深度分析！深入浅出总结手撕SpringMVC要点，建议收藏
2021-01-09 本文已影响0人
996小迁
SpringMVC
你对SpringMVC了解多少呢？SpringMVC可以说得上是当前最优秀的MVC框架，采用了松散耦合可插拔组件结构，比其他MVC框架更具扩展性和灵活性；为了提高框架的扩展性和灵活性，设计了松耦合可插拔的组件。理解SpringMVC的原理，在面试或工作中都十分的重要。
SpringMVC的原理在网络上到处都可以找得到，但是写得都很概括、零散；对应阅读源码经验较少的小伙伴来说，自己去看源码被很多细节所干扰阻碍，不能够很好地抽离出springMVC原理的主线。
下面就给大家分享一下LZ整理的有关SpringMVC的学习资料，学会用代码说话！
1、创建过程与文件目录
1.1、创建Maven工程
深度分析！深入浅出总结手撕SpringMVC要点，建议收藏
深度分析！深入浅出总结手撕SpringMVC要点，建议收藏
深度分析！深入浅出总结手撕SpringMVC要点，建议收藏
深度分析！深入浅出总结手撕SpringMVC要点，建议收藏
2、pom依赖与配置文件
2.1、pom依赖
<?xml version="1.0" encoding="UTF-8"?>
<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.zhz</groupId>
<artifactId>simulation-springmvc</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<name>simulation-springmvc Maven Webapp</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
<version>1.6.1</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.5</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.12</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.1</version>
</dependency>
</dependencies>
<build>
<finalName>simulation-springmvc</finalName>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
2.2、springmvc配置类
<?xml version="1.0" encoding="UTF-8" ?>
<beans>
<!--配置创建容器时要扫描的包-->
<component-scan base-package="com.zhz.controller,com.zhz.service"></component-scan>
</beans>
2.3、web.xml
<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
<display-name>Archetype Created Web Application</display-name>
<!--配置前端控制器-->
<servlet>
<servlet-name>DispatcherServlet</servlet-name>
<servlet-class>com.zhz.springmvc.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc.xml</param-value>
</init-param>
<!--Web服务器一旦启动，Servlet就会实例化创建对象，然后初始化(预备创建对象)-->
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>DispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
3、实体类（User）
实体类：User.java
package com.zhz.bean;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
/**
* @author ：zhz
* @date ：Created in 2021/01/04
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description: 实体类
**/
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
private Integer id;
private String name;
private String password;
}
4、控制器（UserController）
package com.zhz.controller;
import com.zhz.bean.User;
import com.zhz.service.UserService;
import com.zhz.springmvc.annotation.Autowired;
import com.zhz.springmvc.annotation.Controller;
import com.zhz.springmvc.annotation.RequestMapping;
import com.zhz.springmvc.annotation.ResponseBody;
/**
* @author ：zhz
* @date ：Created in 2021/01/03
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description: 控制器
**/
@Controller
public class UserController {
@Autowired(value = "userService")
private UserService userService;
@RequestMapping("/listUsers")
public String listUsers(){
userService.listUsers();
return "forward:/success.jsp";
}
@RequestMapping("/getData")
@ResponseBody //返回json格式的数据
public User getData(){
//调用服务层
return userService.getUser();
}
}
5、业务处理类与实现类（UserService，UserServiceImpl）
package com.zhz.service;
import com.zhz.bean.User;
/**
* @author ：zhz
* @date ：Created in 2021/01/03
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description:
**/
public interface UserService {
void listUsers();
User getUser();
}
package com.zhz.service.impl;
import com.zhz.bean.User;
import com.zhz.service.UserService;
import com.zhz.springmvc.annotation.Service;
/**
* @author ：zhz
* @date ：Created in 2021/01/03
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description:
**/
@Service("userService")
