the state of aop · 2013. 3. 21. · core aop concepts join point an identifiable point in the...

September 2006

The State of AOP

Ramnivas Laddad

Principal, Interface21

Author, AspectJ in Action

[email protected]

September 2006

Speaker introduction

� Principal at Interface21� Specializing in aspect-oriented programming and enterprise Java

� Author of books and articles� AspectJ in Action: Practical Aspect-Oriented Programming

� Several articles on IBM developerWorks,TheServerSide, JavaWorld and other publications

� Speaker at many professional conferences� No Fluff Just Stuff, JavaOne, JavaPolis, Software Development, EclipseCon, O’Reilly OSCON etc.

� Active involvement in AspectJ since its early form

September 2006

Agenda

An introduction to AOP

New and cool in AspectJ

Spring AOP

Spring AspectJ integration

Demos

Q&A

September 2006

In the beginning…

� Class ATM � Class Account

package banking;

public class ATM {

private String _id;

private String _address;

private transient ATMCard _currentATMCard;

private transient Account _currentAccount;

public ATM(String id, String address) {

_id = id;

_address = address;

}

public String getID() {

return _id;

}

public String getAddress() {

return _address;

}

public void setCurrentATMCard(ATMCard currentATMCard) {

_currentATMCard = currentATMCard;

}

public void setCurrentAccount(Account currentAccount) {

_currentAccount = currentAccount;

}

public void credit( float amount) {

_currentATMCard.getBankLiaison()

.credit(_currentAccount, amount);

}

public void debit( float amount) throws InsufficientBalanceException {


.debit(_currentAccount, amount);

}

public float getBalance() {

return _currentATMCard.getBankLiaison()

.getBalance(_currentAccount);

}

}

package banking;

public class Account {private int _accountNumber;private float _balance;

public Account( int accountNumber) { _accountNumber = accountNumber;

}

public int getAccountNumber() {return _accountNumber;

}

public void credit( float amount) {_balance = _balance + amount;

}

public void debit( float amount)throws InsufficientBalanceException {if (_balance < amount) {

throw new InsufficientBalanceException("Total balance not sufficient" );

} else {_balance = _balance - amount;

}}

public float getBalance() {return _balance;

}

public String toString() {return "Account: " + _accountNumber;

}

}

September 2006

Let’s add logging…


package banking;

import java.util.logging.*;

public class ATM {

...

private static Logger _logger= Logger.getLogger( "banking" );

...

public void credit( float amount) {_logger.logp(Level.INFO,

"ATM" , "credit" , "Entering" );


.credit(_currentAccount, amount);

}

public void debit( float amount)throws InsufficientBalanceException {_logger.logp(Level.INFO,

"ATM" , "debit" , "Entering" );


.debit(_currentAccount, amount);

}

...

}

package banking;


public class Account {

...

private static Logger _logger= Logger.getLogger( "banking" );

...

public void credit( float amount) {_logger.logp(Level.INFO,

"Account" , "credit" , "Entering" );_balance = _balance + amount;

}

public void debit( float amount)throws InsufficientBalanceException {_logger.logp(Level.INFO,

"Account" , "debit" , "Entering" );if (_balance < amount) {

throw new InsufficientBalanceException("Total balance not sufficient" );

} else {_balance = _balance - amount;

}}

...

}

September 2006

…and access control


package banking;

import java.security.*;

import javax.security.auth.*;


public class ATM {

...

private Subject _atmSubject;

private static Logger _logger = Logger.getLogger( "banking" );

...

public void credit( final float amount) {

_logger.logp(Level.INFO, "ATM" , "credit" , "Entering" );PrivilegedAction worker

= new PrivilegedAction() {public Object run() {

_currentATMCard.getBankLiaison().credit(_currentAcc ount, amount);

return null ;}};

Subject.doAsPrivileged(_atmSubject, worker, null );}

public void debit( final float amount) throws InsufficientBalanceException {_logger.logp(Level.INFO, "ATM" , "debit" , "Entering" );

PrivilegedExceptionAction worker= new PrivilegedExceptionAction() {

public Object run() throws Exception {_currentATMCard.getBankLiaison().debit(_currentAcco unt, amount);return null ;

}};

try {Subject.doAsPrivileged(_atmSubject, worker, null );

} catch (PrivilegedActionException ex) {Throwable cause = ex.getCause();

if (cause instanceof InsufficientBalanceException) {throw (InsufficientBalanceException)ex.getCause();

}}

}

...

