# HTTP Binding

This binding allows using HTTP to bring external data into openHAB or execute HTTP requests on commands.

# Supported Things

Only one thing named url is available. It can be extended with different channels.

# Thing Configuration

parameter	optional	default	description
`baseURL`	no	-	The base URL (including protocol `http://` or `https://`) for this thing. Can be extended in channel-configuration.
`refresh`	no	30	Time in seconds between two refresh calls for the channels of this thing.
`timeout`	no	3000	Timeout for HTTP requests in ms.
`bufferSize`	no	2048	The buffer size for the response data (in kB).
`delay`	no	0	Delay between two requests in ms (advanced parameter).
`username`	yes	-	Username for authentication (advanced parameter).
`password`	yes	-	Password for authentication (advanced parameter). Also used for the authentication token when using `TOKEN` authentication.
`authMode`	no	BASIC	Authentication mode, `BASIC`, `BASIC_PREEMPTIVE`, `TOKEN` or `DIGEST` (advanced parameter).
`stateMethod`	no	GET	Method used for requesting the state: `GET`, `PUT`, `POST`.
`commandMethod`	no	GET	Method used for sending commands: `GET`, `PUT`, `POST`.
`contentType`	yes	-	MIME content-type of the command requests. Only used for `PUT` and `POST`.
`encoding`	yes	-	Encoding to be used if no encoding is found in responses (advanced parameter).
`headers`	yes	-	Additional headers that are sent along with the request. Format is "header=value". Multiple values can be stored as `headers="key1=value1", "key2=value2", "key3=value3",`
`ignoreSSLErrors`	no	false	If set to true, ignores invalid SSL certificate errors. This is potentially dangerous.
`strictErrorHandling`	no	false	If set to true, thing status is changed depending on last request result (failed = `OFFLINE`). Failed requests result in `UNDEF` for channel values.
`userAgent`	yes	(yes )	Sets a custom user agent (default is "Jetty/version", e.g. "Jetty/9.4.20.v20190813").

Note: Optional "no" means that you have to configure a value unless a default is provided, and you are ok with that setting.

Note: The BASIC_PREEMPTIVE mode adds basic authentication headers even if the server did not request authentication. This is dangerous and might be misused. The option exists to be able to authenticate when the server is not sending the proper 401/Unauthorized code. Authentication might fail if redirections are involved as headers are stripper prior to redirection.

Note: If you rate-limit requests by using the delay parameter you have to make sure that the time between two refreshes is larger than the time needed for one refresh cycle.

Attention: baseUrl (and stateExtension/commandExtension) should not use escaping (e.g. %22 instead of " or %2c instead of ,). URLs are properly escaped by the binding itself before the request is sent. Using escaped strings in URL parameters may lead to problems with the formatting (see below).

# Channels

The thing has two channels of type request-date-time which provide the timestamp of the last successful (last-success) and last failed (last-failure) request.

Additionally, the thing can be extended with data channels. Each item type has its own channel-type. Depending on the channel-type, channels have different configuration options. All channel-types (except image) have stateExtension, commandExtension, stateTransformation, commandTransformation and mode parameters. The image channel-type supports stateExtension only.

parameter	optional	default	description
`stateExtension`	yes	-	Appended to the `baseURL` for requesting states.
`commandExtension`	yes	-	Appended to the `baseURL` for sending commands. If empty, same as `stateExtension`.
`stateTransformation`	yes	-	One or more transformation applied to received values before updating channel.
`commandTransformation`	yes	-	One or more transformation applied to channel value before sending to a remote.
`stateContent`	yes	-	Content for state requests (if method is `PUT` or `POST`)
`mode`	no	`READWRITE`	Mode this channel is allowed to operate. `READONLY` means receive state, `WRITEONLY` means send commands.

Some channels have additional parameters. When concatenating the baseURL and stateExtension or commandExtension the binding checks if a proper URL part separator (/, & or ?) is present and adds a / if missing.

# Value Transformations (`stateTransformation`, `commandTransformation`)

Transformations can be used if the supplied value (or the required value) is different from what openHAB internal types require.

The relevant transformation service needs to be installed via the Main UI or addons.cfg before use.

