如何在Java中处理HTTP错误码

在Java中处理HTTP错误码，通常是通过使用HTTP客户端库来发送HTTP请求并接收响应。当服务器返回一个错误码（如404 Not Found或500 Internal Server Error）时，客户端可以检查响应的状态码并根据需要采取相应的行动。

以下是使用Java内置的HttpURLConnection类和第三方库Apache HttpClient来处理HTTP错误码的示例。

使用HttpURLConnection

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpErrorHandling {
    public static void main(String[] args) {
        try {
            URL url = new URL("http://example.com");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");

            int responseCode = connection.getResponseCode();
            if (responseCode >= 200 && responseCode < 300) {
                // Success
                BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                String inputLine;
                StringBuilder content = new StringBuilder();

                while ((inputLine = in.readLine()) != null) {
                    content.append(inputLine);
                }

                in.close();
                connection.disconnect();

                System.out.println("Response: " + content.toString());
            } else {
                // Error handling
                System.out.println("HTTP Error Code: " + responseCode);
                BufferedReader errorReader = new BufferedReader(new InputStreamReader(connection.getErrorStream()));
                String errorLine;
                StringBuilder errorContent = new StringBuilder();

                while ((errorLine = errorReader.readLine()) != null) {
                    errorContent.append(errorLine);
                }

                errorReader.close();
                connection.disconnect();

                System.out.println("Error Response: " + errorContent.toString());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用Apache HttpClient

首先，你需要将Apache HttpClient库添加到项目的依赖中。如果你使用Maven，可以在pom.xml文件中添加以下依赖：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.13</version>
</dependency>

然后，你可以使用以下代码来处理HTTP错误码：

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpErrorHandling {
    public static void main(String[] args) {
        HttpClient httpClient = HttpClients.createDefault();
        HttpGet request = new HttpGet("http://example.com");

        try {
            HttpResponse response = httpClient.execute(request);
            int statusCode = response.getStatusLine().getStatusCode();

            if (statusCode >= 200 && statusCode < 300) {
                // Success
                String responseBody = EntityUtils.toString(response.getEntity());
                System.out.println("Response: " + responseBody);
            } else {
                // Error handling
                System.out.println("HTTP Error Code: " + statusCode);
                String errorResponseBody = EntityUtils.toString(response.getEntity());
                System.out.println("Error Response: " + errorResponseBody);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

在这两个示例中，我们都检查了HTTP响应的状态码。如果状态码表示成功（2xx），我们读取并打印响应体。如果状态码表示错误（4xx或5xx），我们读取并打印错误响应体。这样，你就可以根据服务器返回的错误码来采取适当的措施。