### Java 中以 `application/x-www-form-urlencoded` 格式发送 POST 请求 为了在 Java 中构建并发送带有 `application/x-www-form-urlencoded` 类型参数的 POST 请求，可以利用 Apache HttpClient 库或者 JDK 自带的 HttpURLConnection 来完成此操作。下面展示了一个基于 Apache HttpClient 的例子[^1]： ```java import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; public class FormUrlEncodedExample { public static void main(String[] args) throws Exception { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { HttpPost httpPost = new HttpPost("http://localhost:8080"); String params = "param1=value1&param2=value2"; StringEntity entity = new StringEntity(params, "UTF-8"); entity.setContentType("application/x-www-form-urlencoded"); httpPost.setEntity(entity); try (CloseableHttpResponse response = httpClient.execute(httpPost)) { System.out.println(EntityUtils.toString(response.getEntity())); } } } } ``` 上述代码创建了一个 HTTP 客户端实例，并设置了目标 URL 和请求体中的键值对字符串作为表单数据。通过设置实体的内容类型为 `application/x-www-form-urlencoded` 并指定字符编码方式来确保正确传输。 如果不想依赖第三方库，则可以通过标准 API 实现相同功能[^2]: ```java import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.URL; public class UrlConnectionFormUrlEncoded { private final static String PARAMS = "param1=value1&param2=value2"; public static void main(String[] args) throws Exception { URL url = new URL("http://localhost:8080/"); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); // 设置必要的连接属性 conn.setRequestMethod("POST"); conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); conn.setRequestProperty("charset", "utf-8"); conn.setDoOutput(true); // 将参数写入流中 try(OutputStream os = conn.getOutputStream()){ byte[] input = PARAMS.getBytes("utf-8"); os.write(input, 0, input.length); } int code = conn.getResponseCode(); System.out.println(code == HttpURLConnection.HTTP_OK ? "Success" : "Failed with error code:" + code); } } ``` 这段代码展示了如何仅依靠 JDK 提供的功能来进行同样的任务。这里同样指定了正确的 MIME 类型以及 UTF-8 编码用于处理非 ASCII 字符串的情况。