SpringBoot自动配置

项目内部配置第三方bean

第三方的bean通过配置类的@bean注入，项目内部引用使用@Import配置类的class
解耦引入的第三方配置类，新建一个缓冲类加载需要引入的配置类
将需要引入第三方配置类加入Mate-inf中的factories中
加载返回可以引入第三方的bean
本项目bean和第三方bean冲突，以本项目为准（import先解析被覆盖，默认不可以覆盖）
1. DeferredImportSelector推迟导入，先解析本项目的
2. @ConditionalOnMissingBean本项目没有，则加载第三方的

package com.butch.a41;import org.springframework.boot.autoconfigure.AutoConfigurationPackages;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.*;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.env.MapPropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.ResourcePropertySource;
import org.springframework.core.io.support.SpringFactoriesLoader;
import org.springframework.core.type.AnnotationMetadata;import java.io.IOException;
import java.util.List;
import java.util.Map;public class A41_1 {@SuppressWarnings("all")public static void main(String[] args) throws IOException {GenericApplicationContext context = new GenericApplicationContext();context.getDefaultListableBeanFactory().setAllowBeanDefinitionOverriding(false);context.registerBean("config", Config.class);context.registerBean(ConfigurationClassPostProcessor.class);context.refresh();for (String name : context.getBeanDefinitionNames()) {System.out.println(name);}System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>");System.out.println(context.getBean(Bean1.class));}@Configuration // 本项目的配置类@Import(MyImportSelector.class)static class Config {@Beanpublic Bean1 bean1() {return new Bean1("本项目");}}static class MyImportSelector implements DeferredImportSelector {@Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata) {
//            System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>");//EnableAutoConfiguration为key的类名
//            for (String name : SpringFactoriesLoader.loadFactoryNames(EnableAutoConfiguration.class, null)) {
//                System.out.println(name);
//            }
//            System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>");//获取配置文件中值 也会扫描第三方jar包的factoriesList<String> names = SpringFactoriesLoader.loadFactoryNames(MyImportSelector.class, null);return names.toArray(new String[0]);}}@Configuration // 第三方的配置类static class AutoConfiguration1 {@Bean@ConditionalOnMissingBeanpublic Bean1 bean1() {return new Bean1("第三方");}}static class Bean1 {private String name;public Bean1() {}public Bean1(String name) {this.name = name;}@Overridepublic String toString() {return "Bean1{" +"name='" + name + '\'' +'}';}}@Configuration // 第三方的配置类static class AutoConfiguration2 {@Beanpublic Bean2 bean2() {return new Bean2();}}static class Bean2 {}
}

自动配置实现类

AopAutoConfiguration（AOP）

AOP 自动配置类为 org.springframework.boot.autoconfigure.aop.AopAutoConfiguration
可以通过 spring.aop.auto=false 禁用 aop 自动配置
AOP 自动配置的本质是通过 @EnableAspectJAutoProxy 来开启了自动代理，如果在引导类上自己添加了 @EnableAspectJAutoProxy 那么以自己添加的为准
@EnableAspectJAutoProxy 的本质是向容器中添加了 AnnotationAwareAspectJAutoProxyCreator 这个 bean 后处理器，它能够找到容器中所有切面，并为匹配切点的目标类创建代理，创建代理的工作一般是在 bean 的初始化阶段完成的

多层嵌套的静态内部类，最后一层EnableAspectJAutoProxy 导入代理创建器

spring.aop.auto！= false才加载
@ConditionalOnClass(Advice.class)存在Advice
@ConditionalOnMissingClass("org.aspectj.weaver.Advice") 缺失条件
最终@EnableAspectJAutoProxy 本质是import，proxyTargetClass创建代理的模式，为false会看看有没有实现接口有接口jdk代理
最终注册AnnotationAwareAspectJAutoProxyCreator的bean后处理器，高层转底层创建jdk或者cglib代理