Here are a few examples to unwrap an incoming value via stateTransformation from a complex response:

Received value	Tr. Service	Transformation
`{device: {status: { temperature: 23.2 }}}`	JSONPATH	`JSONPATH:$.device.status.temperature`
`<device><status><temperature>23.2</temperature></status></device>`	XPath	`XPath:/device/status/temperature/text()`
`THEVALUE:23.2°C`	REGEX	`REGEX::(.*?)°`

Transformations can be chained by separating them with the mathematical intersection character "∩". Please note that the values will be discarded if one transformation fails (e.g. REGEX did not match).

The same mechanism works for commands (commandTransformation) for outgoing values.

# `color`

parameter	optional	default	description
`onValue`	yes	-	A special value that represents `ON`
`offValue`	yes	-	A special value that represents `OFF`
`increaseValue`	yes	-	A special value that represents `INCREASE`
`decreaseValue`	yes	-	A special value that represents `DECREASE`
`step`	no	1	The amount the brightness is increased/decreased on `INCREASE`/`DECREASE`
`colorMode`	no	RGB	Mode for color values: `RGB` or `HSB`

All values that are not onValue, offValue, increaseValue, decreaseValue are interpreted as color value (according to the color mode) in the format r,g,b or h,s,v.

# `contact`

parameter	optional	default	description
`openValue`	no	-	A special value that represents `OPEN`
`closedValue`	no	-	A special value that represents `CLOSED`

# `dimmer`

parameter	optional	default	description
`onValue`	yes	-	A special value that represents `ON`
`offValue`	yes	-	A special value that represents `OFF`
`increaseValue`	yes	-	A special value that represents `INCREASE`
`decreaseValue`	yes	-	A special value that represents `DECREASE`
`step`	no	1	The amount the brightness is increased/decreased on `INCREASE`/`DECREASE`

All values that are not onValue, offValue, increaseValue, decreaseValue are interpreted as brightness 0-100% and need to be numeric only.

# `number`

parameter	optional	default	description
`unit`	yes	-	The unit label for this channel

number channels can be used for DecimalType or QuantityType values. If a unit is given in the unit parameter, the binding tries to create a QuantityType state before updating the channel, if no unit is present, it creates a DecimalType. Please note that incompatible units (e.g. °C for a Number:Density item) will fail silently, i.e. no error message is logged even if the state update fails.

# `player`

parameter	optional	default	description
`playValue`	yes	-	A special value that represents `PLAY`
`pauseValue`	yes	-	A special value that represents `PAUSE`
`nextValue`	yes	-	A special value that represents `NEXT`
`previousValue`	yes	-	A special value that represents `PREVIOUS`
`fastforwardValue`	yes	-	A special value that represents `FASTFORWARD`
`rewindValue`	yes	-	A special value that represents `REWIND`

# `rollershutter`

parameter	optional	default	description
`upValue`	yes	-	A special value that represents `UP`
`downValue`	yes	-	A special value that represents `DOWN`
`stopValue`	yes	-	A special value that represents `STOP`
`moveValue`	yes	-	A special value that represents `MOVE`

All values that are not upValue, downValue, stopValue, moveValue are interpreted as position 0-100% and need to be numeric only.

# `switch`

parameter	optional	default	description
`onValue`	no	-	A special value that represents `ON`
`offValue`	no	-	A special value that represents `OFF`

Note: Special values need to be exact matches, i.e. no leading or trailing characters and comparison is case-sensitive.

# URL Formatting

After concatenation of the baseURL and the commandExtension or the stateExtension (if provided) the URL is formatted using the java.util.Formatter (opens new window). The URL is used as format string and two parameters are added:

the current date (referenced as %1$)
the transformed command (referenced as %2$)

After the parameter reference the format needs to be appended. See the link above for more information about the available format parameters (e.g. to use the string representation, you need to append s to the reference, for a timestamp t). When sending an OFF command on 2020-07-06, the URL

http://www.domain.org/home/lights/23871/?status=%2$s&date=%1$tY-%1$tm-%1$td

is transformed to

http://www.domain.org/home/lights/23871/?status=OFF&date=2020-07-06

# Examples

# `demo.things`

Thing http:url:foo "Foo" [
    baseURL="https://example.com/api/v1/metadata-api/web/metadata", 
    headers="key1=value1", "key2=value2", "key3=value3",
    refresh=15] {
        Channels:
            Type string : text "Text" [ stateTransformation="JSONPATH:$.metadata.data" ]
}

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# HTTP Binding

# Supported Things

# Thing Configuration

# Channels

# Value Transformations (stateTransformation, commandTransformation)

# color

# contact

# dimmer

# number

# player

# rollershutter

# switch