一、基礎概念
不同設備之間通過網絡進行數據傳輸，并且基于通用的網絡協議作為多種設備的兼容標準，稱為網絡通信；
(資料圖片)
以C/S架構來看，在一次請求當中，客戶端和服務端進行數據傳輸的交互時，在不同階段和層次中需要遵守的網絡通信協議也不一樣；
應用層：HTTP超文本傳輸協議，基于TCP/IP通信協議來傳遞數據；
傳輸層：TCP傳輸控制協議，采用三次握手的方式建立連接，形成數據傳輸通道；
網絡層：IP協議，作用是把各種傳輸的數據包發送給請求的接收方；
通信雙方進行交互時，發送方數據在各層傳輸時，每通過一層就會添加該層的首部信息；接收方與之相反，每通過一次就會刪除該層的首部信息；
二、JDK源碼在java.net?源碼包中，提供了與網絡編程相關的基礎API；
1、InetAddress封裝了對IP地址的相關操作，在使用該API之前可以先查看本機的??hosts??的映射，Linux系統中在??/etc/hosts??路徑下；
import java.net.InetAddress;public class TestInet { public static void main(String[] args) throws Exception { // 獲取本機 InetAddress 對象 InetAddress localHost = InetAddress.getLocalHost(); printInetAddress(localHost); // 獲取指定域名 InetAddress 對象 InetAddress inetAddress = InetAddress.getByName("www.baidu.com"); printInetAddress(inetAddress); // 獲取本機配置 InetAddress 對象 InetAddress confAddress = InetAddress.getByName("nacos-service"); printInetAddress(confAddress); } public static void printInetAddress (InetAddress inetAddress){ System.out.println("InetAddress："+inetAddress); System.out.println("主機名："+inetAddress.getHostName()); System.out.println("IP地址："+inetAddress.getHostAddress()); }}2、URL統一資源定位符，URL一般包括：協議、主機名、端口、路徑、查詢參數、錨點等，路徑+查詢參數，也被稱為文件；
import java.net.URL;public class TestURL { public static void main(String[] args) throws Exception { URL url = new URL("https://www.baidu.com:80/s?wd=Java#bd") ; printURL(url); } private static void printURL (URL url){ System.out.println("協議：" + url.getProtocol()); System.out.println("域名：" + url.getHost()); System.out.println("端口：" + url.getPort()); System.out.println("路徑：" + url.getPath()); System.out.println("參數：" + url.getQuery()); System.out.println("文件：" + url.getFile()); System.out.println("錨點：" + url.getRef()); }}3、HttpURLConnection作為URLConnection的抽象子類，用來處理針對Http協議的請求，可以設置連接超時、讀取超時、以及請求的其他屬性，是服務間通信的常用方式；
public class TestHttp { public static void main(String[] args) throws Exception { // 訪問 網址 內容 URL url = new URL("https://www.jd.com"); HttpURLConnection httpUrlConnection = (HttpURLConnection) url.openConnection(); printHttp(httpUrlConnection); // 請求 服務 接口 URL api = new URL("http://localhost:8082/info/99"); HttpURLConnection apiConnection = (HttpURLConnection) api.openConnection(); apiConnection.setRequestMethod("GET"); apiConnection.setConnectTimeout(3000); printHttp(apiConnection); } private static void printHttp (HttpURLConnection httpUrlConnection) throws Exception{ try (InputStream inputStream = httpUrlConnection.getInputStream()) { BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8)); String line ; while ((line = bufferedReader.readLine()) != null) { System.out.println(line); } } }}三、通信編程1、SocketSocket也被稱為套接字，是兩臺設備之間通信的端點，會把網絡連接當成流處理，則數據以IO形式傳輸，這種方式在當前被普遍采用；
從網絡編程直接跳到Socket套接字，概念上確實有較大跨度，概念過度抽象時，可以看看源碼的核心結構，在理解時會輕松很多，在JDK中重點看SocketImpl抽象類；
public abstract class SocketImpl implements SocketOptions { // Socket對象，客戶端和服務端 Socket socket = null; ServerSocket serverSocket = null; // 套接字的文件描述對象 protected FileDescriptor fd; // 套接字的路由IP地址 protected InetAddress address; // 套接字連接到的遠程主機上的端口號 protected int port; // 套接字連接到的本地端口號 protected int localport;}套接字的抽象實現類，是實現套接字的所有類的公共超類，可以用于創建客戶端和服務器套接字；
所以到底如何理解Socket概念？從抽象類中來看，套接字就是指代網絡通訊中系統資源的核心標識，比如通訊方IP地址、端口、狀態等；
2、SocketServer創建Socket服務端，并且在8989端口監聽，接收客戶端的連接請求和相關信息，并且響應客戶端，發送指定的數據；
