手写springboot--依据原理（内置tomcat的手写，以及内置springmvc的手写）撰写
声明：本文针对于含有springboot基础上讲解，至少涉猎过springboot的原理。
一、首先我们先来复习下springboot的核心原理要点。
1.基于SpringMVC无配置文件（纯Java）完全注解化+内置tomcat-embed-core实现SpringBoot框架，Main函数启动。
2.SpringBoot核心快速整合第三方框架原理:Maven继承依赖关系
3.SpringBoot内嵌入tomcat-embed-core
4.SpringBoot采用SpringMVC注解版本实现无配置效果
PS:本文说的不是SpringBoot流程，而是SpringBoot核心原理
二、依据上述原理，我们可以知道主要需要实现内置tomcat和内置springmvc的手写
1、内置tomcat容器（Java提供内置Tomcat容器框架，使用Java语言操作Tomcat容器）
①、首先我们需要导入实现java内置tomcat的依赖
<dependencies>
<dependency>
<groupId>org.apache.tomcat.embedgroupId>
<artifactId>tomcat-embed-coreartifactId>
<version>8.5.16version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-webartifactId>
<version>5.0.4.RELEASEversion>
<scope>compilescope>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-webmvcartifactId>
<version>5.0.4.RELEASEversion>
<scope>compilescope>
dependency>
<dependency>
<groupId>org.apache.tomcatgroupId>
<artifactId>tomcat-jasperartifactId>
<version>8.5.16version>
dependency>
dependencies>
②、然后手写创建一个Servlet
publicclass IndexServetextends HttpServlet {
@Override
protectedvoiddoGet(HttpServletRequest req,HttpServletResponse resp) throwsServletException, IOException {
doPost(req, resp);
}
@Override
protectedvoiddoPost(HttpServletRequest req,HttpServletResponse resp) throwsServletException, IOException {
resp.getWriter().print("springboot2.0 内置Tomcat的Servlet");
}
}
③、创建Tomcat进行运行（创建一个类 名为AppTomcat，复制下列代码）
//端口号
private static int port=9090;
//项目访问路径
private static String CONTACT_PATH="/RollinSpark";
public static void main(String[] args) {
start();
}
private static void start() {
// TODO Auto-generated method stub
//创建Tomcat服务器
Tomcat tomcat=new Tomcat();
//设置端口号
tomcat.setPort(port);
tomcat.getHost().setAutoDeploy(false);
// 创建Context上下文
StandardContext standardContext=new StandardContext();
standardContext.setPath(CONTACT_PATH);
standardContext.addLifecycleListener(new FixContextListener());
// tomcat容器添加standardContext
tomcat.getHost().addChild(standardContext);
// 创建servlet
tomcat.addServlet(CONTACT_PATH, "IndexServlet", new IndexServlet());
// 添加servleturl映射
standardContext.addServletMappingDecoded("/index", "IndexServlet");
try {
tomcat.start();
System.out.println("tomcat启动成功...");
} catch (LifecycleException e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("tomcat启动失败...");
}
//服务阻塞等待
tomcat.getServer().await();
}
④、启动AppTomcat类，运行效，访问http://localhost:9090/RollinSpark/index可以看到效果
2、SpringMVC无注解启动方式回顾
DispatcherServlet是Spring MVC的核心，每当应用接受一个HTTP请求，由DispatcherServlet负责将请求分发给应用的其他组件。
在旧版本中，DispatcherServlet之类的servlet一般在web.xml文件中配置，该文件一般会打包进最后的war包种；但是Spring 3引入了注解，我们这节课讲解，如何基于注解配置Spring MVC。
3、整合SpringMVC和内置Tomcat实现SpringBoot的功能
①、新建Maven项目，设置为war工程
②、添加Maven依赖
<dependencies>
<dependency>
<groupId>org.apache.tomcat.embedgroupId>
<artifactId>tomcat-embed-coreartifactId>
<version>8.5.16version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-webartifactId>
<version>5.0.4.RELEASEversion>
<scope>compilescope>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-webmvcartifactId>
<version>5.0.4.RELEASEversion>
<scope>compilescope>
dependency>
<dependency>
<groupId>org.apache.tomcatgroupId>
<artifactId>tomcat-jasperartifactId>
<version>8.5.16version>
dependency>
dependencies>
③、加载SpringMVCDispatcherServlet
package com.rollin.config;import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
/**
*
