SpringBoot自动配置原理

1 SpringBoot 特点

1.1 依赖管理

父项目做依赖管理

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.3.4.RELEASE</version>
</parent>

无需关注版本号，版本自动仲裁（引入非仲裁版本的jar，需要写版本号）

父项目的父项目
<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-dependencies</artifactId>
  <version>2.3.4.RELEASE</version>
</parent>

父项目的父项目中定义了常用jar 版本号
<properties>
    <activemq.version>5.15.13</activemq.version>
    <antlr2.version>2.7.7</antlr2.version>
    <appengine-sdk.version>1.9.82</appengine-sdk.version>
    <artemis.version>2.12.0</artemis.version>
    <aspectj.version>1.9.6</aspectj.version>
    <assertj.version>3.16.1</assertj.version>
    <atomikos.version>4.0.6</atomikos.version>
    <awaitility.version>4.0.3</awaitility.version>
    <bitronix.version>2.1.4</bitronix.version>
    <build-helper-maven-plugin.version>3.1.0</build-helper-maven-plugin.version>
    <byte-buddy.version>1.10.14</byte-buddy.version>
    <caffeine.version>2.8.5</caffeine.version>
    <cassandra-driver.version>4.6.1</cassandra-driver.version>
    <classmate.version>1.5.1</classmate.version>
    <commons-codec.version>1.14</commons-codec.version>
    <commons-dbcp2.version>2.7.0</commons-dbcp2.version>
    <commons-lang3.version>3.10</commons-lang3.version>
    <commons-pool.version>1.6</commons-pool.version>
    <commons-pool2.version>2.8.1</commons-pool2.version>
    <couchbase-client.version>3.0.8</couchbase-client.version>
    <db2-jdbc.version>11.5.4.0</db2-jdbc.version>
    <dependency-management-plugin.version>1.0.10.RELEASE</dependency-management-plugin.version>
    <derby.version>10.14.2.0</derby.version>
    <dropwizard-metrics.version>4.1.12.1</dropwizard-metrics.version>
    <ehcache.version>2.10.6</ehcache.version>
    <ehcache3.version>3.8.1</ehcache3.version>
    <elasticsearch.version>7.6.2</elasticsearch.version>
    <embedded-mongo.version>2.2.0</embedded-mongo.version>
    <exec-maven-plugin.version>1.6.0</exec-maven-plugin.version>
    <flatten-maven-plugin.version>1.2.5</flatten-maven-plugin.version>
    <flyway.version>6.4.4</flyway.version>
    <freemarker.version>2.3.30</freemarker.version>
    <git-commit-id-plugin.version>3.0.1</git-commit-id-plugin.version>
    <glassfish-el.version>3.0.3</glassfish-el.version>
    <glassfish-jaxb.version>2.3.3</glassfish-jaxb.version>
    <groovy.version>2.5.13</groovy.version>
    <gson.version>2.8.6</gson.version>
    <h2.version>1.4.200</h2.version>
    <hamcrest.version>2.2</hamcrest.version>
    <hazelcast.version>3.12.9</hazelcast.version>
    <hazelcast-hibernate5.version>1.3.2</hazelcast-hibernate5.version>
    <hibernate.version>5.4.21.Final</hibernate.version>
    <hibernate-validator.version>6.1.5.Final</hibernate-validator.version>
    <hikaricp.version>3.4.5</hikaricp.version>
    <hsqldb.version>2.5.1</hsqldb.version>
    <htmlunit.version>2.40.0</htmlunit.version>
    <httpasyncclient.version>4.1.4</httpasyncclient.version>
    <httpclient.version>4.5.12</httpclient.version>
    <httpcore.version>4.4.13</httpcore.version>
    <infinispan.version>10.1.8.Final</infinispan.version>
    <influxdb-java.version>2.18</influxdb-java.version>
    <jackson-bom.version>2.11.2</jackson-bom.version>
    <jakarta-activation.version>1.2.2</jakarta-activation.version>
    <jakarta-annotation.version>1.3.5</jakarta-annotation.version>
    <jakarta-jms.version>2.0.3</jakarta-jms.version>
    <jakarta-json.version>1.1.6</jakarta-json.version>
    <jakarta-json-bind.version>1.0.2</jakarta-json-bind.version>
    <jakarta-mail.version>1.6.5</jakarta-mail.version>
    <jakarta-persistence.version>2.2.3</jakarta-persistence.version>
    <jakarta-servlet.version>4.0.4</jakarta-servlet.version>
    <jakarta-servlet-jsp-jstl.version>1.2.7</jakarta-servlet-jsp-jstl.version>
    <jakarta-transaction.version>1.3.3</jakarta-transaction.version>
    <jakarta-validation.version>2.0.2</jakarta-validation.version>
