nosum-spring/src/main/java/cn/nosum/framework/mvc/v1/servlet/DispatcherServlet.java

package cn.nosum.framework.mvc.v1.servlet;

import cn.nosum.framework.annotation.Autowired;
import cn.nosum.framework.annotation.Controller;
import cn.nosum.framework.annotation.RequestMapping;
import cn.nosum.framework.annotation.Service;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.*;

public class DispatcherServlet extends HttpServlet {
    private Map<String, Object> mapping = new HashMap<String, Object>();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        try {
            doDispatch(req, resp);
        } catch (Exception e) {
            resp.getWriter().write("500 Exception " + Arrays.toString(e.getStackTrace()));
        }
    }

    /**
     * 进行URL的映射
     */
    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception {
        String url = req.getRequestURI();
        String contextPath = req.getContextPath();
        // 去除 URL 中的前缀并且将多个 / 替换为一个
        url = url.replace(contextPath, "").replaceAll("/+", "/");
        // 找不到页面
        if (!this.mapping.containsKey(url)) {
            resp.getWriter().write("404 Not Found!!");
            return;
        }
        // 根据 URL 取得对应的方法映射
        Method method = (Method) this.mapping.get(url);
        // 取得所有的参数
        Map<String, String[]> params = req.getParameterMap();
        // 调用方法
        method.invoke(this.mapping.get(method.getDeclaringClass().getName()), new Object[]{req, resp, params.get("name")[0]});
    }

    /**
     * 初始化所有的相关的类，IOC容器、servletBean
     */
    @Override
    public void init(ServletConfig config) throws ServletException {
        InputStream is = null;
        try {
            Properties configContext = new Properties();
            // 取得 application.properties
            is = this.getClass().getClassLoader().getResourceAsStream(config.getInitParameter("contextConfigLocation"));
            configContext.load(is);
            // 获取定义的扫描包路径
            String scanPackage = configContext.getProperty("scanPackage");
            // 将指定路径中的类名进行缓存
            doScanner(scanPackage);
            // 初始化 IOC 容器
            for (String className : mapping.keySet()) {
                if (!className.contains(".")) {
                    continue;
                }
                Class<?> clazz = Class.forName(className);
                if (clazz.isAnnotationPresent(Controller.class)) {
                    // 保存 Controller 实例
                    mapping.put(className, clazz.getDeclaredConstructor().newInstance());
                    String baseUrl = "";
                    if (clazz.isAnnotationPresent(RequestMapping.class)) {
                        RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
                        baseUrl = requestMapping.value();
                    }
                    Method[] methods = clazz.getMethods();
                    for (Method method : methods) {
                        if (!method.isAnnotationPresent(RequestMapping.class)) {
                            continue;
                        }
                        RequestMapping requestMapping = method.getAnnotation(RequestMapping.class);
                        String url = (baseUrl + "/" + requestMapping.value()).replaceAll("/+", "/");
                        // 保存 URL 对应的方法引用
                        mapping.put(url, method);
                        System.out.println("Mapped " + url + "," + method);
                    }
                } else if (clazz.isAnnotationPresent(Service.class)) {
                    Service service = clazz.getAnnotation(Service.class);
                    String beanName = service.value();
                    if ("".equals(beanName)) {
                        beanName = clazz.getName();
                    }
                    Object instance = clazz.getDeclaredConstructor().newInstance();
                    mapping.put(beanName, instance);
                    // 如果当前实例具备有父接口，保存父接口包名
                    for (Class<?> i : clazz.getInterfaces()) {
                        mapping.put(i.getName(), instance);
                    }
                } else {
                    continue;
                }
            }

            // 依赖注入
            for (Object object : mapping.values()) {
                if (object == null) {
                    continue;
                }
                Class clazz = object.getClass();
                if (clazz.isAnnotationPresent(Controller.class)) {
                    // 取得所有的成员变量
                    Field[] fields = clazz.getDeclaredFields();
                    for (Field field : fields) {
                        if (!field.isAnnotationPresent(Autowired.class)) { continue; }
                        Autowired autowired = field.getAnnotation(Autowired.class);
                        String beanName = autowired.value();
                        if ("".equals(beanName)) {
                            beanName = field.getType().getName();
                        }
                        field.setAccessible(true);
                        try {
                            // 从容器中，注入实例
                            field.set(mapping.get(clazz.getName()), mapping.get(beanName));
                        } catch (IllegalAccessException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        } catch (Exception ignored) {
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        System.out.print("MVC Framework is init");
    }


    /**
     * 将指定路径中的 class 名称保存
     */
    private void doScanner(String scanPackage) {
        // 将 . 替换为 /
        URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll("\\.", "/"));
        File classDir = new File(url.getFile());
        // 扫描包所有的 class 文件
        for (File file : classDir.listFiles()) {
            if (file.isDirectory()) {
                // 如果是文件夹，递归调用
                doScanner(scanPackage + "." + file.getName());
            } else {
                if (!file.getName().endsWith(".class")) {
                    continue;
                }
                String clazzName = (scanPackage + "." + file.getName().replace(".class", ""));
                mapping.put(clazzName, null);
            }
        }
    }
}