一、筑基篇:初识HttpURLConnection
1.1 基础开光(创建连接)
URL url = new URL("https://api.example.com/data");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 注意!此处可能抛出MalformedURLException,建议用try-catch护体
1.2 设置请求方法(选择渡劫姿势)
conn.setRequestMethod("GET"); // 可选GET/POST/PUT/DELETE等
// 重要!POST方法必须开启输出模式:
conn.setDoOutput(true);
二、金丹篇:配置渡劫参数
2.1 设置请求头(佩戴防御法宝)
conn.setRequestProperty("User-Agent", "Mozilla/5.0"); // 伪装浏览器
conn.setRequestProperty("Content-Type", "application/json"); // JSON格式
conn.setRequestProperty("Authorization", "Bearer your_token"); // 令牌认证
2.2 超时设置(防止天劫过久)
conn.setConnectTimeout(5000); // 5秒连接超时
conn.setReadTimeout(10000); // 10秒读取超时
三、元婴篇:发送不同天劫(处理各类请求)
3.1 GET请求(基础天劫)
// 自动触发,无需额外配置
int responseCode = conn.getResponseCode(); // 获取状态码
if (responseCode == HttpURLConnection.HTTP_OK) {try (BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()))) {String inputLine;StringBuilder response = new StringBuilder();while ((inputLine = in.readLine()) != null) {response.append(inputLine);}System.out.println("渡劫成功:" + response);}
}
3.2 POST请求(携带渡劫物资)
// 需要先开启输出模式
conn.setDoOutput(true);// 发送JSON数据(推荐使用try-with-resources自动关闭)
try (OutputStream os = conn.getOutputStream();BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, StandardCharsets.UTF_8))) {String jsonInput = "{\"name\":\"张三\",\"age\":25}";writer.write(jsonInput);writer.flush();
}// 处理响应(同上GET流程)
四、化神篇:高级渡劫技巧
4.1 处理重定向(避免迷失虚空)
// 自动跟随重定向(默认true,需要关闭时)
conn.setInstanceFollowRedirects(false); // 手动处理重定向
if (responseCode == HttpURLConnection.HTTP_MOVED_PERM) {String newUrl = conn.getHeaderField("Location");// 重新开启新连接...
}
4.2 文件上传(渡劫物资运输)
// 设置multipart/form-data
String boundary = "===" + System.currentTimeMillis() + "===";
conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);try (OutputStream os = conn.getOutputStream();PrintWriter writer = new PrintWriter(new OutputStreamWriter(os, StandardCharsets.UTF_8))) {// 上传文件部分writer.append("--" + boundary).append("\r\n");writer.append("Content-Disposition: form-data; name=\"file\"; filename=\"test.txt\"\r\n");writer.append("Content-Type: text/plain\r\n\r\n");writer.flush();Files.copy(Paths.get("test.txt"), os);os.flush();// 结束标记writer.append("\r\n--" + boundary + "--\r\n");
}
五、大乘篇:渡劫安全指南
5.1 HTTPS防护(抗心魔结界)
// 自定义信任所有证书(仅测试环境使用!)
TrustManager[] trustAllCerts = new TrustManager[]{new X509TrustManager() {public void checkClientTrusted(X509Certificate[] chain, String authType) {}public void checkServerTrusted(X509Certificate[] chain, String authType) {}public X509Certificate[] getAcceptedIssuers() { return new X509Certificate[0]; }}
};SSLContext sslContext = SSLContext.getInstance("SSL");
sslContext.init(null, trustAllCerts, new SecureRandom());
HttpsURLConnection.setDefaultSSLSocketFactory(sslContext.getSocketFactory());
5.2 异常处理(渡劫失败预案)
try {// 正常请求流程...
} catch (IOException e) {// 读取错误信息(重要!)String errorResponse = readErrorStream(conn);System.err.println("渡劫失败:" + errorResponse);
} finally {conn.disconnect(); // 必须断开连接!
}private static String readErrorStream(HttpURLConnection conn) {try (InputStream es = conn.getErrorStream();BufferedReader reader = new BufferedReader(new InputStreamReader(es))) {return reader.lines().collect(Collectors.joining());} catch (IOException ex) {return "无法读取错误信息";}
}
六、飞升篇:性能优化与最佳实践
6.1 连接池管理(节省灵力)
// HttpURLConnection默认使用Keep-Alive
// 可通过系统属性配置:
System.setProperty("http.maxConnections", "20");
6.2 使用try-with-resources(自动资源回收)
try (HttpURLConnection autoCloseConn = (HttpURLConnection) url.openConnection()) {// 请求流程...
} // 自动关闭连接(Java 9+)
渡劫成功总结
- 基本流程:创建连接 → 设置参数 → 发送数据 → 处理响应
- 必点技能:异常处理、资源关闭、编码设置
- 安全守则:HTTPS证书验证、输入过滤、超时设置
- 性能心法:连接重用、流式处理、异步改造(需搭配线程池)
渡劫后选择:
- 继续苦修:深入OkHttp/Apache HttpClient等高级法宝
- 飞升仙界:直接使用Spring RestTemplate/WebClient
- 闭关研究:手写HTTP协议实现(警告:可能走火入魔)