手写spring+springmvc+mybatis框架篇——springmvc

本文转自：https://blog.csdn.net/qq_27631217/article/details/80977120

先放一张网上的很好的一张原理图

图片出自，这篇博客原理也写的很清晰明了。我的实现也是借鉴了这张图

https://www.cnblogs.com/xiaoxi/p/6164383.html

先说一下我的实现思路：

1. 在MyDispatcherServlet中的servlet初始化的时候，绑定标有@MyController注解类下面的@MyRequestMappign的value值和对应的方法。绑定的方式是放在map集合中。这个map集合就是上图说的handlerMapping，返回的handler也就是一组键值对。

2 找到对应的方法后，反射执行方法，在方法中创建一个modelandview对象，model也就是我们说的数据域，view返回的是一个视图名称，也就是我们说的视图域，当然，我这里只有jsp，spring做的很复杂。支持多种类型。最后所谓的渲染，也就是将这个数据域中的数据会添加到request请求中，然后转发。返回客户端。

3 绑定参数模型这一部分略为复杂。在下面讲解

下面是MyDispatcherServlet 

这个servlet的作用就是接收用户请求，然后派发注意标红处bingdingMethodParamters方法，这个方法实现了参数的绑定。

package spring.servlet;

import lombok.extern.slf4j.Slf4j;
import spring.factory.InitBean;
import spring.springmvc.Binding;
import spring.springmvc.Handler;
import spring.springmvc.MyModelAndView;
import spring.springmvc.ViewResolver;
import javax.servlet.ServletContext;
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 java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;
import java.util.Map;
import java.util.Set;
import static spring.springmvc.BindingRequestAndModel.bindingRequestAndModel;
/**
 * Created by Xiao Liang on 2018/6/27.
 */
@WebServlet(name = "MyDispatcherServlet")
@Slf4j
public class MyDispatcherServlet extends HttpServlet {
    /**
     * 初始化servlet，将bean容器和HandlerMapping放到servlet的全局变量中
     */
    @Override
    public void init() {
        InitBean initBean = new InitBean();
        initBean.initBeans();
        //根据bean容器中注册的bean获得HandlerMapping
        Map<String, Method> bindingRequestMapping = Handler.bindingRequestMapping(initBean.beanContainerMap);
        ServletContext servletContext = this.getServletContext();
        servletContext.setAttribute("beanContainerMap", initBean.beanContainerMap);
        servletContext.setAttribute("bindingRequestMapping", bindingRequestMapping);
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            doDispatch(request, response);
        } catch (Exception e) {
            log.error("控制器处理异常");
            e.printStackTrace();
        }
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    //接收到请求后转发到相应的方法上
    private void doDispatch(HttpServletRequest request, HttpServletResponse response) throws IOException, InvocationTargetException, IllegalAccessException, InstantiationException {
        ServletContext servletContext = this.getServletContext();
        //获取扫描controller注解后url和方法绑定的mapping，也就是handlerMapping
        Map<String, Method> bindingRequestMapping =
                (Map<String, Method>) servletContext.getAttribute("bindingRequestMapping");
        //获取实例化的bean容器
        Map<String, Object> beanContainerMap = (Map<String, Object>) servletContext.getAttribute("beanContainerMap");
        String url = request.getServletPath();
        Set<Map.Entry<String, Method>> entries = bindingRequestMapping.entrySet();
        List<Object> resultParameters = Binding.bingdingMethodParamters(bindingRequestMapping, request);
        for (Map.Entry<String, Method> entry :
                entries) {
            if (url.equals(entry.getKey())) {
                Method method = entry.getValue();
                Class<?> returnType = method.getReturnType();
                    //如果返回值是MyModelAndView，开始绑定
                if ("MyModelAndView".equals(returnType.getSimpleName())){
                    Object object = beanContainerMap.get(method.getDeclaringClass().getName());
                    //获取springmvc.xml中配置的视图解析器
                    ViewResolver viewResolver = (ViewResolver) beanContainerMap.get("spring.springmvc.ViewResolver");
                    String prefix = viewResolver.getPrefix();
                    String suffix = viewResolver.getSuffix();
                    MyModelAndView myModelAndView = (MyModelAndView) method.invoke(object, resultParameters.toArray());
                    //将request和model中的数据绑定，也就是渲染视图
                    bindingRequestAndModel(myModelAndView,request);
                    String returnViewName = myModelAndView.getView();
                    //返回的路径
                    String resultAddress = prefix + returnViewName + suffix;
                    try {
                        request.getRequestDispatcher(resultAddress).forward(request,response);
                    } catch (ServletException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}