    <jakarta-websocket.version>1.1.2</jakarta-websocket.version>
    <jakarta-ws-rs.version>2.1.6</jakarta-ws-rs.version>
    <jakarta-xml-bind.version>2.3.3</jakarta-xml-bind.version>
    <jakarta-xml-soap.version>1.4.2</jakarta-xml-soap.version>
    <jakarta-xml-ws.version>2.3.3</jakarta-xml-ws.version>
    <janino.version>3.1.2</janino.version>
    <javax-activation.version>1.2.0</javax-activation.version>
    <javax-annotation.version>1.3.2</javax-annotation.version>
    <javax-cache.version>1.1.1</javax-cache.version>
    <javax-jaxb.version>2.3.1</javax-jaxb.version>
    <javax-jaxws.version>2.3.1</javax-jaxws.version>
    <javax-jms.version>2.0.1</javax-jms.version>
    <javax-json.version>1.1.4</javax-json.version>
    <javax-jsonb.version>1.0</javax-jsonb.version>
    <javax-mail.version>1.6.2</javax-mail.version>
    <javax-money.version>1.0.3</javax-money.version>
    <javax-persistence.version>2.2</javax-persistence.version>
    <javax-transaction.version>1.3</javax-transaction.version>
    <javax-validation.version>2.0.1.Final</javax-validation.version>
    <javax-websocket.version>1.1</javax-websocket.version>
    <jaxen.version>1.2.0</jaxen.version>
    <jaybird.version>3.0.9</jaybird.version>
    <jboss-logging.version>3.4.1.Final</jboss-logging.version>
    <jboss-transaction-spi.version>7.6.0.Final</jboss-transaction-spi.version>
    <jdom2.version>2.0.6</jdom2.version>
    <jedis.version>3.3.0</jedis.version>
    <jersey.version>2.30.1</jersey.version>
    <jetty-el.version>8.5.54</jetty-el.version>
    <jetty-jsp.version>2.2.0.v201112011158</jetty-jsp.version>
    <jetty-reactive-httpclient.version>1.1.4</jetty-reactive-httpclient.version>
    <jetty.version>9.4.31.v20200723</jetty.version>
    <jmustache.version>1.15</jmustache.version>
    <johnzon.version>1.2.8</johnzon.version>
    <jolokia.version>1.6.2</jolokia.version>
    <jooq.version>3.13.4</jooq.version>
    <json-path.version>2.4.0</json-path.version>
    <json-smart.version>2.3</json-smart.version>
    <jsonassert.version>1.5.0</jsonassert.version>
    <jstl.version>1.2</jstl.version>
    <jtds.version>1.3.1</jtds.version>
    <junit.version>4.13</junit.version>
    <junit-jupiter.version>5.6.2</junit-jupiter.version>
    <kafka.version>2.5.1</kafka.version>
    <kotlin.version>1.3.72</kotlin.version>
    <kotlin-coroutines.version>1.3.8</kotlin-coroutines.version>
    <lettuce.version>5.3.4.RELEASE</lettuce.version>
    <liquibase.version>3.8.9</liquibase.version>
    <log4j2.version>2.13.3</log4j2.version>
    <logback.version>1.2.3</logback.version>
    <lombok.version>1.18.12</lombok.version>
    <mariadb.version>2.6.2</mariadb.version>
    <maven-antrun-plugin.version>1.8</maven-antrun-plugin.version>
    <maven-assembly-plugin.version>3.3.0</maven-assembly-plugin.version>
    <maven-clean-plugin.version>3.1.0</maven-clean-plugin.version>
    <maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
    <maven-dependency-plugin.version>3.1.2</maven-dependency-plugin.version>
    <maven-deploy-plugin.version>2.8.2</maven-deploy-plugin.version>
    <maven-enforcer-plugin.version>3.0.0-M3</maven-enforcer-plugin.version>
    <maven-failsafe-plugin.version>2.22.2</maven-failsafe-plugin.version>
    <maven-help-plugin.version>3.2.0</maven-help-plugin.version>
    <maven-install-plugin.version>2.5.2</maven-install-plugin.version>
    <maven-invoker-plugin.version>3.2.1</maven-invoker-plugin.version>
    <maven-jar-plugin.version>3.2.0</maven-jar-plugin.version>
    <maven-javadoc-plugin.version>3.2.0</maven-javadoc-plugin.version>
    <maven-resources-plugin.version>3.1.0</maven-resources-plugin.version>
    <maven-shade-plugin.version>3.2.4</maven-shade-plugin.version>
    <maven-source-plugin.version>3.2.1</maven-source-plugin.version>
    <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
    <maven-war-plugin.version>3.2.3</maven-war-plugin.version>
    <micrometer.version>1.5.5</micrometer.version>
