手写一个Tomcat

ゞ浴缸里的玫瑰 2022-12-04 09:18 245阅读 0赞

作为一个java学习的起步者，对tomcat的认识还是有很多的欠缺，在无意中发现了这篇文章，便在自己的环境下尝试搭建，收获良多：  
分以下几个步骤：  
（1）提供Socket服务  
（2）进行请求的转发  
（3）把请求和响应封装成request/response  
**代码实现如下：**  
1、工程截图：  
![在这里插入图片描述][20181109175657519.png]  
2、封装请求对象：通过输入流，对HTTP协议进行解析，拿到了HTTP请求头的方法和URL：

/**
     * @author wangjie
     * @version 2018/11/9
     * 封装请求对象
     * 通过输入流，对http协议进行解析，拿到http请求头的方法和url
     */
    public class MyRequest {
        private String url;
        private String method;
    
        public MyRequest(InputStream inputStream) throws IOException{
            String httpRequest ="";
            byte[] httpRequestBytes =new byte[1024];
            int length =0;
            if((length=inputStream.read(httpRequestBytes)) >0){
                httpRequest=new String(httpRequestBytes,0,length);
            }
    
            String httpHead = httpRequest.split("\n")[0];
            url=httpHead.split("\\s")[1];
            method=httpHead.split("\\s")[0];
            System.out.println(this);
        }
        public String getUrl() {
            return url;
        }
        public void setUrl(String url) {
            this.url = url;
        }
        public String getMethod() {
            return method;
        }
        public void setMethod(String method) {
            this.method = method;
        }
    }

3、封装响应对象：基于HTTP协议的格式进行输出写入。

/**
     * @author wangjie
     * @version 2018/11/9
     * 封装响应对象
     * 基于HTTP协议的格式进行输出写入。
     */
    public class MyResponse {
        private OutputStream outputStream;
    
        public MyResponse(OutputStream outputStream){
            this.outputStream = outputStream;
        }
    
        public void write(String content)throws IOException {
            StringBuffer httpResponse = new StringBuffer();
            httpResponse.append("HTTP/1.1 200 OK\n")
                    .append("Content-Type: text/html\n")
                    .append("\r\n")
                    .append("<html><body>")
                    .append(content)
                    .append("</body></html>");
            outputStream.write(httpResponse.toString().getBytes());
            outputStream.close();
        }
    }

4、servlet请求处理基类：Tomcat是满足Servlet规范的容器，所以Tomcat需要提供API：doGet/doPost/service。

/**
     * @author wangjie
     * @version 2018/11/9
     * Servlet请求处理基类
     */
    public abstract class MyServlet {
        public abstract void doGet(MyRequest myRequest,MyResponse myResponse);
        public abstract void doPost(MyRequest myRequest,MyResponse myResponse);
        public void service(MyRequest myRequest,MyResponse myResponse){
            if(myRequest.getMethod().equalsIgnoreCase("POST")){
                doPost(myRequest,myResponse);
            }else if(myRequest.getMethod().equalsIgnoreCase("GET")){
                doGet(myRequest,myResponse);
            }
        }
    }

5、Servlet实现类：提供2个实现类，用于测试。

/**
     * @author wangjie
     * @version 2018/11/9
     * servlet实现类
     */
    public class FindGirlServlet extends MyServlet{
        @Override
        public void doGet(MyRequest myRequest,MyResponse myResponse){
            try{
                myResponse.write("get gril....");
            }catch (IOException e){
                e.printStackTrace();
            }
        }
        @Override
        public void doPost(MyRequest myRequest,MyResponse myResponse){
            try{
                myResponse.write("post girl...");
            } catch (IOException e){
                e.printStackTrace();
            }
        }
    }

/**
     * @author wangjie
     * @version 2018/11/9
     */
    public class HelloWorldServlet extends MyServlet {
        @Override
        public void doGet(MyRequest myRequest,MyResponse myResponse){
            try{
                myResponse.write("get world...");
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    
        @Override
        public void doPost(MyRequest myRequest,MyResponse myResponse){
            try{
                myResponse.write("post world...");
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }

