java 怎么实现post和get请求

在Java中，通常我们会使用HTTP客户端库如`java.net.HttpURLConnection`或者第三方库如`Apache HttpClient`或`OkHttp`来发送POST和GET请求。以下是基本的示例：

**使用HttpURLConnection发送GET请求：**

URL url = new URL("http://example.com/api");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.connect();

int responseCode = connection.getResponseCode();
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String inputLine;
StringBuilder content = new StringBuilder();

while ((inputLine = in.readLine()) != null) {
    content.append(inputLine);
}

in.close();
connection.disconnect();

if (responseCode == HttpURLConnection.HTTP_OK) {
    System.out.println(content.toString());
} else {
    System.err.println("Request failed with code " + responseCode);
}

**使用HttpURLConnection发送POST请求（包含表单数据）：**

URL url = new URL("http://example.com/api");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setDoOutput(true); // 设置可以输出数据
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

try (OutputStream os = conn.getOutputStream()) {
    byte[] data = ("key1=value1&key2=value2").getBytes(StandardCharsets.UTF_8);
    os.write(data);
    os.flush();
}

int responseCode = conn.getResponseCode();
BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
// ... 同样处理响应...

conn.disconnect();

**使用OkHttp发送GET请求：**

OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
        .url("http://example.com/api")
        .build();
Response response = client.newCall(request).execute();
System.out.println(response.body().string());

**使用OkHttp发送POST请求：**

FormBody.Builder bodyBuilder = new FormBody.Builder();
bodyBuilder.add("key1", "value1");
bodyBuilder.add("key2", "value2");
RequestBody requestBody = bodyBuilder.build();

OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
        .url("http://example.com/api")
        .post(requestBody)
        .build();
Response response = client.newCall(request).execute();