Proxy Deep Dive Voxxed Belgrad 2015

prepare for…..
Proxy Deep Dive
Voxxed Days Belgrad 2015
1
@SvenRuppert

@SvenRuppert
has been coding java since 1996
Fellow / Senior Manager
reply Group
Germany - Munich
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@SvenRuppert
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@SvenRuppert
Projects in the ﬁeld of:
•Automobile-industry
•Energy
•Finance / Leasing
•Space- Satellit-
•Government / UN / World-bank
Where?
•Europe
•Asia - from India up to Malaysia
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Why a Proxy ?
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@SvenRuppert
Proxies you can use them for :
generic parts inside your application
hiding technical stuff
decouple parts of your applications

Why a Proxy ?
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@SvenRuppert
but it must be easy to use like…

Why a Proxy ?
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@SvenRuppert
ﬁnal InnerDemoClass original = new InnerDemoClass();

Why a Proxy ?
5
@SvenRuppert
ﬁnal InnerDemoInterface demoLogic =

Why a Proxy ?
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@SvenRuppert
ProxyBuilder.createBuilder(InnerDemoInterface.class, original)

Why a Proxy ?
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@SvenRuppert
.addLogging()

Why a Proxy ?
5
@SvenRuppert
.addLogging()
.addMetrics()

Why a Proxy ?
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@SvenRuppert
.addLogging()
.addMetrics()
.addSecurityRule(() -> true)

Why a Proxy ?
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@SvenRuppert
.addLogging()
.addMetrics()

Why a Proxy ?
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@SvenRuppert
.addLogging()
.addMetrics()
.build();

Why a Proxy ?
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@SvenRuppert
@Inject
@Proxy(virtual = true, metrics = true)
Service service;

Adapter v Proxy - Pattern Hello World
Adapter - called Wrapper
maybe : Use an Adapter if you have to use an incompatible
interface between two systems.
In detail I am using/talking about an Adapter with Delegator.
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@SvenRuppert

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@SvenRuppert

public class LegacyWorker { 
public void writeTheStrings(String[] strArray){ 
Arrays.stream(strArray).forEach(System.out::println); 
} 
}
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@SvenRuppert

} 
}
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public interface WorkerAdapter { 
public void workOnSomething(List<String> stringListe); 
}
@SvenRuppert

} 
}
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public interface WorkerAdapter { 
public void workOnSomething(List<String> stringListe); 
}
public class Adapter implements WorkerAdapter { 
private LegacyWorker worker = new LegacyWorker(); 
@Override 
public void workOnSomething(List<String> stringListe) { 
ﬁnal String[] strings = stringListe.toArray(new String[0]); 
worker.writeTheStrings(strings); 
} 
}
@SvenRuppert

public class Main { 
public static void main(String[] args) { 
ﬁnal ArrayList<String> strings = new ArrayList<>(); 
Collections.addAll(strings, "A","B","C","D"); 
new Adapter().workOnSomething(strings); 
} 
}
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@SvenRuppert

} 
}
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• No need to know the LegacyWorker
@SvenRuppert

} 
}
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• No inheritance between LegacyWorker and Adapter
@SvenRuppert

} 
}
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• only a transformation of an interface
@SvenRuppert

} 
}
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• only a transformation of an interface
• same creation time for Delegator and Adapter
@SvenRuppert

Proxy - the easiest version
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@SvenRuppert
We need a few steps to come from an Adapter with
Delegator to a Proxy

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• We need to know the LegacyWorker
@SvenRuppert

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• Inheritance between LegacyWorker and Adapter
@SvenRuppert

10
• do not use it like an Adapter !
@SvenRuppert

10
• do not use it like an Adapter !
@SvenRuppert
please show the code

Proxy - the easiest version - (Delegator)
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@SvenRuppert

public interface Service { 
String work(String txt); 
}
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@SvenRuppert

}
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@SvenRuppert
public class ServiceImpl implements Service { 
public String work(String txt) { 
return "ServiceImpl - " + txt; 
} 
}

}
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@SvenRuppert
} 
}
public class ServiceProxy implements Service { 
private Service service = new ServiceImpl(); 
public String work(String txt) { return service.work(txt); } 
}

Security Proxy
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@SvenRuppert

Security Proxy
12
@SvenRuppert
}

Security Proxy
12
@SvenRuppert
}
What could we
change now ?

