package com.hy.servlet;

import java.io.IOException;

import java.io.InputStream;

import java.util.Map;

import java.util.concurrent.ConcurrentHashMap;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

@WebServlet("*.do")

public class DispatcherServlet extends HttpServlet {

    private Map<String, Object> map = new ConcurrentHashMap<>();

    public DispatcherServlet() {

        try {

            InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("applicationContext.xml");

            // 1,通过工厂模式，创建documentBuilderFactory工厂对象

            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();

            // 2,创建DocumentBuilder对象

            DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();

            // 3,得到Document对象( 注意导入org.w3c.dom包中的)

            Document document = documentBuilder.parse(inputStream);

            // 4,获得所有的bean标签

            NodeList nodeList = document.getElementsByTagName("bean");

            for (int i = 0; i < nodeList.getLength(); i++) {

                Node node = nodeList.item(i);

                if (node.getNodeType() == Node.ELEMENT_NODE) {

                    //(注意导入org.w3c.dom包中的)

                    //强转成Element类的对象，里面有比Node类更方便的方法

                    Element element = (Element) node;

                    String id = element.getAttribute("id");

                    String className = element.getAttribute("class");

                    boolean flag = map.containsKey(id);

                    if (flag == true)

                        return;

                    Object xxxController = Class.forName(className).newInstance();

                    map.put(id, xxxController);

                }

            }

        } catch (ParserConfigurationException | SAXException | IOException | ClassNotFoundException | InstantiationException | IllegalAccessException e) {

            e.printStackTrace();

        }

    }

    @Override

    protected void service(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // 设置编码

        request.setCharacterEncoding("UTF-8");

        response.setCharacterEncoding("UTF-8");

        response.setContentType("text/html;charset=UTF-8");

        // 假设url是： http://localhost:8080/mymvc2/hello.do

        // ServletPath是Servlet的访问路径： /hello.do

        // 思路是：

        // 第1步： /hello.do -> hello 或者 /book.do -> book

        // 第2步： hello -> HelloController 或者 book -> BookController

        String servletPath = request.getServletPath(); // /hello.do

        int lastDotIndex = servletPath.lastIndexOf(".do");

        servletPath = servletPath.substring(1, lastDotIndex); // hello

    }

}