}

package banking;


import java.security.AccessController;


...


...


AccessController.checkPermission(

new BankingPermission( "accountOperation" ));

_logger.logp(Level.INFO,

"Account" , "credit" , "Entering" );

_balance = _balance + amount;

}





"Account" , "debit" , "Entering" );

if (_balance < amount) {

throw new InsufficientBalanceException(

"Total balance not sufficient" );

} else {

_balance = _balance - amount;

}

}

...

}

September 2006

…and access control


package banking;

import java.security.*;import javax.security.auth.*;


public class ATM {...

private Subject _atmSubject;


...

public void credit( final float amount) {_logger.logp(Level.INFO, "ATM" , "credit" , "Entering" );PrivilegedAction worker

= new PrivilegedAction() {public Object run() {

_currentATMCard.getBankLiaison().credit(_currentAcc ount, amount);return null ;

}};Subject.doAsPrivileged(_atmSubject, worker, null );

}

public void debit( final float amount) throws InsufficientBalanceException {_logger.logp(Level.INFO, "ATM" , "debit" , "Entering" );

PrivilegedExceptionAction worker

= new PrivilegedExceptionAction() {public Object run() throws Exception {

_currentATMCard.getBankLiaison().debit(_currentAcco unt, amount);return null ;

}};

try {Subject.doAsPrivileged(_atmSubject, worker, null );

} catch (PrivilegedActionException ex) {

Throwable cause = ex.getCause();if (cause instanceof InsufficientBalanceException) {

throw (InsufficientBalanceException)ex.getCause();}

}

}

...

}

package banking;


import java.security.AccessController;


...


...





"Account" , "credit" , "Entering" );

_balance = _balance + amount;

}





"Account" , "debit" , "Entering" );

if (_balance < amount) {

throw new InsufficientBalanceException(

"Total balance not sufficient" );

} else {

_balance = _balance - amount;

}

}

...

}

September 2006

…and so it goes

� Transaction management

� Thread safety

� Caching

� Resource pooling

� Profiling

� Policy enforcement

� Monitoring

� Testing

� Statement generation

� Service level agreement enforcement

� Business rules

September 2006

A quick intro to AOP

� Crosscutting concerns

� Functionality whose implementation spans multiple modules

� Many examples: Logging and tracing, Transaction management, security, caching, error handling, business rules, performance monitoring…

� AOP

� A programming methodology to help with crosscutting concerns

September 2006

ATM Account

System Evolution: Conventional

Codescattering

…

…

Codetangling

September 2006

System Evolution: AOP based

Loggingaspect

Access controlaspect

ATM Account …

…

…

September 2006

Core AOP concepts

� Join point

� An identifiable point in the execution of a program.

� Central, distinguishing concept in AOP

� Pointcut

� Program construct that selects join points and collects context at those points.

� Advice

� Code to be executed at a join point that has been selected by a pointcut

� Introduction

� Additional data or method to existing types, implementing new interfaces

September 2006

Pointcut

� Selects join points and collects context at those points

� Example:pointcut release(Connection conn)

: call ( void Connection.close()) && target (conn);

pointcut accountCreation(Account account)

: execution (Account. new()) && this (account);

pointcut service()

: execution (* Remote+.*(..) throws RemoteException);

pointcut accountChangeFromATM(ATM atm, Account account)

: cflow (atmRequest(atm)) && accountChange(account);

September 2006

Dynamic crosscutting: Advice

� Code to be executed at a join point that has been selected by a pointcut

� Three kinds:

� Beforebefore () : call (* ATM.*(..)) {

...

}

� Afterafter (Account account) returning : accountOperation(account) {

...

}

� AroundObject around () : call (* Remote+.*(..) throws RemoteException) {

try {

... proceed (); ... Retry logic ...

