Writing a Web Service Client App for Android

Writing a Web Service Client App for Android

Copyright © 2010-2012, Wolf Paulus - http://wolfpaulus.com - A Tech Casita Production. All rights reserved.

http://wolfpaulus.com


Agenda

Server Side (e.g. Tomcat)

Hessian, Binary Protocol

Http-Session Support

Client

hessdroid

remote calls / async




Quick Tips

Use Android’s Resources ( R.class )

Auto-Launch an Intent at boot time

Client

Things that can will go wrong

AgendaCopyright © 2010-2012, Wolf Paulus - http://wolfpaulus.com - A Tech Casita Production. All rights reserved.



Switch Activity

Switch Activity

Remote call

reload users

Remote Call to getNext

Four item main menu




Exposing a Service Class: Hessian Binary Web Service Protocol




Java Hessian




package com.carlsbadcubes.api;

import java.util.Collection;

public interface CommService { Collection<Message> getMessages();

Collection<User> getUsers();}




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

<servlet> <servlet-name>myservice</servlet-name> <servlet-class>com.caucho.hessian.server.HessianServlet</servlet-class>

<init-param> <param-name>service-class</param-name> <param-value>com.carlsbadcubes.impl.CommServiceImpl</param-value> </init-param>

<init-param> <param-name>api-class</param-name> <param-value>com.carlsbadcubes.api.CommService</param-value> </init-param>

</servlet>

<servlet-mapping> <servlet-name>myservice</servlet-name> <url-pattern>/service/*</url-pattern> </servlet-mapping>

</web-app>

Interface

Implementation

defined in hessian.jar

No SessionNo DiscoveryCopyright © 2010-2012, Wolf Paulus - http://wolfpaulus.com - A Tech Casita Production. All rights reserved.



Servlet

Thread

Thread

Thread

m_var

http requests

ServiceClassimpl.

ServiceAPI

created in servlet.init()

(1)

(1)

(1)

(n)

::




http response

JSESSIONID = 123

JSESSIONID = 789

JSESSIONID = 357

SessionMap

123

789357

Servlet

Thread

Thread

Thread

m_var

ServiceClassimpl.

ServiceAPI

::

request.getSession()




http response

JSESSIONID = 123

JSESSIONID = 789

JSESSIONID = 357

SessionMap

123

789357

http request Servlet

Thread

Thread

Thread

m_var

ServiceClassimpl.

ServiceAPI

::

123ThreadLocal

789ThreadLocal

357ThreadLocal




The ThreadLocal Class:

public class ThreadLocal<T> { public void set( T newValue ); public T get(); public void remove(); protected T initialValue();}




HessianHttpServlet extends HessianServlet implements HessianHttpService {

... }

... not in hessian.jar




.. all of HessianServlet

Discovery Service for Android Clients

Map<String, String> getServices()

puts HttpSession Map into ThreadLocal

memory

HessianHttpServlet extends HessianServlet implements HessianHttpService




HessianHttpServlet@Overrideinit() .. // // introspect service implementation to find out if we have to put the servlet into a session // if ( getInitParameter("service-class") != null ) { String className = getInitParameter("service-class"); if (className != null) { this.requiresSessionSupport = StateKeeper.class.isAssignableFrom(loadClass(className)); } if (this.requiresSessionSupport) { System.out.println(className + " has been registered for session support."); } }

@Overrideservice() ..

if (this.requiresSessionSupport) { HttpServletRequest req = (HttpServletRequest) request; ThreadLocalAttrMap.set( req.getSession( true ) ); }




= Client




String url = “http://hostname.domain:port/service”;

ServiceProxyFactory factory = new HessianProxyFactory();factory.set ..(..);factory.set ..(..).

CommService cs = factory.create( CommService.class, url , getClassLoader());

hessdroidhttp://code.google.com/p/hessdroid/


http://www.caucho.com/hessian/test/basic

http://www.caucho.com/hessian/test/basic

http://code.google.com/p/hessdroid/




HessDroid Generified ...HessianProxyFactory:public <T>T create( Class<T> api,

String urlName, ClassLoader loader);

Clientside code without casting:Service s = (Service) factory.create( Service.class, url, cl );







Creates a Cookie Map,Maintains HttpSessions

HessianHttpProxyFactory extends HessianProxyFactory {

... }







Service Discovery:maps Interfaces to URLs

HessianFactory.initialize( )

... not in hessdroid.jar




Hessian Client

CommService cs = HessianFactory.create( CommService.class, getClassLoader() )




DemoTomcat Server with a Hessian Service and a Hessian based Android Client




Async ....

Don’t run HessionFactory.create(..) in the main threadDon’t run remote method calls in the main thread either.




Interface Garage { void openDoor();

Car getCar();}

Interface Car {void openDoor();Color getColor();

}




Garage garage = HessianFactory.create( Garage.class, getClassLoader() );

// The interface Garage and the class CarImpl// need to be available on the client to make this work:

garage.openDoor(); // remote callgarage.getCar().openDoor(); // local call




Unlocking Android

Android Wireless Application Development

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Writing a Web Service Client App for Android

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