    <mimepull.version>1.9.13</mimepull.version>
    <mockito.version>3.3.3</mockito.version>
    <mongodb.version>4.0.5</mongodb.version>
    <mssql-jdbc.version>7.4.1.jre8</mssql-jdbc.version>
    <mysql.version>8.0.21</mysql.version>
    <nekohtml.version>1.9.22</nekohtml.version>
    <neo4j-ogm.version>3.2.16</neo4j-ogm.version>
    <netty.version>4.1.52.Final</netty.version>
    <netty-tcnative.version>2.0.34.Final</netty-tcnative.version>
    <nio-multipart-parser.version>1.1.0</nio-multipart-parser.version>
    <oauth2-oidc-sdk.version>7.1.1</oauth2-oidc-sdk.version>
    <nimbus-jose-jwt.version>8.19</nimbus-jose-jwt.version>
    <ojdbc.version>19.3.0.0</ojdbc.version>
    <okhttp3.version>3.14.9</okhttp3.version>
    <oracle-database.version>19.3.0.0</oracle-database.version>
    <pooled-jms.version>1.1.2</pooled-jms.version>
    <postgresql.version>42.2.16</postgresql.version>
    <prometheus-pushgateway.version>0.9.0</prometheus-pushgateway.version>
    <quartz.version>2.3.2</quartz.version>
    <querydsl.version>4.3.1</querydsl.version>
    <r2dbc-bom.version>Arabba-SR7</r2dbc-bom.version>
    <rabbit-amqp-client.version>5.9.0</rabbit-amqp-client.version>
    <reactive-streams.version>1.0.3</reactive-streams.version>
    <reactor-bom.version>Dysprosium-SR12</reactor-bom.version>
    <rest-assured.version>3.3.0</rest-assured.version>
    <rsocket.version>1.0.2</rsocket.version>
    <rxjava.version>1.3.8</rxjava.version>
    <rxjava-adapter.version>1.2.1</rxjava-adapter.version>
    <rxjava2.version>2.2.19</rxjava2.version>
    <saaj-impl.version>1.5.2</saaj-impl.version>
    <selenium.version>3.141.59</selenium.version>
    <selenium-htmlunit.version>2.40.0</selenium-htmlunit.version>
    <sendgrid.version>4.4.8</sendgrid.version>
    <servlet-api.version>4.0.1</servlet-api.version>
    <slf4j.version>1.7.30</slf4j.version>
    <snakeyaml.version>1.26</snakeyaml.version>
    <solr.version>8.5.2</solr.version>
    <spring-amqp.version>2.2.11.RELEASE</spring-amqp.version>
    <spring-batch.version>4.2.4.RELEASE</spring-batch.version>
    <spring-data-releasetrain.version>Neumann-SR4</spring-data-releasetrain.version>
    <spring-framework.version>5.2.9.RELEASE</spring-framework.version>
    <spring-hateoas.version>1.1.2.RELEASE</spring-hateoas.version>
    <spring-integration.version>5.3.2.RELEASE</spring-integration.version>
    <spring-kafka.version>2.5.6.RELEASE</spring-kafka.version>
    <spring-ldap.version>2.3.3.RELEASE</spring-ldap.version>
    <spring-restdocs.version>2.0.5.RELEASE</spring-restdocs.version>
    <spring-retry.version>1.2.5.RELEASE</spring-retry.version>
    <spring-security.version>5.3.4.RELEASE</spring-security.version>
    <spring-session-bom.version>Dragonfruit-SR1</spring-session-bom.version>
    <spring-ws.version>3.0.10.RELEASE</spring-ws.version>
    <sqlite-jdbc.version>3.31.1</sqlite-jdbc.version>
    <sun-mail.version>1.6.5</sun-mail.version>
    <thymeleaf.version>3.0.11.RELEASE</thymeleaf.version>
    <thymeleaf-extras-data-attribute.version>2.0.1</thymeleaf-extras-data-attribute.version>
    <thymeleaf-extras-java8time.version>3.0.4.RELEASE</thymeleaf-extras-java8time.version>
    <thymeleaf-extras-springsecurity.version>3.0.4.RELEASE</thymeleaf-extras-springsecurity.version>
    <thymeleaf-layout-dialect.version>2.4.1</thymeleaf-layout-dialect.version>
    <tomcat.version>9.0.38</tomcat.version>
    <unboundid-ldapsdk.version>4.0.14</unboundid-ldapsdk.version>
    <undertow.version>2.1.4.Final</undertow.version>
    <versions-maven-plugin.version>2.7</versions-maven-plugin.version>
    <webjars-hal-browser.version>3325375</webjars-hal-browser.version>
    <webjars-locator-core.version>0.45</webjars-locator-core.version>
    <wsdl4j.version>1.6.3</wsdl4j.version>
    <xml-maven-plugin.version>1.0.2</xml-maven-plugin.version>
    <xmlunit2.version>2.7.0</xmlunit2.version>
  </properties>