首先是绑定方法和url，是Handler类，用如下对象绑定

 Map<String, Method> handlerMapping = new ConcurrentHashMap<>();

package spring.springmvc;
import lombok.extern.slf4j.Slf4j;
import spring.Utils.AnnotationUtils;
import spring.annotation.MyController;
import spring.annotation.MyRequestMapping;
import spring.exception.springmvcException;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @ClassName Handler
 * @Description  遍历bean容器，在有controller注解的类中有requestmapping扫描的方法，则将方法和url和方法绑定
 * @Data 2018/7/3
 * @Author xiao liang
 */
@Slf4j
public class Handler {
    public static Map<String, Method> bindingRequestMapping(Map<String, Object> beanContainerMap){
        Map<String, Method> handlerMapping = new ConcurrentHashMap<>();
        if (beanContainerMap != null){
            Set<Map.Entry<String, Object>> entries = beanContainerMap.entrySet();
            for (Map.Entry<String, Object> entry :
                    entries) {
                Class aClass = entry.getValue().getClass();
                Annotation annotation = aClass.getAnnotation(MyController.class);
                Method[] methods = aClass.getMethods();
                if (!AnnotationUtils.isEmpty(annotation) && methods != null){
                    for (Method method:
                            aClass.getMethods()) {
                        MyRequestMapping requestMappingAnnotation = method.getAnnotation(MyRequestMapping.class);
                        if (!AnnotationUtils.isEmpty(requestMappingAnnotation)){
                            String key = requestMappingAnnotation.value();
                            handlerMapping.put(key,method);
                        }
                    }
                }
            }
        }
        else{
            throw new springmvcException("实例化bean异常，没有找到容器");
        }
        return handlerMapping;
    }
}

参数绑定支持

1.@MyRequestMapping（用来绑定简单数据类型）

2.@MyModelAndAttribute（绑定实体类）

3.不写注解，直接写实体类。

下面先贴一下这一部分的结构关系图

这里用多态的设计思想，对于bindingParamter方法写了两种实现，方便大家自行扩展

package spring.springmvc;

