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Groovy Documentation | |||||||
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SUMMARY: NESTED | FIELD | PROPERTY | CONSTR | METHOD | DETAIL: FIELD | PROPERTY | CONSTR | METHOD |
java.lang.Objectgpars.agent.AgentCore
gpars.agent.Agent
class Agent extends AgentCore
A special-purpose thread-safe non-blocking reference implementation inspired by Agents in Clojure. Agents safe-guard mutable values by allowing only a single agent-managed thread to make modifications to them. The mutable values are not directly accessible from outside, but instead requests have to be sent to the agent and the agent guarantees to process the requests sequentially on behalf of the callers. Agents guarantee sequential execution of all requests and so consistency of the values. An agent wraps a reference to mutable state, held inside a single field, and accepts code (closures / commands) as messages, which can be sent to the Agent just like to any other actor using the '<<' operator or any of the send() methods. After reception of a closure / command, the closure is invoked against the internal mutable field. The closure is guaranteed to be run without intervention from other threads and so may freely alter the internal state of the Agent held in the internal data field. The return value of the submitted closure is sent in reply to the sender of the closure. If the message sent to an agent is not a closure, it is considered to be a new value for the internal reference field. The internal reference can also be changed using the updateValue() method from within the received closures. The 'val' property of an agent will safely return the current value of the Agent, while the valAsync() method will do the same without blocking the caller. The 'instantVal' property will retrieve the current value of the Agent without having to wait in the queue of tasks. The initial internal value can be passed to the constructor. The two-parameter constructor allows to alter the way the internal value is returned from val/valAsync. By default the original reference is returned, but in many scenarios a copy or a clone might be more appropriate.
Field Summary | |
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protected Object |
data
Holds the internal mutable state |
Property Summary | |
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groovy.lang.Closure |
copy
Function converting the internal state during read to prevent internal state escape from the protected boundary of the agent |
Constructor Summary | |
Agent()
Creates a new Agent with the internal state set to null |
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Agent(Object data)
Creates a new Agent around the supplied modifiable object |
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Agent(Object data, groovy.lang.Closure copy)
Creates a new Agent around the supplied modifiable object |
Method Summary | |
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static Agent
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agent(def state)
Creates an agent instance initialized with the given state. |
static Agent
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agent(def state, groovy.lang.Closure copy)
Creates an agent instance initialized with the given state. |
void
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await()
Blocks until all messages in the queue prior to call to await() complete. |
static Agent
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fairAgent(def state)
Creates an agent instance initialized with the given state, which will cooperate in thread sharing with other Agent instances in a fair manner. |
static Agent
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fairAgent(def state, groovy.lang.Closure copy)
Creates an agent instance initialized with the given state, which will cooperate in thread sharing with other Agent instances in a fair manner. |
Object
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getInstantVal()
A shorthand method for safe message-based retrieval of the internal state. |
Object
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getVal()
A shorthand method for safe message-based retrieval of the internal state. |
void
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handleMessage(Object message)
Dynamically dispatches the method call |
void
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onMessage(org.codehaus.groovy.runtime.NullObject obj)
Accepts a NullObject instance and sets the internal state to null |
void
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onMessage(groovy.lang.Closure code)
Accepts and invokes the closure |
void
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onMessage(Object message)
Other messages than closures are accepted as new values for the internal state |
def
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sendAndWait(groovy.lang.Closure message)
Submits the closure waiting for the result |
void
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updateValue(Object newValue)
Allows closures to set the new internal state as a whole |
void
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valAsync(groovy.lang.Closure callback)
A shorthand method for safe asynchronous message-based retrieval of the internal state. |
Methods inherited from class AgentCore | |
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attachToThreadPool, call, getErrors, getThreadPool, isFair, leftShift, makeFair, run, send, setPGroup |
Field Detail |
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protected Object data
Property Detail |
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final groovy.lang.Closure copy
Constructor Detail |
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Agent()
Agent(Object data)
data
- The object to use for storing the internal state of the variable
Agent(Object data, groovy.lang.Closure copy)
data
- The object to use for storing the internal state of the variablecopy
- A closure to use to create a copy of the internal state when sending the internal state out
Method Detail |
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static final Agent agent(def state)
state
- The initial internal state of the new Agent instance
static final Agent agent(def state, groovy.lang.Closure copy)
state
- The initial internal state of the new Agent instancecopy
- A closure to use to create a copy of the internal state when sending the internal state out
final void await()
static final Agent fairAgent(def state)
state
- The initial internal state of the new Agent instance
static final Agent fairAgent(def state, groovy.lang.Closure copy)
state
- The initial internal state of the new Agent instancecopy
- A closure to use to create a copy of the internal state when sending the internal state out
final Object getInstantVal()
@SuppressWarnings("GroovyAssignabilityCheck") final Object getVal()
void handleMessage(Object message)
final void onMessage(org.codehaus.groovy.runtime.NullObject obj)
final void onMessage(groovy.lang.Closure code)
final void onMessage(Object message)
final def sendAndWait(groovy.lang.Closure message)
final void updateValue(Object newValue)
final void valAsync(groovy.lang.Closure callback)
callback
- A closure to invoke with the internal state as a parameter
Groovy Documentation