首先了解一下SpringBean的生命周期：
937513-20160507202024015-234747937.png
工程目录结构如图所示:
jjmvc.PNG
注解类JJAutowired：
package jj.mvc.anonation;
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;
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target({ElementType.FIELD})
public @interface JJAutowired {
String value() default "";
}
注解类JJController：
package jj.mvc.anonation;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target({ElementType.TYPE})
public @interface JJController {
String value() default "";
}
注解类JJRequestMapping：
package jj.mvc.anonation;
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;
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target({ElementType.TYPE,ElementType.METHOD})
public @interface JJRequestMapping {
String value() default "";
}
注解类JJService：
package jj.mvc.anonation;
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;
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target({ElementType.TYPE})
public @interface JJService {
String value() default "";
}
controller实现，我们的请求派发入口:
package jj.mvc.controller;
import jj.mvc.anonation.JJAutowired;
import jj.mvc.anonation.JJController;
import jj.mvc.anonation.JJRequestMapping;
import jj.mvc.anonation.JJService;
@JJController
@JJRequestMapping("jj/mv/controller")
public class BaseController {
@JJAutowired
private MyService myservice;
@JJRequestMapping("/test1")
public String test1(String name) {
return "hello "+name;
}
}
简单的service接口和实现：
package jj.mvc.service;
public interface MyService {
String doService(String name);
}
下面实现mvc核心的servlet相关：
首先是web.xml:
Archetype Created Web Application
jjmvc
org.springframework.web.servlet.DispatcherServlet
contextConfigLocation
configMVC.properties
1
jjmvc
/*
配置文件configMVC.properties很简单，一个mvc包扫描字面量：
scanBase=jj.mvc
适配器类：
package jj.mvc.servlet;
import java.lang.reflect.Method;
public class HandlerAdapter {
Class handlerClazz ;
Method handlerMethod;
String[] parameters;
public Class getHandlerClazz() {
return handlerClazz;
}
public void setHandlerClazz(Class handlerClazz) {
this.handlerClazz = handlerClazz;
}
public Method getHandlerMethod() {
return handlerMethod;
}
public void setHandlerMethod(Method handlerMethod) {
this.handlerMethod = handlerMethod;
}
public String[] getParameters() {
return parameters;
}
public void setParameters(String[] parameters) {
this.parameters = parameters;
}
}
最重要的代码,servlet，重点看doDispatch方法实现:
package jj.mvc.servlet;
import jj.mvc.anonation.JJAutowired;
import jj.mvc.anonation.JJController;
import jj.mvc.anonation.JJRequestMapping;
import jj.mvc.anonation.JJService;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
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.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.*;
import java.util.Map.Entry;
public class JJservlet extends HttpServlet{
/**
*
*/
private static final long serialVersionUID = 1L;
private Properties properties=new Properties() ;
private List> clazzList=new ArrayList>();
private Map beanMap=new HashMap();
private Map requestMapping=new HashMap();
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
super.doPost(req, resp);
}
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
try {
Object result=doDispatch(req,resp);
resp.getWriter().println(result);
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void init(ServletConfig config) throws ServletException {
// TODO Auto-generated method stub
super.init(config);
//contextConfigLocation属性时我们在web.xml里注册过的。对应于本案例就是 "configMVC.properties"
String contextConfigLocation=config.getInitParameter("contextConfigLocation");
try {
properties.load(this.getClass().getResourceAsStream(contextConfigLocation));
//我们在configMVC.properties配置的scanBase属性值。
String scanBase=properties.getProperty("scanBase");
//其实就是springMVC的 beanEntry: beanMap.entrySet()) {
Object bean = beanEntry.getValue();
//如果一个bean的属性有autowired注解，那么需要从beanMap中拿出来把它装配进bean
for(Field beanFiled : bean.getClass().getFields()) {
if(beanFiled.isAnnotationPresent(JJAutowired.class)) {
/*System.out.println("beanFiled:"+beanFiled.getType().getName());
System.out.println("beanFiled Simple:"+beanFiled.getType().getSimpleName());*/
//请注意，这里有个问题，如果是被@autowired()注解的bean在initBean时，其beanName不是类名，那么无法装进来，除非实现对@Qualifier注解或者@Resource的提取，这里就不讨论了
String beanFiledType=beanFiled.getType().getSimpleName();
//反射装配
beanFiled.set(bean, beanMap.get(beanFiledType));
}
}
}
}
public void doRequestMapping() {
for(Class clazz:clazzList) {
//映射表注册,因为@JJRequestMapping都在@JJController中，所以遍历@JJController修饰的类
if(clazz.isAnnotationPresent(JJController.class)) {
String urlbase="";
if(clazz.isAnnotationPresent(RequestMapping.class)) {
urlbase=clazz.getAnnotation(JJRequestMapping.class).value();
}
//实际上springMVC的实现不是这样的，估计会加上method.getModifiers()，应该是拿到当前类的public方法，也是为什么非public方法无法做controller映射的原因
for(Method method:clazz.getDeclaredMethods()) {
if(method.isAnnotationPresent(JJRequestMapping.class)) {
//urlMapping = 类的公共JJRequestMapping+方法JJRequestMapping
String urlMapping=urlbase+method.getAnnotation(JJRequestMapping.class).value();
//把处理类，处理方法封装成handlerAdapter，并绑定相应url添加入requestMapping
HandlerAdapter handlerAdapter=new HandlerAdapter();
handlerAdapter.setHandlerClazz(clazz);
handlerAdapter.setHandlerMethod(method);
requestMapping.put(urlMapping, handlerAdapter);
}
}
}
}
}
public Object doDispatch(HttpServletRequest req, HttpServletResponse resp) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {
String url=req.getRequestURI();
//拿到请求参数构建一个入参Map，这里我们只考虑普通的x-www-form-urlencoded提交，其他有关文件和其他流式的方式不做实现
Map parametersMap= req.getParameterMap();
//构建入参数组
String[][] parameters=new String[parametersMap.size()][];
int i=0;
//填充入参数组
for(Entry paraSet : parametersMap.entrySet()) {
parameters[i++]=paraSet.getValue();
}
//requestMapping是一个的map,这是我们通过@JJController的@JJRequestMapping()里的值实现的，servlet在初始化时就已经把映射关系注入了这个map
HandlerAdapter handlerAdapter=requestMapping.get(url);
if(handlerAdapter!=null) {
/**
* 实际SpringMVC的处理很复杂，不是返回一个执行方法这么简单，大家可以去看看源码，大致通过一下几步：
* 1.将映射请求注册到处理器HandlerMapping;
* 2.HandlerMapping会把请求url映射为HandlerExecutionChain类型的handler对象;（包含过滤器的整个执行链）
* 3.将handler对象作为参数传递给HandlerAdapter的实例化对象，调用其handler方法会生成一个ModelAndView对象;并且在这个过程会有过滤器的环绕执行
* 我们这里只是简易的实现,并且也没有抽象成ModelAndView视图对象
*/
Method invokeMethod=handlerAdapter.getHandlerMethod();
//反射调用相关方法，注意：我们这里因为没有ModelAndView所以也就没有做视图处理，service 方法只是单纯的把方法return值通过流写回去。
return invokeMethod.invoke(handlerAdapter.getHandlerClazz(), handlerAdapter.getParameters());
}else {
//找不到则抛出错误；说明该url没有相关JJRequestMapping注册过
throw new IllegalAccessException();
}
}
}
HandlerExecutionChain.png