import spring.Utils.AnnotationUtils;
import spring.Utils.isBasicTypeUtils;
import spring.annotation.MyModelAttribute;
import spring.annotation.MyRequstParam;
import spring.exception.springmvcException;
import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
/**
 * @ClassName Binding
 * @Description
 * @Data 2018/7/4
 * @Author xiao liang
 */
public class Binding {
    public static  List<Object> bingdingMethodParamters(Map<String, Method> bindingRequestMapping, HttpServletRequest request) {
        List<Object> resultParameters  = new ArrayList<>();
        Set<Map.Entry<String, Method>> entries = bindingRequestMapping.entrySet();
        for (Map.Entry<String, Method> entry :
                entries) {
            Method method = entry.getValue();
            Parameter[] parameters = method.getParameters();
            for (Parameter parameter :
                    parameters) {       //遍历每个参数，如果参数存在注解，将这个参数添加到resultParameters中
                if (!AnnotationUtils.isEmpty(parameter.getAnnotations())){
                    Object resultParameter = null;
                    try {
                        resultParameter = bingdingEachParamter(parameter, request);
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                        throw new springmvcException("绑定参数异常");
                    } catch (NoSuchMethodException e) {
                        e.printStackTrace();
                        throw new springmvcException("绑定参数异常");
                    } catch (InstantiationException e) {
                        e.printStackTrace();
                        throw new springmvcException("绑定参数异常");
                    }
                    resultParameters.add(resultParameter);
                }
            }
        }
        return resultParameters;
    }
 private static Object bingdingEachParamter(Parameter parameter, HttpServletRequest request) throws IllegalAccessException, NoSuchMethodException, InstantiationException {
        //如果注解是MyRequstParam，则用BindingByMyRequstParam来执行装配
        if (!AnnotationUtils.isEmpty(parameter.getAnnotation(MyRequstParam.class))){
            BindingParamter bindingParamter = new BindingByMyRequstParam();
            Object resultParameter = bindingParamter.bindingParamter(parameter, request);
            return resultParameter;
        }
        //如果注解是MyModelAttribute，则用BindingByMyModelAttribute来执行装配
        else if (!AnnotationUtils.isEmpty(parameter.getAnnotation(MyModelAttribute.class))){
            BindingParamter bindingParamter = new BindingByMyModelAttribute();
            Object resultParameter = bindingParamter.bindingParamter(parameter,request);
            return resultParameter;
        }
        //在没有注解的时候，自动识别，如果是基本数据类型用MyRequstParam装配，如果是用户自定义类型用MyModelAttribute装配
        else if(parameter.getAnnotations() == null || parameter.getAnnotations().length ==0){
            boolean flag = isBasicTypeUtils.isBasicType(parameter.getType().getSimpleName());
            if (flag){
                BindingParamter bindingParamter = new BindingByMyRequstParam();
                Object resultParameter = bindingParamter.bindingParamter(parameter, request);
                return resultParameter;
            }
            else{
                BindingParamter bindingParamter = new BindingByMyModelAttribute();
                Object resultParameter = bindingParamter.bindingParamter(parameter,request);
                return resultParameter;
            }
        }
        return null;
    }
}

下面是接口BindingParamter 和两个实现类BindingByMyModelAttribute和BindingByMyRequstParam

package spring.springmvc;

import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Parameter;

/**
 * @ClassName BindingRoles
 * @Description
 * @Data 2018/7/4
 * @Author xiao liang
 */
public interface BindingParamter {

     Object bindingParamter(Parameter parameter, HttpServletRequest request) throws IllegalAccessException, InstantiationException, NoSuchMethodException;

}

package spring.springmvc;

import spring.Utils.StringUtils;
import spring.annotation.MyRequstParam;
import spring.exception.springmvcException;

import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Parameter;

/**
 * @ClassName BindingByMyRequstParam
 * @Description 参数注解是MyMyRequstParam时，绑定数据的类
 * @Data 2018/7/4
 * @Author xiao liang
 */
public class BindingByMyRequstParam implements BindingParamter {
    @Override
    public Object bindingParamter(Parameter parameter, HttpServletRequest request) {
        MyRequstParam myRequstParam = parameter.getAnnotation(MyRequstParam.class);
        //获得注解的value值
        String MyRequstParamValue = myRequstParam.value();
        //获得参数的类名
        String parameterType = parameter.getType().getSimpleName();
        String parameter1 = request.getParameter(MyRequstParamValue);
        if (StringUtils.isEmpty(parameter1)) {
            throw new springmvcException("绑定参数异常");
        }
        //parameter1赋值
        if (parameterType.equals("String")) {
            return parameter1;
        } else if (parameterType.equals("Integer") || parameterType.equals("int")) {
          Integer binddingParameter =  Integer.valueOf(parameter1);
          return binddingParameter;
        }
        return null;
    }


