手写迷你Spring框架

随着不断地使用Spring,以及后续的Boot、cloud,不断的体会到这个拯救Java的生态体系的强大,也使我对于这个框架有了极大的好奇心,以至于产生了我为什么不能写一个这样的框架的思考。
通过自学及参考谭勇德(Tom)老师的《Spring 5核心原理》这本书,决定记录我手写Spring的过程,记录此系列博客 。
愿每个想探究Spring原理的人,学习道路一帆风顺


Spring最初的时候,其功能远远不如现在强大,甚至我在看Spring最初版本的时候有种这就是所谓的Spring?的疑问,但随后便恍然大悟,我是站立在历史的下游,用后人的眼光去看前人的作品,当然有种站在制高点俯视的感觉,当我一步一步深入学习Spring的设计思想设计理念以及实现方式的时候,无不为前人那惊天地泣鬼神的思想所震撼。

话不多说进入主题:
正常的创建一个web项目就好
在这里插入图片描述

1 准备阶段——自定义配置

1.1 配置application.properties

为了解析方便,我们用application.properties来作为配置文件,内容很简单,如下:

scanPackage=com.gupaoedu.demo

1.2 配置web.xml文件

大家都知道,所有依赖于Web容器的项目都是从读取web.xml文件开始的。

<?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/j2ee" xmlns:javaee="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/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
	version="2.4">
	<display-name>XiaoZhao Web Application</display-name>
	<servlet>
		<servlet-name>zhao mvc</servlet-name>
		<servlet-class>com.xiaoZhao666.mvcframework.v1.servlet.DispatchServlet</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>zhao mvc</servlet-name>
		<url-pattern>/*</url-pattern>
	</servlet-mapping>
</web-app>

其中DispatchServlet是模拟Spring实现的核心功能类

1.3 自定义注解

做就做全套,我们连注解也给他模拟了,在自己包下创建annotation包,下面用的注解都是咱们自己创建的
在这里插入图片描述

1.3.1 @Service

@Target({
    
    ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Service {
    
    
    String value() default "";
}

1.3.2 @Autowired

@Target({
    
    ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {
    
    
    String value() default "";
}

1.3.3 @Controller

@Target({
    
    ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Controller {
    
    
    String value() default "";
}

1.3.4 @RequestMapping

@Target({
    
    ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestMapping {
    
    
    String value() default "";
}

1.3.5 @RequestParam

@Target({
    
    ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {
    
    
    String value() default "";
}

1.4 配置注解

配置业务实现类,此时文件结构如下
在这里插入图片描述
接口:

public interface IDemoService {
    
    
	
	String get(String name);
	
}

实现类:

/**
 * 核心业务逻辑
 */
@Service
public class DemoService implements IDemoService{
    
    

	@Override
	public String get(String name) {
    
    
		return "My name is " + name + ",from service.";
	}

}

配置请求入口DemoAction:

@Controller
@RequestMapping("/demo")
public class DemoAction {
    
    

  	@Autowired
	private IDemoService demoService;

	@RequestMapping("/query")
	public void query(HttpServletRequest req, HttpServletResponse resp,
					  @RequestParam("name") String name){
    
    
		String result = demoService.get(name);
		try {
    
    
			resp.getWriter().write(result);
		} catch (IOException e) {
    
    
			e.printStackTrace();
		}
	}

	@RequestMapping("/add")
	public void add(HttpServletRequest req, HttpServletResponse resp,
					@RequestParam("a") Integer a, @RequestParam("b") Integer b){
    
    
		try {
    
    
			resp.getWriter().write(a + "+" + b + "=" + (a + b));
		} catch (IOException e) {
    
    
			e.printStackTrace();
		}
	}

	@RequestMapping("/remove")
	public String  remove(@RequestParam("id") Integer id){
    
    
		return "" + id;
	}

}

至此,我们的所有配置就算完成了。

2 容器初始化

2.1 实现Spring 1.0版本

1.0版本只是有了一些简单的逻辑,对于以前写Servlet的老同学来说,看着会无比亲切,这一块没啥好说的,Spring的底层就是Servlet嘛。
核心逻辑都在init方法里了,让我们迅速过度到下一阶段2.0版本

public class DispatcherServlet extends HttpServlet {
    
    
    private Map<String,Object> mapping = 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 {
    
    
            doDispatch(req,resp);
        } catch (Exception e) {
    
    
            resp.getWriter().write("500 Exception " + Arrays.toString(e.getStackTrace()));
        }
    }
    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception {
    
