自动配置
Auto Configuration
spring-boot-autoconfiguration jar 包含 Spring Boot 自动配置代码。
- 开启：@EnableAutoConfiguration
- @SpringBootApplication 已包含 @EnableAutoConfiguration，实际使用直接 @SpringBootApplication
- 若不想使用一些自动配置，@EnableAutoConfiguration(exclude = { DataSourceAutoConfiguration.class }) 使用数据源的自动配置
Spring Boot 都包含哪些自动配置？
org.springframework.boot.autoconfigure.AutoConfigurationImportSelector#selectImports
->org.springframework.boot.autoconfigure.AutoConfigurationImportSelector#getAutoConfigurationEntry
->org.springframework.boot.autoconfigure.AutoConfigurationImportSelector#getCandidateConfigurations
protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
// 打开本jar 下的 META-INF/spring.factories 文件
// org.springframework.boot.autoconfigure.EnableAutoConfiguration 对应的值就是 Spring Boot 包含的所有自动配置类
List<String> configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());
Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");
return configurations;
}
原理
自动配置是如何生效的呢？Condition：通过条件判断生成对应 Bean，完成自动配置
public class DataSourceAutoConfiguration {
@Conditional({DataSourceAutoConfiguration.EmbeddedDatabaseCondition.class})
@ConditionalOnMissingBean({DataSource.class, XADataSource.class})
@Import({EmbeddedDataSourceConfiguration.class})
protected static class EmbeddedDatabaseConfiguration {
protected EmbeddedDatabaseConfiguration() {
}
}
}
- 满足 DataSourceAutoConfiguration.EmbeddedDatabaseCondition getMatchOutcome 函数里的条件
- 不包含 DataSource.class, XADataSource.class Bean
- EmbeddedDataSourceConfiguration 生成 EmbeddedDataSource
观察
Spring Boot 自动配置有很多，怎么知道哪些配置生效/没生效。在程序启动时加 “–debug”，日志级别 DEBUG
- 自动配置已匹配
Positive matches:
-----------------
AopAutoConfiguration matched:
- @ConditionalOnProperty (spring.aop.auto=true) matched (OnPropertyCondition)
AopAutoConfiguration.AspectJAutoProxyingConfiguration matched:
- @ConditionalOnClass found required class 'org.aspectj.weaver.Advice' (OnClassCondition)
...
- 自动配置未匹配
Negative matches:
-----------------
ActiveMQAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required class 'javax.jms.ConnectionFactory' (OnClassCondition)
...
- 自动配置未包含
Exclusions:
-----------
org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration
- 不需要满足条件的自动配置
Unconditional classes:
----------------------
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration
com.tuya.middleware.dubai.utils.Config
...
自定义自动配置
- 编写 Java Config：@Configuration
- 添加条件：@Conditional
- 让Spring Boot 能够找到：META-INF/spring.factories 里写入 Class
起步依赖
Starter Dependency
- dependencyManagement：统一管理 jar 版本
Actuator
监控和管理应用程序
