手写SpringMVC

环境描述

idea

java 8

1. POM文件

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.feng</groupId>
  <artifactId>hand-springmvc</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>hand-springmvc Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>Example Domain</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>

  <dependencies>
    <!--测试-->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <!--日志-->
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.25</version>
    </dependency>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
    </dependency>

    <!--servlet-->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.0.1</version>
    </dependency>
  </dependencies>

  <build>
    <finalName>hand-springmvc</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
    </pluginManagement>
  </build>
</project>

2. log4j.properties

log4j.rootLogger=INFO, console

log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%d{HH:mm:ss,SSS} %-5p %-60c %x - %m%n

3. 项目目录

核心内容是注解+servlet

注解类

org.feng.annotation.Autowired

package org.feng.annotation;

import java.lang.annotation.*;

/**
 * Created by Feng on 2019/12/16 17:58
 * CurrentProject's name is hand-springmvc
 * Autowired 用在变量上
 * @author Feng
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {
    String value() default "";
}

org.feng.annotation.Controller

package org.feng.annotation;

import java.lang.annotation.*;

/**
 * Created by Feng on 2019/12/16 18:01
 * CurrentProject's name is hand-springmvc
 * Controller 用在类上
 * @author Feng
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Controller {
    String value() default "";
}

org.feng.annotation.RequestMapping

package org.feng.annotation;

import java.lang.annotation.*;

/**
 * Created by Feng on 2019/12/16 18:02
 * CurrentProject's name is hand-springmvc
 * RequestMapping可以用在类、方法上
 * @author Feng
 */
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestMapping {
    String value() default "";
}

org.feng.annotation.RequestParam

package org.feng.annotation;

import java.lang.annotation.*;

/**
 * Created by Feng on 2019/12/16 18:06
 * CurrentProject's name is hand-springmvc
 * RequestParam 用在参数上
 * @author Feng
 */
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {
    String value() default "";
}

org.feng.annotation.Service

package org.feng.annotation;

import java.lang.annotation.*;

/**
 * Created by Feng on 2019/12/16 18:05
 * CurrentProject's name is hand-springmvc
 * Service 用在类上
 * @author Feng
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Service {
    String value() default "";
}

核心控制器

package org.feng.servlet;
import org.feng.annotation.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
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.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Created by Feng on 2019/12/16 17:58
 * CurrentProject's name is hand-springmvc<br>
 * 核心控制器：
 * <ul>实现思路
 *      <li>先扫描基础包，获取 {@code class} 文件的路径；其实是为了获取完整类名</li>
 *      <li>根据上边的完整类名以及判断是否有指定创建实例（通过有无注解和注解的类型）并保存实例到 {@code map} 中</li>
 *      <li>依赖注入变量，从实例获得类对象，然后解析 {@code Field} 并赋值给标注了{@link Autowired}的{@code Field}</li>
 *      <li>获取方法上的参数，通过{@link HttpServletRequest}获取</li>
 * </ul>
 * @author Feng
 */
public class DispatcherServlet extends HttpServlet {

    /**
     * 扫描包：基本的包，扫描该路径下的所有类
     */
    private static final String BASE_PACKAGE = "org.feng";

    private static final String WAR_NAME = "/hand_springmvc";
    /**日志*/
    private static final Logger LOGGER = LoggerFactory.getLogger(DispatcherServlet.class);

    /**
     * 保存class文件的路径
     */
    private List<String> classPathList = new ArrayList<>();

    /**
     * IOC容器：存放对象；使用{@link ConcurrentHashMap}保证线程安全
     */
    private Map<String, Object> beans = new ConcurrentHashMap<>(16);

    /**
     * 存放方法映射：使用{@link ConcurrentHashMap}保证线程安全<br>
     * 用于存储方法<br>
     * {@code key = classpath + methodPath; value = method}
     */
    private Map<String, Method> handlerMap = new ConcurrentHashMap<>(16);

    /**
     * 初始化数据：
     * <ul>
     *     <li>扫描所有的类</li>
     *     <li>创建实例并存储进 {@code beans}</li>
     *     <li>依赖注入：使用 {@code Autowired}</li>
     *     <li>拼接请求地址初始化、方法映射</li>
     * </ul>
     */
    @Override
    public void init() {
        LOGGER.info("starting scan package into classpath list");
        scanPackage(BASE_PACKAGE);
        LOGGER.info("scan package end");
        LOGGER.info("classPathList:"+classPathList);

        LOGGER.info("starting create instance into bean map");
        createInstance();
        LOGGER.info("create instance end");
        LOGGER.info("beans:" + beans);

        LOGGER.info("starting autowired field");
        autowiredField();
        LOGGER.info("autowired field end");

        LOGGER.info("starting mapping to url");
        urlMapping();
        LOGGER.info("mapping to url end");
        LOGGER.info("handler mapping:" + handlerMap);
    }

    /**
     * 方法映射
     */
    private void urlMapping() {
        beans.forEach((key, value) -> {
            Class<?> clazz = value.getClass();
            if(clazz.isAnnotationPresent(Controller.class)){
                RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
                String classPath = requestMapping.value();

