在前面使用SSM集成时，我们可以使用注解实现无配置化注入，但是这种依赖被进行“人工干预了的”，换句话就是说我们手动进行装配，那么此时还没有达到SpringBoot这种自动装配的效果，那么究竟SpringBoot如何进行自动装配的呢?下面我们就一探究竟。
一。SpringBoot中创建对象的注解扩充
其实说白了，SpringBoot并不属于一种新的技术，只不过Spring-Boot-Starter-xxxx的启动器帮我们配置了若干个被Spring管理的bean，当我们的项目依赖这些jar并启动Spring应用时，Spring的Container容器已经把jar包下的对象加以创建及管理了，我们请看下面的例子：
该例子是spring-boot-autoconfigure-2.0.0.M7.jar包的内容，我们找到如下类: DispatcherServletAutoConfiguration ，我贴出源代码：
/*
* Copyright 2012-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.boot.autoconfigure.web.servlet;
import java.util.Arrays;
import java.util.List;
import javax.servlet.MultipartConfigElement;
import javax.servlet.ServletRegistration;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.AutoConfigureOrder;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionMessage;
import org.springframework.boot.autoconfigure.condition.ConditionMessage.Style;
import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
import org.springframework.boot.autoconfigure.web.ServerProperties;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.servlet.DispatcherServlet;
/**
* {@link EnableAutoConfiguration Auto-configuration} for the Spring
* {@link DispatcherServlet}. Should work for a standalone application where an embedded
* web server is already present and also for a deployable application using
* {@link SpringBootServletInitializer}.
*
* @author Phillip Webb
* @author Dave Syer
* @author Stephane Nicoll
* @author Brian Clozel
*/
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass(DispatcherServlet.class)
@AutoConfigureAfter(ServletWebServerFactoryAutoConfiguration.class)
@EnableConfigurationProperties(ServerProperties.class)
public class DispatcherServletAutoConfiguration {
/*
* The bean name for a DispatcherServlet that will be mapped to the root URL "/"
*/
public static final String DEFAULT_DISPATCHER_SERVLET_BEAN_NAME = "dispatcherServlet";