package cn.how2j.javaweb;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
 
public class ContextListener implements ServletContextListener {
 
    @Override
    public void contextDestroyed(ServletContextEvent e) {
        System.out.println("监听到web 应用 "+ e.getSource() +" 的销毁事件  ");
    }
 
    @Override
    public void contextInitialized(ServletContextEvent e) {
        System.out.println("监听到web 应用 "+ e.getSource() +" 的初始化事件  ");
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
    <servlet>
        <servlet-name>HelloServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.HelloServlet</servlet-class>
        <init-param>
            <param-name>author</param-name>
            <param-value>how2j(servlet)</param-value>
        </init-param>
        <init-param>
            <param-name>site</param-name>
            <param-value>http://how2j.cn(servlet)</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>HelloServlet</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>ParamServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.ParamServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>ParamServlet</servlet-name>
        <url-pattern>/param</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>HeaderServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.HeaderServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>HeaderServlet</servlet-name>
        <url-pattern>/header</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>SetCookieServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.SetCookieServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>SetCookieServlet</servlet-name>
        <url-pattern>/setCookie</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>GetCookieServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.GetCookieServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>GetCookieServlet</servlet-name>
        <url-pattern>/getCookie</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>SetSessionServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.SetSessionServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>SetSessionServlet</servlet-name>
        <url-pattern>/setSession</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>GetSessionServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.GetSessionServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>GetSessionServlet</servlet-name>
        <url-pattern>/getSession</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>ClientJumpServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.ClientJumpServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ClientJumpServlet</servlet-name>
        <url-pattern>/jump1</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>ServerJumpServlet</servlet-name>
        <servlet-class>cn.how2j.javaweb.ServerJumpServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ServerJumpServlet</servlet-name>
        <url-pattern>/jump2</url-pattern>
    </servlet-mapping>

    <filter>
        <filter-name>URLFilter</filter-name>
        <filter-class>cn.how2j.javaweb.URLFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>URLFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter>
        <filter-name>PfmFilter</filter-name>
        <filter-class>cn.how2j.javaweb.PfmFilter</filter-class>
        <init-param>
            <param-name>author</param-name>
            <param-value>how2j(filter)</param-value>
        </init-param>
        <init-param>
            <param-name>site</param-name>
            <param-value>http://how2j.cn(filter)</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>PfmFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <listener>
        <listener-class>cn.how2j.javaweb.ContextListener</listener-class>
    </listener>

</web-app>

package cn.how2j.diytomcat.catalina;

import cn.how2j.diytomcat.classloader.WebappClassLoader;
import cn.how2j.diytomcat.exception.WebConfigDuplicatedException;
import cn.how2j.diytomcat.http.ApplicationContext;
import cn.how2j.diytomcat.http.StandardServletConfig;
import cn.how2j.diytomcat.util.ContextXMLUtil;
import cn.how2j.diytomcat.watcher.ContextFileChangeWatcher;
import cn.hutool.core.date.DateUtil;
import cn.hutool.core.date.TimeInterval;
import cn.hutool.core.io.FileUtil;
import cn.hutool.core.io.IORuntimeException;
import cn.hutool.core.util.ReflectUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.log.LogFactory;
import org.apache.jasper.compiler.JspRuntimeContext;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import java.io.File;
import java.util.*;
import org.apache.jasper.JspC;

public class Context {
    private String path;
    private String docBase;
    private File contextWebXmlFile;

    private Map<String, String> url_servletClassName;
    private Map<String, String> url_ServletName;
    private Map<String, String> servletName_className;
    private Map<String, String> className_servletName;
    private Map<String, Map<String, String>> servlet_className_init_params;

    private Map<String, List<String>> url_filterClassName;
    private Map<String, List<String>> url_FilterNames;
    private Map<String, String> filterName_className;
    private Map<String, String> className_filterName;
    private Map<String, Map<String, String>> filter_className_init_params;

    private List<String> loadOnStartupServletClassNames;

    private WebappClassLoader webappClassLoader;

    private Host host;
    private boolean reloadable;
    private ContextFileChangeWatcher contextFileChangeWatcher;

    private ServletContext servletContext;
    private Map<Class<?>, HttpServlet> servletPool;
    private Map<String, Filter> filterPool;

    private List<ServletContextListener> listeners;