} catch (...) {

}

}

September 2006

Static crosscutting

� Introduce new parent typesdeclare parents : banking..* implements Loggable;

� Introduce new memberspublic Logger Loggable._logger;

� Soften exceptionsdeclare soft : SQLException

: within (banking.model..*);

� Compile-time errors and warningdeclare error

: call (* Thread.*(..))&& within (javax.ejb.EnterpriseBean+)

: "Use of thread disallowed from EJBs" ;

September 2006

Agenda



Spring AOP


Demos

Q&A

September 2006

AspectJ syntax and weaving

� Three syntaxes

� Language extension• New keywords

• Needs special compiler

� Metadata-based extension (@AspectJ)• Compilable using a plain Java compiler

� XML-based definition• Configuration modifications without recompiling

� AspectJ weaving options

� Compile-time weaver• Aspect and class source code � class files

� Binary weaver (“linker”)• Aspect and class source/binary files � class files

� Load-time weaver• Aspect and class binary files

� Weave class files when being loaded into VM

September 2006

AspectJ syntax guiding principles

� One language

� Multiple development styles

� One semantics

� One weaver

� Syntax and weaving model orthogonal

September 2006

Current AspectJ syntax

public aspect LoggingAspect {

private static Logger _logger = Logger.getLogger( "tracer" );

public pointcut loggedOperations()

: execution (* *.* (..));

before () : loggedOperations() {

Signature sig = thisJoinPointStaticPart .getSignature();


sig.getDeclaringType().getName(),

sig.getName(), "Entering" );

}

}

September 2006

New @AspectJ syntax

@Aspect

public class LoggingAspect {

private static Logger _logger = Logger.getLogger( “tracer" );

@Pointcut(“ execution (* *.* (..))”)

public void loggedOperations() {}

@Before (“loggedOperations()”)

public void log(JoinPoint.StaticPart thisJoinPointStaticPart ) {



sig.getDeclaringType().getName(),

sig.getName(), "Entering" );

}

}

September 2006

XML syntax

� Base aspect expressed in traditional or @AspectJ syntax

public abstract aspect MonitoringAspect {

public abstract pointcut monitoredOps();

Object around () : monitoredOps() {

long startTime = System.nanoTime();

Object ret = proceed ();

long endTime = System.nanoTime();

monitorAgent.record( thisJoinPointStaticPart ,

endTime-startTime);

return ret;

}

...

}

September 2006

XML syntax: Defining concrete aspect<aspectj>

<aspects>

<concrete-aspect

name="com.aspectivity.monitoring.JDBCMonitoringAspe ct"

extends="com.aspectivity.monitoring.MonitoringAspec t">

<pointcut name="monitoredOps"

expression="call(* java.sql.*.*(..))"/>

</concrete-aspect>

...

</aspects>

...

</aspectj>

September 2006

Load-time weaving

� Weave while classes are being loaded

� No explicit compile-time or binary weaving needed

� Agents supported

� JVMTI-based• Application-server agnostic

• VMs supported− All 5.0+ VMs

java -javaagent:aspectjweaver.jar…− JRockit VM 1.3/1.4

java -Xmanagement:class=org.aspectj.weaver.loadtime.JRockitAgent…

� Classloader-based• Application-server specific

− Not available for all app servers

September 2006

LTW deployment: aop.xml

<aspectj>

<aspects>

<aspect name="com.aspectivity.security.FineGrainedS ecurity"/>

<aspect name="com.aspectivity.tracing.ExceptionTrac er"/>

<concrete-aspect

name="com.aspectivity.monitoring.JDBCMonitoringAspe ct"

extends="com.aspectivity.monitoring.MonitoringAspec t">

<pointcut name="monitoredOps"

expression="call(java.sql.*.*(..))"/>

</concrete-aspect>

</aspects>

<weaver>

<include within="com.interface21..*"/>

<exclude within="com.interface21.rss..*/>

</weaver>

</aspectj>

September 2006

Signature-based pointcut

� Utilize join point signatures

� Exploits inherent data associated with signature

� Wildcards select a wide range of join points

� Work well in many cases

� Logging and tracing

� Profiling

� Policy enforcement

� Caching and pooling

� Fault tolerance

� Thread safety

� Business rules

September 2006

Metadata based pointcuts

� Utilize join point metadata

� Often along with join point signature

� Needed in certain cases

� Transaction management

� Authentication

� Authorization

� Concurrency control

� …

September 2006

Selecting annotation based join points

� Execution of all secure operationspointcut secureOps()

: execution (@Secure * *.*(..));

� Access to all sensitive datapointcut sensitiveAccess()

: get (@Sensitive * *);

