一、筑基篇:初识HttpURLConnection
1.1 基础开光(创建连接)
java
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)
java
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)
java
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)
java
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)
java
// 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)
java
// 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)
java
// 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)
java
// 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)
java
// 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)
java
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)
java
// 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)
java
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)