SpringMVC框架运行机制及实现SpringMVC

一、了解SpringMVC运行流程及九大组件

　　1、SpringMVC的运行流程

　　

 

二、梳理自己的SpringMVC的设计思路

三、实现自己的SpringMVC框架

　　1.项目结构

　　

　　     2.pom.xml

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>www.mxh.com</groupId>
  <artifactId>SpringMVC</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>SpringMVC Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <dependency>
       <groupId>javax.servlet</groupId> 
       <artifactId>javax.servlet-api</artifactId> 
       <version>3.0.1</version> 
       <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <finalName>SpringMVC</finalName>
  </build>
</project>

　　　　3.web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">
    <servlet>
        <servlet-name>MySpringMVC</servlet-name>
        <servlet-class>www.mxh.com.servlet.MyDisPatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>application.properties</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>MySpringMVC</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>

　　4.application.properties

# SpringMVC框架启动扫描组件
scanPackage=www.mxh.com.controller

　　5.自定义注解

　　MyController：

package www.mxh.com.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;
import java.lang.annotation.RetentionPolicy;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MyController {

    /**
     *     表示给controller注册别名
     * @return
     */
    String value() default "";

    
}

　　

　　MyRequestMapping：

package www.mxh.com.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MyRequestMapping {
    
    /**
     *     表示访问该方法的url
     * @return
     */
    String value() default "";
    
}

　　

　　MyRequestParam：

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MyRequestParam {

    /**
     *     表示参数的别名，必填
     * @return
     */
    String value();
    
}

　　

　　TestController

package www.mxh.com.controller;

import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import www.mxh.com.annotation.MyController;
import www.mxh.com.annotation.MyRequestMapping;
import www.mxh.com.annotation.MyRequestParam;

@MyController
@MyRequestMapping("/test")
public class TestController {
    
    @MyRequestMapping("/doTest")
    public void test1(HttpServletRequest request, HttpServletResponse response,
            @MyRequestParam("param") String param){
        System.out.println(param);
        try {
            response.getWriter().write( "doTest method success! param:"+param);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

     @MyRequestMapping("/doTest2")
    public void test2(HttpServletRequest request, HttpServletResponse response){
        try {
            response.getWriter().println("doTest2 method success!");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
}

　　

　　MyDisPatcherServlet：

package www.mxh.com.servlet;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import www.mxh.com.annotation.MyController;
import www.mxh.com.annotation.MyRequestMapping;

@SuppressWarnings("serial")
public class MyDisPatcherServlet extends HttpServlet {
    
    //配置文件
    private Properties properties = new Properties();
    
    //扫描到的组件名
    private List<String> classNames = new ArrayList<String>();
    
    //IoC容器
    private Map<String, Object> ioc = new HashMap<String, Object>();
    
    //handlerMapping
    private Map<String, Method> handlerMapping = new  HashMap<String, Method>();
    
    //controllerMap
    private Map<String, Object> controllerMap  = 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 {
            //处理请求
            doDispatch(req, resp);
        } catch (IOException e) {
            resp.getWriter().write("500 error!! Server Exception");
        }
        
    }

    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        if(handlerMapping.isEmpty()){
            return;
        }

        String url =req.getRequestURI();
        String contextPath = req.getContextPath();

        url=url.replace(contextPath, "").replaceAll("/+", "/");

        if(!this.handlerMapping.containsKey(url)){
            resp.getWriter().write("404 NOT FOUND!");
            return;
        }

        Method method =this.handlerMapping.get(url);

        //获取方法的参数列表
        Class<?>[] parameterTypes = method.getParameterTypes();

        //获取请求的参数
        Map<String, String[]> parameterMap = req.getParameterMap();

        //保存参数值
        Object [] paramValues= new Object[parameterTypes.length];

