com.microsoft.azure.sdk.iot.device.twin

Class TwinCollection

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<java.lang.String,java.lang.Object>

com.microsoft.azure.sdk.iot.device.twin.TwinCollection

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map<java.lang.String,java.lang.Object>

public class TwinCollection
extends java.util.HashMap<java.lang.String,java.lang.Object>

Representation of a single Twin collection.

The TwinCollection is an extension of a HashMap of String and Object that contain individual and general versioning mechanism.

By the Twin definition, the Object can contain types of Boolean, Number, String, Object, or a sub-TwinCollection, but it cannot be types defined by the user or arrays.

A TwinCollection can contain up to 5 levels of sub TwinCollections. Once the TwinCollection is a extension of the HashMap, both TwinCollection as well as its sub-TwinCollections can be casted to Map of String and Object.

The collection will be represented in the rest API as a JSON in the body. It can or cannot contain the metadata (identified by the $ character at the beginning of the key.

Because of the Twin metadata, the character $ is not allowed in the entry key.

For instance, the following JSON is a valid TwinCollection with its metadata.

 
 {
     "Color":"White",
     "MaxSpeed":{
         "Value":500,
         "NewValue":300
     },
     "$metadata":{
         "$lastUpdated":"2017-09-21T02:07:44.238Z",
         "$lastUpdatedVersion":4,
         "Color":{
             "$lastUpdated":"2017-09-21T02:07:44.238Z",
             "$lastUpdatedVersion":4,
         },
         "MaxSpeed":{
             "$lastUpdated":"2017-09-21T02:07:44.238Z",
             "$lastUpdatedVersion":4,
             "Value":{
                 "$lastUpdated":"2017-09-21T02:07:44.238Z",
                 "$lastUpdatedVersion":4
             },
             "NewValue":{
                 "$lastUpdated":"2017-09-21T02:07:44.238Z",
                 "$lastUpdatedVersion":4
             }
         }
     },
     "$version":4
 }
 
 

This class exposes the Twin collection with or without metadata as a Map here user can get both the value and the metadata. For instance, in the above TwinCollection, HashMap.get(Object) for Color will return White and the getTwinMetadata(String) for Color will return the Object TwinMetadata that contain TwinMetadata.getLastUpdated() that will returns the Date for example 2017-09-21T02:07:44.238Z, TwinMetadata.getLastUpdatedBy() that will return the String for example testConfig, TwinMetadata.getLastUpdatedByDigest() that will return the String for example 637570515479675333, and TwinMetadata.getLastUpdatedVersion() that will return the Integer for example 4.

For the nested TwinCollection, you can do the same, for instance, the following code will return the value and metadata of the NewValue nested in MaxSpeed:

 
      // Get the value of the MaxSpeed, which is a inner TwinCollection.
      TwinCollection innerMaxSpeed = (TwinCollection) twinCollection.get("MaxSpeed");

      // From the inner TwinCollection, get the value of the NewValue.
      Long maxSpeedNewValue = innerMaxSpeed.get("NewValue");

      // As in the root TwinCollection, the inner TwinCollection contain its own metadata.
      // So, get the metadata information for the inner NewValue.
      TwinMetadata maxSpeedNewValueMetadata = innerMaxSpeed.getTwinMetadata("NewValue");
      Date newValueLastUpdated = maxSpeedNewValueMetadata.getLastUpdated(); //Shall contain `2017-09-21T02:07:44.238Z`
      Integer newValueLastUpdatedVersion = maxSpeedNewValueMetadata.getLastUpdatedVersion(); //Shall contain `4`
 
 

See Also:

Understand and use device twins in IoT Hub, Device Twin Api, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

java.util.Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
TwinCollection() Constructor
TwinCollection(java.util.Map<? extends java.lang.String,java.lang.Object> map) Constructor
TwinCollection(TwinCollection collection) Constructor

Method Summary

Modifier and Type	Method and Description
TwinMetadata	getTwinMetadata() Getter for the TwinCollection metadata
TwinMetadata	getTwinMetadata(java.lang.String key) Getter for the entry metadata in the TwinCollection.
java.lang.Integer	getVersion() Getter for the version.
java.lang.Object	put(java.lang.String key, java.lang.Object value) Add a single new entry in the TwinCollection.
void	putAll(java.util.Map<? extends java.lang.String,?> map) Add all information in the provided Map to the TwinCollection.
void	setVersion(java.lang.Integer version) Setter for the version.
com.google.gson.JsonElement	toJsonElement() Serializer
java.lang.String	toString() Creates a pretty print JSON with the content of this class and subclasses.

