# (DD08) Business Logic — Example.uploadFile() [12 LOC]

| Field | Value |
|-------|-------|
| Fully Qualified Name | `io.github.biezhi.java11.http.Example` |
| Layer | Utility |
| Module | `http` (Package: `io.github.biezhi.java11.http`) |

## 1. Role

### Example.uploadFile()

This method performs a simple HTTP file upload against a locally hosted endpoint. It constructs an `HttpClient`, creates an `HttpRequest` targeting `http://localhost:8080/upload/`, and sends the contents of `/tmp/files-to-upload.txt` as the POST body. The business role is that of a client-side upload example: it demonstrates how the application submits a file payload to an upload service and then captures the HTTP response status for verification.

The method implements a straightforward routing-and-dispatch pattern for a single upload scenario. There are no conditional branches, loops, or alternative service types in this method; instead, the flow is linear and deterministic from client creation through request submission and status printing. In the larger system, it functions as a utility/sample entry point for exercising the server-side upload endpoint rather than as a reusable business service.

Because the method discards the response body, its main concern is transport success rather than response content processing. The only observable output is the returned HTTP status code, which is printed to standard output for quick validation of the upload result.

## 2. Processing Pattern (Detailed Business Logic)

```mermaid
flowchart TD
    START(["uploadFile()"])
    BUILD_CLIENT["Create HttpClient via HttpClient.newHttpClient()"]
    BUILD_REQUEST["Build HttpRequest with target URI and file body publisher"]
    SET_URI["Set URI to http://localhost:8080/upload/"]
    SET_BODY["Set POST body from /tmp/files-to-upload.txt"]
    EXEC_SEND["Send request with HttpClient.send()"]
    DISCARD_BODY["Use BodyHandlers.discarding() to ignore response body"]
    PRINT_STATUS["Print response.statusCode()"]
    END_NODE(["Return"])

    START --> BUILD_CLIENT
    BUILD_CLIENT --> BUILD_REQUEST
    BUILD_REQUEST --> SET_URI
    SET_URI --> SET_BODY
    SET_BODY --> EXEC_SEND
    EXEC_SEND --> DISCARD_BODY
    DISCARD_BODY --> PRINT_STATUS
    PRINT_STATUS --> END_NODE
```

## 3. Parameter Analysis

| No | Parameter Name | Type | Business Description |
|----|---------------|------|---------------------|
| - | (none) | - | - |

This method takes no parameters. It relies only on internally created Java HTTP objects and fixed runtime constants embedded in the source code. The external state read by the method is the local filesystem path `/tmp/files-to-upload.txt` and the HTTP endpoint `http://localhost:8080/upload/`.

## 4. CRUD Operations / Called Services

Analyze all method calls within this method and classify each as a CRUD operation.

| CRUD | SC / CBS | SC Code | Entity / DB | Operation Description |
|------|----------|---------|-------------|----------------------|
| R | `HttpClient.newHttpClient()` | N/A | N/A | Creates a client instance used to read/connect to the HTTP endpoint |
| C | `HttpRequest.newBuilder()` | N/A | N/A | Starts construction of a new outbound request object |
| C | `uri(URI)` | N/A | N/A | Sets the destination address for the upload request |
| C | `POST(BodyPublisher)` | N/A | N/A | Configures the request as a file-upload POST submission |
| C | `BodyPublishers.ofFile(Paths.get(...))` | N/A | Local file `/tmp/files-to-upload.txt` | Reads the local file and packages it as the outbound request body |
| C | `build()` | N/A | N/A | Finalizes the HTTP request object |
| R | `client.send(request, BodyHandlers.discarding())` | N/A | HTTP response | Sends the request and reads the response status result while discarding the body |
| R | `response.statusCode()` | N/A | HTTP response | Reads the response status code for validation |
| R | `System.out.println(...)` | N/A | Console output | Writes the observed status code to the console for operator review |

## 5. Dependency Trace

| # | Caller (Screen/Batch) | Call Chain (Full Path to this Method) | Terminal (SC / CRUD / Entity) |
|---|----------------------|--------------------------------------|-------------------------------|
| 1 | Direct utility invocation | `Example.uploadFile` | `client.send(request, BodyHandlers.discarding()) [R] HTTP response` |

## 6. Per-Branch Detail Blocks

**Block 1** — [SEQUENTIAL] (L103-L114)

> Linear file-upload flow with no branching or looping.

| # | Type | Code |
|---|------|------|
| 1 | SET | `HttpClient client = HttpClient.newHttpClient();` // Create an HTTP client for outbound communication |
| 2 | SET | `HttpRequest request = HttpRequest.newBuilder()` // Start request construction |
| 3 | EXEC | `.uri(new URI("http://localhost:8080/upload/"))` // Set the upload endpoint |
| 4 | EXEC | `.POST(HttpRequest.BodyPublishers.ofFile(Paths.get("/tmp/files-to-upload.txt")))` // Attach the local file as POST body |
| 5 | EXEC | `.build();` // Finalize the request |
| 6 | SET | `HttpResponse<Void> response = client.send(request, HttpResponse.BodyHandlers.discarding());` // Send request and ignore response body |
| 7 | EXEC | `response.statusCode();` // Read the HTTP status code |
| 8 | CALL | `System.out.println(response.statusCode());` // Print status for verification |

## 7. Glossary

| Term | Type | Business Meaning |
|------|------|------------------|
| `uploadFile` | Method | Example method that sends a local file to an upload endpoint |
| `HttpClient` | Technical term | Java HTTP client used to send outbound requests |
| `HttpRequest` | Technical term | Java HTTP request object used to define the upload call |
| `POST` | HTTP method | Request verb used to submit data to the server |
| `BodyPublishers.ofFile` | Technical term | Upload mechanism that streams a local file as the request body |
| `BodyHandlers.discarding` | Technical term | Response handler that ignores the response body |
| `statusCode` | Technical term | HTTP response status used to confirm request outcome |
| `localhost` | Technical term | Loopback host indicating the request targets the local machine |
| `upload` | Business term | Server-side upload endpoint that accepts file content |
| `/tmp/files-to-upload.txt` | File path | Local source file used as the payload for the upload request |