spring boot 如何调用外部api

Spring Boot可以使用Java的HttpURLConnection或者Apache的HttpClient来调用外部API。

以下是使用HttpClient进行调用的示例代码：

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClientBuilder;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class ExternalApiCall {

    public static void main(String[] args) throws Exception {
        HttpClient client = HttpClientBuilder.create().build();
        HttpGet request = new HttpGet("https://example.com/api/data");
        HttpResponse response = client.execute(request);

        BufferedReader bufReader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
        StringBuilder builder = new StringBuilder();
        String line;

        while ((line = bufReader.readLine()) != null) {
            builder.append(line);
            builder.append(System.lineSeparator());
        }

        String result = builder.toString();
        System.out.println(result);
    }
}

以上代码使用HttpClient发送了一个GET请求到"https://example.com/api/data"，并将响应输出到控制台。你可以根据实际情况修改URL、HTTP方法和请求参数等。另外，为了代码的可读性和可维护性，你可以将HttpClient的创建过程封装到一个工具类中。