public class SocketServer { public static void main(String[] args) throws Exception { // 1、創建Socket服務端 ServerSocket serverSocket = new ServerSocket(8989); System.out.println("socket-server:8989，waiting connect..."); // 2、方法阻塞等待，直到有客戶端連接 Socket socket = serverSocket.accept(); System.out.println("socket-server:8989，get connect:"+socket.getPort()); // 3、輸入流，輸出流 InputStream inStream = socket.getInputStream(); OutputStream outStream = socket.getOutputStream(); // 4、數據接收和響應 byte[] buf = new byte[1024]; int readLen = 0; while ((readLen=inStream.read(buf)) != -1){ // 接收數據 String readVar = new String(buf, 0, readLen) ; if ("exit".equals(readVar)){ break ; } System.out.println("recv："+readVar+"；time："+DateTime.now().toString(DatePattern.NORM_DATETIME_PATTERN)); // 響應數據 outStream.write(("resp-time："+DateTime.now().toString(DatePattern.NORM_DATETIME_PATTERN)).getBytes()); } // 5、資源關閉 outStream.close(); inStream.close(); socket.close(); serverSocket.close(); System.out.println("socket-server:8989，exit..."); }}需要注意的是步驟2輸出的端口號是隨機不確定的，結合jps和lsof -i tcp:port?命令查看進程和端口號的占用情況；
3、SocketClient創建Socket客戶端，并且連接到服務端，讀取命令行輸入的內容并發送到服務端，并且輸出服務端的響應數據；
public class SocketClient { public static void main(String[] args) throws Exception { // 1、創建Socket客戶端 Socket socket = new Socket(InetAddress.getLocalHost(), 8989); System.out.println("server-client，connect to:8989"); // 2、輸入流，輸出流 OutputStream outStream = socket.getOutputStream(); InputStream inStream = socket.getInputStream(); // 3、數據發送和響應接收 int readLen = 0; byte[] buf = new byte[1024]; while (true){ // 讀取命令行輸入 BufferedReader bufReader = new BufferedReader(new InputStreamReader(System.in)); String iptLine = bufReader.readLine(); if ("exit".equals(iptLine)){ break; } // 發送數據 outStream.write(iptLine.getBytes()); // 接收數據 if ((readLen = inStream.read(buf)) != -1) { System.out.println(new String(buf, 0, readLen)); } } // 4、資源關閉 inStream.close(); outStream.close(); socket.close(); System.out.println("socket-client，get exit command"); }}測試結果：整個流程在沒有收到客戶端的??exit??退出指令前，會保持連接的狀態，并且可以基于字節流模式，進行持續的數據傳輸；
基于上述的基礎案例，采用字符流的方式進行數據傳輸，客戶端和服務端只進行一次簡單的交互；
-- 1、客戶端BufferedReader bufReader = new BufferedReader(new InputStreamReader(inStream));BufferedWriter bufWriter = new BufferedWriter(new OutputStreamWriter(outStream));// 客戶端發送數據bufWriter.write("hello,server");bufWriter.newLine();bufWriter.flush();// 客戶端接收數據System.out.println("client-read："+bufReader.readLine());-- 2、服務端BufferedReader bufReader = new BufferedReader(new InputStreamReader(inStream));BufferedWriter bufWriter = new BufferedWriter(new OutputStreamWriter(outStream));// 服務端接收數據System.out.println("server-read："+bufReader.readLine());// 服務端響應數據bufWriter.write("hello,client");bufWriter.newLine();bufWriter.flush();5、文件傳輸基于上述的基礎案例，客戶端向服務端發送圖片文件，服務端完成文件的讀取和保存，在處理完成后給客戶端發送結果描述；
-- 1、客戶端// 客戶端發送圖片FileInputStream fileStream = new FileInputStream("Local_File_Path/jvm.png");byte[] bytes = new byte[1024];int i = 0;while ((i = fileStream.read(bytes)) != -1) { outStream.write(bytes);}// 寫入結束標記，禁用此套接字的輸出流，之后再使用輸出流會拋異常socket.shutdownOutput();// 接收服務端響應結果System.out.println("server-resp："+new String(bytes,0,readLen));-- 2、服務端// 接收客戶端圖片FileOutputStream fileOutputStream = new FileOutputStream("Local_File_Path/new_jvm.png");byte[] bytes = new byte[1024];int i = 0;while ((i = inStream.read(bytes)) != -1) { fileOutputStream.write(bytes, 0, i);}// 響應客戶端文件處理結果outStream.write("file-save-success".getBytes());6、TCP協議Socket網絡編程是基于TCP協議的，TCP傳輸控制協議是一種面向連接的、可靠的、基于字節流的傳輸層通信協議，在上述案例中側重基于流的數據傳輸，其中關于連接還涉及兩個核心概念：
三次握手：建立連接的過程，在這個過程中進行了三次網絡通信，當連接處于建立的狀態，就可以進行正常的通信，即數據傳輸；四次揮手：關閉連接的過程，調用??close??方法，即連接使用結束，在這個過程中進行了四次網絡通信；