    
        String url = req.getRequestURI();
        String contextPath = req.getContextPath();
        url = url.replace(contextPath, "").replaceAll("/+", "/");
        if(!this.mapping.containsKey(url)){
    
    resp.getWriter().write("404 Not Found!!");return;}
        Method method = (Method) this.mapping.get(url);
        Map<String,String[]> params = req.getParameterMap();
        method.invoke(this.mapping.get(method.getDeclaringClass().getName()),new Object[]{
    
    req,resp,params.get("name")[0]});
    }

    //当我晕车的时候,我就不去看源码了

    //init方法肯定干得的初始化的工作
    //inti首先我得初始化所有的相关的类,IOC容器、servletBean
    @Override
    public void init(ServletConfig config) throws ServletException {
    
    
        InputStream is = null;
        try{
    
    
            Properties configContext = new Properties();
            is = this.getClass().getClassLoader().getResourceAsStream(config.getInitParameter("contextConfigLocation"));
            configContext.load(is);
            String scanPackage = configContext.getProperty("scanPackage");
            doScanner(scanPackage);
            for (String className : mapping.keySet()) {
    
    
                if(!className.contains(".")){
    
    continue;}
                Class<?> clazz = Class.forName(className);
                if(clazz.isAnnotationPresent(Controller.class)){
    
    
                    mapping.put(className,clazz.newInstance());
                    String baseUrl = "";
                    if (clazz.isAnnotationPresent(RequestMapping.class)) {
    
    
                        RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
                        baseUrl = requestMapping.value();
                    }
                    Method[] methods = clazz.getMethods();
                    for (Method method : methods) {
    
    
                        if (!method.isAnnotationPresent(RequestMapping.class)) {
    
      continue; }
                        RequestMapping requestMapping = method.getAnnotation(RequestMapping.class);
                        String url = (baseUrl + "/" + requestMapping.value()).replaceAll("/+", "/");
                        mapping.put(url, method);
                        System.out.println("Mapped " + url + "," + method);
                    }
                }else if(clazz.isAnnotationPresent(Service.class)){
    
    
                        Service service = clazz.getAnnotation(Service.class);
                        String beanName = service.value();
                        if("".equals(beanName)){
    
    beanName = clazz.getName();}
                        Object instance = clazz.newInstance();
                        mapping.put(beanName,instance);
                        for (Class<?> i : clazz.getInterfaces()) {
    
    
                            mapping.put(i.getName(),instance);
                        }
                }else {
    
    continue;}
            }
            for (Object object : mapping.values()) {
    
    
                if(object == null){
    
    continue;}
                Class clazz = object.getClass();
                if(clazz.isAnnotationPresent(Controller.class)){
    
    
                    Field [] fields = clazz.getDeclaredFields();
                    for (Field field : fields) {
    
    
                        if(!field.isAnnotationPresent(Autowired.class)){
    
    continue; }
                        Autowired autowired = field.getAnnotation(Autowired.class);
                        String beanName = autowired.value();
                        if("".equals(beanName)){
    
    beanName = field.getType().getName();}
                        field.setAccessible(true);
                        try {
    
    
                            field.set(mapping.get(clazz.getName()),mapping.get(beanName));
                        } catch (IllegalAccessException e) {
    
    
                            e.printStackTrace();
                        }
                    }
                }
            }
        } catch (Exception e) {
    
    
        }finally {
    
    
            if(is != null){
    
    
                try {
    
    is.close();} catch (IOException e) {
    
    
                    e.printStackTrace();
                }
            }
        }
        System.out.print("MVC Framework is init");
    }
    private void doScanner(String scanPackage) {
    
