如何通过Java进行网络编程和HTTP服务

原创ゝ一纸荒年。 2024-11-13 23:49 17阅读 0赞

Java网络编程主要涉及到使用Java提供的网络API来创建客户端和服务器应用程序。对于HTTP服务，Java提供了多种方式来实现，包括使用原生的`java.net`包，使用更高级的`java.net.http`包（Java11及以上版本），或者使用第三方库如Apache HttpClient。以下是一些基本的步骤和示例，展示如何使用Java进行网络编程和创建HTTP服务。

###1. 使用`java.net`包创建HTTP客户端#### 发送GET请求```javaimport java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpClientExample {
 public static void main(String[] args) {
 try {
URL url = new URL("http://example.com");
 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
 conn.setRequestMethod("GET");

int responseCode = conn.getResponseCode();
 System.out.println("Response Code: " + responseCode);

BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
String inputLine;
 StringBuffer response = new StringBuffer();

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

//打印结果 System.out.println(response.toString());
} catch (Exception e) {
e.printStackTrace();
 }
 }
}
```#### 发送POST请求```javaimport java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;

public class HttpClientPostExample {
 public static void main(String[] args) {
 try {
URL url = new URL("http://example.com");
 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
 conn.setRequestMethod("POST");
 conn.setRequestProperty("Content-Type", "application/json; utf-8");
 conn.setDoOutput(true);

String jsonInputString = "{\"name\": \"John\", \"age\":30}";

try(OutputStream os = conn.getOutputStream()) {
byte[] input = jsonInputString.getBytes(StandardCharsets.UTF_8);
os.write(input,0, input.length); }

int responseCode = conn.getResponseCode();
 System.out.println("Response Code : " + responseCode);

try(BufferedReader br = new BufferedReader(
 new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8))) {
 StringBuilder response = new StringBuilder();
String responseLine = null;
 while ((responseLine = br.readLine()) != null) {
 response.append(responseLine.trim());
 }
 System.out.println(response.toString());
 }
} catch (Exception e) {
e.printStackTrace();
 }
 }
}
```###2. 使用`java.net.http`包（Java11及以上）

#### 发送GET请求```javaimport java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class HttpClientJava11Example {
 public static void main(String[] args) {
 HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
.uri(URI.create("http://example.com"))
.build();

client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
.thenApply(HttpResponse::body)
.thenAccept(System.out::println)
.join();
 }
}
```###3. 创建HTTP服务器#### 使用`com.sun.net.httpserver`包```javaimport com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;

public class HttpServerExample {
 public static void main(String[] args) throws IOException {
HttpServer server = HttpServer.create(new InetSocketAddress(8000),0);
 server.createContext("/test", new MyHandler());
 server.setExecutor(null); // creates a default executor server.start();
 }

static class MyHandler implements HttpHandler {
@Override public void handle(HttpExchange exchange) throws IOException {
String response = "This is the response";
 exchange.sendResponseHeaders(200, response.length());
OutputStream os = exchange.getResponseBody();
os.write(response.getBytes());
os.close();
 }
 }
}
```请注意，`com.sun.net.httpserver`包不是Java标准库的一部分，它只在JDK中可用，并且可能在未来的版本中被移除。对于生产环境，建议使用成熟的第三方库，如Spring Boot、Jersey或Netty等。

这些示例提供了Java网络编程和HTTP服务的基本框架。根据具体需求，你可能需要添加错误处理、安全性（如HTTPS）、并发处理等高级特性。