可以修改版本号 —— 在当前项目中重写版本号

<properties>
  <mysql.version>5.1.43</mysql.version>
  <maven.compiler.source>8</maven.compiler.source>
  <maven.compiler.target>8</maven.compiler.target>
</properties>

开发导入 starter 场景启动器
- spring-boot-starter-* ，*就指某种场景，只要引入了 starter ，这个场景所有常规需要的依赖都会自动引入；

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>

1.2 自动配置

自动配置好 Tomcat
- 引入 Tomcat 依赖
- 自动配置
自动配置好 SpringMVC
- 引入 SpringMVC 全套组件
- 自动配置好 SpringMVC 常用组件（功能）
自动配置好 Web 常见功能，如：字符编码问题
- 配置好常见 Web 开发场景
默认包的结构
- 主程序
各种配置拥有默认值
按需加载所有配置项

2 容器功能

2.1 组件添加

1. @Configuration

基本使用
Full 模式与 Lite 模式
- lite模式包含：
  
  没有被@Configuration修饰，被@Component修饰
  没有被@Configuration修饰，被@ComponentScan修饰
  没有被@Configuration修饰，被@Import修饰
  没有被@Configuration修饰，被@ImportResource修饰
  没有任何Spring相关注解，类里面有@Bean修饰的方法
  被@Configuration修饰，但是属性proxyBeanMethods = false
- full模式包含：
  
  被@Configuration修饰，且属性proxyBeanMethods = true(proxyBeanMethods 默认为true)
- full模式使用特性：
  
  full模式下的配置类会被CGLIB代理生成代理类取代原始类型(在容器中)
  full模式下的@Bean方法不能是private和final
  单例scope下不同@Bean方法可以互相引用，达到单实例的语义
- lite模式使用特性：
  
  lite模式下的配置类不生成代理，原始类型进入容器
  lite模式下的@Bean方法可以是private和final
  单例scope下不同@Bean方法引用时无法做到单例
示例

MyConfig.java

package site.shaoshao.boot.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import site.shaoshao.boot.bean.Pet;
import site.shaoshao.boot.bean.User;

/**
 * 1. 配置类里面使用@Bean标注在方法上给容器注册组件，默认也是单实例
 * 2. 配置类本身也是组件
 * 3. 5.2后 proxyBeanMethods：代理bean的方法
 *      Full（proxyBeanMethods = true）默认
 *      Lite（proxyBeanMethods = false）
 *      组件依赖
 */