public class UserServiceImpl implements UserService {
@Override
public void listUsers() {
System.out.println("===调用===UserServiceImpl===listUser===");
}
@Override
public User getUser() {
return new User(1,"zhz","123456");
}
}
6、手撕mvc具体代码
6.1、核心annotation注解
package com.zhz.springmvc.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* @Retention注解表示Annotation的保留策略 RetentionPolicy.Class：运行时不保留，不可以通过反射读取。
* RetentionPolicy.RUNTIME：运行是保留，可以通过反射读取。
* RetentionPolicy.SOURCE：丢弃。
*/
@Target(value = ElementType.FIELD) //作用在属性上
@Retention(value = RetentionPolicy.RUNTIME)
public @interface Autowired {
String value();
}
package com.zhz.springmvc.annotation;
import java.lang.annotation.*;
@Target(ElementType.TYPE) // //作用在类上
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Controller {
String value() default "";
}
package com.zhz.springmvc.annotation;
import java.lang.annotation.*;
@Target(ElementType.METHOD) //作用在方法上
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestMapping {
String value() default "";
}
package com.zhz.springmvc.annotation;
import java.lang.annotation.*;
/**
* @BelongsProject: SpringMvc
*/
@Target(ElementType.METHOD) //作用在方法上
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ResponseBody {
}
package com.zhz.springmvc.annotation;
import java.lang.annotation.*;
/**
* @Description: 自定义注解
*/
@Target(ElementType.TYPE) //作用在类上
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Service {
String value();
}
6.2、context上下文（SpringMVC容器）
package com.zhz.springmvc.context;
import com.zhz.springmvc.annotation.Autowired;
import com.zhz.springmvc.annotation.Controller;
import com.zhz.springmvc.annotation.Service;
import com.zhz.springmvc.xml.XmlParse;
import java.io.File;
import java.lang.reflect.Field;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* @author ：zhz
* @date ：Created in 2021/01/03
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description: SpringMVC容器
**/
public class WebApplicationContext {
//classpath:springmvc.xml
String contextConfigLocation;
//定义集合 用于存放 bean 的权限名|包名.类名
List<String> classNameList = new ArrayList<>();
//创建Map集合用于扮演IOC容器： key存放bean的名字 value存放bean实例
public Map<String, Object> iocMap = new ConcurrentHashMap<>();
public WebApplicationContext() {
}
public WebApplicationContext(String contextConfigLocation) {
this.contextConfigLocation = contextConfigLocation;
}
/**
* 初始化Spring容器
*/
public void onRefresh() {
//1、进行解析spring mvc配置文件操作 ==》 com.zhz.controller,com.zhz.service
String basePackage = XmlParse.getBasePackage(contextConfigLocation.split(":")[1]);
//通过"，"来分割com.zhz.controller,com.zhz.service 获得对应的包名
String[] packs = basePackage.split(",");
//2、进行包扫描
for (String pack : packs) {
executeScanPackage(pack);
}
//3、实例化容器中的bean
executeInstance();
//4、进行自动注入操作
executeAutowired();
}
/**
* 进行包扫描
*
* @param pack
*/
private void executeScanPackage(String pack) {
//1、把com.zhz.controller====>com/zhz/controller com.zhz.service====>com/zhz/controller
URL url = this.getClass().getClassLoader().getResource("/" + pack.replaceAll("\\.", "/"));
String path = url.getFile();
//2、/com/zhz/service
File dir = new File(path);
for (File file : dir.listFiles()) {
if (file.isDirectory()) {//说明是com.zhz.service.impl层
executeScanPackage(pack + "." + file.getName());
} else {
//文件目录下文件 获取全路径 UserController.class ==> com.zhz.controller.UserController
String className = pack + "." + file.getName().replaceAll(".class", "");
classNameList.add(className);
}
}
}
/**
* 实例化容器
*/
private void executeInstance() {