� Handler for non-catastrophic exceptionshandler (!@Catastrophic *)

September 2006

Collecting annotation instances

� Select join points with an @Tx annotationpointcut txOps() : @ annotation (Tx);

� Collect the @Tx annotationpointcut txOps(Tx tx) : @ annotation (tx);

� Match all join points with REQUIRED transactional attribute

pointcut txRequiredOps(Tx tx)

: @ annotation (tx)

&& if (tx.value() == TxType.REQUIRED);

September 2006

Annotation-specific pointcuts

� @annotation

� @this

� @target

� @args

� @within

� @withincode

September 2006

New AJDT features

� Improved debugging

� Setting breakpoints in advice or method

� Improved code completion

� And improving…

� Improved editing support

� Eager parsing enabled

� Improved visualization

� New views

� Crosscutting view

� Crosscutting comparison view

September 2006

Crosscutting view

� Replaces AspectJ-aware outline view

� Shows interaction between classes and aspects

� Updates incrementally

September 2006

Crosscutting comparison view

� Allows tracking effects of aspects during evolution

� Methods advised/not advised

� Static structure affected/not affected

September 2006

Layering violation enforcement

� Problem

� UI layer often directly use DAO layer contrary to architectural policies

� No automatic enforcement

� Solution

� One simple, reusable aspect to enforce the policies

• Just add to your build system

September 2006

Layering policy enforcement aspect

public aspect LayeringPolicyEnforcementAspect {

pointcut dataAccess()

: call (* com.mycompany.dao..*.*(..))

|| call (* org.hibernate..*.*(..))

|| call (* *..sql..*.*(..));

declare error : dataAccess()

&& within (com.mycompany.ui..*)

: "UI layer shouldn’t directly access data;

Use business layer instead" ;

}

September 2006

Cross repository contamination enforcement

public aspect RepositoryCrossContaminationEnforcement {

pointcut inAccountRoot()

within (com.mycompany.accounting..*);

declare error : set (com.mycompany.transactions..* *.*)

&& inAccountRoot();

: "Objects in the account root should not hold onto

objects from other roots";

}

September 2006

First failure data capture (FFDC)

� Problem:

� Exception at low level trickles through layers; however, original context is lost

� Solution:

� FFDC aspect logging the exception at the first failure site

September 2006

FFDC: Base aspect

public abstract aspect FFDC {

public abstract pointcut ffdcOp();

after () throwing (Exception ex) : ffdcOp() {

if (_logger.isLoggable(Level.WARNING)) {


logFFDC(sig.getDeclaringType().getName(),

sig.getName(), ex,

thisJoinPoint .getThis(),

thisJoinPoint .getArgs());

}

}

public void logFFDC(String className, String methodName,

Exception ex, Object thiz, Object[] args) {

...

}

}

September 2006

FFDC: Derived aspect

public aspect BlogFFDC extends FFDC {

public pointcut ffdcOp()

: execution (* com.mycompany..*.*(..)

throws RemoteException)

|| execution (* com.mycompany..dao.*.*(..));

}

September 2006

Authorization

� Problem:

� Many methods in the system needs to check for authorized access

� Solution:

� An aspect using JAAS as the underlying authorization mechanism

September 2006

Authorization: Reusable base aspect

public abstract aspect AbstractAuthAspect {

public abstract pointcut authorizedOperations();

public abstract Permission getPermission(

JoinPoint.StaticPart jpsp);

before () : authorizedOperations() {


getPermission( thisJoinPointStaticPart ));

}

}

September 2006

Authorization: Derived aspect

public aspect BankingAuthAspect extends AbstractAuthAspect {

public pointcut authorizedOperations ()

: execution ( public * banking..Account.*(..));

public Permission getPermission(JoinPoint.StaticPart jpsp) {

return new BankingPermission(jpsp.getSignature().getName());

}

}

September 2006

Mix-in implementation

� Problem:

� Boilerplate implementation of an implementation

� Solution:

� Provide the default implementation using static crosscutting

September 2006

Interface needing boilerplate code

public interface ServiceCenter {

public String getId();

public void setId(String id);

public String getAddress();

public void setAddress(String address);

}

September 2006

Interface with mixin implementation

public interface ServiceCenterMixin extends ServiceCenter {

static aspect IMPL {

private String ServiceCenterMixin.id;

private String ServiceCenterMixin.address;

public String ServiceCenterMixin.getId() {

return id;

