手寫tomcat——有線程池化能力的servlet 服務

點選檢視代碼

public class DiyTomcat {

    private int port = 8080;

    public static final HashMap<String, DiyServlet> SERVLET_MAPPING = new HashMap<>();

    public static final HashMap<String,String> URL_MAPPING = new HashMap<>();

    private static ThreadPoolExecutor threadPoolExecutor;

    static {
        loadServlet();
        initExecutors();
    }

    // 線程池化
    private static void initExecutors() {
        int corePoolSize = 10;
        int maximumPoolSize = 50;
        long keepAliveTime = 100L;
        TimeUnit unit = TimeUnit.SECONDS;
        BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(50);
        ThreadFactory threadFactory = Executors.defaultThreadFactory();
        RejectedExecutionHandler handler = new ThreadPoolExecutor.AbortPolicy();
        threadPoolExecutor = new ThreadPoolExecutor(
                corePoolSize,
                maximumPoolSize,
                keepAliveTime,
                unit,
                workQueue,
                threadFactory,
                handler
        );
    }

    private static void loadServlet() {
        try {
            //擷取web.xml目錄位址
            String path = DiyTomcat.class.getResource("/").getPath();
            SAXReader reader = new SAXReader();
            //讀取web.xml檔案
            Document document = reader.read(new File(path + "web.xml"));
            //擷取根标簽（servlet和servlet-mapping），放在一個List中
            Element rootElement = document.getRootElement();
            List<Element> elements = rootElement.elements();
            //循環将映射寫進map映射裡
            for(Element element : elements){
                if ("servlet".equalsIgnoreCase(element.getName())){
                    Element servletName = element.element("servlet-name");
                    Element servletClass = element.element("servlet-class");
                    //需要注意的是servletMapping映射的第二個參數，要通過反射的方式進行執行個體化
                    SERVLET_MAPPING.put(servletName.getText(),
                            (DiyServlet) Class.forName(servletClass.getText().trim()).newInstance());
                }else if ("servlet-mapping".equalsIgnoreCase(element.getName())){
                    Element servletName = element.element("servlet-name");
                    Element urlPattern = element.element("url-pattern");
                    URL_MAPPING.put(urlPattern.getText(), servletName.getText());
                }
            }
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        }
    }

    public void start() throws IOException {
        ServerSocket serverSocket = new ServerSocket(port);
        while (true) {
            Socket socket = serverSocket.accept();
            RequestHandler requestHandler = new RequestHandler(socket);
            // 一個 socket 一個線程
            // new Thread(requestHandler).start();
            // 使用線程組幹活
            threadPoolExecutor.execute(requestHandler);
        }
    }
}

      

1. 通過​

   ​initExecutors​

   ​方法建立出一個線程池

private static void initExecutors() {
// 核心線程數
int corePoolSize = 10;
// 最大線程數
int maximumPoolSize = 50;
// 空閑線程保活時間
long keepAliveTime = 100L;
// 保活機關，目前設定為秒
TimeUnit unit = TimeUnit.SECONDS;
// 線程池隊列
BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(50);
// 線程建立工廠
ThreadFactory threadFactory = Executors.defaultThreadFactory();
// 池子滿後的拒絕請求處理器
RejectedExecutionHandler handler = new ThreadPoolExecutor.AbortPolicy();
threadPoolExecutor = new ThreadPoolExecutor(
corePoolSize,
maximumPoolSize,
keepAliveTime,
unit,
workQueue,
threadFactory,
handler
        );
    }
      

1. ​

   ​accept​

   ​到socket後直接包裝成​

   ​RequestHandler​

   ​交由線程池處理

while (true) {
Socket socket = serverSocket.accept();
RequestHandler requestHandler = new RequestHandler(socket);
// 一個 socket 一個線程
// new Thread(requestHandler).start();
// 使用線程組幹活
threadPoolExecutor.execute(requestHandler);
        }