如何有效處理HTTP請求異常

一、HTTP請求異常的種類

在處理HTTP請求異常之前，我們需要清楚的了解HTTP請求異常的種類。HTTP請求異常包括但不限於：

1、網絡異常：如DNS解析失敗、網絡連接超時等

try{
    httpclient.execute(httpget)
}catch(UnknownHostException | ConnectTimeoutException e){
    //處理網絡異常
}

2、服務器異常：如響應碼不是200、服務器返回的JSON信息格式不規範等

HttpResponse response = httpclient.execute(httpget);
if(response.getStatusLine().getStatusCode() != HttpStatus.SC_OK){
    //處理服務器異常
}

3、業務異常：如用戶登錄信息錯誤、訂單不存在等

HttpResponse response = httpclient.execute(httpget);
String result = EntityUtils.toString(response.getEntity());
ResultDTO resultDTO = JSON.parseObject(result, ResultDTO.class);
if(resultDTO.getCode() != ResultCode.SUCCESS.getCode()){
    //處理業務異常
}

二、如何有效處理HTTP請求異常

在開發過程中，我們需要遵循以下幾個原則來處理HTTP請求異常：

1、明確異常的類型，合理區分異常的處理方式。

2、充分利用HTTP中請求響應的狀態碼和異常信息，特別是在服務器異常時需要充分利用返回的錯誤信息來解決問題。

3、通過記錄日誌的方式，快速定位問題所在。

4、業務異常需要使用自定義異常來處理，一方面能夠更好的維護異常邏輯，另一方面能夠在異常處理層面區分業務異常與其它異常。

三、HTTP請求異常處理的最佳實踐

1、封裝工具類。將HTTP請求的重試、重定向、異常處理封裝到工具類中，使得代碼更簡潔，維護更方便。

public static String get(String url) {
    CloseableHttpClient httpClient = HttpClients.createDefault();
    String result = null;
    HttpGet httpGet = new HttpGet(url);
    try (CloseableHttpResponse response = httpClient.execute(httpGet)) {
        if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                result = EntityUtils.toString(entity, "UTF-8");
            }
        } else {
            throw new RuntimeException("HTTP請求異常！");
        }
    } catch (IOException e) {
        throw new RuntimeException("網絡異常！");
    } finally {
        try {
            httpClient.close();
        } catch (IOException e) {
            throw new RuntimeException("關閉httpClient異常！");
        }
    }
    return result;
}

2、自定義異常。通過自定義異常來對HTTP請求異常進行分類處理。

public class BusinessException extends RuntimeException {

    private static final long serialVersionUID = 1L;
    private Integer code;
    private String message;

    public BusinessException(ResultCode resultCode) {
        super(resultCode.getMessage());
        this.code = resultCode.getCode();
        this.message = resultCode.getMessage();
    }

    public Integer getCode() {
        return code;
    }

    public String getMessage() {
        return message;
    }
}

3、日誌記錄。在處理異常時，需要及時記錄錯誤信息，方便進行問題定位和修復。

private static final Logger logger = LoggerFactory.getLogger(HttpClientUtil.class);

public static String get(String url) {
    CloseableHttpClient httpClient = HttpClients.createDefault();
    String result = null;
    HttpGet httpGet = new HttpGet(url);
    try (CloseableHttpResponse response = httpClient.execute(httpGet)) {
        if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                result = EntityUtils.toString(entity, "UTF-8");
            }
        } else {
            logger.error("請求失敗，url: {}, statusCode: {}", url, response.getStatusLine().getStatusCode());
            throw new BusinessException(ResultCode.HTTP_REQUEST_ERROR);
        }
    } catch (IOException e) {
        logger.error("請求異常，url: {}", url, e);
        throw new BusinessException(ResultCode.NETWORK_ERROR);
    } finally {
        try {
            httpClient.close();
        } catch (IOException e) {
            logger.error("關閉httpClient異常", e);
            throw new BusinessException(ResultCode.HTTP_CLIENT_CLOSE_ERROR);
        }
    }
    return result;
}