}

public void ServiceCenterMixin.setId(String id) {

this .id = id;

}

public String ServiceCenterMixin.getAddress() {

return address;

}

public void ServiceCenterMixin.setAddress(String address) {

this. address = address;

}

}

}

September 2006

Interface implementations

public class ATM extends Teller

implements ServiceCenterMixin {

... No set/getId(), set/getAddress()

... No id, address

}

public class BrickAndMortar extends Teller

implements ServiceCenterMixin {

... No set/getId(), set/getAddress()

... No id, address

}

September 2006

Injecting dependencies using Aspect

� Limitations of Spring’s “traditional” DI

� Injection limited to beans created through configuration

� Not sufficient for objects created thru other mechanisms: Hibernate, JDO, fine grained objects

� Prevents richer domain models prescribed by domain-driven design (DDD)

� Solution: Use aspects to inject dependencies

September 2006

Dependency declaration:Based on template id

@Configurable ( "emailerClient" )

public class Order {

private Emailer emailer ;

public void process() {

...

emailer.send(...)

}

public void setEmailer(Emailer emailer) {

this. emailer = emailer;

}

}

September 2006

Dependency configuration:Based on template id

<beans...>

</beans>

<aop:spring-configured />

<bean id ="smtpEmailer" .../>

<bean id ="emailerClient" scope ="prototype" >

<property name="emailer" ref ="smtpEmailer" />

</ bean >

September 2006

Dependency declaration:Based on template class

@Configurable

public class Order {

private Emailer emailer ;

public void process() {

...

emailer.send(...)

}

public void setEmailer(Emailer emailer) {

this. emailer = emailer;

}

}

September 2006

Dependency configuration: Based on template class

<beans...>

</beans>

<aop:spring-configured />

<bean id ="smtpEmailer" .../>

<bean class ="example.Order" scope ="prototype" >

<property name="emailer" ref ="smtpEmailer" />

</ bean >

September 2006

Agenda



Spring AOP


Demos

Q&A

September 2006

Spring AOP basics

� A proxy-based AOP framework

� JDK proxies

� CGLIB proxies

� Targets many J2EE use cases

� Powerful integration with AspectJ

� Allowing tapping into full AOP features

September 2006

Proxy

Spring AOP schematic

Target

Object

Advice

Advisor

Pointcut

September 2006

Configuring through XML:Defining advisor

<bean id ="spamPreventionAdvisor"

class ="o.s.aop.support.DefaultPointcutAdvisor" >

</ bean >

<property name="advice" >

<bean class ="example.SpamPreventionInterceptor" />

</ property >

<property name="pointcut" >

<bean class ="o.s.aop.support.JdkRegexpMethodPointcut" >

<property name="pattern" value =".*send.*" />

</ bean >

</ property >

September 2006

Configuring through XML:Creating proxy<bean id ="emailerTarget" class ="example.EmailerImpl" >

</ bean >

<bean id ="emailer" class ="o.s.aop.framework.ProxyFactoryBean" >

<property name="target" ref ="emailerTarget" />

<property name="interceptorNames" >

<list >

<value >spamPreventionAdvisor </ value >

</ list >

</ property >

<property name="proxyInterfaces" >

<list >

<value >example.Emailer </ value >

</ list >

</ property >

</ bean >

Target

Advice/Advisor

Proxy interface(optional)

September 2006

Bean client

package example;

...

public class Main {

public static void main(String[] args ) {

ApplicationContext context

= new ClassPathXmlApplicationContext( "beans.xml" );

Emailer emailer = (Emailer)context.getBean( "emailer" );

emailer.send( "[email protected]" ,

"Hi! Your paypal account..." );

emailer.send( "[email protected]" ,

"Hi, I have an AspectJ question..." );

