Accessor: net/KeyValueStore

This accessor reads or writes data to a key-value store web service whenever it receives a trigger input. A URL for the service is specified by the storeLocation parameter. A Ptolemy II model that provides such a key-value store service can be found at https://www.icyphy.org/accessors/demo/KeyValueStore/KeyValueStoreServer.xml. A demo client that uses this accessor is provided at https://www.icyphy.org/accessors/demo/KeyValueStore/KeyValueStoreClient.xml.

The key and the value are both text items provided as inputs. If remove is true and the key is non-empty, then upon firing, this actor will remove the specified key from the store, producing on its output the previous value (if any). If remove is false, then this actor will either set or retrieve a value in the key-value store, depending on whether the value input is non-empty. If the value is non-empty, then this actor sets the value for the specified key. If it is empty, then this actor retrieves the value for the specified key. If no key is given, then this actor retrieves an array of all the keys in the key-value store.

If an error occurs accessing the key-value store (e.g., no store is found at the specified URL, or no value is found with the specified key), then an exception is thrown.

This accessor assumes that the protocol implemented at that location matches the specification below for the default location:

• To store a value with key MY_ID and value MY_VALUE, use

  http://localhost:8077/keyvalue/set?id=MY_ID&value=MY_VALUE

• To retrieve the value, use

  http://localhost:8077/keyvalue/get?id=MY_ID

• To remove a value, use

  http://localhost:8077/keyvalue/delete?id=MY_ID

• To list all the keys, use

  http://localhost:8077/keyvalue/list

  The key and value are both encoded using the JavaScript encodeURIComponent() function, and on retrieval, decoded using decodeURIComponent(), and hence can include any text characters.

  Note that this accessor uses nonblocking reads to access the store, so the output is produced later when the server responds.