Using regular expressions in payloads
In some operations regular expressions can be used, as shown below. The set of supported regular expressions is POSIX Extended (see details here).
Example:
POST /v2/op/query
{
"entities": [
{
"idPattern": ".*",
"type": "Sensor"
}
]
}
The regular expression language allows the usage of backslash (\
). For example, SENSOR\d{2}
matches
strings containing SENSOR followed by two digits. However, note that \
is a special character in JSON,
which, according to the JSON specification, needs to be encoded as \\
.
Example:
POST /v2/op/query
{
"entities": [
{
"idPattern": "SENSOR\\d{2}",
"type": "Sensor"
}
]
}
The issue could be even funnier if you use the shell to send the request. For example, if you use multi-line curl you need
to escape \
at shell level. Eg:
curl localhost:1026/v2/op/query -s -S --header 'Content-Type: application/json' --header 'Accept: application/json' -d @- | python -mjson.tool) <<EOF
{
"entities": [
{
"idPattern": "SENSOR\\\\d{2}",
"type": "Sensor"
}
]
}
EOF
In other words, the SENSOR\\\\d{2}
string at shell level is transformed to SENSOR\\d{2}
at payload level (i.e. the actual HTTP request
that is sent over the wire) which, in sequence, corresponds to the SENSOR\d{2}
regular expression after JSON parsing stage at Orion. However, note that
if you use a file for your payload, the shell escaping isn't needed, i.e.:
curl localhost:1026/v2/op/query -s -S --header 'Content-Type: application/json' --header 'Accept: application/json' -d @payload.json
would use the following payload.json file:
{
"entities": [
{
"idPattern": "SENSOR\\d{2}",
"type": "Sensor"
}
]
}
More details on this can be found in the following issue comment at github.