    
        URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll("\\.","/"));
        File classDir = new File(url.getFile());
        for (File file : classDir.listFiles()) {
    
    
            if(file.isDirectory()){
    
     doScanner(scanPackage + "." +  file.getName());}else {
    
    
                if(!file.getName().endsWith(".class")){
    
    continue;}
                String clazzName = (scanPackage + "." + file.getName().replace(".class",""));
                mapping.put(clazzName,null);
            }
        }
    }
}

2.2 实现Spring 2.0版本

让我们迅速过度到2.0版本,改造1.0版本的DispatchServlet。
我们在1.0的版本上进行优化,加入Spring中使用的设计模式(工厂模式,单例模式,委派模式,策略模式),将init()方法中的代码进行封装。按照Spring框架的实现思路,先搭基础框架,再“填肉注血”,具体代码如下:

2.2.1 将init()方法中的代码进行改造

    @Override
    public void init(ServletConfig config) throws ServletException {
    
    
        //1、加载配置文件
        doLoadConfig(config.getInitParameter("contextConfigLocation"));

        //2、扫描相关的类
        doScanner(contextConfig.getProperty("scanPackage"));

        //==============IoC部分==============
        //3、初始化IoC容器,将扫描到的相关的类实例化,保存到IcC容器中
        doInstance();

        //AOP,新生成的代理对象

        //==============DI部分==============
        //4、完成依赖注入
        doAutowired();

        //==============MVC部分==============
        //5、初始化HandlerMapping
        doInitHandlerMapping();

        System.out.println("GP Spring framework is init.");
    }

然后声明全局成员变量,其中IOC容器就是注册时单例的具体案例

2.2.2 在类的开头声明变量

    //保存application.properties配置文件中的内容
    private Properties contextConfig = new Properties();

    //享元模式,缓存
    //保存扫描的所有的类名
    private List<String> classNames = new ArrayList<String>();
    
    //这就是传说中的IOC容器
    //为了简化程序,先不考虑ConcurrentHashMap,主要还是关注设计思想和原理
    //key默认是类名首字母小写,value就是对应的实例对象
    private Map<String,Object> ioc = new HashMap<String,Object>();

    //保存url和Method的对应关系
    private Map<String,Method> handlerMapping = new HashMap<String, Method>();

按照init方法的步骤,实现doLoadConfig()方法:

2.2.3 实现doLoadConfig()方法

    //加载配置文件
    private void doLoadConfig(String contextConfigLocation) {
    
    
        //直接通过类路径找到Spring主配置文件所在的路径,并且将其读取出来放在Properties对象中
        InputStream is = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation);
        try {
    
    
            contextConfig.load(is);
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }finally {
    
    
            if(null != is){
    
    
                try {
    
    
                    is.close();
                } catch (IOException e) {
    
    
                    e.printStackTrace();
                }
            }
        }
    }

2.2.4 实现doScanner()方法

    //扫描相关的类
    private void doScanner(String scanPackage) {
    
    
        //jar 、 war 、zip 、rar
        //转换为文件路径,实际上就是把 . 替换为 / 
        URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll("\\.","/"));
        File classPath = new File(url.getFile());

        //当成是一个ClassPath文件夹
        for (File file : classPath.listFiles()) {
    
    
            if(file.isDirectory()){
    
    
                doScanner(scanPackage + "." + file.getName());
            }else {
    
    
                if(!file.getName().endsWith(".class")){
    
    continue;}
                //全类名 = 包名.类名
                String className = (scanPackage + "." + file.getName().replace(".class", ""));
                //Class.forName(className);
                classNames.add(className);
            }
        }
    }

2.2.5 实现doInstance()方法

doInstance()方法就是工厂模式的具体实现:

    private void doInstance() {
    
    
        //初始化,为DI做准备
        if(classNames.isEmpty()){
    
    return;}

        try {
    
    
            for (String className : classNames) {
    
    
                Class<?> clazz = Class.forName(className);
                //什么样的类才需要初始化呢?———
                // 加了注解的类才初始化>>>模拟Spring框架中的注解开发——
                // 只用@Controller和@Service举例
                if(clazz.isAnnotationPresent(Controller.class)) {
    
