SpringBoot中提供了很多Enable开头的注解，这些注解都是用于动态启用某些功能的。而其底层原理是使用@Import注 解导入一些配置类，实现Bean的动态加载。
提问：SpringBoot 工程是否可以直接获取jar包中定义的Bean？
答：不可以
案例：
两个子模块
①子模块要得到
②子模块的User类的bean（这里用编号表示）
方法一：使用@ComponentScan扫描com.itheima.springbooyembal包
package com.enable.entity;
public class User {
}package com.enable.config;
import com.enable.entity.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class UserConfig {
@Bean
public User user(){
return new User();
}
}
引入依赖：
<dependency>
<groupId>com.enable</groupId>
<artifactId>springboot-enable-other</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>使用ComponentScan：
package com.example.demo;
import com.enable.config.EnableUser;
import com.enable.config.UserConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
@SpringBootApplication
@ComponentScan("com.enable.config")
public class SpringbootApplication {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(SpringbootApplication.class, args);
Object user = context.getBean("user");
System.out.println(user);
}
}测试如下：
方法二：可以使用@Import注解，加载类，这些类都会被Spring创建，并放入IOC容器。
package com.enable.entity;
public class User {
}package com.enable.config;
import com.enable.entity.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class UserConfig {
@Bean
public User user(){
return new User();
}
}
引入依赖
<dependency>
<groupId>com.enable</groupId>
<artifactId>springboot-enable-other</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>使用Import注解
package com.example.demo;
import com.enable.config.EnableUser;
import com.enable.config.UserConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
@SpringBootApplication
@Import(UserConfig.class)
public class SpringbootApplication {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(SpringbootApplication.class, args);
Object user = context.getBean("user");
System.out.println(user);
}
}测试如下：
方法三：对@Import注解进行封装
自定义@EnableUser注解
package com.enable.config;
import org.springframework.context.annotation.Import;
import java.lang.annotation.*;
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(UserConfig.class)
public @interface EnableUser {
}自定义配置类
package com.enable.config;
import com.enable.entity.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class UserConfig {
@Bean
public User user(){
return new User();
}
}新建实体类：
package com.enable.entity;
public class User {
}
引入依赖
<dependency>
<groupId>com.enable</groupId>
<artifactId>springboot-enable-other</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>使用自定义的注解
package com.example.demo;
import com.enable.config.EnableUser;
import com.enable.config.UserConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
@SpringBootApplication
@EnableUser
public class SpringbootApplication {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(SpringbootApplication.class, args);
Object user = context.getBean("user");
System.out.println(user);
}
}测试如下：