    public Context(String path, String docBase, Host host, boolean reloadable) {
        TimeInterval timeInterval = DateUtil.timer();
        this.host = host;
        this.reloadable = reloadable;

        this.path = path;
        this.docBase = docBase;
        this.contextWebXmlFile = new File(docBase, ContextXMLUtil.getWatchedResource());

        this.url_servletClassName = new HashMap<>();
        this.url_ServletName = new HashMap<>();
        this.servletName_className = new HashMap<>();
        this.className_servletName = new HashMap<>();
        this.servlet_className_init_params = new HashMap<>();

        this.url_filterClassName = new HashMap<>();
        this.url_FilterNames = new HashMap<>();
        this.filterName_className = new HashMap<>();
        this.className_filterName = new HashMap<>();
        this.filter_className_init_params = new HashMap<>();

        this.loadOnStartupServletClassNames = new ArrayList<>();

        this.servletContext = new ApplicationContext(this);

        ClassLoader commonClassLoader = Thread.currentThread().getContextClassLoader();
        this.webappClassLoader = new WebappClassLoader(docBase, commonClassLoader);

        this.servletPool = new HashMap<>();
        this.filterPool = new HashMap<>();

        listeners=new ArrayList<ServletContextListener>();

        LogFactory.get().info("Deploying web application directory {}", this.docBase);
        deploy();
        LogFactory.get().info("Deployment of web application directory {} has finished in {} ms", this.docBase,timeInterval.intervalMs());
    }

    public void reload() {
        host.reload(this);
    }

    private void deploy() {
        loadListeners();

        init();

        if(reloadable){
            contextFileChangeWatcher = new ContextFileChangeWatcher(this);
            contextFileChangeWatcher.start();
        }

        JspC c = new JspC();
        new JspRuntimeContext(servletContext, c);
    }

    private void init() {
        if (!contextWebXmlFile.exists())
            return;

        try {
            checkDuplicated();
        } catch (WebConfigDuplicatedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return;
        }

        String xml = FileUtil.readUtf8String(contextWebXmlFile);
        Document d = Jsoup.parse(xml);
        parseServletMapping(d);
        parseFilterMapping(d);

        parseServletInitParams(d);
        parseFilterInitParams(d);

        initFilter();

        parseLoadOnStartup(d);
        handleLoadOnStartup();

        fireEvent("init");
    }

    private void parseServletMapping(Document d) {
        // url_ServletName
        Elements mappingurlElements = d.select("servlet-mapping url-pattern");
        for (Element mappingurlElement : mappingurlElements) {
            String urlPattern = mappingurlElement.text();
            String servletName = mappingurlElement.parent().select("servlet-name").first().text();
            url_ServletName.put(urlPattern, servletName);
        }
        // servletName_className / className_servletName
        Elements servletNameElements = d.select("servlet servlet-name");
        for (Element servletNameElement : servletNameElements) {
            String servletName = servletNameElement.text();
            String servletClass = servletNameElement.parent().select("servlet-class").first().text();
            servletName_className.put(servletName, servletClass);
            className_servletName.put(servletClass, servletName);
        }
        // url_servletClassName
        Set<String> urls = url_ServletName.keySet();
        for (String url : urls) {
            String servletName = url_ServletName.get(url);
            String servletClassName = servletName_className.get(servletName);
            url_servletClassName.put(url, servletClassName);
        }
    }

    private void checkDuplicated(Document d, String mapping, String desc) throws WebConfigDuplicatedException {
        Elements elements = d.select(mapping);
        // 判断逻辑是放入一个集合，然后把集合排序之后看两临两个元素是否相同
        List<String> contents = new ArrayList<>();
        for (Element e : elements) {
            contents.add(e.text());
        }

        Collections.sort(contents);

        for (int i = 0; i < contents.size() - 1; i++) {
            String contentPre = contents.get(i);
            String contentNext = contents.get(i + 1);
            if (contentPre.equals(contentNext)) {
                throw new WebConfigDuplicatedException(StrUtil.format(desc, contentPre));
            }
        }

