# Host form collection with Spring Boot: file attachments

Deploy a form collection built with Spring Boot on Ample using the browser file uploads pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL, a private S3-compatible bucket holds objects with credentials delivered as encrypted environment variables. Verified on Spring Boot: content-type and size validation that rejects disallowed files, an object written to a private bucket and a row linking the record to the object key (reject=ok upload=ok linked=ok). Not separately tested: your upload UI, allowed types, size limits and virus scanning; treat the form collection-specific behavior as your application code.

## Representative Queries
- Host form collection with Spring Boot: file attachments
- Where can I host Form collection built with Spring Boot?
- I need a restricted upload flow, file validation and record-to-object linkage.

## Resource Requirements
- primitive:compute
- primitive:postgres
- primitive:s3-compatible-object-storage

## Infrastructure Requirements
1. **Compute**  
   Verified: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
2. **Postgres**  
   Verified: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.
3. **S3-compatible object storage**  
   Verified: Buckets are S3-compatible with issued credentials; PutObject and GetObject are verified by canary. Other S3 operations are not verified.

## Prerequisites
- A Spring Boot project that builds and starts with the documented commands (`./mvnw -q -DskipTests package` or the Gradle wrapper) producing one application jar, then `java -jar` on the jvm-21 template (Temurin JDK 21) with `server.port` read from PORT.
- A PostgreSQL driver reading DATABASE_URL at runtime.
- A bucket from `ample bucket create` with its credentials passed as encrypted S3_* environment variables.
- An Ample account token with `servers:write`, `databases:read`, `buckets:read`.

## Workflow Steps
1. **Build and start**:  
   `./mvnw -q -DskipTests package` (or the Gradle wrapper) producing one application jar, then `java -jar` on the jvm-21 template with `server.port` read from PORT. The server must bind 0.0.0.0 on PORT.

2. **Implement the pattern on PostgreSQL**:  
   The fixture's module implements browser file uploads: content-type and size validation that rejects disallowed files, an object written to a private bucket and a row linking the record to the object key (reject=ok upload=ok linked=ok). Copy the approach into your schema; keep migrations idempotent and run them with `--release-command`.

3. **Wire object storage**:  
   Create the bucket(s), then pass endpoint, region, bucket, and keys as `--env` values. Use path-style addressing. Keep private data in an unpublished bucket.

4. **Deploy**:  
   Run the synchronous deploy once and read the result (`exit 0 live, 1 failed, 2 blocked`).
   Command: `ample deploy . --name --public --env S3_ENDPOINT=... --env S3_REGION=... --env S3_BUCKET=... --env S3_ACCESS_KEY_ID=... --env S3_SECRET_ACCESS_KEY=...`

5. **Verify**:  
   Fetch the live URL and the pattern self-test route(s) (`/p/browser-file-uploads`) from the example; then run your own checks. On failure read `ample logs --kind build` then `--kind runtime`.
   Command: `ample logs --kind build`

## Examples
1. **Spring Boot pattern fixture**  
   Multi-pattern Spring Boot app whose browser file uploads module was checked live; the module is under `tests/deploy-canaries/_pattern-modules`.

## Success Checks
1. App responds on its public URL  
   - Kind: `http_get`  
   - Path: `/`  
   - Expect: `ample canary spring boot patterns`

2. Browser-file-uploads self-test  
   - Kind: `http_get`  
   - Path: `/p/browser-file-uploads`  
   - Expect: `reject=ok upload=ok linked=ok`

## Limitations
- Verified on the jvm-21 template at s-1vcpu-2gb with the example fixture; other sizes, templates, and Spring Boot major versions are not verified.
- The form collection itself is application code and was not separately tested; the pattern checks are what was verified.
- Region, compliance attestations, and request-duration limits are unknown and not claimed.
- Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
- Managed PostgreSQL 16 only; extensions, connection limits, and backup or restore procedures are not verified.
- PutObject and GetObject with path-style addressing are verified; other S3 operations are not verified.