    
                    //key提取出来了,把value也搞出来
                    //Spring默认类名首字母小写
                    String beanName = toLowerFirstCase(clazz.getSimpleName());
                    Object instance = clazz.newInstance();
                    ioc.put(beanName, instance);
                }else if(clazz.isAnnotationPresent(Service.class)){
    
    
                    //1、在多个包下出现相同的类名,只能寄几(自己)起一个全局唯一的名字
                    //自定义命名
                    String beanName = clazz.getAnnotation(Service.class).value();
                    if("".equals(beanName.trim())){
    
    
                        beanName = toLowerFirstCase(clazz.getSimpleName());
                    }
                    //2、默认的类名首字母小写
                    Object instance = clazz.newInstance();
                    ioc.put(beanName, instance);
                    //3、如果是接口————投机取巧一下,嘿嘿
                    //判断有多少个实现类,如果只有一个,默认就选择这个实现类
                    //如果有多个,只能抛异常
                    for (Class<?> i : clazz.getInterfaces()) {
    
    
                        if(ioc.containsKey(i.getName())){
    
    
                            throw new Exception("The " + i.getName() + " is exists!!");
                        }
                        //直接把接口的类型当成key
                        ioc.put(i.getName(),instance);
                    }

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

    }

这里为了处理方便,自己实现了toLowerFirstCase()方法,来实现类名首字母小写:

    //自己写,自己用
    private String toLowerFirstCase(String simpleName) {
    
    
        char [] chars = simpleName.toCharArray();
        //之所以要加法,是因为大小写字母的ASCII码相差32
        chars[0] += 32;
        return String.valueOf(chars);
    }

2.2.6 实现doAutowired()方法

.实现依赖注入:

    private void doAutowired() {
    
    
        if(ioc.isEmpty()){
    
    return;}

        for (Map.Entry<String,Object> entry : ioc.entrySet()) {
    
    

            //把所有的包括private/protected/default/public 修饰字段都取出来
            for (Field field : entry.getValue().getClass().getDeclaredFields()) {
    
    
                if(!field.isAnnotationPresent(Autowired.class)){
    
     continue; }

                Autowired autowired = field.getAnnotation(Autowired.class);

                //如果用户没有自定义的beanName,就默认根据类型注入
                String beanName = autowired.value().trim();
                if("".equals(beanName)){
    
    
                    //field.getType().getName() 获取字段的类型
                    beanName = field.getType().getName();
                }

                //暴力访问
                field.setAccessible(true);

                try {
    
    
                    //用反射机制动态给字段赋值
                    field.set(entry.getValue(),ioc.get(beanName));
                } catch (IllegalAccessException e) {
    
    
                    e.printStackTrace();
                }
            }

        }
    }

2.2.7 实现doInitHandlerMapping()方法

这一步其实就到了部分MVC的部分了。另外HandlerMapping是策略模式的案例

    //初始化url和Method的一对一关系
    private void doInitHandlerMapping() {
    
    
        if(ioc.isEmpty()){
    
     return;}

        for (Map.Entry<String,Object> entry : ioc.entrySet()) {
    
    
            Class<?> clazz = entry.getValue().getClass();

            if(!clazz.isAnnotationPresent(Controller.class)){
    
     continue; }


            //相当于提取 class上配置的url
            //也就是@RequestMapping上的路径
            String baseUrl = "";
            if(clazz.isAnnotationPresent(RequestMapping.class)){
    
    
                RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
                baseUrl = requestMapping.value();
            }

            //只获取public的方法
            for (Method method : clazz.getMethods()) {
    
    
                if(!method.isAnnotationPresent(RequestMapping.class)){
    
    continue;}
                //提取每个方法上面配置的url
                RequestMapping requestMapping = method.getAnnotation(RequestMapping.class);

                // //demo//query
                String url = ("/" + baseUrl + "/" + requestMapping.value()).replaceAll("/+","/");
                handlerMapping.put(url,method);
                System.out.println("Mapped : " + url + "," + method);
            }