try {
// com.zhz.controller.UserController com.zhz.service.impl.UserServiceImpl
for (String className : classNameList) {
Class<?> clazz = Class.forName(className);
if (clazz.isAnnotationPresent(Controller.class)) {
//控制层的bean,得到类的简写名称也就是UserController
String beanName = clazz.getSimpleName().substring(0, 1).toLowerCase()+clazz.getSimpleName().substring(1);//首位变为小写
iocMap.put(beanName, clazz.newInstance());
} else if (clazz.isAnnotationPresent(Service.class)) {
//Service层，主要是为了获得他的value
Service service = clazz.getAnnotation(Service.class);
String beanName = service.value();
iocMap.put(beanName, clazz.newInstance());
}
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
}
/**
* 进行自动注入操作
*/
private void executeAutowired() {
try {
//从容器中取出bean，然后判断bean中是否有属性上使用Autowired，如果使用了该注解，就需要进行自动注入操作
for (Map.Entry<String, Object> entry : iocMap.entrySet()) {
//取出容器中的bean
Object bean = entry.getValue();
//从bean中获取属性
Field[] fields = bean.getClass().getDeclaredFields();
for (Field field : fields) {
if (field.isAnnotationPresent(Autowired.class)) {
//获取注解中的value值,该值是bean的name
Autowired autowired = field.getAnnotation(Autowired.class);
String beanName = autowired.value();
;
//取消检查机制
field.setAccessible(true);
field.set(bean, iocMap.get(beanName));
}
}
}
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
6.3、映射处理（url与ccontroller之间的映射）
package com.zhz.springmvc.handler;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.lang.reflect.Method;
/**
* @author ：zhz
* @date ：Created in 2021/01/04
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description:
**/
@Data
@AllArgsConstructor
@NoArgsConstructor
public class HandlerMapping {
//请求URL地址
private String url;
//控制器
private Object controller;
//控制器的方法
private Method method;
}
6.4、前端处理器
package com.zhz.springmvc.servlet;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.zhz.springmvc.annotation.Controller;
import com.zhz.springmvc.annotation.RequestMapping;
import com.zhz.springmvc.annotation.ResponseBody;
import com.zhz.springmvc.context.WebApplicationContext;
import com.zhz.springmvc.handler.HandlerMapping;
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.PrintWriter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* @author ：zhz
* @date ：Created in 2021/01/03
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description: 前端控制器
**/
public class DispatcherServlet extends HttpServlet {
//指定SpringMvc容器
private WebApplicationContext webApplicationContext;
//创建集合，用于存放映射关系、映射地址与控制器.方法，用于发送请求直接从该集合中进行匹配
List<HandlerMapping> handList = new ArrayList<>();
@Override
public void init() throws ServletException {
//1、从web.xml中获得加载初始化参数contextConfigLocation的值classpath:springmvc.xml
String configLocation = this.getServletConfig().getInitParameter("contextConfigLocation");
//2、创建SpringMVC容器
webApplicationContext = new WebApplicationContext(configLocation);
//3、进行初始化操作
webApplicationContext.onRefresh();
//4、初始化请求映射关系 /findUser ===》控制器.方法
initHandlerMapping();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//进行请求分发处理
doDispatcher(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
/**
* 初始化请求映射关系(获取链接地址0
*/
private void initHandlerMapping() {
//遍历map， key存放bean的名字 value存放bean实例
for (Map.Entry<String, Object> entry : webApplicationContext.iocMap.entrySet()) {
//获得bean的class类型
Class<?> clazz = entry.getValue().getClass();
if (clazz.isAnnotationPresent(Controller.class)) {
//获取bean中所有的方法，为这些方法建立映射关系
Method[] methods = clazz.getDeclaredMethods();
for (Method method : methods) {