}

package spring.springmvc;

import lombok.extern.slf4j.Slf4j;
import spring.Utils.AnnotationUtils;
import spring.Utils.ConvertUtis;
import spring.Utils.GetMethodName;
import spring.Utils.StringUtils;
import spring.annotation.MyModelAttribute;
import spring.exception.springmvcException;

import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
/**
 * @ClassName BindingByMyModelAttribute
 * @Description 参数注解是MyModelAttribute时，绑定数据的类
 * @Data 2018/7/4
 * @Author xiao liang
 */
@Slf4j
public class BindingByMyModelAttribute implements   BindingParamter {
    @Override
    public Object bindingParamter(Parameter parameter, HttpServletRequest request) throws IllegalAccessException, InstantiationException, NoSuchMethodException {
        MyModelAttribute myModelAttribute = parameter.getAnnotation(MyModelAttribute.class);
        //获得参数的类名
        Class<?> aClass = parameter.getType();
        if (!AnnotationUtils.isEmpty(myModelAttribute)){
            if (!aClass.getSimpleName().equals(myModelAttribute.value())){
                throw new springmvcException("实体类绑定异常，请重新检查");
            }
        }
        Field[] fields = aClass.getDeclaredFields();
        Object object = aClass.newInstance();
        //遍历每个属性，用set注入将值注入到对象中
        for (Field field :
                fields) {
            //获得用户传来的值
            String parameter1 = request.getParameter(field.getName());
            if (!StringUtils.isEmpty(parameter1)){
                //将用户传过来的值转换成对应的参数类型
                Object setObject = ConvertUtis.convert(field.getType().getSimpleName(),parameter1);
                String methodName = GetMethodName.getSetMethodNameByField(field.getName());
                Method method = aClass.getMethod(methodName, field.getType());
                try {
                    //反射set注入
                    method.invoke(object,setObject);
                } catch (InvocationTargetException e) {
                    log.error("{}属性赋值异常",field.getName());
                    e.printStackTrace();
                }
            }
        }
        //返回对注入值后的对象
        return object;
    }
}

绑定完参数，就该返回ModelAndView了，

package spring.springmvc;

import lombok.Data;
/**
 * @ClassName MyModelAndView
 * @Description
 * @Data 2018/7/4
 * @Author xiao liang
 */
@Data
public class MyModelAndView {
    private String view;
    private MyModelMap modelMap;
    public MyModelAndView(String view) {
        this.view = view;
    }
}

view是视图名称，还有viewResolver，用来接收xml文件中定义的前缀和后缀。modelMap是数据域，最后渲染的时候要绑定到request中。

package spring.springmvc;

import lombok.Data;
/**
 * @ClassName ViewResolver
 * @Description 视图解析器 前缀和后缀
 * @Data 2018/7/4
 * @Author xiao liang
 */
@Data
public class ViewResolver {
    private String prefix = "";
    private String suffix = "";
}

最后的渲染类

package spring.springmvc;

import javax.servlet.http.HttpServletRequest;
import java.util.Map;
import java.util.Set;
/**
 * @ClassName BindingRequestAndModel
 * @Description
 * @Data 2018/7/6
 * @Author xiao liang
 */
public class BindingRequestAndModel {
    //遍历modelMap，然后将model中的数据绑定到requst中
    public static void bindingRequestAndModel(MyModelAndView myModelAndView, HttpServletRequest request) {
        MyModelMap myModelMap = myModelAndView.getModelMap();
        if (!myModelMap.isEmpty()){
            Set<Map.Entry<String, Object>> entries1 = myModelMap.entrySet();
            for (Map.Entry<String, Object> entryMap :
                    entries1) {
                String key = entryMap.getKey();
                Object value = entryMap.getValue();
                request.setAttribute(key,value);
            }
        }
    }
}

至此，最后在MyDispatcherServlet中用转发操作将试图返回。

request.getRequestDispatcher(resultAddress).forward(request,response);

此项目上传到了github，需要的童鞋可以自行下载。

https://github.com/836219171/MySSM