Security Proxy
12
@SvenRuppert
}
What could we
change now ?
SecurityProxy:
execute only if it is allowed

Security Proxy
12
@SvenRuppert
}
What could we
change now ?
SecurityProxy:
execute only if it is allowed
public class ServiceSecurityProxy implements Service { 
private String code; //who will set this ? 
if(code.equals(„hoppel")) { return service.work(txt); } 
else { return "nooooop"; } 
} 
}

Remote Proxy - JDK only
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@SvenRuppert

13
@SvenRuppert
}

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@SvenRuppert
}
What could we
change now ?

13
@SvenRuppert
}
What could we
change now ?
RemoteProxy:
execute outside of my process

13
@SvenRuppert
}
What could we
change now ?
RemoteProxy:
Service proxy = new ServiceRemoteProxy(); 
String hello = proxy.work(„Hello");

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@SvenRuppert
}
What could we
change now ?
RemoteProxy:
Service proxy = new ServiceRemoteProxy(); 
String hello = proxy.work(„Hello");
some work needed

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@SvenRuppert

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@SvenRuppert
Proxy

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@SvenRuppert
Proxy
Interface

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@SvenRuppert
Proxy
Interface
remote communication

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@SvenRuppert
Proxy
Interface
Interface

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server

15
@SvenRuppert
@WebService 
@SOAPBinding(style = SOAPBinding.Style.RPC) 
@WebMethod 
public String work(String txt); 
}

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server

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@SvenRuppert
@SOAPBinding(style = SOAPBinding.Style.RPC) 
@WebService(endpointInterface = "org.rapidpm.Service") 
@Override 
} 
}

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server

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@SvenRuppert
final String address = "http://localhost:9999/ws/service"; 
final ExecutorService threadPool = Executors.newFixedThreadPool(10); 
final Endpoint endpoint = Endpoint.create(new ServiceImpl()); 
endpoint.setExecutor(threadPool); 
endpoint.publish(address); 
System.out.println("endpoint = " + endpoint.isPublished());

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server

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@SvenRuppert
public class ServiceRemoteProxy implements Service { 
 
private URL url; 
private Service realSubject; 
ﬁnal String namespaceURI = "http://rapidpm.org/"; 
ﬁnal String localPart = "ServiceImplService"; 
 
public ServiceRemoteProxy() { 
try { 
url = new URL("http://localhost:9999/ws/service?wsdl"); 
QName qname = new QName(namespaceURI, localPart); 
javax.xml.ws.Service service = javax.xml.ws.Service.create(url, qname); 
realSubject = service.getPort(Service.class); 
} catch (MalformedURLException e) { 
e.printStackTrace(); 
} 
} 
public String work(String txt){ 
return realSubject.work(txt); 
} 
}

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server
• remote communication

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server
• most of this is technology based work

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@SvenRuppert
Proxy
Remote
ServiceInterface
Interface
client server
• most of this is technology based work
• goal: developer will see no remote
communication

Virtual Proxy
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@SvenRuppert
}

Virtual Proxy
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@SvenRuppert
}
What could we
change now ?

Virtual Proxy
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@SvenRuppert
}
What could we
change now ?
Virtual Proxy:
create the Delegator later

Virtual Proxy
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@SvenRuppert
}
What could we
change now ?
Virtual Proxy:
create the Delegator later
public class VirtualService implements Service { 
private Service service = null; 
if(service == null) { service = new ServiceImpl(); } 
return service.work(txt); 
} 
}

Virtual Proxy
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@SvenRuppert
if(service == null) { service = new ServiceImpl(); }
 
} 
}

Virtual Proxy
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@SvenRuppert
 
} 
}
This is NOT ThreadSave

Virtual Proxy
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@SvenRuppert
 
} 
}
ﬁxed decision for
an implementation

Virtual Proxy
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@SvenRuppert
 
} 
}
ﬁxed decision for
an implementation
how to combine it with
a FactoryPattern ?