        }
    }

到这里容器初始化的部分就完成了,接下来只要完成运行时的处理逻辑就行了,一起来写doGet和doPost叭

2.2.8 doGet和doPost的doDispatch

    @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 {
    
    
		//记得刚才init方法的5步吗,这是第六步
        //6、委派,根据URL去找到一个对应的Method并通过response返回
        try {
    
    
            doDispatch(req,resp);
        } catch (Exception e) {
    
    
            e.printStackTrace();
            resp.getWriter().write("500 Exception,Detail : " + Arrays.toString(e.getStackTrace()));
        }

    }

这里doDispatch用到了委派模式,代码如下:

    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception {
    
    
        String url = req.getRequestURI();
        String contextPath = req.getContextPath();
        url = url.replaceAll(contextPath,"").replaceAll("/+","/");
        if(!this.handlerMapping.containsKey(url)){
    
    
            resp.getWriter().write("404 Not Found!!!");
            return;
        }
        Method method = this.handlerMapping.get(url);
        //第一个参数:方法所在的实例
        //第二个参数:调用时所需要的实参
        //保存请求的url参数列表
        Map<String,String[]> params = req.getParameterMap();
        //获取形参列表
        Class<?> [] parameterTypes = method.getParameterTypes();
        //保存赋值参数的位置
        Object [] paramValues = new Object[parameterTypes.length];
        //根据参数位置动态赋值
        for (int i = 0; i < parameterTypes.length; i++) {
    
    
            Class paramterType = parameterTypes[i];
            if(paramterType == HttpServletRequest.class){
    
    
                paramValues[i] = req;
            }else if(paramterType == HttpServletResponse.class){
    
    
                paramValues[i] = resp;
            }else if(paramterType == String.class){
    
    
                //通过运行时的状态去拿到你
                Annotation[] [] pa = method.getParameterAnnotations();
                for (int j = 0; j < pa.length ; j ++) {
    
    
                    for(Annotation a : pa[i]){
    
    
                        if(a instanceof RequestParam){
    
    
                            String paramName = ((RequestParam) a).value();
                            if(!"".equals(paramName.trim())){
    
    
                               String value = Arrays.toString(params.get(paramName))
                                       .replaceAll("\\[|\\]","")
                                       .replaceAll("\\s+",",");
                                paramValues[i] = value;
                            }
                        }
                    }
                }

            }
        }


        //暂时硬编码
        String beanName = toLowerFirstCase(method.getDeclaringClass().getSimpleName());
        //赋值实参列表
        method.invoke(ioc.get(beanName),paramValues);

    }

2.3 实现Spring 3.0版本

在2.0版本中,基本功能已经实现,但是代码还不够优雅,比如HandlerMapping还不能像真正的Spring一样支持正则,url参数还不能支持强制类型转换,在反射调用前还需要重新获取beanName,我们来继续优化

首先改造HandlerMapping,在真实的Spring源码中,HandlerMapping其实是一个List而不是一个Map。List中的元素是自定义类型的。现在我们来仿写这一段,定义一个内部类Handler:

2.3.1 HandlerMapping内部类Handler

    //保存一个url和一个Method的关系
    public class Handler {
    
    
        //必须把url放到HandlerMapping才好理解吧
        private Pattern pattern;  //正则
        private Method method;//保存映射的方法
        private Object controller;//保存方法对应的实例
        private Class<?> [] paramTypes;
        //形参列表
        //参数的名字作为key,参数的顺序,位置作为值
        private Map<String,Integer> paramIndexMapping;

        public Pattern getPattern() {
    
    
            return pattern;
        }

        public Method getMethod() {
    
    
            return method;
        }

        public Object getController() {
    
    
            return controller;
        }

        public Class<?>[] getParamTypes() {
    
    
            return paramTypes;
        }



        public Handler(Pattern pattern, Object controller, Method method) {
    
    
            this.pattern = pattern;
            this.method = method;
            this.controller = controller;

            paramTypes = method.getParameterTypes();

            paramIndexMapping = new HashMap<String, Integer>();
            putParamIndexMapping(method);
        }

        private void putParamIndexMapping(Method method){
    
    

            //提取方法中加了注解的参数
            //把方法上的注解拿到,得到的是一个二维数组
            //因为一个参数可以有多个注解,而一个方法又有多个参数
            Annotation [] [] pa = method.getParameterAnnotations();
            for (int i = 0; i < pa.length ; i ++) {
    
    
                for(Annotation a : pa[i]){
    
    
                    if(a instanceof RequestParam){
    
    
                        String paramName = ((RequestParam) a).value();
                        if(!"".equals(paramName.trim())){
    