/**
	proxyBeanMethods这个属性是并不是决定容器中的组件是单例还是多例的。如果说他是true，就是单例。如果说是false，但却不是多
例。当他为true的时候，我们在容器中获取到的对象总是同一个，即便是我们调用了创建对象的方法，那获取到的还是同一个。但是当是多例的
时候，如果我们调用了创建对象的方法，那就不是同一个了。但是我们如果是用getBeans方法去获取的话，那样还是单例的，我们得到的还是同
一个对象。
	但是我们这样去思考还是太简单了。其实，proxyBeanMethods代表的是，如果是true的话，那么这个配置类就会被代理了，如果是false
的话，那么就不会被代理。
	当我们使用代理对象的时候，调用它的方法，他会检测容器中是不是有了这样的组件，如果有，则不再新建组件，直接将已经有的组件返
回。如果说没有的话，才会新建组件。这样保证了容器中的组件始终就保持单一性。不过这也有一个不好的地方，那就是每次都要检测，会降低
速度。
	当不是代理对象的时候，则不会检测，直接创建新的组件了。
*/
@Configuration(proxyBeanMethods = false)  //告诉Springboot这是一个配置类 == 配置文件
public class MyConfig {

    /**
     * 外部无论对配置文类中的这个组件注册方法调用多少次，获取到的都是之前注册到容器中的单实例对象
     */
    @Bean   //给容器中添加组件。以方法名
    public User user01(){
        User zhangsan = new User("zhangsan", 18);
        //user组件依赖了pet组件
        zhangsan.setPet(pet01());
        return zhangsan;
    }

    @Bean("tom")
    public Pet pet01(){
        return new Pet("tom");
    }
}

MainApplication.java

package site.shaoshao.boot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import site.shaoshao.boot.bean.Pet;
import site.shaoshao.boot.bean.User;
import site.shaoshao.boot.config.MyConfig;

/**
 * 主程序类
 */
@SpringBootApplication
public class MainApplication {
    public static void main(String[] args) {
        // 返回IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
        // 查看容器中组件
        String[] names = run.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
        // 从容器中获取组件
        Pet tom01 = run.getBean("tom", Pet.class);
        Pet tom02 = run.getBean("tom", Pet.class);
        System.out.println("组件单实例："+(tom01==tom02));// true

        MyConfig bean = run.getBean(MyConfig.class);
        User user01 = bean.user01();
        User user02 = bean.user01();
        //如果@Configuration(proxyBeanMethods = true)代理对象调用方法。springboot总会检查这个组件是否在容器中注册
        //保持组件单实例
        //System.out.println("proxyBeanMethods = true: user01 == user02: "+(user01 == user02)); // true
        System.out.println("proxyBeanMethods = false: user01 == user02: "+(user01 == user02)); // false

        User user = run.getBean("user01", User.class);
        Pet tom = run.getBean("tom",Pet.class);
        //System.out.println("proxyBeanMethods = true: 用户宠物是否为容器中的宠物：" + (user.getPet() == tom)); // true
        System.out.println("proxyBeanMethods = false: 用户宠物是否为容器中的宠物：" + (user.getPet() == tom)); // false
    }
}

最佳实战
- 配置类组件之间无依赖关系用 Lite 模式加速容器启动过程，减少判断
- 配置类组件之间有依赖关系，方法会被调用得到之前单实例组件，用 Full 模式

2. @Bean、@Component、@Controller、@Service、@Repository

3. @ComponentScan、@Import

@Import(Class[])
- @Import({User.class, DBHelper.class})
- 给容器中自动创建出这两个类型的组件
- @Import 高级用法： https://www.bilibili.com/video/BV1gW411W7wy?p=8

4. @Conditioal

MyConfig.java

package site.shaoshao.boot.config;

import ch.qos.logback.core.db.DBHelper;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import site.shaoshao.boot.bean.Pet;
import site.shaoshao.boot.bean.User;

/**
 * 1. 配置类里面使用@Bean标注在方法上给容器注册组件，默认也是单实例
 * 2. 配置类本身也是组件
 * 3. 5.2后 proxyBeanMethods：代理bean的方法
 *      Full（proxyBeanMethods = true）
 *      Lite（proxyBeanMethods = false）
 *      组件依赖
 *
 * 4. @Import({User.class, DBHelper.class})
 *      给容器中自动创建出这两个类型的组件
 *
 */
@ConditionalOnBean(name = "tom")
@Import({User.class, DBHelper.class})
@Configuration(proxyBeanMethods = true)  //告诉Springboot这是一个配置类 == 配置文件
public class MyConfig {

