手写MVC实现过程

一.手写mvc前基础知识

1.mvc是什么？

MVC是一种基于Java的实现了Web MVC设计模式的请求驱动类型的轻量级Web框架，即使用了MVC架构模式的思想，将web层进行职责解耦，基于请求驱动指的就是使用请求-响应模型，框架的目的就是帮助我们简化开发，Spring Web MVC也是要简化我们日常Web开发的。

2.mvc能帮我们做什么？

1.让我们能非常简单的设计出干净的Web层和薄薄的Web层；

2.进行更简洁的Web层的开发；

3.提供强大的约定大于配置的契约式编程支持；

4.能简单的进行Web层的单元测试；

5.支持灵活的URL到页面控制器的映射；

6.非常灵活的数据验证、格式化和数据绑定机制，能使用任何对象进行数据绑定，不必实现特定框架的API

7.更加简单的异常处理。

等等...

3.spring mvc 架构图

二. 手写mvc实现过程

1.定义配置标记

1.@RequestMapping：标识Controller的方法与请求路径和请求方法的映射关系

2.@RequestParam：请求的方法参数名称

3.@ResponseBody：用于标记自动对返回值进行json处理

2.转发控制器

核心流程：

1.初始化

• 1.初始化容器
• 2.doAop
• 3.doIoc
• 4.初始化请求处理器责任链

2.处理请求

• 1.创建责任链对象实例

• 2.通过责任链模式来依次调用请求处理器对请求进行处理

• 3.对处理结果进行渲染

package org.simplespring.mvc;
import org.simplespring.aop.AspectWeaver;
import org.simplespring.core.BeanContainer;
import org.simplespring.inject.DependencyInjector;
import org.simplespring.mvc.processor.RequestProcessor;
import org.simplespring.mvc.processor.impl.ControllerRequestProcessor;
import org.simplespring.mvc.processor.impl.JspRequestProcessor;
import org.simplespring.mvc.processor.impl.PreRequestProcessor;
import org.simplespring.mvc.processor.impl.StaticResourceRequestProcessor;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.ArrayList;
import java.util.List;

/**
 * 请求转发器
 */
@WebServlet("/*")
public class DispatcherServlet extends HttpServlet {
    List<RequestProcessor> PROCESSOR = new ArrayList<>();

    /**
     * 初始化
     * 1.初始化容器
     * 2.doAop
     * 3.doIoc
     * 4.初始化请求处理器责任链
     */
    @Override
    public void init(){
        //1.初始化容器
        BeanContainer beanContainer = BeanContainer.getInstance();
        beanContainer.loadBeans("com.zhangtianci");
        new AspectWeaver().doAop();
        new DependencyInjector().doIoc();
        //2.初始化请求处理器责任链
        PROCESSOR.add(new PreRequestProcessor());
        PROCESSOR.add(new StaticResourceRequestProcessor(getServletContext()));
        PROCESSOR.add(new JspRequestProcessor(getServletContext()));
        PROCESSOR.add(new ControllerRequestProcessor());
    }

    /**
     * 1.创建责任链对象实例
     * 2.通过责任链模式来依次调用请求处理器对请求进行处理
     * 3.对处理结果进行渲染
     * @param req
     * @param resp
     */
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) {
        //1.创建责任链对象实例
        RequestProcessorChain requestProcessorChain = new RequestProcessorChain(PROCESSOR.iterator(), req, resp);
        //2.通过责任链模式来依次调用请求处理器对请求进行处理
        requestProcessorChain.doRequestProcessorChain();
        //3.对处理结果进行渲染
        requestProcessorChain.doRender();
    }
}

3.请求处理责任链

1.以责任链的模式执行注册的请求处理器

2.委派给特定的Render实例对处理后的结果进行渲染

package org.simplespring.mvc;

import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.simplespring.mvc.processor.RequestProcessor;
import org.simplespring.mvc.render.DefaultResultRender;
import org.simplespring.mvc.render.InternalErrorResultRender;
import org.simplespring.mvc.render.ResultRender;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Iterator;

