初始化

.gitignore

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+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

.idea/.gitignore

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+# 默认忽略的文件
+/shelf/
+/workspace.xml
+# 基于编辑器的 HTTP 客户端请求
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

.idea/aws.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="accountSettings">
+    <option name="activeRegion" value="us-east-1" />
+    <option name="recentlyUsedRegions">
+      <list>
+        <option value="us-east-1" />
+      </list>
+    </option>
+  </component>
+</project>

.idea/encodings.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Encoding">
+    <file url="file://$PROJECT_DIR$/src/main/java" charset="UTF-8" />
+    <file url="file://$PROJECT_DIR$/src/main/resources" charset="UTF-8" />
+  </component>
+</project>

.idea/misc.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CodeInsightWorkspaceSettings">
+    <option name="optimizeImportsOnTheFly" value="true" />
+  </component>
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="MarkdownSettingsMigration">
+    <option name="stateVersion" value="1" />
+  </component>
+  <component name="MavenProjectsManager">
+    <option name="originalFiles">
+      <list>
+        <option value="$PROJECT_DIR$/pom.xml" />
+      </list>
+    </option>
+  </component>
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" project-jdk-name="17" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

.idea/vcs.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>

pom.xml

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+<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>com.brave</groupId>
+  <artifactId>untitled7</artifactId>
+  <packaging>war</packaging>
+  <version>1.0-SNAPSHOT</version>
+  <name>untitled7 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>4.0.1</version>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.reflections</groupId>
+      <artifactId>reflections</artifactId>
+      <version>0.9.11</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-maven-plugin</artifactId>
+      <version>2.5.2</version>
+    </dependency>
+
+
+
+
+  </dependencies>
+  <build>
+    <resources>
+      <resource>
+        <directory>src/main/java</directory>
+        <includes>
+          <include>**/*.*</include>
+        </includes>
+      </resource>
+      <resource>
+        <directory>src/main/resources</directory>
+        <includes>
+          <include>**/*.*</include>
+        </includes>
+      </resource>
+    </resources>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+        <version>2.5.2</version>
+      </plugin>
+    </plugins>
+  </build>
+
+
+</project>

src/main/java/com/brave/annotation/MyController.java

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+package com.brave.annotation;
+
+
+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)
+public @interface MyController {
+
+
+    String value() default "";
+}

src/main/java/com/brave/annotation/MyRequestMapping.java

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+package com.brave.annotation;
+
+
+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)
+public @interface MyRequestMapping {
+
+    String value() default "";
+}

src/main/java/com/brave/controller/TestController.java

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+package com.brave.controller;
+
+import com.brave.annotation.MyController;
+import com.brave.annotation.MyRequestMapping;
+
+@MyRequestMapping(value = "/test")
+@MyController
+public class TestController {
+
+    @MyRequestMapping(value = "/test1")
+    public void test1() {
+        System.out.println("test1被调用");
+    }
+
+    @MyRequestMapping(value = "/test2")
+    public void test2() {
+        System.out.println("test2被调用了");
+    }
+
+    @MyRequestMapping(value = "/test3")
+    public void test3(){
+        System.out.println("test3被调用了");
+    }
+}