if (method.isAnnotationPresent(RequestMapping.class)) {
RequestMapping requestMapping = method.getAnnotation(RequestMapping.class);
//获取注解中的值
String url = requestMapping.value();
//建立映射地址，与控制器 方法
HandlerMapping handlerMapping = new HandlerMapping(url, entry.getValue(), method);
handList.add(handlerMapping);
}
}
}
}
}
/**
* 进行请求分发处理
*
* @param request
* @param response
*/
private void doDispatcher(HttpServletRequest request, HttpServletResponse response) {
try {
//根据用户的请求地址（/listUsers）查找Controller
HandlerMapping handlerMapping = getHandler(request);
if (handlerMapping == null) {
response.getWriter().print("<h1>404 NOT FOUND!</h1>");
} else {
//调用处理方法之前 进行参数的注入
//调用目标方法---》获得方法的返回值类型
Object result = handlerMapping.getMethod().invoke(handlerMapping.getController());
if (result instanceof String){
//跳转到JSP中
String viewName = (String)result;
//forward:/success.jsp重定向
if (viewName.contains(":")){
String viewType=viewName.split(":")[0];//也就是forward或者redirect
String viewPage=viewName.split(":")[1];//跳转的页面
if (viewType.equals("forward")){//请求转发
request.getRequestDispatcher(viewPage).forward(request,response);
}else{//重定向
response.sendRedirect(viewPage);
}
}else{
//默认请求转发
request.getRequestDispatcher(viewName).forward(request,response);
}
}else{
//返回JSON格式数据
Method method=handlerMapping.getMethod();
if (method.isAnnotationPresent(ResponseBody.class)){
//将返回值转换成 json格式数据
ObjectMapper objectMapper = new ObjectMapper();
String json = objectMapper.writeValueAsString(result);
response.setContentType("text/html;charset=utf-8");
PrintWriter writer= response.getWriter();
writer.print(json);
writer.flush();
writer.close();
}
}
}
} catch (IOException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (ServletException e) {
e.printStackTrace();
}
}
/**
* 根据用户请求查找对应的Handler======>获取请求对应的handler(也就是从handList中取出)
*
* @param request
* @return
*/
private HandlerMapping getHandler(HttpServletRequest request) {
String requestURI = request.getRequestURI();
for (HandlerMapping handlerMapping : handList) {
//从容器的Handle取出URL 和 用户的请求地址进行匹配，找到满足条件的Handler(controller)
if (handlerMapping.getUrl().equals(requestURI)) {
return handlerMapping;
}
}
return null;
}
}
6.5、解析XML
package com.zhz.springmvc.xml;
import lombok.val;
import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import java.io.File;
import java.io.InputStream;
/**
* @author ：zhz
* @date ：Created in 2021/01/04
* @version: V1.0
* @slogan: 天下风云出我辈，一入代码岁月催
* @description: 解析spring mvc.xml
**/
public class XmlParse {
public static String getBasePackage(String xml){
try {
SAXReader saxReader=new SAXReader();
// 通过reader对象的read方法加载spring mvc.xml文件,获取docuemnt对象。
InputStream inputStream = XmlParse.class.getClassLoader().getResourceAsStream(xml);
Document document = saxReader.read(inputStream);
// 通过document对象获取根节点beans
Element rootElement = document.getRootElement();
// 通过element对象的返回给定本地名称和任何名称空间的第一个元素
Element componentScan = rootElement.element("component-scan");
//返回componentScan的参数
Attribute attribute = componentScan.attribute("base-package");
//返回base-package的值
String basePackage = attribute.getText();
return basePackage;
} catch (DocumentException e) {
e.printStackTrace();
}
return "";
}
}
7、前端页面
7.1、index.jsp
<html>
<body>
<h2>Hello World!</h2>
</body>
</html>
7.2、succes.jsp
<html>
<body>
<h2>Hello World!</h2>
跳转至success.jsp页面
</body>
</html>
总结
这篇关于手撕springMVC的文章就先更到这里了，感谢你看到这里，文章有什么不足还请指正，觉得文章对你有帮助的话记得给我点个赞，SpringMVC其实并不算是一个很难的知识点，用点心多看就很简单
每天都会分享java相关技术文章或行业资讯，欢迎大家关注和转发文章！