/**
 * 请求处理责任链
 *
 * 1.以责任链的模式执行注册的请求处理器
 * 2.委派给特定的Render实例对处理后的结果进行渲染
 */
@Data
@Slf4j
public class RequestProcessorChain {
    //请求处理器迭代器
    private Iterator<RequestProcessor> requestProcessorIterator;
    //请求request
    private HttpServletRequest request;
    //请求response
    private HttpServletResponse response;
    //http请求方法
    private String requestMethod;
    //http请求路径
    private String requestPath;
    //http响应状态码
    private  int responseCode;
    //请求结果渲染器
    private ResultRender resultRender;

    public RequestProcessorChain(Iterator<RequestProcessor> iterator, HttpServletRequest req, HttpServletResponse resp) {
        this.requestProcessorIterator = iterator;
        this.request = req;
        this.response = resp;
        this.requestMethod = req.getMethod();
        this.requestPath = req.getPathInfo();
        this.responseCode  = HttpServletResponse.SC_OK;
    }
    /**
     * 以责任链的模式执行请求链
     */
    public void doRequestProcessorChain() {
        //1.通过迭代器遍历注册的请求处理器实现类列表
        try{
        while(requestProcessorIterator.hasNext()){
            //2.直到某个请求处理器执行后返回为false为止
            if(!requestProcessorIterator.next().process(this)){
                break;
            }
        }} catch (Exception e){
            //3.期间如果出现异常，则交由内部异常渲染器处理
            this.resultRender = new InternalErrorResultRender(e.getMessage());
            log.error("doRequestProcessorChain error:", e);
        }


    }
    /**
     * 执行处理器
     */
    public void doRender() {
        //1.如果请求处理器实现类均未选择合适的渲染器，则使用默认的
        if(this.resultRender == null){
            this.resultRender = new DefaultResultRender();
        }
        //2.调用渲染器的render方法对结果进行渲染
        try {
            this.resultRender.render(this);
        } catch (Exception e) {
            log.error("doRender error: ", e);
            throw new RuntimeException(e);
        }
    }
}

4.定义RequestProcessor矩阵

定义处理动作规范

/**
 * 请求执行器接口
 */
public interface RequestProcessor {
    boolean process(RequestProcessorChain requestProcessorChain) throws Exception;
}

请求预处理器

package org.simplespring.mvc.processor.impl;

import lombok.extern.slf4j.Slf4j;
import org.simplespring.mvc.RequestProcessorChain;
import org.simplespring.mvc.processor.RequestProcessor;

/**
 * 请求预处理，包括编码以及路径处理
 */
@Slf4j
public class PreRequestProcessor implements RequestProcessor {
    @Override
    public boolean process(RequestProcessorChain requestProcessorChain) throws Exception {
        // 1.设置请求编码，将其统一设置成UTF-8
        requestProcessorChain.getRequest().setCharacterEncoding("UTF-8");
        // 2.将请求路径末尾的/剔除，为后续匹配Controller请求路径做准备
        // （一般Controller的处理路径是/aaa/bbb，所以如果传入的路径结尾是/aaa/bbb/，
        // 就需要处理成/aaa/bbb）
        String requestPath = requestProcessorChain.getRequestPath();
        //http://localhost:8080/simpleframework requestPath="/"
        if(requestPath.length() > 1 && requestPath.endsWith("/")){
            requestProcessorChain.setRequestPath(requestPath.substring(0, requestPath.length() - 1));
        }
        log.info("preprocess request {} {}", requestProcessorChain.getRequestMethod(), requestProcessorChain.getRequestPath());
        return true;
    }
}

静态资源请求处理器

package org.simplespring.mvc.processor.impl;

import lombok.extern.slf4j.Slf4j;
import org.simplespring.mvc.RequestProcessorChain;
import org.simplespring.mvc.processor.RequestProcessor;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;