package com.butch.a41;import org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator;
import org.springframework.boot.autoconfigure.aop.AopAutoConfiguration;
import org.springframework.context.annotation.*;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.env.SimpleCommandLinePropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.core.type.AnnotationMetadata;public class TestAopAuto {public static void main(String[] args) {GenericApplicationContext context = new GenericApplicationContext();StandardEnvironment env = new StandardEnvironment();env.getPropertySources().addLast(new SimpleCommandLinePropertySource("--spring.aop.auto=true"));context.setEnvironment(env);AnnotationConfigUtils.registerAnnotationConfigProcessors(context.getDefaultListableBeanFactory());context.registerBean(Config.class);context.refresh();for (String name : context.getBeanDefinitionNames()) {System.out.println(name);}//org.springframework.boot.autoconfigure.aop.AopAutoConfiguration$AspectJAutoProxyingConfiguration$CglibAutoProxyConfiguration//org.springframework.aop.config.internalAutoProxyCreator//org.springframework.boot.autoconfigure.aop.AopAutoConfiguration$AspectJAutoProxyingConfiguration//org.springframework.boot.autoconfigure.aop.AopAutoConfigurationSystem.out.println(">>>>>>>>>>>>>>>");//查看代理实现类型AnnotationAwareAspectJAutoProxyCreator creator = context.getBean("org.springframework.aop.config.internalAutoProxyCreator", AnnotationAwareAspectJAutoProxyCreator.class);System.out.println(creator.isProxyTargetClass());}@Configuration@Import(MyImportSelector.class)static class Config {}static class MyImportSelector implements DeferredImportSelector {@Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata) {return new String[]{AopAutoConfiguration.class.getName()};}}
}

Datasource

对应的自动配置类为：org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration
它内部采用了条件装配，通过检查容器的 bean，以及类路径下的 class，来决定该 @Bean 是否生效

简单说明一下，Spring Boot 支持两大类数据源：

EmbeddedDatabase - 内嵌数据库连接池
PooledDataSource - 非内嵌数据库连接池

PooledDataSource 又支持如下数据源

hikari 提供的 HikariDataSource
tomcat-jdbc 提供的 DataSource
dbcp2 提供的 BasicDataSource
oracle 提供的 PoolDataSourceImpl

如果知道数据源的实现类类型，即指定了 spring.datasource.type，理论上可以支持所有数据源，但这样做的一个最大问题是无法订制每种数据源的详细配置（如最大、最小连接数等）

dataSource

@Conditional(PooledDataSourceCondition.class)进入带有连接池的数据源
集成mybaits依赖jdbc进入@ConditionalOnClass(HikariDataSource.class)
@EnableConfigurationProperties(DataSourceProperties.class)封装绑定键值信息，spring.datasourcexxxxx
1. 创建datasource绑定键值信息

mybits

MyBatis 自动配置类为 org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration
它主要配置了两个 bean
- SqlSessionFactory - MyBatis 核心对象，用来创建 SqlSession
- SqlSessionTemplate - SqlSession 的实现，此实现会与当前线程绑定
- 用 ImportBeanDefinitionRegistrar 的方式扫描所有标注了 @Mapper 注解的接口
- 用 AutoConfigurationPackages 来确定扫描的包
还有一个相关的 bean：MybatisProperties，它会读取配置文件中带 mybatis. 前缀的配置项进行定制配置

@MapperScan 注解的作用与 MybatisAutoConfiguration 类似，会注册 MapperScannerConfigurer 有如下区别

@MapperScan 扫描具体包（当然也可以配置关注哪个注解）
@MapperScan 如果不指定扫描具体包，则会把引导类范围内，所有接口当做 Mapper 接口
MybatisAutoConfiguration 关注的是所有标注 @Mapper 注解的接口，会忽略掉非 @Mapper 标注的接口
其实并非将接口交给 Spring 管理，而是每个接口会对应一个 MapperFactoryBean，是后者被 Spring 所管理，接口只是作为 MapperFactoryBean 的一个属性来配置