        //方法的参数列表
        for (int i = 0; i<parameterTypes.length; i++){  
            //根据参数名称，做某些处理  
            String requestParam = parameterTypes[i].getSimpleName();  

            if (requestParam.equals("HttpServletRequest")){  
                //参数类型已明确，这边强转类型  
                paramValues[i]=req;
                continue;  
            }  
            if (requestParam.equals("HttpServletResponse")){  
                paramValues[i]=resp;
                continue;  
            }
            if(requestParam.equals("String")){
                for (Entry<String, String[]> param : parameterMap.entrySet()) {
                    String value =Arrays.toString(param.getValue()).replaceAll("\\[|\\]", "").replaceAll(",\\s", ",");
                    paramValues[i]=value;
                }
            }
        }  
        //利用反射机制来调用
        try {
            method.invoke(this.controllerMap.get(url), paramValues);//第一个参数是method所对应的实例 在ioc容器中
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void init(ServletConfig config) throws ServletException {
        // TODO Auto-generated method stub
        super.init(config);
        
        //1.加载配置文件
        doLoadConfig(config.getInitParameter("contextConfigLocation"));

        //2.初始化所有相关联的类,扫描用户设定的包下面所有的类
        doScanner(properties.getProperty("scanPackage"));

        //3.拿到扫描到的类,通过反射机制,实例化,并且放到ioc容器中(k-v  beanName-bean) beanName默认是首字母小写
        doInstance();

        //4.初始化HandlerMapping(将url和method对应上)
        initHandlerMapping();
    }

    /**
     *     初始化HandMapping 将url与method对应上
     */
    private void initHandlerMapping() {
        if(ioc.isEmpty()){
            return;
        }
        try {
            for (Entry<String, Object> entry: ioc.entrySet()) {
                Class<? extends Object> clazz = entry.getValue().getClass();
                if(!clazz.isAnnotationPresent(MyController.class)){
                    continue;
                }

                //拼url时,是controller头的url拼上方法上的url
                String baseUrl ="";
                if(clazz.isAnnotationPresent(MyRequestMapping.class)){
                    MyRequestMapping annotation = clazz.getAnnotation(MyRequestMapping.class);
                    baseUrl=annotation.value();
                }
                Method[] methods = clazz.getMethods();
                for (Method method : methods) {
                    if(!method.isAnnotationPresent(MyRequestMapping.class)){
                        continue;
                    }
                    MyRequestMapping annotation = method.getAnnotation(MyRequestMapping.class);
                    String url = annotation.value();

                    url =(baseUrl+"/"+url).replaceAll("/+", "/");
                    handlerMapping.put(url,method);
                    controllerMap.put(url,clazz.newInstance());
                    System.out.println(url+","+method);
                }

            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     *     实例化对象并注入IoC容器
     */
    private void doInstance() {
        if (classNames.isEmpty()) {
            return;
        }   
        for (String className : classNames) {
            try {
                //把类搞出来,反射来实例化(只有加@MyController需要实例化)
                Class<?> clazz =Class.forName(className);
               if(clazz.isAnnotationPresent(MyController.class)){
                    ioc.put(toLowerFirstWord(clazz.getSimpleName()),clazz.newInstance());
                }else{
                    continue;
                }

            } catch (Exception e) {
                e.printStackTrace();
                continue;
            }
        }
    }

    /**
     *     把字符串的首字母小写
     * @param name
     * @return
     */
    private String toLowerFirstWord(String simpleName) {
         char[] charArray = simpleName.toCharArray();
         charArray[0] += 32;
         return String.valueOf(charArray);
    }

    /**
     *     扫描包下的类
     * @param packageName
     */
    private void doScanner(String packageName) {
        //把所有的.替换成/
        URL url  =this.getClass().getClassLoader().getResource("/"+packageName.replaceAll("\\.", "/"));
        File dir = new File(url.getFile());
        for (File file : dir.listFiles()) {
            if(file.isDirectory()){
                //递归读取包
                doScanner(packageName+"."+file.getName());
            }else{
                String className =packageName +"." +file.getName().replace(".class", "");
                classNames.add(className);
            }
        }
    }

    /**
     *     加载配置文件
     * @param initConfig
     */
    private void doLoadConfig(String initConfig) {
        //把web.xml中的contextConfigLocation对应value值的文件加载到流里面
        InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(initConfig);
        try {
            //用Properties文件加载文件里的内容
            properties.load(resourceAsStream);
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //关流
            if(null!=resourceAsStream){
                try {
                    resourceAsStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    
    
}

 

posted @ 2019-07-09 22:05  尘世间迷茫的小书童  阅读(599)  评论(0)    收藏  举报