/**
 * 静态资源请求处理,包括但不限于图片、css、以及js文件等 - DefaultServlet
 */
@Slf4j
public class StaticResourceRequestProcessor implements RequestProcessor {
    public static final String DEFAULT_TOMCAT_SERVLET = "default";
    public static final String STATIC_RESOURCE_PREFIX = "/static/";
    //tomcat默认请求派发器RequestDispatcher的名称
    RequestDispatcher defaultDispatcher;

    public StaticResourceRequestProcessor(ServletContext servletContext) {
        this.defaultDispatcher = servletContext.getNamedDispatcher(DEFAULT_TOMCAT_SERVLET);
        if(this.defaultDispatcher == null){
            throw new RuntimeException("There is no default tomcat servlet");
        }
        log.info("The default servlet for static resource is {}", DEFAULT_TOMCAT_SERVLET);
    }

    @Override
    public boolean process(RequestProcessorChain requestProcessorChain) throws Exception {
        //1.通过请求路径判断是否是请求的静态资源 webapp/static
        if(isStaticResource(requestProcessorChain.getRequestPath())){
            //2.如果是静态资源，则将请求转发给default servlet处理
            defaultDispatcher.forward(requestProcessorChain.getRequest(), requestProcessorChain.getResponse());
            return false;
        }
        return true;
    }
    //通过请求路径前缀（目录）是否为静态资源 /static/
    private boolean isStaticResource(String path){
        return path.startsWith(STATIC_RESOURCE_PREFIX);
    }
}

jsp资源请求处理器

package org.simplespring.mvc.processor.impl;

import org.simplespring.mvc.RequestProcessorChain;
import org.simplespring.mvc.processor.RequestProcessor;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;

/**
 * jsp资源请求处理
 */
public class JspRequestProcessor implements RequestProcessor {

    //jsp请求的RequestDispatcher的名称
    private static final String JSP_SERVLET = "jsp";
    //Jsp请求资源路径前缀
    private static final String  JSP_RESOURCE_PREFIX = "/templates/";

    /**
     * jsp的RequestDispatcher,处理jsp资源
     */
    private RequestDispatcher jspServlet;

    public JspRequestProcessor(ServletContext servletContext) {
        jspServlet = servletContext.getNamedDispatcher(JSP_SERVLET);
        if (null == jspServlet) {
            throw new RuntimeException("there is no jsp servlet");
        }
    }

    @Override
    public boolean process(RequestProcessorChain requestProcessorChain) throws Exception {
        if (isJspResource(requestProcessorChain.getRequestPath())) {
            jspServlet.forward(requestProcessorChain.getRequest(), requestProcessorChain.getResponse());
            return false;
        }
        return true;
    }

    /**
     * 是否请求的是jsp资源
     */
    private boolean isJspResource(String url) {
        return url.startsWith(JSP_RESOURCE_PREFIX);
    }

}

Controller请求处理器

package org.simplespring.mvc.processor.impl;

import lombok.extern.slf4j.Slf4j;
import org.simplespring.core.BeanContainer;
import org.simplespring.mvc.RequestProcessorChain;
import org.simplespring.mvc.annotation.RequestMapping;
import org.simplespring.mvc.annotation.RequestParam;
import org.simplespring.mvc.annotation.ResponseBody;
import org.simplespring.mvc.processor.RequestProcessor;
import org.simplespring.mvc.render.JsonResultRender;
import org.simplespring.mvc.render.ResourceNotFoundResultRender;
import org.simplespring.mvc.render.ResultRender;
import org.simplespring.mvc.render.ViewResultRender;
import org.simplespring.mvc.type.ControllerMethod;
import org.simplespring.mvc.type.RequestPathInfo;
import org.simplespring.util.ConverterUtil;
import org.simplespring.util.ValidationUtil;
import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Controller请求处理器
 */
@Slf4j
public class ControllerRequestProcessor implements RequestProcessor {
    //IOC容器
    private BeanContainer beanContainer;
    //请求和controller方法的映射集合
    private Map<RequestPathInfo, ControllerMethod> pathControllerMethodMap = new ConcurrentHashMap<>();