Methods inherited from class java.util.HashMap

clear, clone, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, forEach, get, getOrDefault, isEmpty, keySet, merge, putIfAbsent, remove, remove, replace, replace, replaceAll, size, values

Methods inherited from class java.util.AbstractMap

equals, hashCode

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Detail

TwinCollection

public TwinCollection()

Constructor

Creates an empty collection. Fill it with put(String, Object) or putAll(Map).

TwinCollection

public TwinCollection(java.util.Map<? extends java.lang.String,java.lang.Object> map)

Constructor

Creates a new Twin collection coping the provided Map.

Parameters:

map - the Map of ? extends String and Object with the Twin collection

TwinCollection

public TwinCollection(TwinCollection collection)

Constructor

Creates a new Twin collection coping the provided collection.

Parameters:

collection - the Collection of ? extends String and Object with the Twin collection

Method Detail

putAll

public void putAll(java.util.Map<? extends java.lang.String,?> map)

Add all information in the provided Map to the TwinCollection.

Override HashMap.putAll(Map).

This function will add all entries in the Map to the TwinCollection. If the provided key already exists, it will replace the value by the new one. This function will not delete or change the content of the other keys in the Map.

As defined by the Twin, the value of a entry can be an inner Map. TwinCollection will accept up to 5 levels of inner Maps.

Specified by:

putAll in interface java.util.Map<java.lang.String,java.lang.Object>

Overrides:

putAll in class java.util.HashMap<java.lang.String,java.lang.Object>

Parameters:

map - A Map of entries to add to the TwinCollection.

put

public java.lang.Object put(java.lang.String key,
                            java.lang.Object value)

Add a single new entry in the TwinCollection.

Override HashMap.put(String, Object).

This function will add a single pair key value to the TwinCollection. By the Twin definition, the Object can contain types of Boolean, Number, String, Object, or up to 5 levels of sub-TwinCollection, but it cannot be types defined by the user or arrays.

Specified by:

put in interface java.util.Map<java.lang.String,java.lang.Object>

Overrides:

put in class java.util.HashMap<java.lang.String,java.lang.Object>

Parameters:

key - the String that represents the key of the new entry. It cannot be null or empty.

value - the Object that represents the value of the new entry. It cannot be user defined type or array.

Returns:

The Object that correspond to the last value of this key. It will be null if there is no previous value.

toJsonElement

public com.google.gson.JsonElement toJsonElement()

Serializer

Creates a JsonElement, which the content represents the information in this class and its subclasses in a JSON format.

This is useful if the caller will integrate this JSON with JSON from other classes to generate a consolidated JSON.

Returns:

The JsonElement with the content of this class.

getVersion

public final java.lang.Integer getVersion()

Getter for the version.

Returns:

The Integer with the version content. It can be null.

setVersion

public final void setVersion(java.lang.Integer version)

Setter for the version.

getTwinMetadata

public final TwinMetadata getTwinMetadata()

Getter for the TwinCollection metadata

Returns:

the TwinMetadata of the Whole TwinCollection. It can be null.

getTwinMetadata

public final TwinMetadata getTwinMetadata(java.lang.String key)

Getter for the entry metadata in the TwinCollection.

Parameters:

key - the String with the name of the entry to retrieve the metadata.

Returns:

the TwinMetadata ot the specific entry in the TwinCollection. It can be null.

toString

public java.lang.String toString()

Creates a pretty print JSON with the content of this class and subclasses.

Overrides:

toString in class java.util.AbstractMap<java.lang.String,java.lang.Object>

Returns:

The String with the pretty print JSON.