总感觉这个概念，和研发有点脱节；
一、基础概念
不同设备之间通过网络进行数据传输，并且基于通用的网络协议作为多种设备的兼容标准，称为网络通信；
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以C/S架构来看，在一次请求当中，客户端和服务端进行数据传输的交互时，在不同阶段和层次中需要遵守的网络通信协议也不一样；
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应用层：HTTP超文本传输协议，基于TCP/IP通信协议来传递数据；
传输层：TCP传输控制协议，采用三次握手的方式建立连接，形成数据传输通道；
网络层：IP协议，作用是把各种传输的数据包发送给请求的接收方；
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通信双方进行交互时，发送方数据在各层传输时，每通过一层就会添加该层的首部信息；接收方与之相反，每通过一次就会删除该层的首部信息；
二、JDK源码
在java.net源码包中，提供了与网络编程相关的基础API；
1、InetAddress
封装了对IP地址的相关操作，在使用该API之前可以先查看本机的hosts的映射，Linux系统中在/etc/hosts路径下；
import java.net.InetAddress;
public class TestInet {
public static void main(String[] args) throws Exception {
// 获取本机 InetAddress 对象
InetAddress localHost = InetAddress.getLocalHost();
printInetAddress(localHost);
// 获取指定域名 InetAddress 对象
InetAddress inetAddress = InetAddress.getByName("www.baidu.com");
printInetAddress(inetAddress);
// 获取本机配置 InetAddress 对象
InetAddress confAddress = InetAddress.getByName("nacos-service");
printInetAddress(confAddress);
}
public static void printInetAddress (InetAddress inetAddress){
System.out.println("InetAddress："+inetAddress);
System.out.println("主机名："+inetAddress.getHostName());
System.out.println("IP地址："+inetAddress.getHostAddress());
}
}
2、URL
统一资源定位符，URL一般包括：协议、主机名、端口、路径、查询参数、锚点等，路径+查询参数，也被称为文件；
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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("协议：" + url.getProtocol());
System.out.println("域名：" + url.getHost());
System.out.println("端口：" + url.getPort());
System.out.println("路径：" + url.getPath());
System.out.println("参数：" + url.getQuery());
System.out.println("文件：" + url.getFile());
System.out.println("锚点：" + url.getRef());
}
}
3、HttpURLConnection
作为URLConnection的抽象子类，用来处理针对Http协议的请求，可以设置连接超时、读取超时、以及请求的其他属性，是服务间通信的常用方式；
public class TestHttp {
public static void main(String[] args) throws Exception {
// 访问 网址 内容
URL url = new URL("https://www.jd.com");
HttpURLConnection httpUrlConnection = (HttpURLConnection) url.openConnection();
printHttp(httpUrlConnection);
// 请求 服务 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、通信编程
1、Socket
Socket也被称为套接字，是两台设备之间通信的端点，会把网络连接当成流处理，则数据以IO形式传输，这种方式在当前被普遍采用；
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从网络编程直接跳到Socket套接字，概念上确实有较大跨度，概念过度抽象时，可以看看源码的核心结构，在理解时会轻松很多，在JDK中重点看SocketImpl抽象类；
public abstract class SocketImpl implements SocketOptions {
// Socket对象，客户端和服务端
Socket socket = null;
ServerSocket serverSocket = null;
// 套接字的文件描述对象
protected FileDescriptor fd;
// 套接字的路由IP地址
protected InetAddress address;
// 套接字连接到的远程主机上的端口号
protected int port;
// 套接字连接到的本地端口号
protected int localport;
}
套接字的抽象实现类，是实现套接字的所有类的公共超类，可以用于创建客户端和服务器套接字；
所以到底如何理解Socket概念？从抽象类中来看，套接字就是指代网络通讯中系统资源的核心标识，比如通讯方IP地址、端口、状态等；
2、SocketServer
创建Socket服务端，并且在8989端口监听，接收客户端的连接请求和相关信息，并且响应客户端，发送指定的数据；
public class SocketServer {
public static void main(String[] args) throws Exception {
// 1、创建Socket服务端
ServerSocket serverSocket = new ServerSocket(8989);
System.out.println("socket-server:8989，waiting connect...");
// 2、方法阻塞等待，直到有客户端连接
Socket socket = serverSocket.accept();
System.out.println("socket-server:8989，get connect:"+socket.getPort());
// 3、输入流，输出流
InputStream inStream = socket.getInputStream();
OutputStream outStream = socket.getOutputStream();
// 4、数据接收和响应
byte[] buf = new byte[1024];
int readLen = 0;
while ((readLen=inStream.read(buf)) != -1){
// 接收数据
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));
// 响应数据
outStream.write(("resp-time："+DateTime.now().toString(DatePattern.NORM_DATETIME_PATTERN)).getBytes());
}
// 5、资源关闭
outStream.close();
inStream.close();
socket.close();
serverSocket.close();
System.out.println("socket-server:8989，exit...");
}
}
需要注意的是步骤2输出的端口号是随机不确定的，结合jps和lsof -i tcp:port命令查看进程和端口号的占用情况；
3、SocketClient
创建Socket客户端，并且连接到服务端，读取命令行输入的内容并发送到服务端，并且输出服务端的响应数据；