    }

    private void checkDuplicated() throws WebConfigDuplicatedException {
        String xml = FileUtil.readUtf8String(contextWebXmlFile);
        Document d = Jsoup.parse(xml);

        checkDuplicated(d, "servlet-mapping url-pattern", "servlet url 重复,请保持其唯一性:{} ");
        checkDuplicated(d, "servlet servlet-name", "servlet 名称重复,请保持其唯一性:{} ");
        checkDuplicated(d, "servlet servlet-class", "servlet 类名重复,请保持其唯一性:{} ");
    }

    public String getServletClassName(String uri) {
        return url_servletClassName.get(uri);
    }

    public String getPath() {
        return path;
    }

    public void setPath(String path) {
        this.path = path;
    }

    public String getDocBase() {
        return docBase;
    }

    public void setDocBase(String docBase) {
        this.docBase = docBase;
    }

    public WebappClassLoader getWebappClassLoader() {
        return webappClassLoader;
    }

    public void stop() {
        webappClassLoader.stop();
        contextFileChangeWatcher.stop();

        destroyServlets();

        fireEvent("destroy");
    }

    public boolean isReloadable() {
        return reloadable;
    }

    public void setReloadable(boolean reloadable) {
        this.reloadable = reloadable;
    }

    public ServletContext getServletContext() {
        return servletContext;
    }

    public synchronized HttpServlet  getServlet(Class<?> clazz)
            throws InstantiationException, IllegalAccessException, ServletException {
        HttpServlet servlet = servletPool.get(clazz);

        if (null == servlet) {
            servlet = (HttpServlet) clazz.newInstance();
            ServletContext servletContext = this.getServletContext();

            String className = clazz.getName();
            String servletName = className_servletName.get(className);

            Map<String, String> initParameters = servlet_className_init_params.get(className);
            ServletConfig servletConfig = new StandardServletConfig(servletContext, servletName, initParameters);

            servlet.init(servletConfig);
            servletPool.put(clazz, servlet);
        }

        return servlet;
    }

    private void parseServletInitParams(Document d) {
        Elements servletClassNameElements = d.select("servlet-class");
        for (Element servletClassNameElement : servletClassNameElements) {
            String servletClassName = servletClassNameElement.text();

            Elements initElements = servletClassNameElement.parent().select("init-param");
            if (initElements.isEmpty())
                continue;

            Map<String, String> initParams = new HashMap<>();

            for (Element element : initElements) {
                String name = element.select("param-name").get(0).text();
                String value = element.select("param-value").get(0).text();
                initParams.put(name, value);
            }

            servlet_className_init_params.put(servletClassName, initParams);

        }

//		System.out.println("class_name_init_params:" + servlet_className_init_params);

    }
    private void destroyServlets() {
        Collection<HttpServlet> servlets = servletPool.values();
        for (HttpServlet servlet : servlets) {
            servlet.destroy();
        }
    }

    public void parseLoadOnStartup(Document d) {
        Elements es = d.select("load-on-startup");
        for (Element e : es) {
            String loadOnStartupServletClassName = e.parent().select("servlet-class").text();
            loadOnStartupServletClassNames.add(loadOnStartupServletClassName);
        }
    }
    public void handleLoadOnStartup() {
        for (String loadOnStartupServletClassName : loadOnStartupServletClassNames) {
            try {
                Class<?> clazz = webappClassLoader.loadClass(loadOnStartupServletClassName);
                getServlet(clazz);
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | ServletException e) {
                e.printStackTrace();
            }
        }
    }

    public WebappClassLoader getWebClassLoader() {
        return webappClassLoader;
    }

    public void parseFilterMapping(Document d) {
        // filter_url_name
        Elements mappingurlElements = d.select("filter-mapping url-pattern");
        for (Element mappingurlElement : mappingurlElements) {
            String urlPattern = mappingurlElement.text();
            String filterName = mappingurlElement.parent().select("filter-name").first().text();

            List<String> filterNames= url_FilterNames.get(urlPattern);
            if(null==filterNames) {
                filterNames = new ArrayList<>();
                url_FilterNames.put(urlPattern, filterNames);
            }
            filterNames.add(filterName);
        }
        // class_name_filter_name
        Elements filterNameElements = d.select("filter filter-name");
        for (Element filterNameElement : filterNameElements) {
            String filterName = filterNameElement.text();
            String filterClass = filterNameElement.parent().select("filter-class").first().text();
            filterName_className.put(filterName, filterClass);
            className_filterName.put(filterClass, filterName);
        }
        // url_filterClassName