                Method[] methods = clazz.getDeclaredMethods();
                for (Method method : methods) {
                    if(method.isAnnotationPresent(RequestMapping.class)){
                        RequestMapping requestMapping1 = method.getAnnotation(RequestMapping.class);
                        String methodPath = requestMapping1.value();
                        handlerMap.put(classPath + methodPath, method);
                    }
                }
            }
        });
    }

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

    /**
     * 解析调用方法后的返回值：当为String类型时，得到其是转发还是重定向；
     * @param invokeReturn invoke方法时得到的返回值
     * @param req 请求对象
     * @param resp 响应对象
     */
    private void forwardOrRedirect(Object invokeReturn, HttpServletRequest req,
                                   HttpServletResponse resp) throws IOException, ServletException {
        final String forward = "forward:";
        final String redirect = "redirect:";

        // 当反向调用方法有返回值
        if(invokeReturn != null){
            // 返回值是字符串：解析字符串
            if(invokeReturn.getClass() == String.class){
                req.setCharacterEncoding("UTF-8");
                resp.setCharacterEncoding("UTF-8");
                String returnStr = invokeReturn.toString();

                if(returnStr.startsWith(forward)){
                    returnStr = returnStr.substring(8);
                    LOGGER.info(forward + returnStr);
                    req.getRequestDispatcher(WAR_NAME + returnStr).forward(req, resp);
                } else if(returnStr.startsWith(redirect)){
                    returnStr = returnStr.substring(9);
                    LOGGER.info(redirect + returnStr);
                    resp.sendRedirect(WAR_NAME + returnStr);
                } else {
                    LOGGER.info(redirect + returnStr);
                    resp.sendRedirect(returnStr);
                }
            }
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
        // 请求的地址
        String uri = req.getRequestURI();
        uri = uri.replace(WAR_NAME, "");

        int index = uri.indexOf("/", 1);
        String controllerUrl = uri.substring(0, index);
        Method method = handlerMap.get(uri);
        LOGGER.info("get method " + method);

        beans.forEach((key, value) -> {
            Class<?> clazz = value.getClass();
            if(clazz.isAnnotationPresent(Controller.class)){
                RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
                String valueTemp = requestMapping.value();
                if(controllerUrl.equals(valueTemp)){
                    try {
                        LOGGER.info("invoking " + controllerUrl + "." + value);
                        Object invokeReturn = method.invoke(value, getArgs(req, resp, method));
                        // 控制：转发或重定向
                        forwardOrRedirect(invokeReturn, req, resp);
                    } catch (IllegalAccessException | InvocationTargetException e) {
                        LOGGER.error("invoke error in " + controllerUrl);
                    } catch (ServletException | IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }

    /**
     * 解析标注有{@link RequestParam}的方法参数，并赋值
     * @param req 请求对象
     * @param resp 响应对象
     * @param method 方法对象
     * @return 赋值后的参数
     */
    private Object[] getArgs(HttpServletRequest req, HttpServletResponse resp, Method method) {
        // 拿到当前类待执行的方法参数
        Class<?>[] clazzParams = method.getParameterTypes();

        // 定义存储参数的数组
        Object[] args = new Object[clazzParams.length];

        int argsIndex = 0;
        // 判定此 class 对象所表示的类或接口与指定的 class 参数所表示的类或接口是否相同
        // 或是否是其超类或超接口
        for (int index = 0; index < clazzParams.length; index++) {
            if(ServletRequest.class.isAssignableFrom(clazzParams[index])){
                args[argsIndex ++] = req;
            }
            if(ServletResponse.class.isAssignableFrom(clazzParams[index])){
                args[argsIndex ++] = resp;
            }

            Annotation[] annotations = method.getParameterAnnotations()[index];
            if(annotations.length > 0){
                for (Annotation annotation : annotations) {
                    if(RequestParam.class.isAssignableFrom(annotation.getClass())){
                        RequestParam requestParam = (RequestParam) annotation;
                        // 找到注解的名字
                        args[argsIndex ++] = req.getParameter(requestParam.value());
                    }
                }
            }
        }
        return args;
    }

    /**
     * 依赖注入：对带有{@link org.feng.annotation.Autowired}的属性赋值
     */
    private void autowiredField() {
        beans.forEach((key, value) ->{
            Class<?> clazz = value.getClass();
            if(clazz.isAnnotationPresent(Controller.class)){
                // 获取属性
                Field[] declaredFields = clazz.getDeclaredFields();
                for (Field declaredField : declaredFields) {
                   if(!declaredField.isAnnotationPresent(Autowired.class)){
                        continue;
                   }

                   // 当存在 Autowired 标注的属性时
                   Autowired autowired = declaredField.getAnnotation(Autowired.class);
                   String beanName;
                   if("".equals(autowired.value())){
                       beanName = lowerFirstChar(declaredField.getType().getSimpleName());
                   } else {
                       beanName = autowired.value();
                   }

                   // 设置访问控制权限：原先是 private 不能访问
                   declaredField.setAccessible(true);

