java中怎样使用HttpHelper

Java中可以使用HttpURLConnection或者HttpClient库来发送HTTP请求和接收HTTP响应。

使用HttpURLConnection发送HTTP请求：

import java.net.URL;
import java.net.HttpURLConnection;
import java.io.BufferedInputStream;
import java.io.InputStream;

public class HttpHelper {

    public static String sendGetRequest(String urlString) throws Exception {
    
        URL url = new URL(urlString); // 创建URL对象
        HttpURLConnection conn = (HttpURLConnection) url.openConnection(); // 建立HTTP连接
        
        conn.setRequestMethod("GET"); // 设置请求方法为GET
        conn.connect(); // 发送请求
        
        int responseCode = conn.getResponseCode(); // 获取HTTP响应码
        if (responseCode != 200) { // 处理HTTP错误
            throw new Exception("HTTP error code: " + responseCode);
        }
        
        InputStream in = new BufferedInputStream(conn.getInputStream()); // 获取HTTP响应数据流
        String response = streamToString(in); // 将HTTP响应数据流转化为字符串
        
        return response; // 返回HTTP响应字符串
    }
    
    private static String streamToString(InputStream in) throws Exception {
        StringBuilder sb = new StringBuilder(); // 创建StringBuilder对象
        byte[] buffer = new byte[1024]; // 创建一个长度为1024的byte数组
        
        int len = -1;
        while ((len = in.read(buffer)) != -1) { // 从HTTP响应数据流中读取数据，直到读到末尾
            String s = new String(buffer, 0, len, "UTF-8"); // 将读到的数据转化为字符串
            sb.append(s); // 使用StringBuilder对象拼接字符串
        }
        
        return sb.toString(); // 返回拼接好的字符串
    }
}

使用HttpClient发送HTTP请求：

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

public class HttpHelper {

    public static String sendGetRequest(String urlString) throws Exception {
    
        HttpClient client = HttpClientBuilder.create().build(); // 创建HttpClient对象
        HttpGet request = new HttpGet(urlString); // 创建HttpGet对象
        
        HttpResponse response = client.execute(request); // 使用HttpClient对象发送HTTP请求，并获取HttpResponse对象
        int statusCode = response.getStatusLine().getStatusCode(); // 获取HTTP响应码
        if (statusCode != 200) { // 处理HTTP错误
            throw new Exception("HTTP error code: " + statusCode);
        }
        
        String responseString = EntityUtils.toString(response.getEntity(), "UTF-8"); // 将HTTP响应数据转化为字符串
        
        return responseString; // 返回HTTP响应字符串
    }
}

以上代码只是简单的示例，实际使用中应该加入错误处理和异常处理等内容。