java前端调用后端接口

Java前端调用后端接口可以使用Java的HttpURLConnection或者Apache HttpClient等工具。

下面以HttpURLConnection为例，示范如何使用Java代码调用后端接口：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;

public class HttpUrlConnectionDemo {

    public static void main(String[] args) {
        try {
            URL url = new URL("http://localhost:8080/api/getUserInfo?id=123"); // 接口地址
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept", "application/json");

            if (conn.getResponseCode() != 200) {
                throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
            }

            BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream()), StandardCharsets.UTF_8));

            String output;
            System.out.println("Output from Server .... \n");
            while ((output = br.readLine()) != null) {
                System.out.println(output);
            }

            conn.disconnect();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

以上代码中，我们使用HttpURLConnection向 http://localhost:8080/api/getUserInfo 接口发送了一个GET请求，并且设置了请求头Accept为application/json。如果请求成功，我们就可以通过conn.getInputStream()获取响应结果，然后进行处理。