                   // 自定义接口实现类：以Impl结尾，前边拼接接口名（首字母小写）
                   if(beanName.endsWith("Impl")){
                       beanName = beanName.replace("Impl", "");
                   }
                   if(beans.get(beanName) != null){
                       try {
                           // 给声明的变量赋值：注入实例
                           declaredField.set(value, beans.get(beanName));
                       } catch (IllegalAccessException e) {
                           e.printStackTrace();
                       }
                   }
                }
            }
        });
    }

    /**
     * 创建实例：遍历所有的{@code class}文件，创建需要创建的实例存储到beans中<br>
     * 判断：是否被指定注解标注了
     * <ul>
     *     <li>首先判断是不是{@link org.feng.annotation.Service}注解的类，若是则判断有没有传入的{@code service}名称</li>
     *     <li>其他情况，包括是{@link org.feng.annotation.Controller}的情况，全部使用小写类名为{@code key}</li>
     * </ul>
     */
    private void createInstance() {
        try {
            // 遍历所有的.class文件；将需要实例化的类创建实例
            for (String classPath : classPathList) {
                Class<?> clazz = Class.forName(classPath.replace(".class", ""));

                if(clazz.isAnnotationPresent(Service.class)){
                    Service service = clazz.getAnnotation(Service.class);
                    String key = service.value();
                    // 当传入了注解中参数时
                    if(!"".equals(key)){
                        beans.put(key, clazz.newInstance());
                        LOGGER.info("created instance by " + classPath);
                    } else {
                        // 获取第一个接口的简单名称，首字母小写
                        beans.put(lowerFirstChar(clazz.getInterfaces()[0].getSimpleName()), clazz.newInstance());
                        LOGGER.info("created instance by " + classPath);
                    }
                } else if(clazz.isAnnotationPresent(Controller.class)){
                    // 以类名小写首字母为key
                    beans.put(lowerFirstChar(clazz.getSimpleName()), clazz.newInstance());
                    LOGGER.info("created instance by " + classPath);
                }
            }
        } catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {
            LOGGER.error("error in createInstance", e);
        }
    }

    /**
     * 将类名中的首字母小写
     * @param simpleName 类名（不含包名）
     */
    private String lowerFirstChar(String simpleName) {
        char[] chars = simpleName.toCharArray();
        chars[0] += 32;
        return new String(chars);
    }

    /**
     * 先通过传入的包名拼接出文件路径:
     * <p>
     * {@code "org.feng".replace(".", "/");}
     * </p>
     * 递归扫描指定路径下的所有{@code class}文件；
     * 存储{@code class}文件路径到集合中
     * @param basePackage 扫描包的包名
     */
    private void scanPackage(String basePackage) {

        // 将包名转换为class文件路径
        String resourceName = "/" + basePackage.replace(".", "/");
        URL url = this.getClass().getClassLoader().getResource(resourceName);

        // 获取文件
        assert url != null;
        String filename = url.getFile();
        File file = new File(filename);

        // 获取所有文件
        String[] files = file.list();
        assert files != null;
        for (String path : files) {
            File fileTemp = new File(filename + path);
            // 当前如果是目录，递归扫描包
            String packageName = basePackage + "." + path;
            if(fileTemp.isDirectory()){
                scanPackage(packageName);
            } else {
                // 当扫描到文件(.class文件)，增加到类路径集合
                classPathList.add(packageName);
                LOGGER.info("scan " + packageName + " into classpath list");
            }
        }
    }
}

测试

org.feng.service.MyService

package org.feng.service;

/**
 * Created by Feng on 2019/12/17 9:23
 * CurrentProject's name is hand-springmvc
 * @author Feng
 */
public interface MyService {
    /**
     * 说
     * @return 字符串
     */
    String say();

org.feng.service.impl.MyServiceImpl

package org.feng.service.impl;

import org.feng.annotation.Service;
import org.feng.service.MyService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Created by Feng on 2019/12/17 9:25
 * CurrentProject's name is hand-springmvc
 * @author Feng
 */
@Service
public class MyServiceImpl implements MyService {

    private static final Logger LOGGER = LoggerFactory.getLogger(MyServiceImpl.class);

    public MyServiceImpl(){
        LOGGER.info("no args constructor MyServiceImpl.class");
    }

    @Override
    public String say() {
        return "MyServiceImpl invoking say()";
    }
}

org.feng.controller.MyController

package org.feng.controller;

import org.feng.annotation.Autowired;
import org.feng.annotation.Controller;
import org.feng.annotation.RequestMapping;
import org.feng.annotation.RequestParam;
import org.feng.service.MyService;

/**
 * Created by Feng on 2019/12/17 9:27
 * CurrentProject's name is hand-springmvc
 */
@RequestMapping("/MyController")
@Controller
public class MyController {

    @Autowired
    private MyService myService;

    @RequestMapping("/say.do")
    public String say(@RequestParam("name") String name, @RequestParam("info") String info){
        System.out.println("name = " + name + ", info = " + info);
        myService.say();
        return "redirect:/index.jsp";
    }
}

运行

配置tomcat

运行结果：

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