1.新建maven项目 2.到pom中添加servlet依赖
<groupId>com.justin.springmvc</groupId> <artifactId>springmvc</artifactId> <version>1.0-SNAPSHOT</version> <packaging>war</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> </dependencies> </project> 3.新建web.xml文件(src下main下webapp下WEB-INF下)
<?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" 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>com.justin.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.新建application.properties文件(resources下) 配置待扫描的包
scanPackage=com.justin.core 5.新建包com.justin.annotation 6.创建自己的controller注解
package com.justin.annotation; import java.lang.annotation.*; @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyController { /** * 给MyController注册别名 * * @return 别名 */ String value() default ""; }
7.创建自己的MyRequestMapping注解
package com.justin.annotation; import java.lang.annotation.*; @Target({ElementType.TYPE, ElementType.METHOD}) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyRequestMapping { /** * 访问该方法的url * * @return url */ String value() default ""; }
8.创建自己的MyRequestParam
package com.justin.annotation; import java.lang.annotation.*; @Target(ElementType.PARAMETER) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyRequestParam { /** * 参数的别名,必填 * * @return 别名 */ String value(); }
9.新建com.justin.servlet包 10.新建MyDispatcherServlet
package com.justin.servlet; import com.justin.annotation.MyController; import com.justin.annotation.MyRequestMapping; 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.io.InputStream; import java.lang.reflect.Method; import java.net.URL; import java.util.*; public class MyDispatcherServlet extends HttpServlet { private Properties properties = new Properties(); private List<String> classNames = new ArrayList<>(); private Map<String, Object> ioc = new HashMap<>(); private Map<String, Method> handlerMapping = new HashMap<>(); private Map<String, Object> conntrollerMap = new HashMap<>(); @Override public void init(ServletConfig config) throws ServletException { //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(); } @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 (Exception e) { resp.getWriter().write("500!! Server Exception"); } } private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception { 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 (Map.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 { //第一个参数是method所对应的实例 在ioc容器中 method.invoke(this.conntrollerMap.get(url), paramValues); } catch (Exception e) { e.printStackTrace(); } } private void doLoadConfig(String location) { //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(location); try { properties.load(resourceAsStream); } catch (IOException e) { e.printStackTrace(); } finally { if (null != resourceAsStream) { try { resourceAsStream.close(); } catch (IOException e) { e.printStackTrace(); } } } } 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()) { doScanner(packageName + "." + file.getName()); } else { String className = packageName + "." + file.getName().replace(".class", ""); classNames.add(className); } } } 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; } } } private void initHandlerMapping() { if (ioc.isEmpty()) { return; } try { for (Map.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); conntrollerMap.put(url, clazz.newInstance()); System.out.println(url + "," + method); } } } catch (Exception e) { e.printStackTrace(); } } /** * 把字符串的首字母小写 * * @param name 代转字符串 * @return 转出结果 */ private String toLowerFirstWord(String name) { char[] charArray = name.toCharArray(); charArray[0] += 32; return String.valueOf(charArray); } }
11.新建com.justin.core.controller 12.新建TestController
package com.justin.core.controller; import com.justin.annotation.MyController; import com.justin.annotation.MyRequestMapping; import com.justin.annotation.MyRequestParam; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @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(); } } }
13.大功告成,通过tomcat或jetty启动项目 14.访问localhost:8080/test/doTest?param=justin 15.没报异常错误则说明构建成功,否则请根据异常自行检查!