在服務通信時依賴網絡，而對于編程來說，更常見的是的Http的組件，在微服務架構中，涉及到Http組件工具有很多，例如Spring框架中的RestTemplate，Feign框架支持ApacheHttp和OkHttp；下面圍繞幾個常用的組件編寫測試案例；
1、基礎接口@RestControllerpublic class BizWeb { @GetMapping("/getApi/{id}") public Rep getApi(@PathVariable Integer id){ log.info("id={}",id); return Rep.ok(id) ; } @GetMapping("/getApi_v2/{id}") public Rep getApiV2(HttpServletRequest request, @PathVariable Integer id, @RequestParam("name"){ String token = request.getHeader("Token"); log.info("token={},id={},name={}",token,id,name); return Rep.ok(id) ; } @PostMapping("/postApi") public Rep postApi(HttpServletRequest request,@RequestBody IdKey idKey){ String token = request.getHeader("Token"); log.info("token={},idKey={}", token,JSONUtil.toJsonStr(idKey)); return Rep.ok(idKey) ; } @PutMapping("/putApi") public Rep putApi(@RequestBody IdKey idKey){ log.info("idKey={}", JSONUtil.toJsonStr(idKey)); return Rep.ok(idKey) ; } @DeleteMapping("/delApi/{id}") public Rep delApi(@PathVariable Integer id){ log.info("id={}",id); return Rep.ok(id) ; }} 2、ApacheHttppublic class TestApacheHttp { private static final String BASE_URL = "http://localhost:8083" ; public static void main(String[] args){ BasicHeader header = new BasicHeader("Token","ApacheSup") ; // 1、發送Get請求 Map param = new HashMap<>() ; param.put("name","cicada") ; Rep getRep = doGet(BASE_URL+"/getApi_v2/3",header,param, Rep.class); System.out.println("get："+getRep); // 2、發送Post請求 IdKey postBody = new IdKey(1,"id-key-我") ; Rep postRep = doPost (BASE_URL+"/postApi", header, postBody, Rep.class); System.out.println("post："+postRep); } /** * 構建HttpClient對象 */ private static CloseableHttpClient buildHttpClient (){ // 請求配置 RequestConfig reqConfig = RequestConfig.custom().setConnectTimeout(6000).build(); return HttpClients.custom() .setDefaultRequestConfig(reqConfig).build(); } /** * 執行Get請求 */ public static T doGet (String url, Header header, Map param, Class repClass){ // 創建Get請求 CloseableHttpClient httpClient = buildHttpClient(); HttpGet httpGet = new HttpGet(); httpGet.addHeader(header); try { URIBuilder builder = new URIBuilder(url); if (param != null) { for (String key : param.keySet()) { builder.addParameter(key, param.get(key)); } } httpGet.setURI(builder.build()); // 請求執行 HttpResponse httpResponse = httpClient.execute(httpGet); if (httpResponse.getStatusLine().getStatusCode() == 200) { // 結果轉換 String resp = EntityUtils.toString(httpResponse.getEntity()); return JSONUtil.toBean(resp, repClass); } } catch (Exception e) { e.printStackTrace(); } finally { IoUtil.close(httpClient); } return null; } /** * 執行Post請求 */ public static T doPost (String url, Header header, Object body,Class repClass){ // 創建Post請求 CloseableHttpClient httpClient = buildHttpClient(); HttpPost httpPost = new HttpPost(url); httpPost.addHeader(header); StringEntity conBody = new StringEntity(JSONUtil.toJsonStr(body),ContentType.APPLICATION_JSON); httpPost.setEntity(conBody); try { // 請求執行 HttpResponse httpResponse = httpClient.execute(httpPost); if (httpResponse.getStatusLine().getStatusCode() == 200) { // 結果轉換 String resp = EntityUtils.toString(httpResponse.getEntity()); return JSONUtil.toBean(resp, repClass); } } catch (Exception e) { e.printStackTrace(); }finally { IoUtil.close(httpClient); } return null; }} 3、OkHttppublic class TestOkHttp { private static final String BASE_URL = "http://localhost:8083" ; public static void main(String[] args){ Headers headers = new Headers.Builder().add("Token","OkHttpSup").build() ; // 1、發送Get請求 Rep