    /**
     * 外部无论对配置文类中的这个组件注册方法调用多少次，获取到的都是之前注册到容器中的单实例对象
     */
    @Bean   //给容器中添加组件。以方法名
    public User user01(){
        User zhangsan = new User("zhangsan", 18);
        //user组件依赖了pet组件
        zhangsan.setPet(pet01());
        return zhangsan;
    }

    @Bean("tom1")
    public Pet pet01(){
        return new Pet("tom");
    }
}

MainApplication.java

package site.shaoshao.boot;

import ch.qos.logback.core.db.DBHelper;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import site.shaoshao.boot.bean.Pet;
import site.shaoshao.boot.bean.User;
import site.shaoshao.boot.config.MyConfig;

/**
 * 主程序类
 */
//@SpringBootApplication
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan("site.shaoshao.boot")
public class MainApplication {
    public static void main(String[] args) {
        // 返回IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
//        // 查看容器中组件
//        String[] names = run.getBeanDefinitionNames();
//        for (String name : names) {
//            System.out.println(name);
//        }
//        // 从容器中获取组件
//        Pet tom01 = run.getBean("tom", Pet.class);
//        Pet tom02 = run.getBean("tom", Pet.class);
//        System.out.println("组件单实例："+(tom01==tom02));// true
//
//        MyConfig bean = run.getBean(MyConfig.class);
//        User user01 = bean.user01();
//        User user02 = bean.user01();
//        //如果@Configuration(proxyBeanMethods = true)代理对象调用方法。springboot总会检查这个组件是否在容器中注册
//        //保持组件单实例
//        //System.out.println("proxyBeanMethods = true: user01 == user02: "+(user01 == user02)); // true
//        System.out.println("proxyBeanMethods = false: user01 == user02: "+(user01 == user02)); // false
//
//        User user = run.getBean("user01", User.class);
//        Pet tom = run.getBean("tom",Pet.class);
//        //System.out.println("proxyBeanMethods = true: 用户宠物是否为容器中的宠物：" + (user.getPet() == tom)); // true
//        System.out.println("proxyBeanMethods = false: 用户宠物是否为容器中的宠物：" + (user.getPet() == tom)); // false
//
//        String[] beanNamesForType = run.getBeanNamesForType(User.class);
//        System.out.println("===============");
//        for (String s : beanNamesForType) {
//            System.out.println(s);
//        }
//
//        DBHelper bean1 = run.getBean(DBHelper.class);
//        System.out.println(bean1);
        boolean tom = run.containsBean("tom");
        System.out.println("容器中含有tom组件：" + tom);//false

        boolean user01 = run.containsBean("user01");
        System.out.println("容器中含有tom组件：" + user01);//false

        boolean tom1 = run.containsBean("tom1");
        System.out.println("容器中含有tom组件：" + tom1);
        //@ConditionalOnBean(name = "tom") 标注在类上===>false
        //@ConditionalOnBean(name = "tom") 标注在方法上===>true
    }
}

2.2 原生配置文件引入

1. @ImportResource

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="haha" class="site.shaoshao.boot.bean.User">
        <property name="username" value="zhangsan"></property>
        <property name="age" value="18"></property>
    </bean>
    <bean id="hehe" class="site.shaoshao.boot.bean.Pet">
        <property name="name" value="tom"></property>
    </bean>
</beans>

MyConfig.java

package site.shaoshao.boot.config;

import ch.qos.logback.core.db.DBHelper;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.ImportResource;
import site.shaoshao.boot.bean.Pet;
import site.shaoshao.boot.bean.User;

/**
 * 1. 配置类里面使用@Bean标注在方法上给容器注册组件，默认也是单实例
 * 2. 配置类本身也是组件
 * 3. 5.2后 proxyBeanMethods：代理bean的方法
 *      Full（proxyBeanMethods = true）
 *      Lite（proxyBeanMethods = false）
 *      组件依赖
 *
 * 4. @Import({User.class, DBHelper.class})
 *      给容器中自动创建出这两个类型的组件
 *
 */
//@ConditionalOnBean(name = "tom")
//@Import({User.class, DBHelper.class})
@Configuration(proxyBeanMethods = false)  //告诉Springboot这是一个配置类 == 配置文件
@ImportResource("classpath:beans.xml")
public class MyConfig {

