Professional Open Source © JBoss, Inc. 2003-2005. 1 2/6/2014 Professional Open Source © JBoss...

Professional Open Source™

© JBoss, Inc. 2003-2005. 104/10/23

Professional Open Source

© JBoss Inc., 2003-2005. 1

Implementing Middleware with AOPJBoss Aspect Oriented Middleware

© JBoss, Inc. 2003-2005. 2


© JBoss Inc., 2003-2005. 2

Topics

Overview From Interceptors to Aspects

– J2EE a la carte– AOP + metadata

From Aspects to EJB3– Proxy based AOP– AOP Domains– Annotations as Meta Model– XML + Annotations

Dynamic AOP– Transparent caching– JBoss Cache Demo– Designing a Cache

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© JBoss Inc., 2003-2005. 3

AOP and Middleware

Middleware is but a collection of cross-cutting concerns Most middleware already sort of aspectized

– CORBA and JBoss heavy use of interceptors

Basing designs on AOP natural step Expensive to use regular OOP techniques to mix/match

configurations Application is just configuration a set of cross-cutting concerns

– Natural step is to implement middleware using AOP– More modular designs– Less code clutter

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© JBoss Inc., 2003-2005. 4

AOP and Middleware

Aspect Oriented Middleware brings transparency System aspects can be made orthonogal Application code can free of system programming Middleware can be made simpler to use

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© JBoss Inc., 2003-2005. 5

AOP Makes things Easier

AOP to implement Ease-of-Use– EJB 3 and annotation library implemented with AOP

AOP for Ease-of-Extension– Ease-of-use frameworks written on top of AOP– AOP gives easy consistent way to extend behavior


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© JBoss Inc., 2003-2005. 6

From Interceptors To AspectsJBoss 3.x to JBoss AOP

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© JBoss Inc., 2003-2005. 7

JBoss 3.x Architecture

– J2EE behavior expressed as interceptors

– Detyped method invocations

Client JVMJM

X Microkernel

JMX M

icrokernel

Server JVM

EJB Container MBean

011101010101

RemoteInvokerRemoteInvoker

Typed Interface

Client Proxy


EJB Container MBean

Service MBean

Invocation

Port 1234

Port 4321ClientClient

– Internally invocation objects are routed within the kernel

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© JBoss Inc., 2003-2005. 8

Cross-cutting Concern

<container-configuration>

<container-name>Standard CMP 2.x EntityBean</container-name>

<container-interceptors>

<interceptor>org.jboss.ejb.plugins.ProxyFactoryFinderInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.LogInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.SecurityInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.TxInterceptorCMT</interceptor>

<interceptor>org.jboss.ejb.plugins.CallValidationInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.EntityCreationInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.EntityLockInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.EntityInstanceInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.EntityReentranceInterceptor</interceptor>

<interceptor>org.jboss.resource.connectionmanager.CachedConnectionInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.EntitySynchronizationInterceptor</interceptor>

<interceptor>org.jboss.ejb.plugins.cmp.jdbc.JDBCRelationInterceptor</interceptor>

</container-interceptors>

















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© JBoss Inc., 2003-2005. 9

































Cross-cutting Concern

Extract Aspects

Extract Aspects

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© JBoss Inc., 2003-2005. 10

Interceptors to Aspects

Aspectizing JBoss seemed like logical next step Leverage pointcut expressions Bring J2EE a la cart to plain Java Leverage our existing interceptor design


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© JBoss Inc., 2003-2005. 11

J2EE a la carte

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© JBoss Inc., 2003-2005. 12

Transaction Demarcation

Transaction demarcation (method, field, constructor) You can specify transaction boundaries within code Tags can transparently interact with Transaction Manager

– Begin, suspend, commit and rollback transactions

– On method, field, or constructor execution

EJB adjectives used to specify transactional behavior– Required, RequiresNew, Supports, Never, NotSupported, Mandatory

Complete control over when a rollback is triggered– i.e. which thrown exceptions cause a rollback

© JBoss, Inc. 2003-2005. 13


© JBoss Inc., 2003-2005. 13

Transaction Demarcation

Annotations or XML metadata can specify annotation

@Tx(TxType.REQUIRED)

public void somepojoMethod() { … }

@Tx(TxType.REQUIRED)

public void somepojoMethod() { … }

<metadata tag="transaction" class="org.jboss.test.POJO">

<method name="somepojoMethod“>

<value>RequiresNew</value>

</method></metadata>

<metadata tag="transaction" class="org.jboss.test.POJO">

<method name="somepojoMethod“>

<value>RequiresNew</value>

</method></metadata>

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© JBoss Inc., 2003-2005. 14

Roled-based Security

Secured access to any method, field, or constructor Only users of a certain role allowed to access Authentication/Authorization integrated with JBoss Security