public class SocketClient {
public static void main(String[] args) throws Exception {
// 1、创建Socket客户端
Socket socket = new Socket(InetAddress.getLocalHost(), 8989);
System.out.println("server-client，connect to:8989");
// 2、输入流，输出流
OutputStream outStream = socket.getOutputStream();
InputStream inStream = socket.getInputStream();
// 3、数据发送和响应接收
int readLen = 0;
byte[] buf = new byte[1024];
while (true){
// 读取命令行输入
BufferedReader bufReader = new BufferedReader(new InputStreamReader(System.in));
String iptLine = bufReader.readLine();
if ("exit".equals(iptLine)){
break;
}
// 发送数据
outStream.write(iptLine.getBytes());
// 接收数据
if ((readLen = inStream.read(buf)) != -1) {
System.out.println(new String(buf, 0, readLen));
}
}
// 4、资源关闭
inStream.close();
outStream.close();
socket.close();
System.out.println("socket-client，get exit command");
}
}
测试结果：整个流程在没有收到客户端的exit退出指令前，会保持连接的状态，并且可以基于字节流模式，进行持续的数据传输；
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4、字符流使用
基于上述的基础案例，采用字符流的方式进行数据传输，客户端和服务端只进行一次简单的交互；
-- 1、客户端
BufferedReader bufReader = new BufferedReader(new InputStreamReader(inStream));
BufferedWriter bufWriter = new BufferedWriter(new OutputStreamWriter(outStream));
// 客户端发送数据
bufWriter.write("hello,server");
bufWriter.newLine();
bufWriter.flush();
// 客户端接收数据
System.out.println("client-read："+bufReader.readLine());
-- 2、服务端
BufferedReader bufReader = new BufferedReader(new InputStreamReader(inStream));
BufferedWriter bufWriter = new BufferedWriter(new OutputStreamWriter(outStream));
// 服务端接收数据
System.out.println("server-read："+bufReader.readLine());
// 服务端响应数据
bufWriter.write("hello,client");
bufWriter.newLine();
bufWriter.flush();
5、文件传输
基于上述的基础案例，客户端向服务端发送图片文件，服务端完成文件的读取和保存，在处理完成后给客户端发送结果描述；
-- 1、客户端
// 客户端发送图片
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);
}
// 写入结束标记，禁用此套接字的输出流，之后再使用输出流会抛异常
socket.shutdownOutput();
// 接收服务端响应结果
System.out.println("server-resp："+new String(bytes,0,readLen));
-- 2、服务端
// 接收客户端图片
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);
}
// 响应客户端文件处理结果
outStream.write("file-save-success".getBytes());
6、TCP协议
Socket网络编程是基于TCP协议的，TCP传输控制协议是一种面向连接的、可靠的、基于字节流的传输层通信协议，在上述案例中侧重基于流的数据传输，其中关于连接还涉及两个核心概念：
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三次握手：建立连接的过程，在这个过程中进行了三次网络通信，当连接处于建立的状态，就可以进行正常的通信，即数据传输；四次挥手：关闭连接的过程，调用close方法，即连接使用结束，在这个过程中进行了四次网络通信；
四、Http组件
在服务通信时依赖网络，而对于编程来说，更常见的是的Http的组件，在微服务架构中，涉及到Http组件工具有很多，例如Spring框架中的RestTemplate，Feign框架支持ApacheHttp和OkHttp；下面围绕几个常用的组件编写测试案例；
1、基础接口
@RestController
public class BizWeb {
@GetMapping("/getApi/{id}")
public Rep<Integer> getApi(@PathVariable Integer id){
log.info("id={}",id);
return Rep.ok(id) ;
}
@GetMapping("/getApi_v2/{id}")
public Rep<Integer> getApiV2(HttpServletRequest request,
@PathVariable Integer id,
@RequestParam("name") String name){
String token = request.getHeader("Token");
log.info("token={},id={},name={}",token,id,name);
return Rep.ok(id) ;
}
@PostMapping("/postApi")
public Rep<IdKey> 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<IdKey> putApi(@RequestBody IdKey idKey){
log.info("idKey={}", JSONUtil.toJsonStr(idKey));
return Rep.ok(idKey) ;
}
@DeleteMapping("/delApi/{id}")
public Rep<Integer> delApi(@PathVariable Integer id){
log.info("id={}",id);
return Rep.ok(id) ;
}
}
2、ApacheHttp
public class TestApacheHttp {
private static final String BASE_URL = "http://localhost:8083" ;
public static void main(String[] args) {
BasicHeader header = new BasicHeader("Token","ApacheSup") ;
// 1、发送Get请求
Map<String,String> 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、发送Post请求
IdKey postBody = new IdKey(1,"id-key-我") ;
Rep postRep = doPost (BASE_URL+"/postApi", header, postBody, Rep.class);
System.out.println("post："+postRep);
}
/**
* 构建HttpClient对象
*/
private static CloseableHttpClient buildHttpClient (){
// 请求配置
RequestConfig reqConfig = RequestConfig.custom().setConnectTimeout(6000).build();