getRep = execute(BASE_URL+"/getApi/1", Method.GET.name(), headers, null, Rep.class); System.out.println("get："+getRep); // 2、發送Post請求 IdKey postBody = new IdKey(1,"id-key") ; Rep postRep = execute(BASE_URL+"/postApi", Method.POST.name(), headers, buildBody(postBody), Rep.class); System.out.println("post："+postRep); // 3、發送Put請求 IdKey putBody = new IdKey(2,"key-id") ; Rep putRep = execute(BASE_URL+"/putApi", Method.PUT.name(), headers, buildBody(putBody), Rep.class); System.out.println("put："+putRep); // 4、發送Delete請求 Rep delRep = execute(BASE_URL+"/delApi/2", Method.DELETE.name(), headers, null, Rep.class); System.out.println("del："+delRep); } /** * 構建JSON請求體 */ public static RequestBody buildBody (Object body){ MediaType mediaType = MediaType.parse("application/json; charset=utf-8"); return RequestBody.create(mediaType, JSONUtil.toJsonStr(body)) ; } /** * 構建OkHttpClient對象 */ public static OkHttpClient buildOkHttp (){ return new OkHttpClient.Builder() .readTimeout(10, TimeUnit.SECONDS).connectTimeout(6, TimeUnit.SECONDS) .connectionPool(new ConnectionPool(15, 5, TimeUnit.SECONDS)) .build(); } /** * 執行請求 */ public static T execute (String url, String method, Headers headers, RequestBody body, Class repClass){ // 請求創建 OkHttpClient httpClient = buildOkHttp() ; Request.Builder requestBuild = new Request.Builder() .url(url).method(method, body); if (headers != null) { requestBuild.headers(headers); } try { // 請求執行 Response response = httpClient.newCall(requestBuild.build()).execute(); // 結果轉換 InputStream inStream = null; if (response.isSuccessful()) { ResponseBody responseBody = response.body(); if (responseBody != null) { inStream = responseBody.byteStream(); } } if (inStream != null) { try { byte[] respByte = IoUtil.readBytes(inStream); if (respByte != null) { return JSONUtil.toBean(new String(respByte, Charset.defaultCharset()), repClass); } } catch (Exception e) { e.printStackTrace(); } finally { IoUtil.close(inStream); } } } catch (Exception e) { e.printStackTrace(); } return null; }} 4、RestTemplatepublic class TestRestTemplate { private static final String BASE_URL = "http://localhost:8083" ; public static void main(String[] args){ RestTemplate restTemplate = buildRestTemplate() ; // 1、發送Get請求 Map paramMap = new HashMap<>() ; Rep getRep = restTemplate.getForObject(BASE_URL+"/getApi/1",Rep.class,paramMap); System.out.println("get："+getRep); // 2、發送Post請求 IdKey idKey = new IdKey(1,"id-key") ; Rep postRep = restTemplate.postForObject(BASE_URL+"/postApi",idKey,Rep.class); System.out.println("post："+postRep); // 3、發送Put請求 IdKey idKey2 = new IdKey(2,"key-id") ; restTemplate.put(BASE_URL+"/putApi",idKey2,paramMap); // 4、發送Delete請求 restTemplate.delete(BASE_URL+"/delApi/2",paramMap); // 5、自定義Header請求 HttpHeaders headers = new HttpHeaders(); headers.add("Token","AdminSup"); HttpEntity requestEntity = new HttpEntity<>(idKey, headers); ResponseEntity respEntity = restTemplate.exchange(BASE_URL+"/postApi", HttpMethod.POST, requestEntity, Rep.class); System.out.println("post-header："+respEntity.getBody()); } private static RestTemplate buildRestTemplate (){ // 1、參數配置 SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory(); factory.setReadTimeout(3000); factory.setConnectTimeout(6000); // 2、創建對象 return new RestTemplate(factory) ; }} 五、參考源碼編程文檔：https://gitee.com/cicadasmile/butte-java-note
應用倉庫：https://gitee.com/cicadasmile/butte-flyer-parent
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