本文是为了学习Tomcat源码之前，先理解web服务器的思想而写的
Tomcat作为web服务器，其实就是和客户端建立socket连接，然后解析http数据报，然后转发给servlet类
http请求类
负责解析http数据报，获得uri和method，封装成一个对象
public class HTTPRequest {
private String uri;
private String method;
public HTTPRequest(InputStream inputStream) throws IOException {
byte[] bytes = new byte[1024];
String httpRequest = "";
int length = -1;
if ((length = inputStream.read(bytes)) > 0) {
httpRequest = new String(bytes, 0, length);
}
// http报文格式：
// GET /favicon.ico HTTP/1.1
// Exception in thread "Thread-5" java.lang.NullPointerException
// Host: localhost:8888
// Connection: keep-alive
// Pragma: no-cache
// Cache-Control: no-cache
// at com.example.fall.WebServer.WebServer.dispatcher(WebServer.java:76)
// User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36
// Accept: image/webp,image/apng,image/*,*/*;q=0.8
// Referer: http://localhost:8888/hello
// at com.example.fall.WebServer.WebServer.service(WebServer.java:63)
// Accept-Encoding: gzip, deflate, br
// Accept-Language: zh-CN,zh;q=0.9
// Cookie: 省略
// 获得http请求头
String httpHeader = httpRequest.split("\n")[0];
// 获取请求头的里方法和uri
method = httpHeader.split("\\s")[0];
uri = httpHeader.split("\\s")[1];
}
public String getUri() {
return uri;
}
public void setUri(String uri) {
this.uri = uri;
}
public String getMethod() {
return method;
}
public void setMethod(String method) {
this.method = method;
}
}
http响应类
负责将数据返回给前端
public class HTTPResponse {
private OutputStream outputStream;
public HTTPResponse(OutputStream outputStream) {
this.outputStream = outputStream;
}
public void write(String message) throws IOException {
// 必须加在响应头中
outputStream.write("HTTP/1.1 200 OK\n".getBytes());
outputStream.write("Content-Type: text/html; charset=UTF-8\n\n".getBytes());
outputStream.write(message.getBytes());
}
}
抽象servlet类
封装了处理的过程
public abstract class Servlet {
public abstract void doGet(HTTPRequest httpRequest, HTTPResponse httpResponse) throws IOException;
public abstract void doPost(HTTPRequest httpRequest, HTTPResponse httpResponse) throws IOException;
public void service(HTTPRequest httpRequest, HTTPResponse httpResponse) throws IOException {
if ("GET".equals(httpRequest.getMethod())) {
doGet(httpRequest, httpResponse);
} else if ("POST".equals(httpRequest.getMethod())) {
doPost(httpRequest, httpResponse);
}
}
}
一个简单的hello响应类
public class HelloServlet extends Servlet {
@Override
public void doGet(HTTPRequest httpRequest, HTTPResponse httpResponse) throws IOException {
httpResponse.write("hello Get");
}
@Override
public void doPost(HTTPRequest httpRequest, HTTPResponse httpResponse) throws IOException {
httpResponse.write("hello Post");
}
}
Mapping对象
保存了映射关系
public class ServletMapping {
private String servletName;
private String uri;
private String clazz;
public ServletMapping(String servletName, String uri, String clazz) {
this.servletName = servletName;
this.uri = uri;
this.clazz = clazz;
}
public String getServletName() {
return servletName;
}
public void setServletName(String servletName) {
this.servletName = servletName;
}
public String getUri() {
return uri;
}
public void setUri(String uri) {
this.uri = uri;
}
public String getClazz() {
return clazz;
}
public void setClazz(String clazz) {
this.clazz = clazz;
}
}
Mapping配置类
Servlet中的web.xml就是保存了映射关系，这边模拟了xml加载的过程
public class ServletMappingConfig {
public static List<ServletMapping> list = new ArrayList<>();
static {
list.add(new ServletMapping("hello","/hello","com.example.fall.WebServer.HelloServlet"));
}
}
Server主类
public class WebServer {
private static Logger logger = LoggerFactory.getLogger(WebServer.class);
private int port;
private ServerSocket serverSocket;
private HashMap<String, ServletMapping> hashMap;
public WebServer(int port) throws IOException {
this.port = port;
init();
}
private void init() throws IOException {
serverSocket = new ServerSocket(port);
hashMap = new HashMap<>();
for (ServletMapping i : ServletMappingConfig.list) {
hashMap.put(i.getUri(), i);
}
logger.info("服务器启动");
}
private void start() throws IOException {
while (true) {
Socket socket = serverSocket.accept();
logger.info("接收到客户端连接, " + socket.getInetAddress() + ":" + socket.getPort());
new Thread(new Runnable() {
@Override
public void run() {
service(socket);
}
}).start();
}
}
private void service(Socket socket) {
InputStream in = null;
OutputStream out = null;
try {
in = socket.getInputStream();
out = socket.getOutputStream();
HTTPRequest httpRequest = new HTTPRequest(in);
HTTPResponse httpResponse = new HTTPResponse(out);
dispatcher(httpRequest, httpResponse);
} catch (IOException | ClassNotFoundException | IllegalAccessException | InstantiationException e) {
e.printStackTrace();
} finally {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void dispatcher(HTTPRequest httpRequest, HTTPResponse httpResponse) throws IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {
String clazz = hashMap.get(httpRequest.getUri()).getClazz();
Class<Servlet> servletClass = (Class<Servlet>) Class.forName(clazz);
Servlet servlet = servletClass.newInstance();
servlet.service(httpRequest, httpResponse);
}
public static void main(String[] args) throws IOException {
new WebServer(8888).start();
}
}
访问http://localhost:8888/hello
页面上会显示hello Get
这样我们已经初步完成了一个简单的web服务器，在这里我们为每一个socket都分配了一个子线程完成任务，一旦连接很多就会发生严重阻塞，所以我们接下来需要逐步为这个简单的web服务器增加NIO，注解Mapping，参数解析等功能，使其具有一个简单web服务器应有的功能