    /**
     * 依靠容器的能力，建立起请求路径、请求方法与Controller方法实例的映射
     */
    public ControllerRequestProcessor() {
        this.beanContainer = BeanContainer.getInstance();
        Set<Class<?>> requestMappingSet = beanContainer.getClassesByAnnotation(RequestMapping.class);
        initPathControllerMethodMap(requestMappingSet);
    }

    private void initPathControllerMethodMap(Set<Class<?>> requestMappingSet) {
        if (ValidationUtil.isEmpty(requestMappingSet)) {
            return;
        }
        //1.遍历所有被@RequestMapping标记的类，获取类上面该注解的属性值作为一级路径
        for (Class<?> requestMappingClass : requestMappingSet) {
            RequestMapping requestMapping = requestMappingClass.getAnnotation(RequestMapping.class);
            String basePath = requestMapping.value();
            if (!basePath.startsWith("/")) {
                basePath = "/" + basePath;
            }
            //2.遍历类里所有被@RequestMapping标记的方法，获取方法上面该注解的属性值，作为二级路径
            Method[] methods = requestMappingClass.getDeclaredMethods();
            if (ValidationUtil.isEmpty(methods)) {
                continue;
            }
            for (Method method : methods) {
                if (method.isAnnotationPresent(RequestMapping.class)) {
                    RequestMapping methodRequest = method.getAnnotation(RequestMapping.class);
                    String methodPath = methodRequest.value();
                    if (!methodPath.startsWith("/")) {
                        methodPath = "/" + basePath;
                    }
                    String url = basePath + methodPath;
                    //3.解析方法里被@RequestParam标记的参数，
                    // 获取该注解的属性值，作为参数名，
                    // 获取被标记的参数的数据类型，建立参数名和参数类型的映射
                    Map<String, Class<?>> methodParams = new HashMap<>();
                    Parameter[] parameters = method.getParameters();
                    if (!ValidationUtil.isEmpty(parameters)) {
                        for (Parameter parameter : parameters) {
                            RequestParam param = parameter.getAnnotation(RequestParam.class);
                            //目前暂定为Controller方法里面所有的参数都需要@RequestParam注解
                            if (param == null) {
                                throw new RuntimeException("The parameter must have @RequestParam");
                            }
                            methodParams.put(param.value(), parameter.getType());
                        }
                    }
                    //4.将获取到的信息封装成RequestPathInfo实例和ControllerMethod实例，放置到映射表里
                    String httpMethod = String.valueOf(methodRequest.method());
                    RequestPathInfo requestPathInfo = new RequestPathInfo(httpMethod, url);
                    if (this.pathControllerMethodMap.containsKey(requestPathInfo)) {
                        log.warn("duplicate url:{} registration，current class {} method{} will override the former one",
                                requestPathInfo.getHttpPath(), requestMappingClass.getName(), method.getName());
                    }
                    ControllerMethod controllerMethod = new ControllerMethod(requestMappingClass, method, methodParams);
                    this.pathControllerMethodMap.put(requestPathInfo, controllerMethod);
                }
            }
        }

    }

    @Override
    public boolean process(RequestProcessorChain requestProcessorChain) throws Exception {
        //1.解析HttpSevletRequest的请求方法,请求路径，获取对应的ControllerMethod实例
        String method = requestProcessorChain.getRequestMethod();
        String path = requestProcessorChain.getRequestPath();
        ControllerMethod controllerMethod = this.pathControllerMethodMap.get(new RequestPathInfo(method, path));
        if (controllerMethod == null) {
            requestProcessorChain.setResultRender(new ResourceNotFoundResultRender(method, path));
            return false;
        }
        //2.解析请求参数，并传递给获取到的ControllerMethod实例去执行
        Object result = invokeControllerMethod(controllerMethod, requestProcessorChain.getRequest());
        //3.根据处理的结果，选择对应的render进行渲染
        setResultRender(result, controllerMethod, requestProcessorChain);
        return true;
    }

