本文的目的是讲解如何使用Java编写一个简单的Tomcat,以及这个Tomcat的基本原理和用法。
在阅读本文之前,你需要掌握一些Java编程基础,如基本语法、OOP思想、多线程等知识。同时,你需要对Tomcat有一定的了解,如Tomcat的工作原理、Servlet容器等。
HttpServer类是整个Tomcat的入口,负责接受并处理请求。
我们需要在HttpServer类中创建一个ServerSocket实例,用于监听HTTP请求。当有一个请求到达时,我们需要使用Socket获取请求信息,然后将请求信息封装到HttpServletRequest对象中,创建HttpServletResponse对象,然后将HttpServletRequest对象和HttpServletResponse对象传递给Servlet。
以下是HttpServer类的一个简单示例:
public class HttpServer {
public static void main(String[] args) {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(8080);
System.out.println("Tomcat started on port 8080");
while (true) {
Socket socket = serverSocket.accept();
InputStream is = socket.getInputStream();
OutputStream os = socket.getOutputStream();
HttpServletRequest request = new HttpServletRequest(is);
HttpServletResponse response = new HttpServletResponse(os);
Servlet servlet = ServletContainer.getServlet(request.getRequestURI());
servlet.service(request, response);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
HttpServletRequest类用于封装HTTP请求信息。
我们需要在HttpServletRequest类中解析HTTP请求,获取请求方法、请求路径、请求头和请求体等信息,并将这些信息封装到HttpServletRequest对象中。以下是HttpServletRequest类的一个简单示例:
public class HttpServletRequest {
private String method;
private String requestURI;
private Map<String, String> headers = new HashMap<>();
private String body;
public HttpServletRequest(InputStream is) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
String line = reader.readLine();
while (line != null && !line.equals("")) {
if (line.startsWith("GET")) {
method = "GET";
requestURI = line.split(" ")[1];
} else if (line.startsWith("POST")) {
method = "POST";
requestURI = line.split(" ")[1];
} else if (line.startsWith("Content-Length")) {
int contentLength = Integer.parseInt(line.split(" ")[1]);
char[] chars = new char[contentLength];
reader.read(chars, 0, contentLength);
body = new String(chars);
} else {
String[] header = line.split(": ");
headers.put(header[0], header[1]);
}
line = reader.readLine();
}
}
public String getMethod() {
return method;
}
public String getRequestURI() {
return requestURI;
}
public String getHeader(String name) {
return headers.get(name);
}
public String getBody() {
return body;
}
}
HttpServletResponse类用于封装HTTP响应信息。
我们需要在HttpServletResponse类中构建HTTP响应,包括响应头、响应体等信息,并将这些信息写入到OutputStream中。以下是HttpServletResponse类的一个简单示例:
public class HttpServletResponse {
private OutputStream os;
private String contentType = "text/html";
private Map<String, String> headers = new HashMap<>();
private StringBuilder body = new StringBuilder();
public HttpServletResponse(OutputStream os) {
this.os = os;
}
public void setContentType(String contentType) {
this.contentType = contentType;
setHeader("Content-Type", contentType);
}
public void setHeader(String name, String value) {
headers.put(name, value);
}
public void setStatus(int status) throws IOException {
String statusText = "";
switch (status) {
case 200:
statusText = "OK";
break;
case 404:
statusText = "Not Found";
break;
}
String response = "HTTP/1.1 " + status + " " + statusText + "\r\n";
write(response);
}
public void write(String data) throws IOException {
body.append(data);
os.write(data.getBytes());
}
public void flushBuffer() throws IOException {
String response = "HTTP/1.1 200 OK\r\n";
response += "Content-Type: " + contentType + "\r\n";
response += "Content-Length: " + body.toString().getBytes().length + "\r\n";
for (String name : headers.keySet()) {
response += name + ": " + headers.get(name) + "\r\n";
}
response += "\r\n";
response += body.toString();
os.write(response.getBytes());
os.flush();
}
}
Servlet接口是Tomcat中的核心接口,用于处理HTTP请求并生成HTTP响应。
我们需要定义一个Servlet接口,为其定义service方法,其中HttpServletRequest对象和HttpServletResponse对象可以传递到service方法中,Servlet可以获取HttpServletRequest对象中的请求信息,根据请求信息生成HttpServletResponse对象中的响应信息。
以下是Servlet接口的一个简单示例:
public interface Servlet {
void service(HttpServletRequest request, HttpServletResponse response);
}
ServletContainer类用于创建Servlet实例,根据请求路径获取相应的Servlet实例。
以下是ServletContainer类的一个简单示例:
public class ServletContainer {
private static Map<String, Servlet> servletMapping = new HashMap<>();
static {
servletMapping.put("/hello", new HelloServlet());
}
public static Servlet getServlet(String uri) {
return servletMapping.get(uri);
}
}
Servlet实现类是具体的处理HTTP请求的类,可以根据请求信息生成HTTP响应信息。
以下是HelloServlet的一个简单示例:
public class HelloServlet implements Servlet {
@Override
public void service(HttpServletRequest request, HttpServletResponse response) {
try {
response.setContentType("text/html");
response.setStatus(200);
response.write("<html><body><h1>Hello World</h1></body></html>");
response.flushBuffer();
} catch (IOException e) {
e.printStackTrace();
}
}
}
在命令行中运行HttpServer类,得到以下输出:
Tomcat started on port 8080
在浏览器中访问http://localhost:8080/hello,得到以下输出:
Hello World
在命令行中运行HttpServer类,得到以下输出:
Tomcat started on port 8080
使用telnet工具模拟一个HTTP请求:
$ telnet localhost 8080
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
GET /hello HTTP/1.1
Host: localhost:8080
在命令行中得到以下输出:
HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 31
<html><body><h1>Hello World</h1></body></html>
本文链接:http://task.lmcjl.com/news/7934.html