brown.tracingplane.impl

Class BDLContext

java.lang.Object

brown.tracingplane.impl.BDLContext

All Implemented Interfaces:

BaggageContext

public class BDLContext
extends java.lang.Object
implements BaggageContext

The full-featured BaggageContext implementation used by the tracing plane using atoms and the baggage protocol, intended for use in conjunction with BDL-compiled accessor classes.

The typical way to store and manipulate data within BDLContext instances is to compile a BDL delcaration using the BDL compiler. The generated objects will provide accessor methods for getting data out of BDLContext instances.

Note: BDL-compiled objects must be registered with a static bag number in order to be used. In concept, this is similar to how protocols get mapped to ports (e.g., SSH maps to port 22, etc.). To register a bag, either specify it as a command line configuration value:

 -Dbag.22=my.compiled.object.MyObject
 

or in your application.conf:

 bag.22 = "my.compiled.object.MyObject"
 

or statically in code:

 BaggageHandlerRegistry.add(BagKey.indexed(22), my.compiled.object.MyObject.Handler.instance);
 

If you don't register a handler to a bag number, then any data found within a BDLContext will be kept in atom-form. It will be correctly propagated, however, it will not be accessible within this process in object form.

All data within a BDLContext has an underlying atom-based representation, and the serialization methods in BDLContextProvider transform contexts to and from this atom-based representation. In memory, BDLContext data is maintained in object representation.

This class provides some static methods for registering BaggageListener instances.

This class also provides some utility methods for attaching objects to BDLContext instances. Attached objects do not propagate across network communication; it is purely to piggyback additional state

Constructor Summary

Constructors

Constructor and Description
BDLContext()

Method Summary

Modifier and Type	Method and Description
BDLContext	attach(java.lang.Object key, java.lang.Object value) Maps the provided key to the provided value.
void	clearAttachments() Removes all attachments from this BDLContext.
BDLContext	detach(java.lang.Object key) Removes the object mapped to the specified key.
Bag	get(BagKey key) Get the value mapped to a key, or null if no mapping
java.lang.Object	getAttachment(java.lang.Object key) Gets the attachment mapped to the specified key, if there is one; returns null otherwise.
BDLContext	put(BagKey key, Bag value) Set the value for a key.
BDLContext	remove(BagKey key) Remove the mapping for the specified key.
java.lang.String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

BDLContext

public BDLContext()

Method Detail

get

public Bag get(BagKey key)

Get the value mapped to a key, or null if no mapping

remove

public BDLContext remove(BagKey key)

Remove the mapping for the specified key. Returns this object

put

public BDLContext put(BagKey key,
                      Bag value)

Set the value for a key. Returns this object

getAttachment

public java.lang.Object getAttachment(java.lang.Object key)

Gets the attachment mapped to the specified key, if there is one; returns null otherwise.

detach

public BDLContext detach(java.lang.Object key)

Removes the object mapped to the specified key. Attachments are not to be confused with bags; attachments are just additional application-level objects that can be attached to BDLContexts, that are not included with the context during serialization.

attach

public BDLContext attach(java.lang.Object key,
                         java.lang.Object value)

Maps the provided key to the provided value. The key-value pair will be carried in this BDLContext while it is propagated within the current process. The k-v pair will not be included when the BDLContext is serialized. Attachments are not to be confused with bags; attachments are just additional application-level objects that can be attached to BDLContexts, that are not included with the context during serialization.

clearAttachments

public void clearAttachments()

Removes all attachments from this BDLContext.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object