– Various Security Domains (LDAP, RDBMS, SRP, etc…)

Access to username available within other interceptors

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© JBoss Inc., 2003-2005. 15

Role-Based security

JDK 5.0 Annotations are usable

@SecurityDomain(“other”)

public class POJO {

@Unchecked public POJO() {}

@Exclude public exlucedMethod() {…}

@Permissions({“admin”, “manager”})

public void someMethod() {…}

@Permissions({“user”})

public static int status;

}

@SecurityDomain(“other”)

public class POJO {

@Unchecked public POJO() {}

@Exclude public exlucedMethod() {…}

@Permissions({“admin”, “manager”})

public void someMethod() {…}

@Permissions({“user”})

public static int status;

}

© JBoss, Inc. 2003-2005. 16


© JBoss Inc., 2003-2005. 16

Role-Based security

XML metadata can specify annotation

<metadata tag="security" class="org.jboss.test.aop.bean.SecuredPOJO"> <security-domain>other</security-domain> <method-permission> <role-name>allowed</role-name> <method><method-name>someMethod</method-name></method> </method-permission> <constructor-permission> <unchecked/> <constructor><constructor-params/></constructor> </constructor-permission> <exclude-list> <description>Methods that connect be used</description> <method> <method-name>excluded</method-name> </method> </exclude-list></metadata>

<metadata tag="security" class="org.jboss.test.aop.bean.SecuredPOJO"> <security-domain>other</security-domain> <method-permission> <role-name>allowed</role-name> <method><method-name>someMethod</method-name></method> </method-permission> <constructor-permission> <unchecked/> <constructor><constructor-params/></constructor> </constructor-permission> <exclude-list> <description>Methods that connect be used</description> <method> <method-name>excluded</method-name> </method> </exclude-list></metadata>


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© JBoss Inc., 2003-2005. 17

Metadata

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© JBoss Inc., 2003-2005. 18

Metadata

J2EE a la carte examples show importance of metadata Pointcut expressions aren’t always the silver bullet Can be confusing to developers

– Developers want simple, familiar ways of applying aspects

– Some developers like annotations

– Others prefer XML to externalize configuration

– An AOP framework needs to be aware of both.

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© JBoss Inc., 2003-2005. 19

Metadata

JBoss AOP requirements– Support annotations in pointcut expressions

– Support annotation overrides at runtime

– Support untyped metadata

– Support metadata/annotation defaults

– Support XML externalization of metadata

Allow metadata/annotations to be attached without modifying bytecode Metadata changeable on a per-deployment basis through XML Allow pointcut expressions to be aware of this attached metadata.

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© JBoss Inc., 2003-2005. 20

Dynamic Metadata

Aspects can resolve metadata dynamically The AOP Invocation object (ThisJoinPoint) gives hooks for this. Metadata can be attached to a invocation and propagated

– Aspects can pass information to one another locally or remotely

Metadata can be overridden on a per Thread basis– Change behavior per Thread

– Provide simple mechanism to clear all Thread metadata (Thread Pooling)

Default values can be defined/managed per VM or per Cluster

Invocation Thread Class VM Cluster


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© JBoss Inc., 2003-2005. 21

EJB 3.0 and JBoss AOPAn aspect-oriented EJB container

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© JBoss Inc., 2003-2005. 22

EJB 3.0 and JBoss AOP

Can EJB be implemented using AOP? “Traditional” AspectJ like weaving not possible

– EJB is a proxy architecture by definition

– proxy.someMethod() different behavior than this.someMethod()

– Same class can be deployed in multiple containers

– Mix/match of XML and Annotations

JBoss 3.x and lower showed AOP was the right approach A Proxy-based AOP container was needed.

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© JBoss Inc., 2003-2005. 23


JBoss AOP binds aspects at class load time Since binding is java.lang.reflection based Very easy to create a proxy container a.k.a an EJB container

Client JVMJB

oss Rem

otingJB

oss Rem

oting

Server JVM

AOP Container

011101010101


Typed Interface

Client Proxy


AOP ContainerInvocation

Port 1234

Port 4321ClientClient

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© JBoss Inc., 2003-2005. 24


Why re-architect within an AOP Container?– Full pointcut expressions available

– Per method advice chains

– Pluggable annotations

– Pluggable behavior

– Reuse existing Aspect Library

Remember?– If middleware is easy to use…

– …it should also be easy to extend

– AOP allows us to easily extend EJB behavior

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© JBoss Inc., 2003-2005. 25


The next issue: EJB Containers have similar, but different aspects

– Stateless, Stateful, MDB (and JBoss extensions)