}

}

September 2006

Agenda



Spring AOP


Demos

Q&A

September 2006

Proxy

Where AspectJ helps Spring AOP

Target

Object

Typed AdviceAspectJ Expression Pointcut

@AspectJ Aspects

September 2006

Spring-AspectJ integration

� Provides power of AspectJ in Spring

� Levels of integration

� Proxy-based mechanism—no special compiler• AspectJ pointcut expression

−Easier and expressive way to select pointcuts

• Typed advice−XML-based aspects definition with plain Java classes

•@AspectJ aspects−Express aspects with little XML

� Special compiler or weaver• Full power AspectJ

September 2006

AspectJ pointcut expression

� AspectJExpressionPointcut

� Still uses proxy-based mechanism

• Limitation of method-only interception

<bean id ="spamPreventor"

class ="o.s.aop.support.DefaultPointcutAdvisor" >

<property name="advice" >

<bean class ="example.SpamPreventionInterceptor" />

</ property >

<property name="pointcut" >

<bean class ="o.s.aop.aspectj.AspectJExpressionPointcut" >

<property name="expression"

value ="execution(* send(..))" />

</ bean >

</ property >

</ bean >

September 2006

Typed advice

� Problem: MethodInterceptor and its cousins take parameters of type Object.

� Solution: Use AspectJ style type-safe interception

September 2006

Typed advice: Defining aspect

<beans ...><aop:config >

<aop:aspect id ="emailLoggerBean"ref ="emailerLogger" >

<aop:beforepointcut ="execution(* send(String, String))

and args(address, *)" method ="log" />

</ aop:aspect ></ aop:config >

<bean id ="emailerLogger" class ="example.EmailLogger" />

...</beans>

September 2006

Plain Java aspect

package example;

public class EmailLogger {

public void log(JoinPoint.StaticPart tjpsp,

String address) {

System.err.println(

"Invoking " + tjpsp.getSignature() +

" for " + address);

}

}void before(Method method, Object[] args,

Object target) throws Throwable;

September 2006

Do away with XML: @AspectJ

package example;

@Aspectpublic class EmailLogger {

@Before( execution(* send(String, String))

&& args(address, *)" )

public void log(JoinPoint.StaticPart tjpsp, String address) {

System.err.println("Invoking " + tjpsp.getSignature() + " for " + address);

}}

September 2006

Using @AspectJ aspect

<beans ...>

<aop:autoproxy/ >

<bean id ="emailerLogger"

class ="example.EmailLogger" />

... Other beans ...

</beans>

September 2006

Choosing Spring AOP vs. AspectJ

� Use Spring AOP when

� Method-only interception is sufficient

• Full power of AOP overwhelming

� Don’t want to use special compiler

� Domain object’s don’t need to be crosscutted

� Pre-written aspects meet your needs

� Use AspectJ when

� Otherwise…

September 2006

Summary

� Spring AOP is simple, yet powerful way to modularize crosscutting concerns

� AspectJ integration bring full power of AOP in the Spring environment

� Incremental path from Spring AOP to AspectJ is available

The fun has just began…

September 2006

Resources

� Spring books

� Pro Spring, by Rob Harrop and Jan Machacek

� Professional Java Development with the Spring Framework, by Rod Johnson, Rod Johnson, Juergen Hoeller, Alef Arendsen, Thomas Risberg, ColinSampaleanu

� Spring in Action, by Craig Walls

� AspectJ books

� AspectJ in Action, by Ramnivas Laddad

� Eclipse AspectJ, by Adrian Colyer, Andy Clement, George Harley, Matthew Webster

� DI using aspect� Adrian Coyler, Dependency injection with AspectJ and Spring

http://www.ibm.com/developerworks/java/library/j-aopwork13.html

September 2006

AOP training from the source

Core AOP:

Simplifying Enterprise Applications

with AOP

November 7-10, Washington, DC

http://interface21.com/training

Spring Conference: The Spring Experience 2006December 7th – 10th, Hollywood Florida

by Interface21 and NoFluffJustStuff Java Symposiums

� World-class technical conference for the Spring community� 3 full days, 5 concurrent tracks, 60 sessions

• Core Spring 2.0• Core Enterprise 2.0• Core Web 2.0• Domain Driven Design• Just Plain Cool

� Enjoy five-star beach resort and amenities� Converse with core Spring team and industry experts

� Rod Johnson, Adrian Colyer, Ramnivas Laddad, Juergen Hoeller, etc.� Registration at http://www.thespringexperience.com

September 2006

Questions?

Ramnivas Laddad

Email: [email protected]

Web: http://interface21.com

Blog: http://ramnivas.com/blog

the state of aop · 2013. 3. 21. · core aop concepts join point an identifiable point in the...

Documents