Virtual Proxy
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@SvenRuppert

Virtual Proxy
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@SvenRuppert
public interface ServiceFactory { 
Service createInstance(); 
}

Virtual Proxy
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@SvenRuppert
public interface ServiceFactory { 
Service createInstance(); 
}
public interface ServiceStrategyFactory { 
Service realSubject(ServiceFactory factory); 
}

Virtual Proxy - Not - ThreadSave
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@SvenRuppert

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@SvenRuppert
private ServiceFactory serviceFactory = ServiceImpl::new;

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@SvenRuppert
public class ServiceStrategyFactoryImpl implements ServiceStrategyFactory { 
Service realSubject; 
public Service realSubject(ﬁnal ServiceFactory factory) { 
if (realSubject == null) { 
realSubject = factory.createInstance(); 
} 
return realSubject; 
} 
}

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@SvenRuppert
public static class ServiceProxy implements Service { 
 
private ServiceFactory serviceFactory = ServiceImpl::new; 
private ServiceStrategyFactory strategyFactory = new ServiceStrategyFactoryImpl(); 
 
@Override 
return strategyFactory.realSubject(serviceFactory).work(txt); 
} 
}

Virtual Proxy - Synchronized
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@SvenRuppert

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@SvenRuppert

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@SvenRuppert
public class ServiceStrategyFactorySynchronized implements ServiceStrategyFactory { 
public synchronized Service realSubject(ﬁnal ServiceFactory factory) { 
} 
} 
}

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@SvenRuppert
public class ServiceStrategyFactorySynchronized implements ServiceStrategyFactory { 
public synchronized Service realSubject(ﬁnal ServiceFactory factory) { 
} 
} 
}
This is ThreadSave

Combining Proxies
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@SvenRuppert
Security Proxy Virtual ProxyRemote Proxy
Security ProxyVirtual ProxyRemote Proxy
Security ProxyVirtual Proxy Remote Proxy
VirtualProxies are mostly the last one
combining Proxies is easy
SecurityProxies are mostly the ﬁrst one ?

Combining Proxies - SecureVirtualProxy
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@SvenRuppert
Security Proxy Virtual Proxy
public class VirtualProxy implements Service { 
public VirtualProxy() { out.println("VirtualProxy " + now()); } 
} 
}
public class SecureVirtualProxy implements Service { 
public SecureProxy() { out.println("SecureProxy " + now()); } 
private Service service = new VirtualProxy(); 
//SNIPP…. 
if(code.equals("hoppel")) { return service.work(txt); } 
return { return "nooooop"; } 
} 
}

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@SvenRuppert
} 
}
//SNIPP…. 
} 
}
hard wired proxies

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@SvenRuppert
} 
}
//SNIPP…. 
} 
}
hard wired proxies
What could we
change now ?

31
@SvenRuppert
hard wired proxies
What could we
change now ?
we need a Generic Proxy

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@SvenRuppert
hard wired proxies
What could we
change now ?
since JDK1.3 we have it

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@SvenRuppert
hard wired proxies
What could we
change now ?
since JDK1.3 we have it
the DynamicProxy

Dynamic Proxy - Hello World
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@SvenRuppert
How to use it ?