    /**
     * 根据不同情况设置不同的渲染器
     */
    private void setResultRender(Object result, ControllerMethod controllerMethod, RequestProcessorChain requestProcessorChain) {
        if (result == null) {
            return;
        }
        ResultRender resultRender;
        boolean isJson = controllerMethod.getInvokeMethod().isAnnotationPresent(ResponseBody.class);
        if (isJson) {
            resultRender = new JsonResultRender(result);
        } else {
            resultRender = new ViewResultRender(result);
        }
        requestProcessorChain.setResultRender(resultRender);
    }

    private Object invokeControllerMethod(ControllerMethod controllerMethod, HttpServletRequest request) {
        //1.从请求里获取GET或者POST的参数名及其对应的值
        Map<String, String> requestParamMap = new HashMap<>();
        //GET，POST方法的请求参数获取方式
        Map<String, String[]> parameterMap = request.getParameterMap();
        for (Map.Entry<String, String[]> parameter : parameterMap.entrySet()
        ) {
            if (!ValidationUtil.isEmpty(parameter.getValue())) {
                //只支持一个参数对应一个值的形式
                requestParamMap.put(parameter.getKey(), parameter.getValue()[0]);
            }
        }
        //2.根据获取到的请求参数名及其对应的值，以及controllerMethod里面的参数和类型的映射关系，去实例化出方法对应的参数
        List<Object> methodParams = new ArrayList<>();
        Map<String, Class<?>> methodParamMap = controllerMethod.getMethodParameters();
        for (String paramName : methodParamMap.keySet()) {
            Class<?> type = methodParamMap.get(paramName);
            String requestValue = requestParamMap.get(paramName);
            Object value;
            //只支持String 以及基础类型char,int,short,byte,double,long,float,boolean,及它们的包装类型
            if (requestValue == null) {
                //将请求里的参数值转成适配于参数类型的空值
                value = ConverterUtil.primitiveNull(type);
            } else {
                value = ConverterUtil.convert(type, requestValue);
            }
            methodParams.add(value);
        }
        //3.执行Controller里面对应的方法并返回结果
        Object controller = beanContainer.getBean(controllerMethod.getControllerClass());
        Method invokeMethod = controllerMethod.getInvokeMethod();
        invokeMethod.setAccessible(true);
        Object result;
        try {
            if (methodParams.size() == 0) {
                result = invokeMethod.invoke(controller);
            } else {
                result = invokeMethod.invoke(controller, methodParams.toArray());
            }
        } catch (InvocationTargetException e) {
            //如果是调用异常的话，需要通过e.getTargetException()
            // 去获取执行方法抛出的异常
            throw new RuntimeException(e.getTargetException());
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }
        return result;
    }
}

5.定义Render矩阵

定义渲染动作规范

/**
 * 渲染请求结果
 */
public interface ResultRender {
    //执行渲染
    void render(RequestProcessorChain requestProcessorChain) throws Exception;
}

默认渲染器

/**
 * 默认渲染器
 */
public class DefaultResultRender implements ResultRender {
    @Override
    public void render(RequestProcessorChain requestProcessorChain) throws Exception {
        requestProcessorChain.getResponse().setStatus(requestProcessorChain.getResponseCode());
    }
}

内部异常渲染器

/**
 * 内部异常渲染器
 */
public class InternalErrorResultRender implements ResultRender{
    private String errorMsg;
    public InternalErrorResultRender(String  errorMsg){
        this.errorMsg = errorMsg;
    }
    @Override
    public void render(RequestProcessorChain requestProcessorChain) throws Exception {
        requestProcessorChain.getResponse().sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, errorMsg);
    }
}

Json渲染器

package org.simplespring.mvc.render;

import com.google.gson.Gson;
import org.simplespring.mvc.RequestProcessorChain;

import java.io.PrintWriter;

