手写springmvc框架

思路：

1.编写servlet用来接收前端所有请求

    1.1 扫描contrller包 ，返回list 集合

    1.2 遍历list集合 得出 所有 contrller 类 与 方法，分辨用两个集合装，key为 请求路径

下面是代码：

package com.springmvc.servlet;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.springmvc.annotation.ZPController;
import com.springmvc.annotation.ZPRequestMapping;

/**
 * 2018年6月4日10:27:19
 * @author 
 *
 */
public class DispatcherServlet extends HttpServlet{

	private static final long serialVersionUID = 1L;
	
	private List<String> packageNames = new ArrayList<String>(); //所有的类
	private Map<String, Object> instanceMap = new HashMap<String, Object>();  //所有的contrller
	private Map<String, Object> handerMap = new HashMap<String, Object>();    //与url关联的方法

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

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		
		String url = req.getRequestURI();  
        String context = req.getContextPath();  
        String path = url.replace(context, "");  
        Method method = (Method) handerMap.get(path);  
        
        //如果url key没有匹配的方法，就提示404
        if(method==null){
        	resp.getWriter().write("not find 404");
        	return;
        }
        
        //根据url key 获得 contrllor
        Object obj = instanceMap.get(path);

        try {  
        	//根据url key 调用对应处理方法
            Object rest = method.invoke(obj);
            resp.getWriter().write(rest.toString());
        } catch (IllegalAccessException e) {  
            e.printStackTrace();  
        } catch (IllegalArgumentException e) {  
            e.printStackTrace();  
        } catch (InvocationTargetException e) {  
            e.printStackTrace();  
        }  
		
	}

	@Override
	public void init() throws ServletException {
		//扫描contrller
        scanPackage("com.springmvc.contrller");  
        try {  
//            filterAndInstance();  
        	
        	//url 关联 方法 
            handerMap();  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
        
	}
	
	private String replaceTo(String path) {  
        return path.replaceAll("\\.", "/");  
    }
	
	private void scanPackage(String Package) {  
        URL url = this.getClass().getClassLoader().getResource("/" + replaceTo(Package));
        String pathFile = url.getFile();  
        File file = new File(pathFile);  
        String fileList[] = file.list();  
        for (String path : fileList) {  
            File eachFile = new File(pathFile + path);  
            if (eachFile.isDirectory()) {  
                scanPackage(Package + eachFile.getName());  
            } else {  
                packageNames.add(Package + "." + eachFile.getName());  
            }  
        }  
    }  
	
	private void filterAndInstance() throws Exception {  
        if (packageNames.size() <= 0) {  
            return;  
        }  
        for (String className : packageNames) {  
            Class<?> cName = Class.forName(className.replace(".class", "").trim());  
            if (cName.isAnnotationPresent(ZPController.class)) {  
                Object instance = cName.newInstance();  
                ZPController controller = (ZPController) cName.getAnnotation(ZPController.class);  
                String key = controller.value();  
                instanceMap.put(key, instance);  
            }  else {  
                continue;  
            }  
        }  
    }  
	
    private void handerMap() throws ClassNotFoundException, InstantiationException, IllegalAccessException {  
        if (packageNames.size() <= 0) {  
            return;  
        }  
        
        //遍历所有contrller 
        for (String className : packageNames) {  
            Class<?> cName = Class.forName(className.replace(".class", "").trim());  
            
            //判断哪些类，有加 @contrller 注解
            if (cName.isAnnotationPresent(ZPController.class)) {  
            	
            	//取出累上面的 @ZPRequestMapping 注解值
            	ZPRequestMapping requestMapping = (ZPRequestMapping) cName.getAnnotation(ZPRequestMapping.class);  
            	String ctvalue = "";
            	
            	if(requestMapping!=null){
            		ctvalue = requestMapping.value();  
            	}
            	
            	
            	//取出类里面的 所有方法
                Method[] methods = cName.getMethods();  
                
                for (Method method : methods) {  
                	
                	//判断哪些方法 有加 @ZPRequestMapping
                    if (method.isAnnotationPresent(ZPRequestMapping.class)) {  
                    	//取出注解值
                    	ZPRequestMapping rm = (ZPRequestMapping) method.getAnnotation(ZPRequestMapping.class);  
                        String rmvalue = rm.value();  
                        
                        //拼接 类的 @ZPRequestMapping 值与 方法上面的@ZPRequestMapping 当成key
                        //别人添加 类 与 方法，url路径当成key 
                        handerMap.put(ctvalue + rmvalue, method);  
                        instanceMap.put(ctvalue + rmvalue, cName.newInstance());  
                    } else {  
                        continue;  
                    }  
                }  
            } else {  
                continue;  
            }  
  
        }  
    }  

	
}

Contrller 注解：

package com.springmvc.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 })  
@Retention(RetentionPolicy.RUNTIME)  
@Documented  
public @interface ZPController {
	String value() default "";
}

RequestMapping 注解：

package com.springmvc.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 ZPRequestMapping {
	String value() default "";  
}

例子  Contrller 类：

package com.springmvc.contrller;

import com.springmvc.annotation.ZPController;
import com.springmvc.annotation.ZPRequestMapping;

@ZPController
public class MyContrller {
	
	@ZPRequestMapping("/test")
	public String test(){
		System.out.println("22222222222222222222");
		return "1111111111111";
	}
}

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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.test</groupId>
  <artifactId>demo2</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  
  
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
	<dependency>
	    <groupId>javax.servlet</groupId>
	    <artifactId>javax.servlet-api</artifactId>
	    <version>3.1.0</version>
	    <scope>provided</scope>
	</dependency>
    
  </dependencies>
</project>