---

# (DD06) Business Logic — Example.downloadFile() [13 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.downloadFile()

This method performs a simple HTTP file download demonstration using the Java 11 `HttpClient` API. It creates a client, builds a GET request to the fixed external URL `https://labs.consol.de/`, and streams the response body directly into a newly created temporary HTML file on disk. The method then prints the HTTP status code and the local file path so the caller can confirm the remote request succeeded and the payload was persisted locally.

From a business perspective, this is a reusable utility-style example for outbound content retrieval and local storage, not a domain workflow with branching business rules. It demonstrates the “download and persist” integration pattern: remote resource access, local file allocation, and response-body-to-file handling. The method does not route by service type or order category; it executes a single linear flow for one target endpoint.

In the larger system, the method serves as a technical sample for network I/O and file handling in the `http` package. It acts as an entry-point utility that can be run independently to validate the Java 11 HTTP client behavior, verify connectivity, and observe the downloaded file location.

## 2. Processing Pattern (Detailed Business Logic)

```mermaid
flowchart TD
    START(["downloadFile()"])
    BUILD_CLIENT["Create HttpClient"]
    BUILD_REQUEST["Build GET HttpRequest for https://labs.consol.de/"]
    CREATE_FILE["Create temp file with prefix consol-labs-home and suffix .html"]
    SEND_REQUEST["Send request with BodyHandlers.ofFile(tempFile)"]
    PRINT_STATUS["Print response status code"]
    PRINT_BODY["Print downloaded file path"]
    END_NODE(["Return / Next"])

    START --> BUILD_CLIENT
    BUILD_CLIENT --> BUILD_REQUEST
    BUILD_REQUEST --> CREATE_FILE
    CREATE_FILE --> SEND_REQUEST
    SEND_REQUEST --> PRINT_STATUS
    PRINT_STATUS --> PRINT_BODY
    PRINT_BODY --> END_NODE
```

## 3. Parameter Analysis

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

External state read by the method:
- The fixed remote endpoint `https://labs.consol.de/`.
- The local filesystem temp directory used by `Files.createTempFile(...)`.
- Standard output via `System.out.println(...)`.

## 4. CRUD Operations / Called Services

| CRUD | SC / CBS | SC Code | Entity / DB | Operation Description |
|------|----------|---------|-------------|----------------------|
| R | `HttpClient.send` | - | Remote HTTP resource `https://labs.consol.de/` | Issues an outbound GET request and reads the remote content stream into a local file. |

Notes:
- `HttpClient.newHttpClient()` and `HttpRequest.newBuilder()` are object construction steps, not CRUD service calls.
- `Files.createTempFile(...)` performs local file creation but does not target a business entity or database table.
- No SC/CBS method names, entity classes, or DB tables are present in this method.

## 5. Dependency Trace

| # | Caller (Screen/Batch) | Call Chain (Full Path to this Method) | Terminal (SC / CRUD / Entity) |
|---|----------------------|--------------------------------------|-------------------------------|
| 1 | No internal Java callers found | `Example.downloadFile` | `HttpClient.send [R] Remote HTTP resource` |

## 6. Per-Branch Detail Blocks

**Block 1** — [SEQUENCE] (L88-L100)

> Linear file download flow with no conditional branching.

| # | Type | Code |
|---|------|------|
| 1 | SET | `HttpClient client = HttpClient.newHttpClient();` // create the HTTP client |
| 2 | SET | `HttpRequest request = HttpRequest.newBuilder()` // start request construction |
| 3 | EXEC | `.uri(new URI("https://labs.consol.de/"))` // set the fixed download target |
| 4 | EXEC | `.GET()` // define the request method |
| 5 | EXEC | `.build();` // finalize the request object |
| 6 | SET | `Path tempFile = Files.createTempFile("consol-labs-home", ".html");` // allocate local storage for the downloaded HTML |
| 7 | CALL | `HttpResponse<Path> response = client.send(request, HttpResponse.BodyHandlers.ofFile(tempFile));` // execute the outbound download and store the body in the temp file |
| 8 | EXEC | `System.out.println(response.statusCode());` // print HTTP completion status |
| 9 | EXEC | `System.out.println(response.body());` // print the file path of the downloaded content |

## 7. Glossary

| Term | Type | Business Meaning |
|------|------|------------------|
| `HttpClient` | Technical term | Java HTTP client used to send outbound network requests. |
| `HttpRequest` | Technical term | Immutable HTTP request definition containing the target URI and method. |
| `BodyHandlers.ofFile` | Technical term | Response handler that streams the response body directly to a file. |
| `Files.createTempFile` | Technical term | Creates a temporary file on the local filesystem for download storage. |
| `statusCode` | Technical term | HTTP result code returned by the remote server. |
| `body` | Technical term | The response payload; here it resolves to the downloaded file path. |
| `https://labs.consol.de/` | Business term | Fixed external web resource used as the download source in this example. |
| `tempFile` | Technical term | Local temporary file that receives the downloaded HTML content. |