Java HTTP客户端在处理异步请求时的回调问题

原创￡神魔★判官ぃ 2024-10-20 13:39 27阅读 0赞

在Java中，处理HTTP异步请求并使用回调是一种常见的编程模式。以下是一个基本的例子，使用java.net.URLConnection和Handler接口来实现：

```java
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class AsyncHttpClient {
    private URL url;
    private ExecutorService executor;

public AsyncHttpClient(URL url) {
        this.url = url;
        // 创建线程池
        executor = Executors.newSingleThreadExecutor();
    }

// 异步HTTP请求
    public void asyncRequest(String method, String data, final Callback callback) {
        Runnable requestTask = () -> {
            HttpURLConnection connection = null;
            try {
                connection = (HttpURLConnection) url.openConnection();
                // 设置方法，一般为GET或POST
                connection.setRequestMethod(method);
                
                if (method.equals("POST")) {
                    // 设置请求数据
                    connection.setDoOutput(true);
                    DataOutputStream dos = new DataOutputStream(connection.getOutputStream());
                    dos.writeBytes(data);
                    dos.flush();
                    dos.close();
                }

int responseCode = connection.getResponseCode();
                callback.handle(responseCode, responseConnectionToString(connection)));
            } catch (Exception e) {
                callback.error(e.getMessage(), null));
            } finally {
                // 关闭连接
                if (connection != null) {
                    connection.disconnect();
                }
            }
        };

executor.execute(requestTask);
    }

private String responseConnectionToString(HttpURLConnection connection) {
        StringBuilder responseStringBuilder = new StringBuilder();
        responseStringBuilder.append("Response Code: ").append(connection.getResponseCode()).append("\n");
        responseStringBuilder.append("Response Header:\n").append(connection.getHeaderFieldString(null)).trim());
        return responseStringBuilder.toString();
    }

// 回调接口
    interface Callback {
        void handle(int responseCode, String responseBody));
        void error(String errorMessage, Object errorData));
    }
}
```

在这个例子中，`AsyncHttpClient`类创建了一个异步HTTP客户端。`asyncRequest`方法接收HTTP请求的各种参数（如方法、数据等），并通过一个回调接口处理响应。

调用者需要实现`Callback`接口，并在请求时传递给`AsyncHttpClient`的实例。