Error codes¶

How failure is reported depends on which library you use:

Client (via Android Solid Services)API (direct to the pod)

Calls throw a subtype of SolidException. The hierarchy is sealed, so a when over it is exhaustive.

Calls return SolidResult<T>. Unwrap with getOrThrow() to get the same exceptions, or match on SolidResult.Failure to handle them without throwing.

The hierarchy¶

SolidException
├── SolidAppNotFoundException                    — Android Solid Services is not installed
├── SolidServiceConnectionException              — the IPC binding failed or dropped
├── SolidNotLoggedInException                    — no account signed in for that WebID
├── SolidServicesDrawPermissionDeniedException   — legacy; only the removed requestLogin path
├── SolidResourceException
│   ├── NotSupportedClassException               — class does not extend RDFResource/NonRDFResource
│   ├── NotPermissionException                   — your app has no grant for this account
│   ├── NullWebIdException                       — no WebID supplied for the call
│   └── UnknownException                         — unexpected server or protocol error
└── SolidSharingException
    ├── AccessDeniedException                    — the pod refused the access change
    ├── NoInboxException                         — the receiver advertises no inbox
    ├── InboxUnauthorizedException               — their inbox needs credentials you do not have
    ├── InboxForbiddenException                  — their inbox refused your post
    ├── NotificationDeliveryException            — the notification could not be delivered
    ├── ImpersonationDetectedException           — a notification claimed a sender it cannot prove
    ├── StaleAclException                        — the ACL changed under a conditional write
    └── UnsupportedAuthBackendException          — the server speaks neither WAC nor ACP

What to do about each¶

Setup and connection¶

Exception	Cause	Fix
`SolidAppNotFoundException`	the host app is not on the device	prompt to install it, or switch to the `api` library
`SolidServiceConnectionException`	the binding failed, or the host app was stopped or updated	the connector rebinds itself; collect the connection-state flow and retry once it emits `true`
`SolidNotLoggedInException`	no session for that WebID — signed out, or removed in Settings	send the user back through sign-in
`NullWebIdException`	a call was made with no WebID	keep the WebID you got at sign-in and pass it to every call

Permission¶

Exception	Cause	Fix
`NotPermissionException`	the user has not granted your app access to this account	ask again; the grant dialog is shown by the host app, and the user can revoke at any time
`AccessDeniedException`	the pod refused the access change you asked for	usually you are not the owner, or the server enforces a policy you cannot override
A bare `403` from a write	signed in, but without write access there	see Sharing — the owner has to grant it

A failure is not a denial

probeAccess throws on anything indeterminate — a 401 blip, a 5xx, a dropped connection — rather than returning Denied. Treating those as "no access" hides controls the user is actually allowed to use.

Writes and concurrency¶

Symptom	Cause	Fix
`412 Precondition Failed`	someone else wrote between your read and your write	re-read, merge or ask the user, then write again
`StaleAclException`	the ACL moved under a conditional access change	re-read the current shares and reapply
`404` on a write	the parent container does not exist	call `ensureContainer` first
`TransactionTooLargeException`	a body over roughly 1 MB crossed Binder	use `writeStream`/`readStream`, which pass a file descriptor instead

Exception	Cause	Fix
`NoInboxException`	the receiver's profile advertises no inbox	the share still works; only the notification cannot be delivered
`InboxUnauthorizedException` / `InboxForbiddenException`	their inbox rejected the post	nothing to fix on your side — treat delivery as best-effort
`NotificationDeliveryException`	delivery failed in transit	the access change already happened; retry the notification only
`ImpersonationDetectedException`	an inbox message claimed a sender it could not prove	drop it — this is the anti-spoofing gate doing its job
`UnsupportedAuthBackendException`	the server speaks neither WAC nor ACP	sharing is not available against that server

Content and protocol¶

Exception	Cause	Fix
`NotSupportedClassException`	the class passed to `read`/`create` extends neither base type	extend `RDFResource` or `NonRDFResource`
`UnsupportedRdfContentTypeException`	the server answered Turtle	reads negotiate for JSON-LD or N-Triples; see the notes under Resources
`UnknownException`	anything unclassified	check the message — it carries the server's response

Server-specific behaviour¶

Some failures are a particular pod server rather than your code. The ones already handled for you, and the ones that are not, are in Troubleshooting.