– Using a webbrowser

• Note that some service providers listed in

the UBR charge consumers that access their

Web services

UDDI – Inquiry by ....

• Open the registry startpage and select „Find“

• Choose

– „Business“ if you know company names and want

to search by company name

– „Service“ if you know the name of the service you

want or want to search by service name

– „Technical Model“ if you are searching with

WSDL descriptions

• Use the % sign as a joker (wildchar) character

Homework

• See

http://www.itec.uni-klu.ac.at/~csb/ds2003webservices.tar

• Implement TimeServer with webservices !

• (Deadline: 25.06.2003)