业务功能

浏览器发送请求给服务器,服务器根据请求的分给不同的Servlet的doGet或doPost的方法,并把响应结果返回给页面。

实体类

请求类:SelfHttpRequest
响应类:SelfHttpResponse
抽象共用的Servlet:SelfHttpServlet
远程服务器:SelfTomcat

代码实现

SelfHttpRequest

public class SelfHttpRequest {
    private String requestUrl;
    private String requestMethod;
    public SelfHttpRequest(InputStream inputStream) {
        byte[] buffer = new byte[1024];
        try {
            int length = 0;
            String context = null;
            if((length = inputStream.read(buffer)) > 0){
                context = new String(buffer, 0, length);
            }

            String firstRow = context.split("\n")[0];
            String[] firstColumn = firstRow.split(" ");
            requestMethod = firstColumn[0];
            requestUrl = firstColumn[1];
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public String getRequestUrl() {
        return requestUrl;
    }
    public String getRequestMethod() {
        return requestMethod;
    }
}

SelfHttpResponse

public class SelfHttpResponse {
    private OutputStream outputStream;

    public SelfHttpResponse(OutputStream outputStream) {
        this.outputStream = outputStream;
    }

    /**
     * post方法
     */
    public void write(String content) throws IOException {
        //用的是HTTP协议，输出也要遵循HTTP协议
        StringBuilder sb = new StringBuilder();
        sb.append("HTTP/1.1 200 OK\n")
                .append("Content-Type: text/html;\n")
                .append("\r\n")
                .append(content);
        outputStream.write(sb.toString().getBytes());
    }
}

SelfHttpServlet

public abstract class SelfHttpServlet {
    /**
     * doService
     */
    public void doService(SelfHttpRequest request, SelfHttpResponse response) throws IOException {
        if("get".equals(request.getRequestMethod().toLowerCase())){
            doGet(request, response);
        }else{
            doPost(request, response);
        }
    }
    /**
     * get方法
     */
    public abstract void doGet(SelfHttpRequest request, SelfHttpResponse response) throws IOException;
    /**
     * post方法
     */
    public abstract void doPost(SelfHttpRequest request, SelfHttpResponse response) throws IOException;
}

SelfTomcat

public class SelfTomcat {
    private Integer port;
    private Map<String, Object> urlInstanceMap = new HashMap<>();

    public SelfTomcat(Integer port) {
        this.port = port;

        init();
    }

    /**
     * 初始化
     */
    private void init(){
        //加载配置文件
        Properties properties = new Properties();
        String configUrl = this.getClass().getClassLoader().getResource("web.properties").getFile();
        try {
            properties.load(new FileInputStream(configUrl));
        } catch (IOException e) {
            e.printStackTrace();
        }

        //初始化对象
        try {
            Set<String> requestUrlKeys = properties.stringPropertyNames().stream().filter(item -> item.endsWith(".url"))
                    .collect(Collectors.toSet());
            for (String requestUrlKey : requestUrlKeys) {
                String requestUrl = properties.getProperty(requestUrlKey);
                String classNameKey = requestUrlKey.substring(0, requestUrlKey.lastIndexOf(".url")) + ".className";
                String className = properties.getProperty(classNameKey);
                Object instance = Class.forName(className).newInstance();
                urlInstanceMap.put(requestUrl, instance);
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    /**
     * 启动
     */
    public void start(){
        try {
            ServerSocket serverSocket = new ServerSocket(port);
            while(true){
                Socket socket = serverSocket.accept();
                handleRequest(socket);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /**
     * 处理请求
     */
    private void handleRequest(Socket socket) throws Exception {
        SelfHttpRequest request = new SelfHttpRequest(socket.getInputStream());
        SelfHttpResponse response = new SelfHttpResponse(socket.getOutputStream());
        if(request.getRequestUrl() == null){
            return;
        }
        Object instance = urlInstanceMap.get(request.getRequestUrl());
        if(null == instance){
            throw new RuntimeException("404 NOT FOUND");
        }
        Method method = instance.getClass().getMethod("doService",
                new Class[]{SelfHttpRequest.class, SelfHttpResponse.class});
        method.invoke(instance, request, response);
    }
    public static void main(String[] args) {
        SelfTomcat selfTomcat = new SelfTomcat(8000);
        selfTomcat.start();
    }
}

FirstServlet

public class FirstServlet extends SelfHttpServlet {

    @Override
    public void doGet(SelfHttpRequest request, SelfHttpResponse response) throws IOException {
        response.write("调用FirstServlet的get方法");
    }

    @Override
    public void doPost(SelfHttpRequest request, SelfHttpResponse response) throws IOException {
        response.write("调用FirstServlet的post方法");
    }
}

SecondServlet

public class SecondServlet extends SelfHttpServlet {
    @Override
    public void doGet(SelfHttpRequest request, SelfHttpResponse response) throws IOException{
        response.write("调用SecondServlet的get方法");
    }

    @Override
    public void doPost(SelfHttpRequest request, SelfHttpResponse response) throws IOException {
        response.write("调用SecondServlet的get方法");
    }
}

配置

servlet.one.url=/firstServlet.do
servlet.one.className=com.tomcat.servlet.FirstServlet
servlet.two.url=/secondServlet.do
servlet.two.className=com.tomcat.servlet.SecondServlet