package com.butch.a41;import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.annotation.MapperScan;
import org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration;
import org.springframework.boot.autoconfigure.AutoConfigurationPackages;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration;
import org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigUtils;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.DeferredImportSelector;
import org.springframework.context.annotation.Import;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.env.SimpleCommandLinePropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.core.type.AnnotationMetadata;public class TestDataSourceAuto {@SuppressWarnings("all")public static void main(String[] args) {GenericApplicationContext context = new GenericApplicationContext();StandardEnvironment env = new StandardEnvironment();//添加配置源env.getPropertySources().addLast(new SimpleCommandLinePropertySource("--spring.datasource.url=jdbc:mysql://localhost:3306/test","--spring.datasource.username=root","--spring.datasource.password=123456"));context.setEnvironment(env);AnnotationConfigUtils.registerAnnotationConfigProcessors(context.getDefaultListableBeanFactory());context.registerBean(Config.class);String packageName = TestDataSourceAuto.class.getPackage().getName();System.out.println("当前包名:" + packageName);AutoConfigurationPackages.register(context.getDefaultListableBeanFactory(),packageName);context.refresh();for (String name : context.getBeanDefinitionNames()) {String resourceDescription = context.getBeanDefinition(name).getResourceDescription();if (resourceDescription != null)System.out.println(name + " 来源:" + resourceDescription);//dataSource 来源:class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]//hikariPoolDataSourceMetadataProvider 来源:class path resource [org/springframework/boot/autoconfigure/jdbc/metadata/DataSourcePoolMetadataProvidersConfiguration$HikariPoolDataSourceMetadataProviderConfiguration.class]//sqlSessionFactory 来源:class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]//sqlSessionTemplate 来源:class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]//transactionManager 来源:class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceTransactionManagerAutoConfiguration$DataSourceTransactionManagerConfiguration.class]//org.springframework.transaction.config.internalTransactionAdvisor 来源:class path resource [org/springframework/transaction/annotation/ProxyTransactionManagementConfiguration.class]//transactionAttributeSource 来源:class path resource [org/springframework/transaction/annotation/ProxyTransactionManagementConfiguration.class]//transactionInterceptor 来源:class path resource [org/springframework/transaction/annotation/ProxyTransactionManagementConfiguration.class]//org.springframework.transaction.config.internalTransactionalEventListenerFactory 来源:class path resource [org/springframework/transaction/annotation/ProxyTransactionManagementConfiguration.class]//transactionTemplate 来源:class path resource [org/springframework/boot/autoconfigure/transaction/TransactionAutoConfiguration$TransactionTemplateConfiguration.class]//platformTransactionManagerCustomizers 来源:class path resource [org/springframework/boot/autoconfigure/transaction/TransactionAutoConfiguration.class]}}@Configuration@Import(MyImportSelector.class)static class Config {}static class MyImportSelector implements DeferredImportSelector {@Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata) {return new String[]{//配置数据源 必选DataSourceAutoConfiguration.class.getName(),//mybit的sqlsession工程mapper扫描MybatisAutoConfiguration.class.getName(),//事务管理DataSourceTransactionManagerAutoConfiguration.class.getName(),//声明式事务管理TransactionAutoConfiguration.class.getName()};}}
}

TransactionAutoConfiguration

事务自动配置类有两个：
- org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration
- org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration
前者配置了 DataSourceTransactionManager 用来执行事务的提交、回滚操作
后者功能上对标 @EnableTransactionManagement，包含以下三个 bean
- BeanFactoryTransactionAttributeSourceAdvisor 事务切面类，包含通知和切点
- TransactionInterceptor 事务通知类，由它在目标方法调用前后加入事务操作
- AnnotationTransactionAttributeSource 会解析 @Transactional 及事务属性，也包含了切点功能
如果自己配置了 DataSourceTransactionManager 或是在引导类加了 @EnableTransactionManagement，则以自己配置的为准

WebMvcAutoConfiguration

配置 DispatcherServlet 的各项组件，提供的 bean 见过的有
- 多项 HandlerMapping
- 多项 HandlerAdapter
- HandlerExceptionResolver