src/main/java/com/brave/servlet/MyDispatcherServlet.java

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+package com.brave.servlet;
+
+import com.brave.annotation.MyController;
+import com.brave.annotation.MyRequestMapping;
+import org.reflections.Reflections;
+
+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.IOException;
+import java.io.InputStream;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.*;
+
+public class MyDispatcherServlet extends HttpServlet {
+    /**
+     * 配置扫描的包，放到一个.properties文件中，在初始化的时候读取
+     */
+    private Properties properties=new Properties();
+
+    /**
+     * 需要一个set，把所有能够相应controller的存起来
+     */
+    private Set<Class<?>> classSet=new HashSet<>();
+
+    /**
+     * SpringMVC容器
+     */
+    private Map<String, Object> springMVCContext=new HashMap<>();
+
+
+    /**
+     * 映射处理器，存储所有的方法
+     */
+    private Map<String, Method> handlerMapping=new HashMap<>();
+
+    /**
+     * 后端处理器的映射关系，存储所有controller
+     */
+    private Map<String,Object> controllerMap=new HashMap<>();
+
+
+    @Override
+    public void init(ServletConfig config) throws ServletException {
+        //加载配置文件，在web.xml中配置的初始化参数contextfigLocation
+        String initParameter = config.getInitParameter("contextConfigLocation");
+        try {
+            loadConfigFile(initParameter);
+        }catch (Exception e){
+            e.printStackTrace();
+        }
+
+        //扫描controller
+        scanPackage(properties.getProperty("package"));
+
+        //初始化controller包
+        initController();
+        //初始化处理器映射器
+        initHandlerMapping();
+    }
+
+    @Override
+    protected void service(HttpServletRequest req, HttpServletResponse resp){
+        //处理请求
+        if (handlerMapping.isEmpty()){
+            return;
+        }
+
+        //获取url
+        String uri = req.getRequestURI();
+        String contextPath = req.getContextPath();
+        String url = uri.replace(contextPath, "");
+        if (!handlerMapping.containsKey(url)){
+            try {
+                resp.getWriter().println("404");
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }else {
+            Method method = handlerMapping.get(url);
+            Object controller = controllerMap.get(url);
+            try {
+                method.invoke(controller);
+            } catch (IllegalAccessException e) {
+                throw new RuntimeException(e);
+            } catch (InvocationTargetException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    private void initHandlerMapping() {
+        if (springMVCContext.isEmpty()){
+            return;
+        }
+
+        for (Map.Entry<String, Object> entry : springMVCContext.entrySet()) {
+            //获取class对象
+            Class<?> aClass = entry.getValue().getClass();
+            if (!aClass.isAnnotationPresent(MyController.class)){
+                continue;
+            }else {
+                String baseUrl="";
+                if (aClass.isAnnotationPresent(MyRequestMapping.class)){
+                    //如果类包含注解MyRequestMapping，获取注解值
+                    MyRequestMapping annotation = aClass.getAnnotation(MyRequestMapping.class);
+                    baseUrl=annotation.value();
+                }
+
+                //获取所有方法
+                Method[] methods=aClass.getMethods();
+                for (Method method : methods) {
+                    //判断方法上含有MyRequestMapping注解
+                    if (method.isAnnotationPresent(MyRequestMapping.class)){
+                        MyRequestMapping annotation = method.getAnnotation(MyRequestMapping.class);
+                        String url = annotation.value();
+                        url = baseUrl +url;
+
+                        //将该放入方法集
+                        handlerMapping.put(url,method);
+
+                        try {
+                            //放入controllerMap中
+                            controllerMap.put(url,aClass.newInstance());
+                        } catch (InstantiationException e) {
+                            throw new RuntimeException(e);
+                        } catch (IllegalAccessException e) {
+                            throw new RuntimeException(e);
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    private void initController() {
+        if (classSet.isEmpty()){
+            return;
+        }
+        for (Class<?> controller : classSet) {
+            try {
+                springMVCContext.put(lowerFirstWord(controller.getSimpleName()), controller.newInstance());
+            } catch (InstantiationException e) {
+                throw new RuntimeException(e);
+            } catch (IllegalAccessException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    private String lowerFirstWord(String simpleName) {
+        char[] array = simpleName.toCharArray();
+        array[0] +=32;
+        return String.valueOf(array);
+    }
+
+    private void scanPackage(String packageName) {
+        Reflections reflections = new Reflections(packageName);
+        classSet=reflections.getTypesAnnotatedWith(MyController.class);
+    }
+
+
+    private void loadConfigFile(String fileName) {
+        //以流的方式获取资源
+        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(fileName);
+
+        try {
+            properties.load(inputStream);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }finally {
+            try {
+                inputStream.close();
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+    }
+}

src/main/webapp/WEB-INF/web.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
+         version="4.0">
+
+  <!-- 配置我们自己的前端控制器，MyDispatcherServlet就是一个servlet，拦截前端发送的请求-->
+  <servlet>
+    <servlet-name>dispatcherServlet</servlet-name>
+    <servlet-class>com.brave.servlet.MyDispatcherServlet</servlet-class>
+    <!--        配置扫描包-->
+    <init-param>
+      <param-name>contextConfigLocation</param-name>
+      <param-value>application.properties</param-value>
+    </init-param>
+  </servlet>
+  <servlet-mapping>
+    <servlet-name>dispatcherServlet</servlet-name>
+    <!-- 拦截所有请求-->
+    <url-pattern>/</url-pattern>
+  </servlet-mapping>
+</web-app>

src/main/webapp/index.jsp

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+<html>
+<body>
+<h2>Hello World!</h2>
+</body>
+</html>