32
@SvenRuppert
How to use it ?
java.lang.reﬂect.Proxy

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@SvenRuppert
How to use it ?
we need an interface : here Service

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@SvenRuppert
How to use it ?
we need an implementation : here ServiceImpl

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@SvenRuppert
How to use it ?
Service proxyInstance = Service.class.cast( Proxy.newProxyInstance( 
Service.class.getClassLoader(), 
new Class<?>[]{Service.class}, 
new InvocationHandler() { 
private ﬁnal ServiceImpl service = new ServiceImpl(); 
@Override 
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
return method.invoke(service, args); 
} 
} 
) 
);

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@SvenRuppert
How to use it ?
Service proxyInstance = Service.class.cast( Proxy.newProxyInstance( 
Service.class.getClassLoader(), 
new Class<?>[]{Service.class}, 
@Override 
return method.invoke(service, args); 
} 
} 
) 
);
OK, step by step , please

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@SvenRuppert

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@SvenRuppert
Service proxyInstance = Service.class.cast (

33
@SvenRuppert
Proxy.newProxyInstance (

33
@SvenRuppert
Service.class.getClassLoader(),

33
@SvenRuppert
new Class<?>[]{Service.class},

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@SvenRuppert
@Override 
public Object invoke(Object proxy, Method m, Object[] args) throws Throwable { 
return m.invoke(service, args); 
} 
}

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@SvenRuppert
@Override 
} 
} 
) 
);

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@SvenRuppert
@Override 
} 
} 
) 
);
how to make a VirtualProxy ?

Dynamic Virtual Proxy
34
@SvenRuppert
) 
);

Dynamic Virtual Proxy
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@SvenRuppert
private ﬁnal ServiceImpl service; 
@Override 
} 
} 
) 
);

Dynamic Proxy - make it generic
35
@SvenRuppert
@Override 
} 
} 
) 
);

35
@SvenRuppert
@Override 
} 
} 
) 
);
get it from outside

35
@SvenRuppert
@Override 
} 
} 
) 
);
get it from outside
we will remove it

35
@SvenRuppert
@Override 
} 
} 
) 
);
get it from outside
we will remove it
we will get it from outside

35
@SvenRuppert
@Override 
} 
} 
) 
);
get it from outside
we will remove it
we will get it from outside
and ﬁnally we will call it ProxyGenerator

36
@SvenRuppert
public class ProxyGenerator { 
public static <P> P makeProxy(Class<P> subject, P realSubject) { 
Object proxyInstance = Proxy.newProxyInstance( 
subject.getClassLoader(), 
new Class<?>[]{subject}, 
@Override 
public Object invoke(final Object proxy, final Method m, final Object[] args) throws Throwable { 
return m.invoke(realSubject, args); 
} 
} 
); 
return subject.cast(proxyInstance); 
} 
}

37
@SvenRuppert
public class ProxyGenerator { 
public static <P> P makeProxy(Class<P> subject, P realSubject) { 
Object proxyInstance = Proxy.newProxyInstance( 
subject.getClassLoader(), 
new Class<?>[]{subject}, 
(proxy, m, args) -> m.invoke(realSubject, args) 
); 
return subject.cast(proxyInstance); 
} 
}

38
@SvenRuppert
with DynamicProxies
- we are writing less (more generic) code
- we can create Virtual-/Remote-/Security Proxies

38
@SvenRuppert
with DynamicProxies
- we are writing less (more generic) code
- we can create Virtual-/Remote-/Security Proxies
but how to combine Proxies more generic ?

39
@SvenRuppert
for this we have to switch from

39
@SvenRuppert
Factory-Method-Pattern

39
@SvenRuppert
Factory-Method-Pattern
Builder-Pattern

DynamicProxyBuilder
40
@SvenRuppert
Security Proxy Virtual ProxySecurity Proxy
let´s think about Two possible ways:

DynamicProxyBuilder
40
@SvenRuppert
1 Security Proxy with 2 Rules and 1 VirtualProxy

DynamicProxyBuilder
40
@SvenRuppert
2 Security Proxies with 1 Rule and 1 VirtualProxy

DynamicProxyBuilder
40
@SvenRuppert
2 Security Proxies with 1 Rule and 1 VirtualProxy
OK, we need a generic CascadedProxy

DynamicProxyBuilder
41
@SvenRuppert
OK, we need a generic CascadedProxy
Proxy n
Proxy n-1
Proxy n-2
Proxy n-3
a child must know his parent
ﬁrst we only add different DynamicProxies
always the same target interface

