java前端怎么调用后端接口

Java前端调用后端接口可以使用Java的HTTP客户端库，比如Apache HttpClient或者OkHttp。以下是一个示例代码：

import org.apache.http.HttpEntity;
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 Main {
    public static void main(String[] args) {
        HttpClient httpClient = HttpClients.createDefault();
        HttpGet httpGet = new HttpGet("http://example.com/api/endpoint");

        try {
            HttpResponse response = httpClient.execute(httpGet);
            HttpEntity entity = response.getEntity();

            if (entity != null) {
                String responseBody = EntityUtils.toString(entity);
                System.out.println(responseBody);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

这个示例使用了Apache HttpClient来发送GET请求并获取响应。你可以根据需要来修改请求的方法、URL以及请求体等信息。然后，通过解析响应体来获取后端接口返回的数据。请确保在调用结束后释放相关资源，比如关闭HttpClient。