Proxies to these container types also similar but different Needed a way to define a template for each of these types Needed a way to define a template for proxy definition Solution:

– JBoss AOP “Aspect Domains”

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© JBoss Inc., 2003-2005. 26

Aspect Domains

Advice Stacks:– Named chain of unbound advices

– Proxies use these to understand what their advices should be

Aspect Domains:– Define a set of pointcuts, metadata overrides, and advice bindings

– Containers reference domains for their advices

– Domains can inherit from one-another

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© JBoss Inc., 2003-2005. 27

Advice stacks

<stack name="SessionBeanClientInterceptors">

<interceptor-ref name="org.jboss.aspects.remoting.IsLocalInterceptor"/>

<interceptor-ref name="org.jboss.aspects.security.SecurityClientInterceptor"/>

<interceptor-ref name="org.jboss.aspects.tx.ClientTxPropagationInterceptor"/>

<interceptor-ref name="org.jboss.aspects.remoting.InvokeRemoteInterceptor"/>

</stack>

<stack name="SessionBeanClientInterceptors">

<interceptor-ref name="org.jboss.aspects.remoting.IsLocalInterceptor"/>

<interceptor-ref name="org.jboss.aspects.security.SecurityClientInterceptor"/>

<interceptor-ref name="org.jboss.aspects.tx.ClientTxPropagationInterceptor"/>

<interceptor-ref name="org.jboss.aspects.remoting.InvokeRemoteInterceptor"/>

</stack>

Containers reference advice stacks when they create proxies Stacks are predefined and configurable

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© JBoss Inc., 2003-2005. 28

<domain name="Stateless Bean">

<bind pointcut="execution(* @org.jboss.ejb3.security.SecurityDomain->*(..))">

<interceptor-ref name="org.jboss.ejb3.security.AuthenticationInterceptorFactory"/>

<interceptor-ref name="org.jboss.ejb3.security.RoleBasedAuthorizationInterceptorFactory"/>

</bind>

<bind pointcut="execution(* @javax.ejb.RunAs->*(..))">

<interceptor-ref name="org.jboss.ejb3.security.RunAsSecurityInterceptor"/>

</bind>

<bind pointcut="execution(* *->*(..))">

<interceptor-ref name="org.jboss.ejb3.stateless.StatelessInstanceInterceptor"/>

<interceptor-ref name="org.jboss.aspects.tx.TxPropagationInterceptor"/>

<interceptor-ref name="org.jboss.ejb3.tx.TxInterceptorFactory"/>

</bind>

<annotation expr="!class(@org.jboss.ejb3.PoolClass)">

@org.jboss.ejb3.PoolClass (value=org.jboss.ejb3.ThreadlocalPool.class, maxSize=30, timeout=10000)

</annotation>

</domain>

<domain name="Stateless Bean">

<bind pointcut="execution(* @org.jboss.ejb3.security.SecurityDomain->*(..))">

<interceptor-ref name="org.jboss.ejb3.security.AuthenticationInterceptorFactory"/>

<interceptor-ref name="org.jboss.ejb3.security.RoleBasedAuthorizationInterceptorFactory"/>

</bind>

<bind pointcut="execution(* @javax.ejb.RunAs->*(..))">

<interceptor-ref name="org.jboss.ejb3.security.RunAsSecurityInterceptor"/>

</bind>

<bind pointcut="execution(* *->*(..))">

<interceptor-ref name="org.jboss.ejb3.stateless.StatelessInstanceInterceptor"/>

<interceptor-ref name="org.jboss.aspects.tx.TxPropagationInterceptor"/>

<interceptor-ref name="org.jboss.ejb3.tx.TxInterceptorFactory"/>

</bind>

<annotation expr="!class(@org.jboss.ejb3.PoolClass)">

@org.jboss.ejb3.PoolClass (value=org.jboss.ejb3.ThreadlocalPool.class, maxSize=30, timeout=10000)

</annotation>

</domain>

Aspect Domains

Annotation Override

Annotations with behavior

Default advices

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© JBoss Inc., 2003-2005. 30

What is Dynamic AOP ?

Hot-deployment of aspects Bind/unbind advices arbitrarily at runtime Per-instance AOP Add advices on a per instance basis

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© JBoss Inc., 2003-2005. 31

What is JBossCache ?

