java http 访问_java代码中如何实现http访问

在Java中，可以使用HttpURLConnection或HttpClient实现HTTP访问。

使用HttpURLConnection:

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

public class HttpExample {

    public static void main(String[] args) {
        try {
            URL url = new URL("http://example.com");
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            con.setRequestMethod("GET");
            BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer content = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                content.append(inputLine);
            }
            in.close();
            System.out.println(content.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

使用HttpClient:

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 HttpExample {

    public static void main(String[] args) {
        try {
            HttpClient client = HttpClientBuilder.create().build();
            HttpGet request = new HttpGet("http://example.com");
            org.apache.http.HttpResponse response = client.execute(request);
            String content = EntityUtils.toString(response.getEntity());
            System.out.println(content);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

以上代码都是简单的GET请求，如果需要POST请求或其他更复杂的请求，需要修改相应的参数和请求方法。