    
                            paramIndexMapping.put(paramName, i);
                        }
                    }
                }
            }

            //提取方法中的request和response参数
            Class<?> [] paramsTypes = method.getParameterTypes();
            for (int i = 0; i < paramsTypes.length ; i ++) {
    
    
                Class<?> type = paramsTypes[i];
                if(type == HttpServletRequest.class ||
                        type == HttpServletResponse.class){
    
    
                    paramIndexMapping.put(type.getName(),i);
                }
            }

        }
    }

然后优化HandlerMapping的结构:

    //思考:为什么不用Map
    //你用Map的话,key,只能是url
    //Handler 本身的功能就是把url和method对应关系,已经具备了Map的功能
    //根据设计原则:冗余的感觉了,单一职责,最少知道原则,帮助我们更好的理解
    private List<Handler> handlerMapping = new ArrayList<Handler>();

2.3.2修改doDispatch()方法

    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception {
    
    

       Handler handler = getHandler(req);
       if(handler == null){
    
    
//        if(!this.handlerMapping.containsKey(url)){
    
    
            resp.getWriter().write("404 Not Found!!!");
            return;
        }

        //获得方法的形参列表
        Class<?> [] paramTypes = handler.getParamTypes();

        Object [] paramValues = new Object[paramTypes.length];

        Map<String,String[]> params = req.getParameterMap();
        for (Map.Entry<String, String[]> parm : params.entrySet()) {
    
    
            String value = Arrays.toString(parm.getValue()).replaceAll("\\[|\\]","")
                    .replaceAll("\\s",",");

            if(!handler.paramIndexMapping.containsKey(parm.getKey())){
    
    continue;}

            int index = handler.paramIndexMapping.get(parm.getKey());
            paramValues[index] = convert(paramTypes[index],value);
        }

        if(handler.paramIndexMapping.containsKey(HttpServletRequest.class.getName())) {
    
    
            int reqIndex = handler.paramIndexMapping.get(HttpServletRequest.class.getName());
            paramValues[reqIndex] = req;
        }

        if(handler.paramIndexMapping.containsKey(HttpServletResponse.class.getName())) {
    
    
            int respIndex = handler.paramIndexMapping.get(HttpServletResponse.class.getName());
            paramValues[respIndex] = resp;
        }

        Object returnValue = handler.method.invoke(handler.controller,paramValues);
        if(returnValue == null || returnValue instanceof Void){
    
     return; }
        resp.getWriter().write(returnValue.toString());
    }
    private Handler getHandler(HttpServletRequest req) {
    
    
        if(handlerMapping.isEmpty()){
    
    return null;}
        //绝对路径
        String url = req.getRequestURI();
        //处理成相对路径
        String contextPath = req.getContextPath();
        url = url.replaceAll(contextPath,"").replaceAll("/+","/");


        for (Handler handler : this.handlerMapping) {
    
    
            Matcher matcher = handler.getPattern().matcher(url);
            if(!matcher.matches()){
    
     continue;}
            return handler;
        }
        return null;
    }
    //url传过来的参数都是String类型的,HTTP是基于字符串协议
    //只需要把String转换为任意类型就好
    private Object convert(Class<?> type,String value){
    
    
        //如果是int
        if(Integer.class == type){
    
    
            return Integer.valueOf(value);
        }
        else if(Double.class == type){
    
    
            return Double.valueOf(value);
        }
        //如果还有double或者其他类型,继续加if
        //这时候,我们应该想到策略模式了
        //在这里暂时不实现,希望小伙伴自己来实现
        return value;
    }

3 至此,运行项目

在浏览器中输入:
localhost:8080/demo/query.json?name=XiaoZhao666
就会得到:
在这里插入图片描述
当然真正的Spring要复杂很多,这里只是手写了解一下Spring的基本设计思路和设计模式的应用

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转载自blog.csdn.net/weixin_44688973/article/details/125899117