Transparent caching Local or replicated

– Synchronous or asynchronous replication (using JGroups)

Transactional or non-transactional– Transactional

• Replication at TX commit

• DB isolation levels supported

• Support for pluggable TxManagers

– Non-Transactional

• Replication after each modification

Pluggable eviction policies– Ships with time-based and size-based (LRU) policies

Cache loader– Persistent backend store (load - store)

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© JBoss Inc., 2003-2005. 32

AOP Cache

Work with POJOs

public class Person { String name=null; int age=0; Map hobbies=null; Address address=null; Set skills; List languages;

public String getName() { return name; }

public void setName(String name) { this.name=name; } ...}

public class Person { String name=null; int age=0; Map hobbies=null; Address address=null; Set skills; List languages;

public String getName() { return name; }

public void setName(String name) { this.name=name; } ...}

public class Address { String street=null; String city=null; int zip=0;

public String getStreet() { return street; }

public void setStreet(String street) { this.street=street; } ...}

public class Address { String street=null; String city=null; int zip=0;

public String getStreet() { return street; }

public void setStreet(String street) { this.street=street; } ...}

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© JBoss Inc., 2003-2005. 33

Interaction With Cache

tree = new TreeCacheAop();

config = new PropertyConfigurator();// configure tree cache.config.configure(tree, "META-INF/replSync-service.xml");

joe = new Person();joe.setName("Joe Black");joe.setAge(31);

addr = new Address();addr.setCity("Sunnyvale");addr.setStreet("123 Albert Ave");addr.setZip(94086);

joe.setAddress(addr);

tree = new TreeCacheAop();

config = new PropertyConfigurator();// configure tree cache.config.configure(tree, "META-INF/replSync-service.xml");

joe = new Person();joe.setName("Joe Black");joe.setAge(31);

addr = new Address();addr.setCity("Sunnyvale");addr.setStreet("123 Albert Ave");addr.setZip(94086);

joe.setAddress(addr);

Use Pojos as Pojos

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© JBoss Inc., 2003-2005. 34

Interaction With Cache

Joe’s state is automatically transactional and replicated State replicated, synchronized at transaction commit/rollback

tree.start(); // kick start tree cachetree.putObject("/aop/joe", joe); // add aop sanctioned object

tx.begin();joe.setAge(41);joe.getAddress().setZip(95124);tx.commit();

tree.start(); // kick start tree cachetree.putObject("/aop/joe", joe); // add aop sanctioned object

tx.begin();joe.setAge(41);joe.getAddress().setZip(95124);tx.commit();

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© JBoss Inc., 2003-2005. 36

How does it work?

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

<aop>

<prepare expr="field(* $instanceof{org.jboss.test.cache.test.standAloneAop.Student}->*)" />

<prepare expr="field(* $instanceof{org.jboss.test.cache.test.standAloneAop.Address}->*)" />

<prepare expr="field(* $instanceof{org.jboss.test.cache.test.standAloneAop.Person}->*)" />

</aop>

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

<aop>

<prepare expr="field(* $instanceof{org.jboss.test.cache.test.standAloneAop.Student}->*)" />

<prepare expr="field(* $instanceof{org.jboss.test.cache.test.standAloneAop.Address}->*)" />

<prepare expr="field(* $instanceof{org.jboss.test.cache.test.standAloneAop.Person}->*)" />

</aop>

Classes must be prepared for field interception This preparation creates AOP hooks Any advice can be added where hooks are instrumented

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© JBoss Inc., 2003-2005. 37

How does it work?

Uses reflection to discover the structure of a POJO– Requires a jboss-aop.xml to declare user-defined class to be “advisable“

– Uses AOP to keep track of changes to a POJO

putObject() breaks an object apart and maps it to the TreeCache– Primitive fields are mapped to entries in a node's attributes

– Complex fields are mapped to child nodes (recursively)

• Transparent handling of object hierarchies

• No need for one-to-one, one-to-many, etc relationship declarations

• POJO inheritance hierarchy is preserved

– We dynamically add a field advice to each complex object to keep track of state changes

© JBoss, Inc. 2003-2005. 38


© JBoss Inc., 2003-2005. 38

JBoss Cache - Advices

Each advice remembers the node to which it maps– On field read: advice returns the value from the TreeCache

– On field write: advice updates the associated node's attributes, e.g.

– person.getAddress().setCity("San Jose“) generates a put("/322649/addr", "city", "San Jose")

On TX commit: modified fields are replicated and written back to the POJO

© JBoss, Inc. 2003-2005. 39


© JBoss Inc., 2003-2005. 39

JBoss Cache - Design

Cache design itself can aspectized Cache Aspects

– CacheLoader, cache persistence

– Replication

– Transactionality

Cannot aspectize using class-level weaving Same classes but configured differently per instance Aspects can only be assembled if AOP framework support Dynamic AOP

© JBoss, Inc. 2003-2005. 40


© JBoss Inc., 2003-2005. 40

JBoss Strategy

Middleware is the perfect application of AOP– Transparency

– Flexibility

Annotations for ease of use AOP for ease of extension

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