DynamicProxyBuilder
42
@SvenRuppert
for example: add n SecurityRules

DynamicProxyBuilder
42
@SvenRuppert
public interface SecurityRule { 
boolean checkRule(); 
}

DynamicProxyBuilder
42
@SvenRuppert
}
functional interface

DynamicProxyBuilder
42
@SvenRuppert
private List<SecurityRule> securityRules = new ArrayList<>();
}

DynamicProxyBuilder
42
@SvenRuppert
private List<SecurityRule> securityRules = new ArrayList<>();
}
Collections.reverse(securityRules); 
securityRules.forEach(this::build_addSecurityRule);

DynamicProxyBuilder
43
@SvenRuppert
private ProxyBuilder<I, T> build_addSecurityRule(SecurityRule rule) { 
final ClassLoader classLoader = original.getClass().getClassLoader(); 
final Class<?>[] interfaces = {clazz}; 
final Object nextProxy = Proxy.newProxyInstance( 
classLoader, interfaces, 
private T original = ProxyBuilder.this.original; 
final boolean checkRule = rule.checkRule(); 
if (checkRule) { 
return method.invoke(original, args); 
} else { 
return null; 
} 
} 
}); 
original = (T) clazz.cast(nextProxy); 
return this; 
}

DynamicProxyBuilder
43
@SvenRuppert
if (checkRule) { 
} else { 
return null; 
} 
} 
}); 
return this; 
}
last child

DynamicProxyBuilder
43
@SvenRuppert
if (checkRule) { 
} else { 
return null; 
} 
} 
}); 
return this; 
}
last child
work on child

DynamicProxyBuilder
43
@SvenRuppert
if (checkRule) { 
} else { 
return null; 
} 
} 
}); 
return this; 
}
last child
work on child
set child for next level

DynamicProxyBuilder
43
@SvenRuppert
if (checkRule) { 
} else { 
return null; 
} 
} 
}); 
return this; 
}
how this will be used ?
last child
work on child
set child for next level

DynamicProxyBuilder
44
@SvenRuppert

DynamicProxyBuilder
44
@SvenRuppert
.addLogging()

DynamicProxyBuilder
44
@SvenRuppert
.addLogging()
.addMetrics()

DynamicProxyBuilder
44
@SvenRuppert
.addLogging()
.addMetrics()
.build();

DynamicObjectAdapter - orig Version
45
@SvenRuppert
the original Version of the DynamicObjectAdapter
was written by Dr. Heinz Kabutz

46
@SvenRuppert

46
@SvenRuppert
Proxy

46
@SvenRuppert
Proxy
orig /
adapter

46
@SvenRuppert
Proxy
orig /
adapter
invoke orig

46
@SvenRuppert
Proxy
orig /
adapter
invoke orig
invoke adapter

46
@SvenRuppert
Proxy
orig /
adapter
invoke orig
invoke adapter
Goal: do not need to write an
Adapter with Delegator

47
@SvenRuppert
core concept:
switching between method implementations

47
@SvenRuppert
core concept:
switching between method implementations
how to identify a method?

48
@SvenRuppert
how to identify a method?
public class MethodIdentifier { 
private final String name; 
private final Class[] parameters; 
 
public MethodIdentifier(Method m) { 
name = m.getName(); 
parameters = m.getParameterTypes(); 
} 
// we can save time by assuming that we only compare against 
// other MethodIdentifier objects 
public boolean equals(Object o) { 
MethodIdentifier mid = (MethodIdentifier) o; 
return name.equals(mid.name) && 
Arrays.equals(parameters, mid.parameters); 
} 
public int hashCode() { return name.hashCode(); } 
}

49
@SvenRuppert
String doWork_A(String txt); 
String doWork_B(String txt); 
}
public static class ServiceImpl implements Service { 
 
public String doWork_A(String txt) { 
return "doWorkd_A_Original"; 
} 
 
public String doWork_B(String txt) { 
return "doWorkd_B_Original"; 
} 
}

50
@SvenRuppert
}
public interface ServiceAdapter_A { 
} 
 
public interface ServiceAdapter_B { 
}

50
@SvenRuppert
}
} 
 
}

51
@SvenRuppert
private Map<MethodIdentiﬁer, Method> adaptedMethods = new HashMap<>(); 
private Map<MethodIdentiﬁer, Object> adapters = new HashMap<>(); 
 
private T original; 
private Class<T> target;