/**
 * Json渲染器
 */
public class JsonResultRender implements ResultRender {
    private Object jsonData;
    public JsonResultRender(Object jsonData) {
        this.jsonData = jsonData;
    }

    @Override
    public void render(RequestProcessorChain requestProcessorChain) throws Exception {
        // 设置响应头
        requestProcessorChain.getResponse().setContentType("application/json");
        requestProcessorChain.getResponse().setCharacterEncoding("UTF-8");
        // 响应流写入经过gson格式化之后的处理结果
        try(PrintWriter writer = requestProcessorChain.getResponse().getWriter()){
            Gson gson = new Gson();
            writer.write(gson.toJson(jsonData));
            writer.flush();
        }
    }
}

资源找不到时使用的渲染器

package org.simplespring.mvc.render;


import org.simplespring.mvc.RequestProcessorChain;

import javax.servlet.http.HttpServletResponse;

/**
 * 资源找不到时使用的渲染器
 */
public class ResourceNotFoundResultRender implements ResultRender {
    private String httpMethod;
    private String httpPath;
    public ResourceNotFoundResultRender(String method, String path) {
        this.httpMethod = method;
        this.httpPath = path;
    }

    @Override
    public void render(RequestProcessorChain requestProcessorChain) throws Exception {
        requestProcessorChain.getResponse().sendError(HttpServletResponse.SC_NOT_FOUND,
                "获取不到对应的请求资源：请求路径[" + httpPath + "]" + "请求方法[" + httpMethod + "]");
    }
}

页面渲染器

package org.simplespring.mvc.render;

import org.simplespring.mvc.RequestProcessorChain;
import org.simplespring.mvc.type.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Map;

/**
 * 页面渲染器
 */
public class ViewResultRender implements ResultRender{
    public static final String VIEW_PATH = "/templates/";
    private ModelAndView modelAndView;
    /**
     * 对传入的参数进行处理，并赋值给ModelAndView成员变量
     * @param mv
     */
    public ViewResultRender(Object mv) {
        if(mv instanceof ModelAndView){
            //1.如果入参类型是ModelAndView，则直接赋值给成员变量
            this.modelAndView = (ModelAndView)mv;
        } else if(mv instanceof  String){
            //2.如果入参类型是String，则为视图，需要包装后才赋值给成员变量
            this.modelAndView = new ModelAndView().setView((String)mv);
        } else {
            //3.针对其他情况，则直接抛出异常
            throw new RuntimeException("illegal request result type");
        }
    }
    /**
     * 将请求处理结果按照视图路径转发至对应视图进行展示
     * @param requestProcessorChain
     * @throws Exception
     */
    @Override
    public void render(RequestProcessorChain requestProcessorChain) throws Exception {
        HttpServletRequest request = requestProcessorChain.getRequest();
        HttpServletResponse response = requestProcessorChain.getResponse();
        String path = modelAndView.getView();
        Map<String, Object> model = modelAndView.getModel();
        for(Map.Entry<String, Object> entry : model.entrySet()){
            request.setAttribute(entry.getKey(), entry.getValue());
        }
        //JSP
        request.getRequestDispatcher(VIEW_PATH +path).forward(request, response);

    }
}

6.其他数据封装包装类和工具类

/**
 * 待执行的Controller及其方法实例和参数的映射
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class ControllerMethod {
    //Controller对应的Class对象
    private Class<?> controllerClass;
    //执行的Controller方法实例
    private Method invokeMethod;
    //方法参数名称以及对应的参数类型
    private Map<String, Class<?>> methodParameters;
}

/**
 * 存储处理完后的结果数据,以及显示该数据的视图
 */
public class ModelAndView {
    //页面所在的路径
    @Getter
    private String view;
    //页面的data数据
    @Getter
    private Map<String, Object> model = new HashMap<>();

    public ModelAndView setView(String view){
        this.view = view;
        return this;
    }
    //modelAndView.setView("addheadline.jsp").addViewData("aaa", "bbb");
    public ModelAndView addViewData(String attributeName,  Object attributeValue){
        model.put(attributeName, attributeValue);
        return this;
    }
}

