---

# (DD01) Business Logic — Example.asyncPost() [25 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.asyncPost()

This method demonstrates an asynchronous HTTP POST workflow using the Java 11 `HttpClient` API. Business-wise, it prepares a simple domain object, serializes it into JSON, and sends that JSON to a remote HTTP endpoint for submission-style integration testing or API communication. The payload includes a user-like name and a GitHub URL, so the method acts as a sample client for posting structured business data rather than performing internal data persistence.

The method follows a straightforward orchestration pattern: construct dependencies, populate a DTO, serialize it, build an outbound request, dispatch the request asynchronously, and handle the completion result. It uses delegation to platform APIs rather than custom business services, and its callback acts as a terminal response handler for either error reporting or response inspection. In the larger system, this method is an example entry point for outbound HTTP integration, showing how a caller can perform non-blocking POST execution and then block only at the end to await completion.

There are two completion branches. If the asynchronous operation fails, the throwable is printed for diagnostics. If it succeeds, the response body and HTTP status code are printed to standard output. No branching occurs on business constants or service categories in this method.

## 2. Processing Pattern (Detailed Business Logic)

```mermaid
flowchart TD
    START(["asyncPost()"])
    CREATE_CLIENT(["Create HttpClient"])
    CREATE_GSON(["Create Gson"])
    CREATE_FOO(["Create Foo and set fields"])
    TO_JSON(["Convert Foo to JSON body"])
    BUILD_REQUEST(["Build POST request to https://httpbin.org/post with application/json"])
    SEND_ASYNC(["Send request asynchronously"])
    WHEN_COMPLETE(["Register completion callback"])
    ERROR_BRANCH(["If throwable is not null, print stack trace"])
    SUCCESS_BRANCH(["Otherwise print response body and status code"])
    JOIN(["Wait for async completion with join()"])
    END_NODE(["Return"])

    START --> CREATE_CLIENT
    CREATE_CLIENT --> CREATE_GSON
    CREATE_GSON --> CREATE_FOO
    CREATE_FOO --> TO_JSON
    TO_JSON --> BUILD_REQUEST
    BUILD_REQUEST --> SEND_ASYNC
    SEND_ASYNC --> WHEN_COMPLETE
    WHEN_COMPLETE --> ERROR_BRANCH
    WHEN_COMPLETE --> SUCCESS_BRANCH
    ERROR_BRANCH --> JOIN
    SUCCESS_BRANCH --> JOIN
    JOIN --> END_NODE
```

## 3. Parameter Analysis

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

External state read by the method:
- Local object state from `Foo` (`name`, `url`) that is converted into the JSON request body.
- The remote endpoint URI `https://httpbin.org/post`, which determines the destination of the outbound integration call.
- The asynchronous response object and throwable supplied by the HTTP client completion callback.

## 4. CRUD Operations / Called Services

This method does not call any internal CRUD services or persistence methods. It only uses Java platform APIs and a JSON serializer to construct and submit an outbound HTTP request.

| CRUD | SC / CBS | SC Code | Entity / DB | Operation Description |
|------|----------|---------|-------------|-----------------------|
| R | `HttpClient.newHttpClient()` | - | - | Creates the HTTP client instance used for outbound communication. |
| C | `gson.toJson(foo)` | - | - | Serializes the local `Foo` object into a JSON payload for request submission. |
| C | `HttpRequest.newBuilder()` | - | - | Creates an outbound POST request builder for the external endpoint. |
| C | `HttpRequest.BodyPublishers.ofString(jsonBody)` | - | - | Places the serialized JSON string into the request body. |
| C | `client.sendAsync(request, HttpResponse.BodyHandlers.ofString())` | - | - | Sends the HTTP POST request asynchronously and initiates remote interaction. |
| R | `resp.body()` | - | - | Reads the returned response payload from the remote service. |
| R | `resp.statusCode()` | - | - | Reads the returned HTTP status for outcome verification. |

