HttpURLConnection发送http、https请求

HttpURLConnection是Java标准库提供的用于发送HTTP和HTTPS请求的类，可以用来获取Web资源，以及与服务器进行通信。下面是发送HTTP和HTTPS请求的示例代码：

### 发送HTTP请求

import java.net.*;
import java.io.*;

public class HttpURLConnectionDemo {
    public static void main(String[] args) throws Exception {
        URL url = new URL("http://www.example.com/");
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");
        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println(inputLine);
        }
        in.close();
    }
}

### 发送HTTPS请求

import java.net.*;
import java.io.*;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

public class HttpsURLConnectionDemo {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://www.example.com/");
        HttpsURLConnection.setDefaultHostnameVerifier(new NullHostnameVerifier());
        HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
        con.setRequestMethod("GET");
        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println(inputLine);
        }
        in.close();
    }

    private static class NullHostnameVerifier implements HostnameVerifier {
        public boolean verify(String hostname, SSLSession session) {
            return true;
        }
    }

    private static class NullTrustManager implements X509TrustManager {
        public void checkClientTrusted(X509Certificate[] certs, String authType) {
        }

        public void checkServerTrusted(X509Certificate[] certs, String authType) {
        }

        public X509Certificate[] getAcceptedIssuers() {
            return new X509Certificate[0];
        }
    }
}

需要注意的是，发送HTTPS请求时需要进行证书验证，但这里我们使用了一个自定义的NullTrustManager类，它不对证书进行任何验证。在实际应用中，不建议使用这种方式，应该使用正确的证书验证机制来保证通信的安全性。