51
@SvenRuppert
 
private void addAdapter(Object adapter) {

51
@SvenRuppert
 
ﬁnal Class<?> adapterClass = adapter.getClass();

51
@SvenRuppert
 
Method[] methods = adapterClass.getDeclaredMethods();

51
@SvenRuppert
 
for (Method m : methods) {

51
@SvenRuppert
 
final MethodIdentifier key = new MethodIdentifier(m);

51
@SvenRuppert
 
adaptedMethods.put(key, m);

51
@SvenRuppert
 
adapters.put(key, adapter);

51
@SvenRuppert
 
} 
}
adapters.put(key, adapter);

52
@SvenRuppert
 

52
@SvenRuppert
 
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

52
@SvenRuppert
 
try { 
final MethodIdentifier key = new MethodIdentifier(method); 
Method other = adaptedMethods.get(key);

52
@SvenRuppert
 
try { 
if (other != null) { 
return other.invoke(adapters.get(key), args); 
} else { 
}

52
@SvenRuppert
 
} catch (InvocationTargetException e) { 
throw e.getTargetException(); 
} 
}
try { 
if (other != null) { 
return other.invoke(adapters.get(key), args); 
} else { 
}

DynamicObjectAdapter - orig Version @SvenRuppert
 
if you will use this without a Builder
you can add useless Adapter !!

 
if you will use this without a Builder
you can add useless Adapter !!
Add some typed with-Methods

public AdapterBuilder<T> withDoWork_A(ServiceAdapter_A adapter) { 
addAdapter(adapter); 
return this; 
}

return this; 
}
remember

return this; 
}
remember public interface Service { 
}

return this; 
}
remember public interface Service { 
}
}

How to use this?

How to use this?
Service service = AdapterBuilder.<Service>newBuilder()

How to use this?
.withTarget(Service.class)

How to use this?
.withOriginal(new ServiceImpl())

How to use this?
.withDoWork_A((txt) -> txt + "_part")

.build();
How to use this?
.withDoWork_A((txt) -> txt + "_part")

generated DynamicObjectAdapterBuilder @SvenRuppert
To much boring code to write
but we want to have a typesave version
if wrong… compile must break

To much boring code to write
but we want to have a typesave version
What could we
change now ?
if wrong… compile must break

remember

remember
}

remember
}
} 
 
}

use Annotation Processing

create a marker like
@DynamicObjectAdapterBuilder

@Retention(RetentionPolicy.SOURCE) 
@Target(ElementType.TYPE) 
public @interface DynamicObjectAdapterBuilder { 
}

@Retention(RetentionPolicy.SOURCE) 
@Target(ElementType.TYPE) 
public @interface DynamicObjectAdapterBuilder { 
}
public class AnnotationProcessor extends AbstractProcessor

with every compile you will get actual

Functional-Interfaces for the Adapters

Functional-Interfaces for the Adapters
generated AdapterBuilder

Summary
60
@SvenRuppert
we got type-save ProxyBuilder
..type-save generated DynamicObjectAdapter
..at runtime we could change the chain of Proxies
..could be used for
(Dynamic)
Dependency Injection Implementations

Summary
61
@SvenRuppert
If you are interested…
have a look at RapidPM on github
rapidpm-proxybuilder
rapidpm-dynamic-cdi
rapidpm-microservice
or contact me ;-) @SvenRuppert

Summary
61
@SvenRuppert
If you are interested…
have a look at RapidPM on github
rapidpm-proxybuilder
rapidpm-dynamic-cdi
rapidpm-microservice
or contact me ;-) @SvenRuppert
Thank You !!!

Proxy Deep Dive Voxxed Belgrad 2015

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