return HttpClients.custom()
.setDefaultRequestConfig(reqConfig).build();
}
/**
* 执行Get请求
*/
public static <T> T doGet (String url, Header header, Map<String,String> param,
Class<T> repClass) {
// 创建Get请求
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());
// 请求执行
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
// 结果转换
String resp = EntityUtils.toString(httpResponse.getEntity());
return JSONUtil.toBean(resp, repClass);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
IoUtil.close(httpClient);
}
return null;
}
/**
* 执行Post请求
*/
public static <T> T doPost (String url, Header header, Object body,Class<T> repClass) {
// 创建Post请求
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 {
// 请求执行
HttpResponse httpResponse = httpClient.execute(httpPost);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
// 结果转换
String resp = EntityUtils.toString(httpResponse.getEntity());
return JSONUtil.toBean(resp, repClass);
}
} catch (Exception e) {
e.printStackTrace();
}finally {
IoUtil.close(httpClient);
}
return null;
}
}
3、OkHttp
public 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、发送Get请求
Rep getRep = execute(BASE_URL+"/getApi/1", Method.GET.name(), headers, null, Rep.class);
System.out.println("get："+getRep);
// 2、发送Post请求
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、发送Put请求
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、发送Delete请求
Rep delRep = execute(BASE_URL+"/delApi/2", Method.DELETE.name(), headers, null, Rep.class);
System.out.println("del："+delRep);
}
/**
* 构建JSON请求体
*/
public static RequestBody buildBody (Object body){
MediaType mediaType = MediaType.parse("application/json; charset=utf-8");
return RequestBody.create(mediaType, JSONUtil.toJsonStr(body)) ;
}
/**
* 构建OkHttpClient对象
*/
public static OkHttpClient buildOkHttp () {
return new OkHttpClient.Builder()
.readTimeout(10, TimeUnit.SECONDS).connectTimeout(6, TimeUnit.SECONDS)
.connectionPool(new ConnectionPool(15, 5, TimeUnit.SECONDS))
.build();
}
/**
* 执行请求
*/
public static <T> T execute (String url, String method,
Headers headers, RequestBody body,
Class<T> repClass) {
// 请求创建
OkHttpClient httpClient = buildOkHttp() ;
Request.Builder requestBuild = new Request.Builder()
.url(url).method(method, body);
if (headers != null) {
requestBuild.headers(headers);
}
try {
// 请求执行
Response response = httpClient.newCall(requestBuild.build()).execute();
// 结果转换
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、RestTemplate
public class TestRestTemplate {
private static final String BASE_URL = "http://localhost:8083" ;
public static void main(String[] args) {
RestTemplate restTemplate = buildRestTemplate() ;
// 1、发送Get请求
Map<String,String> paramMap = new HashMap<>() ;
Rep getRep = restTemplate.getForObject(BASE_URL+"/getApi/1",Rep.class,paramMap);
System.out.println("get："+getRep);
// 2、发送Post请求
IdKey idKey = new IdKey(1,"id-key") ;
Rep postRep = restTemplate.postForObject(BASE_URL+"/postApi",idKey,Rep.class);
System.out.println("post："+postRep);
// 3、发送Put请求
IdKey idKey2 = new IdKey(2,"key-id") ;
restTemplate.put(BASE_URL+"/putApi",idKey2,paramMap);
// 4、发送Delete请求
restTemplate.delete(BASE_URL+"/delApi/2",paramMap);
// 5、自定义Header请求
HttpHeaders headers = new HttpHeaders();
headers.add("Token","AdminSup");
HttpEntity<IdKey> requestEntity = new HttpEntity<>(idKey, headers);
ResponseEntity<Rep> respEntity = restTemplate.exchange(BASE_URL+"/postApi",
HttpMethod.POST, requestEntity, Rep.class);
System.out.println("post-header："+respEntity.getBody());
}
private static RestTemplate buildRestTemplate (){
// 1、参数配置
SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
factory.setReadTimeout(3000);
factory.setConnectTimeout(6000);
// 2、创建对象
return new RestTemplate(factory) ;
}
}
五、参考源码
编程文档：
https://gitee.com/cicadasmile/butte-java-note
应用仓库：
https://gitee.com/cicadasmile/butte-flyer-parent