## 5. Dependency Trace

### Pre-computed evidence from code analysis graph:

No screen/batch entry points found within 8 hops. Direct callers found: 1 methods.
Terminal operations from this method: -

| # | Caller (Screen/Batch) | Call Chain (Full Path to this Method) | Terminal (SC / CRUD / Entity) |
|---|----------------------|--------------------------------------|-------------------------------|
| 1 | Utility: `main()` in `Example` | `Example.main()` -> `Example.asyncPost()` | `sendAsync [C] remote HTTP endpoint https://httpbin.org/post` |

## 6. Per-Branch Detail Blocks

**Block 1** — TRY (implicit method body, L61-L85)

> This block prepares the request payload and sends it asynchronously.

| # | Type | Code |
|---|------|------|
| 1 | SET | `HttpClient client = HttpClient.newHttpClient();` |
| 2 | SET | `Gson gson = new Gson();` |
| 3 | SET | `Foo foo = new Foo();` |
| 4 | SET | `foo.name = "王爵nice";` |
| 5 | SET | `foo.url = "https://github.com/biezhi";` |
| 6 | SET | `String jsonBody = gson.toJson(foo);` |
| 7 | SET | `HttpRequest request = HttpRequest.newBuilder()` |
| 8 | EXEC | `.uri(new URI("https://httpbin.org/post"))` |
| 9 | EXEC | `.header("Content-Type", "application/json")` |
| 10 | EXEC | `.POST(HttpRequest.BodyPublishers.ofString(jsonBody))` |
| 11 | EXEC | `.build();` |
| 12 | CALL | `client.sendAsync(request, HttpResponse.BodyHandlers.ofString())` |
| 13 | EXEC | `.whenComplete((resp, t) -> { ... })` |
| 14 | EXEC | `.join();` |
| 15 | RETURN | `return;` |

**Block 1.1** — IF `(t != null)` (L76)

> Handles failure of the asynchronous HTTP call.

| # | Type | Code |
|---|------|------|
| 1 | EXEC | `t.printStackTrace();` |

**Block 1.2** — ELSE `(t == null)` (L78)

> Handles successful completion of the asynchronous HTTP call.

| # | Type | Code |
|---|------|------|
| 1 | EXEC | `System.out.println(resp.body());` |
| 2 | EXEC | `System.out.println(resp.statusCode());` |

## 7. Glossary

| Term | Type | Business Meaning |
|------|------|------------------|
| `asyncPost` | Method | Example asynchronous POST operation that submits JSON to an external HTTP endpoint. |
| `HttpClient` | Technical term | Java 11 HTTP client used to send outbound network requests. |
| `HttpRequest` | Technical term | HTTP request object used to define method, headers, URI, and body. |
| `BodyPublishers.ofString` | Technical term | Creates a request body publisher from a JSON string payload. |
| `HttpResponse.BodyHandlers.ofString` | Technical term | Reads the HTTP response body as a string. |
| `Foo` | DTO | Sample data object used to build the outbound JSON payload. |
| `Gson` | Library | JSON serialization library used to convert the `Foo` object into request text. |
| `jsonBody` | Field | Serialized JSON payload sent in the HTTP POST body. |
| `resp` | Callback variable | Successful HTTP response returned by the remote server. |
| `t` | Callback variable | Throwable representing a failure during asynchronous execution. |
| `URI` | Technical term | Uniform Resource Identifier that identifies the remote HTTP endpoint. |
| `httpbin.org` | External service | Public HTTP testing service used to receive and echo request data. |
| `Content-Type` | HTTP header | Declares that the request body uses JSON format. |
| `application/json` | MIME type | Standard media type for JSON payloads. |
| `join` | Technical term | Blocks the current thread until the asynchronous request completes. |
| `printStackTrace` | Technical term | Writes diagnostic exception details for troubleshooting. |
| `statusCode` | Field/Method | HTTP response status used to confirm remote call outcome. |
| `body` | Field/Method | Response payload returned by the remote endpoint. |
| `왕爵nice` | Field value | Example sample name embedded in the outgoing payload. |
| `https://github.com/biezhi` | Field value | Example URL included in the sample payload. |