自定义自动配置类

自动配置类本质上就是一个配置类而已，只是用 META-INF/spring.factories 管理，与应用配置类解耦
@Enable 打头的注解本质是利用了 @Import
@Import 配合 DeferredImportSelector 即可实现导入，selectImports 方法的返回值即为要导入的配置类名
DeferredImportSelector 的导入会在最后执行，为的是让其它配置优先解析

package com.butch.a41;import org.springframework.boot.autoconfigure.AutoConfigurationImportSelector;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.*;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.env.SimpleCommandLinePropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.core.io.support.SpringFactoriesLoader;
import org.springframework.core.type.AnnotationMetadata;import java.io.IOException;
import java.util.List;public class A41_2 {@SuppressWarnings("all")public static void main(String[] args) throws IOException {GenericApplicationContext context = new GenericApplicationContext();StandardEnvironment env = new StandardEnvironment();env.getPropertySources().addLast(new SimpleCommandLinePropertySource("--spring.datasource.url=jdbc:mysql://localhost:3306/test","--spring.datasource.username=root","--spring.datasource.password=root"));context.setEnvironment(env);        context.registerBean("config", Config.class);context.registerBean(ConfigurationClassPostProcessor.class);context.refresh();for (String name : context.getBeanDefinitionNames()) {System.out.println(name);}System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>");System.out.println(context.getBean(Bean1.class));}//spring识别的import
//    @Import(AutoConfigurationImportSelector.class)
//    @Import(MyImportSelector.class)@EnableAutoConfiguration@Configuration // 本项目的配置类static class Config {}static class MyImportSelector implements DeferredImportSelector {@Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata) {
//            System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>");//EnableAutoConfiguration为key的类名
//            for (String name : SpringFactoriesLoader.loadFactoryNames(EnableAutoConfiguration.class, null)) {
//                System.out.println(name);
//            }
//            System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>");//获取配置文件中值List<String> names = SpringFactoriesLoader.loadFactoryNames(MyImportSelector.class, null);return names.toArray(new String[0]);}}@Configuration // 第三方的配置类static class AutoConfiguration1 {@Beanpublic Bean1 bean1() {return new Bean1();}}@Configuration // 第三方的配置类static class AutoConfiguration2 {@Beanpublic Bean2 bean2() {return new Bean2();}}static class Bean2 {}static class Bean1 {}
}

条件装配底层

当引入第三方的bean ，增加条件装配

底层使用conditional 配合实现了condition的接口进行检查

本质上是if-else语句

package com.butch.a42;import org.springframework.context.annotation.*;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.ClassUtils;public class A42_2 {public static void main(String[] args) {GenericApplicationContext context = new GenericApplicationContext();context.registerBean("config", Config.class);context.registerBean(ConfigurationClassPostProcessor.class);context.refresh();for (String name : context.getBeanDefinitionNames()) {System.out.println(name);}}@Configuration // 本项目的配置类@Import(MyImportSelector.class)static class Config {}static class MyImportSelector implements DeferredImportSelector {@Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata) {return new String[]{AutoConfiguration1.class.getName(), AutoConfiguration2.class.getName()};}}static class Mycondition1 implements Condition{//检测德鲁伊存在@Overridepublic boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {System.out.println("ClassUtils.isPresent(\"DruidDataSource\", null)" + ClassUtils.isPresent("DruidDataSource", null));return ClassUtils.isPresent("com.alibaba.druid.pool.DruidDataSource" +"", null);}}static class Mycondition2 implements Condition{//检测德鲁伊不存在@Overridepublic boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {return !ClassUtils.isPresent("com.alibaba.druid.pool.DruidDataSource", null);}}//    @ConditionalOnClass(className = "com.alibaba.druid.pool.DruidDataSource", exists = false) //有德鲁伊bean1 无德鲁伊bean2@Configuration // 第三方的配置类@Conditional(Mycondition1.class)static class AutoConfiguration1 {@Beanpublic Bean1 bean1() {return new Bean1();}}@Configuration // 第三方的配置类
//    @ConditionalOnClass(className = "com.alibaba.druid.pool.DruidDataSource", exists = true)@Conditional(Mycondition2.class)static class AutoConfiguration2 {@Beanpublic Bean2 bean2() {return new Bean2();}}static class Bean1 {}static class Bean2 {}
}