    /**
     * 外部无论对配置文类中的这个组件注册方法调用多少次，获取到的都是之前注册到容器中的单实例对象
     */
    @Bean   //给容器中添加组件。以方法名
    public User user01(){
        User zhangsan = new User("zhangsan", 18);
        //user组件依赖了pet组件
        zhangsan.setPet(pet01());
        return zhangsan;
    }

    @Bean("tom1")
    public Pet pet01(){
        return new Pet("tom");
    }
}

MainApplication.java

package site.shaoshao.boot;

import ch.qos.logback.core.db.DBHelper;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;

/**
 * 主程序类
 */
//@SpringBootApplication
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan("site.shaoshao.boot")
public class MainApplication {
    public static void main(String[] args) {
        // 返回IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);

        boolean haha = run.containsBean("haha");
        System.out.println("容器中含有haha组件：" + haha);// true

        boolean hehe = run.containsBean("hehe");
        System.out.println("容器中含有hehe组件：" + hehe);// true
    }
}

2.3 配置绑定

如何使用Java读取到properties文件中的内容，并且把它封装到JavaBean中，以供随时使用；

public class getProperties {
     public static void main(String[] args) throws FileNotFoundException, IOException {
         Properties pps = new Properties();
         pps.load(new FileInputStream("a.properties"));
         Enumeration enum1 = pps.propertyNames();//得到配置文件的名字
         while(enum1.hasMoreElements()) {
             String strKey = (String) enum1.nextElement();
             String strValue = pps.getProperty(strKey);
             System.out.println(strKey + "=" + strValue);
             //封装到JavaBean。
         }
     }
 }

1. @Component + @ConfigurationProperties

application.properties

1 2	mycar.brand=BYD mycar.price=100000

Car.java

package site.shaoshao.boot.bean;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

/**
 * 只有在容器中的组件，才会拥有springboot提供的强大功能
 */
@Component
@ConfigurationProperties(prefix = "mycar")
public class Car {
    private String brand;
    private Integer price;

    public Car() {
    }

    public Car(String brand, Integer price) {
        this.brand = brand;
        this.price = price;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public Integer getPrice() {
        return price;
    }

    public void setPrice(Integer price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Car{" +
                "brand='" + brand + '\'' +
                ", price=" + price +
                '}';
    }
}

Controller.java

package site.shaoshao.boot.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import site.shaoshao.boot.bean.Car;

@RestController
public class HelloController {
    @Autowired
    Car car;

    @RequestMapping("/hello")
    public String handle01(){
        return "hello spring boot!";
    }

    @RequestMapping("/car")		//返回{"brand":"BYD","price":100000}
    public Car car(){
        return car;
    }
}

2. @EnableConfigurationProperties + @ConfigurationProperties

在 MyConfig.java 中添加

1 2	@EnableConfigurationProperties(Car.class) //省略 Car.java 中的 @Condition //1. 开启Car的配置绑定功能 2. 把这个Car这个组件自动注册到容器中

3 自动配置原理入门

3.1 引导加载自动配置类

@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    classes = {TypeExcludeFilter.class}
), @Filter(
    type = FilterType.CUSTOM,
    classes = {AutoConfigurationExcludeFilter.class}
)}
)
public @interface SpringBootApplication{}


========================================

1. @SpringBootConfiguration

@Configuration：代表当前是一个配置类；

2. @ComponentScan

指定扫描哪些包，Spring注解；

3. @EnableAutoConfiguration

1
2
3

@AutoConfigurationPackage
@Import({AutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {}

@AutoConfigurationPackage
- 自动配置包

1
2
3

@Import({Registrar.class})	//给容器中导入一个Registrar组件
						//将指定的包（MainApplication所在的包）下的所有组件导入进来
public @interface AutoConfigurationPackage {}

@Import({AutoConfigurationImportSelector.class})

public String[] selectImports(AnnotationMetadata annotationMetadata) {
    if (!this.isEnabled(annotationMetadata)) {
        return NO_IMPORTS;
    } else {
        AutoConfigurationImportSelector.AutoConfigurationEntry autoConfigurationEntry = this.getAutoConfigurationEntry(annotationMetadata);
        return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
    }
}
1. 利用getAutoConfigurationEntry(annotationMetadata);给容器中批量导入一些组件
2. 调用List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);
		获取到所有需要导入到容器中的配置类（组件）
3. 利用工厂加载 Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader)，得到所有的组件
4. 从 META-INF/spring.factories 位置加载一个文件
	默认扫描我们当前系统里面所有META-INF/spring.factories位置的文件
    spring-boot-autoconfigure-2.3.4.RELEASE.jar包里面也有META-INF/spring.factories

