简易版Tomcat

朱雀 2022-05-09 00:34 182阅读 0赞

## 一、绪论 ##

tomcat实现了基于http协议的双向通信。为简单模拟该功能，我们需要自定义Request,Response,Servlet,并通过Socket为浏览器和服务器建立通信通道。

故，此次简易版Tomcat项目结构因如下所示

![70][]

## 二、创建核心对象 ##

### 2.1 MyRequest ###

简易request需要获取请求体中的访问路径、请求方法、参数内容

/**
     * @author sunyiran
     * @date 2018-09-28
     */
    public class MyRequest {
    
        /**请求相对路径*/
        private String url;
        /**协议请求方式*/
        private String method;
        /**请求参数（简易版不处理）*/
        private HashMap<String,Object> params = new HashMap<>();
    
    
        public MyRequest(InputStream inputStream) throws IOException {
            //available（）效率高但是不可靠
            byte[] b = new byte[inputStream.available()];
            inputStream.read(b);
            String head = new String(b);
    
            /*
             * http请求体内容格式
             * GET /favicon.ico HTTP/1.1
             * Host: localhost:8080
             * Connection: keep-alive
             * .......
             * */
            String[] info = head.split("\\n")[0].split("\\s");
            method = info[0];
            if (info.length > 1) {
                url = info[1];
            }
        }
    
        public String getUrl() {
            return url;
        }
    
        public String getMethod() {
            return method;
        }
    
        public HashMap<String, Object> getParams() {
            return params;
        }
    }

### 2.2 MyResponse ###

/**
     * @author sunyiran
     * @date 2018-09-28
     */
    public class MyResponse {
    
        private OutputStream outputStream;
    
        public MyResponse(OutputStream outputStream) {
            this.outputStream = outputStream;
        }
    
        public void write(String content) {
            StringBuilder sb = new StringBuilder();
            //模拟http响应体
            sb.append("HTTP/1.1 200 OK \n")
                    .append("Content-Type: text/html\n")
                    .append("\r\n").append("<html><body>")
                    .append(content).append("</body></html>");
            try {
                outputStream.write(sb.toString().getBytes());
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

### 2.3 MyServlet ###

/**
     * @author sunyiran
     * @date 2018-09-28
     */
    public abstract class MyServlet {
    
        public abstract void doPost(MyRequest request, MyResponse response);
    
        public abstract void doGet(MyRequest request, MyResponse response);
    
        /**
         * 处理请求
         *
         * @param request
         * @param response
         */
        public void service(MyRequest request, MyResponse response) {
            if (request.getMethod().equals("GET")) {
                doPost(request, response);
            } else {
                doGet(request, response);
            }
        }
    }

### 2.4 MyCat ###

/**
     * @author sunyiran
     * @date 2018-09-28
     */
    public class MyCat {
    
        /**
         * 默认端口
         */
        private int port = 8080;
    
        /**
         * servlet映射
         */
        private static Map<String, String> mappers = new HashMap<>();
    
        public void start() throws Exception {
    
            initMapping();
            ServerSocket serverSocket = new ServerSocket(port);
            System.out.println("MyCat is starting ......");
    
            while (true) {
                //监听port端口
                Socket socket = serverSocket.accept();
                InputStream inputStream = socket.getInputStream();
                OutputStream outputStream = socket.getOutputStream();
                //请求分发
                dispatch(new MyRequest(inputStream), new MyResponse(outputStream));
            }
        }
    
        public void initMapping() {
            //测试映射
            mappers.put("/hello", "com.syr.HelloServlet");
    
        }
    
        /**
         * 根据请求寻找具体处理servlet
         *
         * @param request
         * @param response
         * @throws Exception
         */
        public void dispatch(MyRequest request, MyResponse response) throws Exception {
            String url = request.getUrl();
            if (url == null) {
                response.write("can not find the path");
                return;
            }
            if (url.equalsIgnoreCase("/favicon.ico")) {
                //可以自定义略缩图
                return;
            }
            if (!mappers.containsKey(url)) {
                response.write("can not find the path");
                return;
            }
    
            //反射获取处理对象
            Class<?> aClass = Class.forName(mappers.get(url));
            aClass.getMethod("service", MyRequest.class, MyResponse.class).invoke(aClass.newInstance(), request, response);
    
        }
    
        public static void main(String[] args) throws Exception {
            new MyCat().start();
        }
    }

### 2.5 HelloServlet(测试用) ###

/**
     * @author sunyiran
     * @date 2018-09-28
     */
    public class HelloServlet extends MyServlet {
    
        @Override
        public void doPost(MyRequest request, MyResponse response) {
            doGet(request, response);
        }
    
        @Override
        public void doGet(MyRequest request, MyResponse response) {
            response.write("welcome to myCat");
        }
    }

## 三、测试 ##

![70 1][]

![70 2][]

[70]: /images/20220509/7bba5d6986484a17a0f5d237a1b22d5e.png
[70 1]: /images/20220509/c6f6989b8af74f4bb1005220c4ecd1ec.png
[70 2]: /images/20220509/e421f7bd748c42599d80ba68bcd6a72b.png