/**
 * 目前支持的请求方法
 */
public enum RequestMethod {
    GET,
    POST
}

/**
 * 存储http请求路径和请求方法
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class RequestPathInfo {
    //http请求方法
    private String httpMethod;
    //http请求路径
    private String httpPath;
}

package org.simplespring.util;

public class ConverterUtil {
    /**
     * 返回基本数据类型的空值
     *需要特殊处理的基本类型即intdoubleshortlongytefloatoolean
     * @param type 参数类型
     * @return 对应的空值
     */
    public static Object primitiveNull(Class<?> type) {
        if (type == int.class || type == double.class ||
                type == short.class || type == long.class ||
                type == byte.class || type == float.class) {
            return 0;
        } else if(type == boolean.class){
            return false;
        }
        return null;
    }
    /**
     * String类型转换成对应的参数类型
     *
     * @param type  参数类型
     * @param requestValue 值
     * @return 转换后的Object
     */
    public static Object convert(Class<?> type, String requestValue) {
        if(isPrimitive(type)){
            if(ValidationUtil.isEmpty(requestValue)){
                return primitiveNull(type);
            }
            if (type.equals(int.class) || type.equals(Integer.class)) {
                return Integer.parseInt(requestValue);
            } else if (type.equals(String.class)) {
                return requestValue;
            } else if (type.equals(Double.class) || type.equals(double.class)) {
                return Double.parseDouble(requestValue);
            } else if (type.equals(Float.class) || type.equals(float.class)) {
                return Float.parseFloat(requestValue);
            } else if (type.equals(Long.class) || type.equals(long.class)) {
                return Long.parseLong(requestValue);
            } else if (type.equals(Boolean.class) || type.equals(boolean.class)) {
                return Boolean.parseBoolean(requestValue);
            } else if (type.equals(Short.class) || type.equals(short.class)) {
                return Short.parseShort(requestValue);
            } else if (type.equals(Byte.class) || type.equals(byte.class)) {
                return Byte.parseByte(requestValue);
            }
            return requestValue;
        } else {
            throw new RuntimeException("count not support non primitive type conversion yet");
        }
    }
    /**
     * 判定是否基本数据类型(包括包装类以及String)
     *
     * @param type 参数类型
     * @return 是否为基本数据类型
     */
    private static boolean isPrimitive(Class<?> type) {
        return type == boolean.class
                || type == Boolean.class
                || type == double.class
                || type == Double.class
                || type == float.class
                || type == Float.class
                || type == short.class
                || type == Short.class
                || type == int.class
                || type == Integer.class
                || type == long.class
                || type == Long.class
                || type == String.class
                || type == byte.class
                || type == Byte.class
                || type == char.class
                || type == Character.class;
    }
}

总结一下大致流程：

1.定义配置标记

1.@RequestMapping：标识Controller的方法与请求路径和请求方法的映射关系

2.@RequestParam：请求的方法参数名称

3.@ResponseBody：用于标记自动对返回值进行json处理

2.转发控制器

核心流程：

1.初始化

• 1.初始化容器
• 2.doAop
• 3.doIoc
• 4.初始化请求处理器责任链

2.处理请求

• 1.创建责任链对象实例

• 2.通过责任链模式来依次调用请求处理器对请求进行处理

• 3.对处理结果进行渲染

3.请求处理责任链
1.以责任链的模式执行注册的请求处理器
2.委派给特定的Render实例对处理后的结果进行渲染

4.定义RequestProcessor矩阵

请求预处理器/静态资源请求处理器/jsp资源请求处理器/Controller请求处理器

5.定义Render矩阵
默认渲染器/内部异常渲染器/Json渲染器/资源找不到时使用的渲染器/页面渲染器/

6.其他数据封装包装类和工具类

参考博客：https://www.iteye.com/blog/jinnianshilongnian-1594806