* @author rollin
* 重写web容器配置
* 加载SpringMVCDispatcherServlet
*
*/
public class SpittrWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer{
@Override
protected Class[] getRootConfigClasses() {
// TODO Auto-generated method stub
return new Class[] { RootConfig.class };
}
@Override
protected Class[] getServletConfigClasses() {
// TODO Auto-generated method stub
return new Class[] { WebConfig.class };
}
@Override
protected String[] getServletMappings() {
// TODO Auto-generated method stub
return new String[] { "/" };
}
}
④、加载SpringMVC容器
package com.rollin.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.ViewResolver;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
/**
* @EnableWebMvc 开启SpringMVC功能
* @Configuration 配置
* @author rollin
* 启动webmvc 配置及扫包范围设置
*
*/
@Configuration
@EnableWebMvc
@ComponentScan("com.rollin.controller")
public class WebConfig extends WebMvcConfigurerAdapter{
// 创建SpringMVC视图解析器
@Bean
public ViewResolver viewResolver() {
InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
viewResolver.setPrefix("/WEB-INF/views/");
viewResolver.setSuffix(".jsp");
//可以在JSP页面中通过${}访问beans
viewResolver.setExposeContextBeansAsAttributes(true);
return viewResolver;
}
}
⑤、RootConfig容器
package com.rollin.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
/**
*
* @author rollin
* web根容器
*
*/
@Configuration
@ComponentScan(basePackages = "com.rollin")
public class RootConfig {
}
⑥、建立运行的AppTomcat类
package com.rollin;
import java.io.File;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.WebResourceRoot;
import org.apache.catalina.core.StandardContext;
import org.apache.catalina.startup.Tomcat;
import org.apache.catalina.startup.Tomcat.FixContextListener;
import org.apache.catalina.webresources.DirResourceSet;
import org.apache.catalina.webresources.StandardRoot;
/**
*
* @author rollin
*
*/
public class AppTomcat {
// 端口号
private static int port = 9090;
public static void main(String[] args) {
start();
}
private static void start() {
try {
// TODO Auto-generated method stub
// 创建Tomcat服务器
Tomcat tomcat = new Tomcat();
// 设置端口号
tomcat.setPort(port);
tomcat.getHost().setAutoDeploy(false);
// 创建Context上下文
// 读取项目路径
StandardContext ctx = (StandardContext) tomcat.addWebapp("/", new File("src/main/webapp").getAbsolutePath());
// 禁止重新载入
ctx.setReloadable(false);
// class文件读取地址
File additionWebInfClasses = new File("target/classes");
// 创建WebRoot
WebResourceRoot resources = new StandardRoot(ctx);
// tomcat内部读取Class执行
resources.addPreResources(
new DirResourceSet(resources, "/WEB-INF/classes", additionWebInfClasses.getAbsolutePath(), "/"));
tomcat.start();
System.out.println("tomcat启动成功...");
// 服务阻塞等待
tomcat.getServer().await();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("tomcat启动失败...");
}
}
}
⑦、项目添加逻辑层
Service层：
package com.rollin.service;
import org.springframework.stereotype.Service;
@Service
public class UserService {
public String index() {
return "UserService 访问成功！！--RollinSpark";
}
}
Controller层：
package com.rollin.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.rollin.service.UserService;
@RestController
public class UserController {
@Autowired
private UserService userService;
@RequestMapping(value="/userIndex",produces = "text/html;charset=UTF-8")
public String index() {
return userService.index();
}
}
本文到这里基本结束，集成JSP就省略了，大致就是配置视图解析器，然后跳转页面.....有需要DEMO的可以加我扣扣，2485290255，记得备注说明！！！