Dynamic Service Provider Switching with Spring-Smart-DI's @AutowiredProxySPI

1. spring-smart-di Introduction

spring-smart-di

is an innovative extension of Spring's @Autowired annotation that provides custom autowiring logic. It implements two key annotations: @SmartAutowired and @AutowiredProxySPI. This article focuses on @AutowiredProxySPI for dynamic service provider switching.

2. Quick Start

2.1 Add Dependency

Add the following Maven dependency to pom.xml:

<dependency>
  <groupId>io.github.burukeyou</groupId>
  <artifactId>spring-smart-di-all</artifactId>
  <version>0.2.0</version>
</dependency>

2.2 Enable Functionality

Annotate a Spring configuration class with @EnableSmartDI to activate the framework.

2.3 @EnvironmentProxySPI Annotation Usage

@EnvironmentProxySPI

defines a configuration point that determines how to retrieve the active implementation class. For example, with two SMS providers:

@EnvironmentProxySPI("${sms.impl}")
public interface SmsService {}

@BeanAliasName("某腾短信服务")
@Component
public class ASmsService implements SmsService {}

@BeanAliasName("某移短信服务")
@Component
public class BSmsService implements SmsService {}

The interface is annotated with @EnvironmentProxySPI referencing the property ${sms.impl}. Each implementation gets a @BeanAliasName for identification.

2.4 Configure Active Service Provider

In the configuration file (e.g., YAML), set the active provider using the alias, component name, or fully qualified class name:

sms:
  impl: 某移短信服务

2.5 @AutowiredProxySPI Injection

Inject the service interface using @AutowiredProxySPI just like @Autowired:

@AutowiredProxySPI
private SmsService smsService;

Changing ${sms.impl} takes effect immediately without restart because @AutowiredProxySPI injects a proxy that resolves the current implementation on each invocation.

2.6 Custom Configuration Points

For non-environment configuration sources (e.g., database), create a custom @ProxySPI annotation. Example @DBProxySPI reading from a database:

@Inherited
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@ProxySPI(DbProxyFactory.class)
public @interface DBProxySPI {
  String value();
}

@Component
public class DbProxyFactory implements AnnotationProxyFactory<DBProxySPI> {
  @Autowired
  private SysConfigMapper sysConfigDao;

  @Override
  public Object getProxy(Class<?> targetClass, DBProxySPI spi) {
    String configName = sysConfigDao.getConfig(spi.value());
    return springContext.getBean(configName);
  }
}

@DBProxySPI("${sms.impl}")
public interface SmsService {}

The factory implements AnnotationProxyFactory and uses a mapper to fetch the active implementation name from the database, then returns the corresponding Spring bean.