6、Servlet配置：对比之前在web开发中，会在web.xml中通过和指定哪个URL交给哪个servlet来处理。

/**
     * @author wangjie
     * @version 2018/11/9
     * servlet配置
     */
    public class ServletMapping {
        private String servletName;
        private String url;
        private String clazz;
    
        public ServletMapping(String servletName, String url, String clazz){
            this.servletName=servletName;
            this.url=url;
            this.clazz=clazz;
        }
    
        public String getServletName() {
            return servletName;
        }
        public void setServletName(String servletName) {
            this.servletName = servletName;
        }
        public String getUrl() {
            return url;
        }
        public void setUrl(String url) {
            this.url = url;
        }
        public String getClazz() {
            return clazz;
        }
        public void setClazz(String clazz) {
            this.clazz = clazz;
        }
    }

/**
     * @author wangjie
     * @version 2018/11/9
     */
    public class ServletMappingConfig {
        public static List<ServletMapping> servletMappingList =new ArrayList<>();
        //制定哪个URL交给哪个servlet来处理
        static{
            servletMappingList.add(new ServletMapping("findGirl","/girl","wj.mytomcat.FindGirlServlet"));
            servletMappingList.add(new ServletMapping("helloWorld","/world","wj.mytomcat.HelloWorldServlet"));
        }
    }

7、启动类：  
tomcat的处理流程：把URL对应处理的Servlet关系形成，解析HTTP协议，封装请求/响应对象，利用反射实例化具体的Servlet进行处理。

/**
     * @author wangjie
     * @version 2018/11/9
     * tomcat启动类
     */
    public class MyTomcat {
        private int port=8088;
        private Map<String,String> urlServletMap =new HashMap<String,String>();
        public MyTomcat(int port){
            this.port=port;
        }
    
        public void start(){
    //        初始化URL与对应处理的servlet的关系
            initServletMapping();
    
            ServerSocket serverSocket=null;
            try{
                serverSocket = new ServerSocket(port);
                System.out.println("MyTomcat is start...");
    
                while(true){
                    Socket socket= serverSocket.accept();
                    InputStream inputStream=socket.getInputStream();
                    OutputStream outputStream=socket.getOutputStream();
    
                    MyRequest myRequest= new MyRequest(inputStream);
                    MyResponse myResponse =new MyResponse(outputStream);
    
    //                请求分发
                    dispatch(myRequest,myResponse);
                    socket.close();
                }
            }catch (IOException e){
                e.printStackTrace();
            }finally {
                if (null != serverSocket){
                    try{
                        serverSocket.close();
                    }catch (IOException e){
                        e.printStackTrace();
                    }
                }
            }
        }
    
        private void initServletMapping(){
            for(ServletMapping servletMapping:ServletMappingConfig.servletMappingList){
                urlServletMap.put(servletMapping.getUrl(),servletMapping.getClazz());
            }
        }
    
        public void dispatch(MyRequest myRequest,MyResponse myResponse){
            String clazz =urlServletMap.get(myRequest.getUrl());
    
            //反射
            try{
                Class<MyServlet> myServletClass =(Class<MyServlet>) Class.forName(clazz);
                MyServlet myServlet= myServletClass.newInstance();
    
                myServlet.service(myRequest,myResponse);
            }catch (ClassNotFoundException e){
                e.printStackTrace();
            }catch (InstantiationException e){
                e.printStackTrace();
            }catch (IllegalAccessException e){
                e.printStackTrace();
            }
        }
        public static void main(String[] args){
            new MyTomcat(8088).start();
        }
    }

8、测试：  
运行项目后，在浏览器输入:localhost:8088/girl  
![在这里插入图片描述][2018110918114491.png]  
在浏览器输入：localhost:8088/world  
![在这里插入图片描述][20181109181351989.png]  
实践完成。

[20181109175657519.png]: /images/20221123/230684a66ea344dcabad922a21ccbf14.png
[2018110918114491.png]: /images/20221123/fc3825fc690f44e194c46e37700fae6e.png
[20181109181351989.png]: /images/20221123/2a84e17f6d344b3ca780bc7f126823f8.png