        Set<String> urls = url_FilterNames.keySet();
        for (String url : urls) {
            List<String> filterNames = url_FilterNames.get(url);
            if(null == filterNames) {
                filterNames = new ArrayList<>();
                url_FilterNames.put(url, filterNames);
            }
            for (String filterName : filterNames) {
                String filterClassName = filterName_className.get(filterName);
                List<String> filterClassNames = url_filterClassName.get(url);
                if(null==filterClassNames) {
                    filterClassNames = new ArrayList<>();
                    url_filterClassName.put(url, filterClassNames);
                }
                filterClassNames.add(filterClassName);
            }
        }
    }

    private void parseFilterInitParams(Document d) {
        Elements filterClassNameElements = d.select("filter-class");
        for (Element filterClassNameElement : filterClassNameElements) {
            String filterClassName = filterClassNameElement.text();

            Elements initElements = filterClassNameElement.parent().select("init-param");
            if (initElements.isEmpty())
                continue;

            Map<String, String> initParams = new HashMap<>();

            for (Element element : initElements) {
                String name = element.select("param-name").get(0).text();
                String value = element.select("param-value").get(0).text();
                initParams.put(name, value);
            }

            filter_className_init_params.put(filterClassName, initParams);

        }

    }
    private void initFilter() {
        Set<String> classNames = className_filterName.keySet();
        for (String className : classNames) {
            try {
                Class clazz =  this.getWebClassLoader().loadClass(className);
                Map<String,String> initParameters = filter_className_init_params.get(className);
                String filterName = className_filterName.get(className);

                FilterConfig filterConfig = new StandardFilterConfig(servletContext, filterName, initParameters);

                Filter filter = filterPool.get(clazz);
                if(null==filter) {
                    filter = (Filter) ReflectUtil.newInstance(clazz);
                    filter.init(filterConfig);
                    filterPool.put(className, filter);
                }
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }

    public List<Filter> getMatchedFilters(String uri) {
        List<Filter> filters = new ArrayList<>();
        Set<String> patterns = url_filterClassName.keySet();
        Set<String> matchedPatterns = new HashSet<>();

        for (String pattern : patterns) {
            if(match(pattern,uri)) {
                matchedPatterns.add(pattern);
            }
        }

        Set<String> matchedFilterClassNames = new HashSet<>();
        for (String pattern : matchedPatterns) {
            List<String> filterClassName = url_filterClassName.get(pattern);
            matchedFilterClassNames.addAll(filterClassName);
        }
        for (String filterClassName : matchedFilterClassNames) {
            Filter filter = filterPool.get(filterClassName);
            filters.add(filter);
        }
        return filters;
    }

    private boolean match(String pattern, String uri) {
        // 完全匹配
        if(StrUtil.equals(pattern, uri))
            return true;

        // /* 模式
        if(StrUtil.equals(pattern, "/*"))
            return true;

        // 后缀名 /*.jsp
        if(StrUtil.startWith(pattern, "/*.")) {
            String patternExtName = StrUtil.subAfter(pattern, '.', false);
            String uriExtName = StrUtil.subAfter(uri, '.', false);
            if(StrUtil.equals(patternExtName, uriExtName))
                return true;
        }
        // 其他模式就懒得管了
        return false;
    }
    public void addListener(ServletContextListener listener){
        listeners.add(listener);
    }
    public void removeListener(ServletContextListener listener){
        listeners.remove(listener);
    }

    private void loadListeners()  {
        try {
            if(!contextWebXmlFile.exists())
                return;
            String xml = FileUtil.readUtf8String(contextWebXmlFile);
            Document d = Jsoup.parse(xml);

            Elements es = d.select("listener listener-class");
            for (Element e : es) {
                String listenerClassName = e.text();

                Class<?> clazz= this.getWebClassLoader().loadClass(listenerClassName);
                ServletContextListener listener = (ServletContextListener) clazz.newInstance();
                addListener(listener);

            }
        } catch (IORuntimeException | ClassNotFoundException | InstantiationException | IllegalAccessException e) {
            throw new RuntimeException(e);
        }

    }

    private void fireEvent(String type) {
        ServletContextEvent event = new ServletContextEvent(servletContext);
        for (ServletContextListener servletContextListener : listeners) {
            if("init".equals(type))
                servletContextListener.contextInitialized(event);
            if("destroy".equals(type))
                servletContextListener.contextDestroyed(event);
        }
    }

}