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arangodb/Documentation/Books/Users/FoxxBundledApps/Sessions.mdpp

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!CHAPTER The Sessions App
The sessions app provides a session storage JavaScript API that can be used in other Foxx apps.
```js
var sessionStorage = Foxx.requireApp('/_sessions').sessionStorage;
```
!SECTION Exceptions
!SUBSECTION Session Not Found
Indicates a session could not be found in the database.
`new sessionStorage.errors.SessionNotFound(sessionId)`
Thrown by the session storage's *delete* and *get* methods if passed a session ID that does not exist in the database.
@EXAMPLES
```js
try {
sessionStorage.get(invalidSessionId);
} catch(err) {
assertTrue(err instanceof sessionStorage.errors.SessionNotFound);
}
```
!SUBSECTION Session Expired
Indicates the session exists in the database but has expired.
`new sessionStorage.errors.SessionExpired(sessionId)`
Thrown by the session storage's *get* method if passed a session ID for a session that has expired. See also this app's configuration options.
@EXAMPLES
```js
try {
sessionStorage.get(expiredSessionId);
} catch(err) {
assertTrue(err instanceof sessionStorage.errors.SessionExpired);
assertTrue(err instanceof sessionStorage.errors.SessionNotFound);
}
```
!SECTION The session object
Session objects are instances of a Foxx model with the following attributes:
* *sessionData*: volatile session data. This can be an arbitrary object that will be stored with the session in the database. If you want to store session-specific (rather than user-specific) data in the database, this is the right place for that.
* *uid*: the session's active user's *_key* or *undefined* (no active user).
* *userData*: the session's active user's *userData* attribute or an empty object.
* *created*: timestamp the session was created at.
* *lastAccess*: timestamp of the last time the session was fetched from the database.
* *lastUpdate*: timestamp of the last time the session was written to the database.
!SECTION Create a session
Creates and saves a new instance of the session model.
`sessionStorage.create(sessionData)`
*Parameter*
* *sessionData* (optional): an arbitrary object that will be stored as the session's *sessionData* attribute when the model is saved to the database.
@EXAMPLES
```js
var session = sessionStorage.create(sessionData);
assertEqual(session.get('sessionData'), sessionData);
```
!SECTION Fetch an existing session
There are two ways to fetch a session via the session storage API:
* resolving a session cookie with the *fromCookie* method
* calling the session storage's *get* method with a session ID directly
!SUBSECTION Resolve a session cookie
Fetch a session matching a cookie in a Foxx request.
`sessionStorage.fromCookie(request, cookieName, secret)`
Parses a request's cookies and returns the matching instance of the session model.
The method will return *null* instead of a session object in the following cases:
* the request has no session cookie
* the request's session cookie does not match a known session ID
* the matching session has expired
* the cookie's signature is missing (if a *secret* is provided)
* the cookie's signature does not match (if a *secret* is provided)
*Parameter*
* *request*: a Foxx request object as passed to controller routes.
* *cookieName*: name of the cookie to parse.
* *secret* (optional): secret string to validate the cookie's signature with.
@EXAMPLES
```js
controller.get('/hello', function(request, response) {
var session = sessionStorage.fromCookie(request, cookieName, secret);
response.json(session.get('sessionData'));
});
```
!SUBSECTION Resolve a session ID directly
Fetch a session from the database for a given ID.
`sessionStorage.get(sessionId)`
Attempts to load the session with the given session ID from the database. If the session does not exist, a *SessionNotFound* exception will be thrown. If the session does exist, but has already expired, a *SessionExpired* exception will be thrown instead.
*Parameter*
* *sessionId*: a session *_key*.
@EXAMPLES
```js
var session = sessionStorage.get(sessionId);
```
!SECTION Delete a session
There are two ways to delete a session from the database:
* calling the session storage's *delete* method with a session ID directly
* telling a session to delete itself
!SUBSECTION Delete a session by its ID
Delete a session with a given ID.
`sessionStorage.delete(sessionId)`
Attempts to delete the session with the given session ID from the database. If the session does not exist, a *SessionNotFound* exception will be thrown. The method always returns *null*.
*Parameter*
* *sessionId*: a session *_key*.
@EXAMPLES
```js
sessionStorage.delete(sessionId);
```
!SUBSECTION Tell a session to delete itself
Delete a session from the database.
`session.delete()`
Attempts to delete the session from the database.
Returns *true* if the session was deleted successfully.
Returns *false* if the session already didn't exist.
@EXAMPLES
```js
session.delete();
```
!SECTION Save a session
Save a session to the database.
`session.save()`
If you made any changes to the session and are not using the sessions app via Foxx Authentication, you must call this method to commit the changes to the database.
@EXAMPLES
```js
session.setUser(user);
session.save();
```
!SECTION Set a session's active user
Set the active user of a session.
`session.setUser(user)`
Expects a Foxx model with a *userData* attribute and sets the session's *uid* attribute to the model's *_key* and the session's *userData* attribute to the model's *userData* attribute.
*Parameter*
* *user*: instance of a Foxx model with a *`userData* attribute.
@EXAMPLES
```js
session.setUser(user);
assertEqual(session.get('uid'), user.get('_key'));
assertEqual(session.get('userData'), user.get('userData'));
```
!SECTION Add a session cookie to a response
Add a session cookie to a Foxx response.
`session.addCookie(response, cookieName, secret)`
Adds a session cookie to the response.
If a *secret* string is provided, the cookie is signed using that secret (a second cookie with the name *cookieName + '_sig'* containing the cryptographic signature of the cookie value is added to the response).
If you want to use signed cookies, you must make sure to pass the same *secret* to the *fromCookie* method when fetching the session from a cookie later.
*Parameter*
* *response*: a Foxx response object as passed to controller routes.
* *cookieName*: name of the cookie to parse.
* *secret* (optional): secret string to sign the cookie with.
@EXAMPLES
```js
controller.get('/hello', function(request, response) {
session.addCookie(response, cookieName, secret);
});
```
!SECTION Clear a session cookie
Clear the session cookie of a Foxx response.
`session.clearCookie(response, cookieName, secret)`
Adds a blank expired cookie to clear the user's previously set session cookie.
If the method is passed a *secret* string, a second blank expired cookie is added that overwrites the signature cookie (see above).
*Parameter*
* *response*: a Foxx response object as passed to controller routes.
* *cookieName*: name of the cookie to parse.
* *secret* (optional): indicates the signature should be cleared also.
@EXAMPLES
```js
controller.get('/goodbye', function(request, response) {
session.clearCookie(response, cookieName, secret);
});
```