文件里面写死了spring-boot一启动就要给容器中加载的所有配置类
spring-boot-autoconfigure-2.3.4.RELEASE.jar/META-INF/spring.factories
# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\
org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,\
org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,\
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,\
org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration,\
org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\
org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,\
org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRestClientAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jdbc.JdbcRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,\
org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientAutoConfiguration,\
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\
org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,\
org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\
org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration,\
org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration,\
org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration,\
org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration,\
org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,\
org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,\
org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\
org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,\
org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,\
org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration,\
org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\
org.springframework.boot.autoconfigure.r2dbc.R2dbcAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketStrategiesAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.rsocket.RSocketSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.saml2.Saml2RelyingPartyAutoConfiguration,\
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveOAuth2ClientAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration,\
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\
org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration,\
org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\
org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration,\
org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.ClientHttpConnectorAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.client.WebServiceTemplateAutoConfiguration

3.2 按需开启自动配置项

1 2	虽然我们127个场景的所有自动配置启动的时候默认全部加载。xxxxAutoConfiguration 按照条件装配规则（@Conditional），最终会按需配置。

3.3 修改默认配置

@Bean
@ConditionalOnBean(MultipartResolver.class)  //容器中有这个类型组件
@ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME) //容器中没有这个名字 multipartResolver 的组件
public MultipartResolver multipartResolver(MultipartResolver resolver) {
    //给@Bean标注的方法传入了对象参数，这个参数的值就会从容器中找。
    //SpringMVC multipartResolver。防止有些用户配置的文件上传解析器不符合规范
    // Detect if the user has created a MultipartResolver but named it incorrectly
    return resolver;
}
给容器中加入了文件上传解析器；

SpringBoot默认会在底层配好所有的组件。但是如果用户自己配置了以用户的优先

@Bean
@ConditionalOnMissingBean
public CharacterEncodingFilter characterEncodingFilter() {
}

总结：

SpringBoot先加载所有的自动配置类 xxxxxAutoConfiguration
每个自动配置类按照条件进行生效，默认都会绑定配置文件指定的值。xxxxProperties里面拿。xxxProperties和配置文件进行了绑定
生效的配置类就会给容器中装配很多组件
只要容器中有这些组件，相当于这些功能就有了
定制化配置
- 用户直接自己@Bean替换底层的组件
- 用户去看这个组件是获取的配置文件什么值就去修改。

xxxxxAutoConfiguration —> 组件 —> xxxxProperties里面拿值 —-> application.properties

3.4 最佳实践

引入场景依赖
- https://docs.spring.io/spring-boot/docs/current/reference/html/using-spring-boot.html#using-boot-starter
查看自动配置了哪些（选做）
- 自己分析，引入场景对应的自动配置一般都生效了
- 配置文件中debug=true开启自动配置报告。Negative（不生效）\Positive（生效）
是否需要修改
- 参照文档修改配置项
- - https://docs.spring.io/spring-boot/docs/current/reference/html/appendix-application-properties.html#common-application-properties
  - 自己分析。xxxxProperties绑定了配置文件的哪些。
- 自定义加入或者替换组件
- - @Bean、@Component。。。
- 自定义器 XXXXXCustomizer；
- ……

4 开发小技巧

4.1 Lombok

简化JavaBean开发

<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
</dependency>


idea中搜索安装lombok插件
===============================简化JavaBean开发===================================
@Data                   //gatter、setter方法
@ToString               //toString()方法
@AllArgsConstructor     //全参构造器
@NoArgsConstructor      //无参构造器
@EqualsAndHashCode		//equalsAndHashCode()方法
public class User {

    private String name;
    private Integer age;
    private Pet pet;

    public User(String name,Integer age){
        this.name = name;
        this.age = age;
    }
}



================================简化日志开发===================================
@Slf4j			//日志
@RestController
public class HelloController {
    @RequestMapping("/hello")
    public String handle01(@RequestParam("name") String name){
        
        log.info("请求进来了....");
        
        return "Hello, Spring Boot 2!"+"你好："+name;
    }
}

4.2 dev-tools

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <optional>true</optional>
</dependency>