正常利用springboot的自动装配
ConfB
@Configuration(proxyBeanMethods=false)
public class ConfB {
public ConfB(){
System.out.println("ConfB构造方式执行...");
}
}
不加spring.factories
项目包结构
此时resources中没有spring.factories
执行结果
2023-02-24 13:44:49.809 INFO 33820 --- [ main] test.MyStarterApplication : No active profile set, falling back to default profiles: default
2023-02-24 13:44:50.294 INFO 33820 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2023-02-24 13:44:50.300 INFO 33820 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2023-02-24 13:44:50.300 INFO 33820 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.46]
2023-02-24 13:44:50.354 INFO 33820 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2023-02-24 13:44:50.354 INFO 33820 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 518 ms
2023-02-24 13:44:50.456 INFO 33820 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2023-02-24 13:44:50.954 INFO 33820 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2023-02-24 13:44:51.004 INFO 33820 --- [ main] test.MyStarterApplication : Started MyStarterApplication in 1.422 seconds (JVM running for 2.013)
没看到ConfB构造方法执行，因为执行类·MyStarterApplication·在test包下，test和conf包是并列关系，所以启动时是扫描不到conf包下的内容的，又因为没有spring.factories所以没有加载到ConfB是正常情况。下面加 spring.factories
添加spring.factories
项目包结构
spring.factories
执行结果
2023-02-24 13:46:21.289 INFO 6400 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2023-02-24 13:46:21.294 INFO 6400 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2023-02-24 13:46:21.294 INFO 6400 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.46]
2023-02-24 13:46:21.349 INFO 6400 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2023-02-24 13:46:21.349 INFO 6400 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 515 ms
2023-02-24 13:46:21.445 INFO 6400 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
ConfB构造方式执行...
2023-02-24 13:46:21.944 INFO 6400 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2023-02-24 13:46:21.977 INFO 6400 --- [ main] test.MyStarterApplication : Started MyStarterApplication in 1.397 seconds (JVM running for 1.97)
看到ConfB被正常加载了
其实ConfB已经在spring.factories中指定了，所以类上不加@Configuration注解也可以加载的，如果加的话也是使用@Configuration(proxyBeanMethods=false)
@AutoConfigureBefore、@AutoConfigureAfter的注意事项
@AutoConfigureBefore、@AutoConfigureAfter是用来控制bean之间的加载顺序的，但也有很多的问题要注意
新增ConfA 和ConfC
ConfA
public class ConfA {
public ConfA(){
System.out.println("ConfA构造方式执行...");
}
}
ConfB
@AutoConfigureAfter(ConfA.class)
@AutoConfigureBefore(ConfC.class)
public class ConfB {
public ConfB(){
System.out.println("ConfB构造方式执行...");
}
}
ConfC
public class ConfC {
public ConfC(){
System.out.println("ConfC构造方式执行...");
}
}
正常的控制加载顺序
项目结构
spring.factories
执行结果
2023-02-24 13:49:20.099 INFO 23672 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2023-02-24 13:49:20.099 INFO 23672 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.46]
2023-02-24 13:49:20.157 INFO 23672 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2023-02-24 13:49:20.157 INFO 23672 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 528 ms
2023-02-24 13:49:20.253 INFO 23672 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
ConfA构造方式执行...
ConfB构造方式执行...
ConfC构造方式执行...
2023-02-24 13:49:20.740 INFO 23672 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2023-02-24 13:49:20.796 INFO 23672 --- [ main] test.MyStarterApplication : Started MyStarterApplication in 1.427 seconds (JVM running for 2.048)
可以看到@AutoConfigureBefore、@AutoConfigureAfter作用生效了ConfA 、ConfB 、ConfC 按照指定的顺序进行了加载
不能进行加载
项目结构不变，把ConfA 、ConfC 从spring.factories去除，然后在这两个类上加上@Configuration(proxyBeanMethods=false)注解再试试
ConfA
@Configuration(proxyBeanMethods=false)
public class ConfA {
public ConfA(){
System.out.println("ConfA构造方式执行...");
}
}
ConfC
@Configuration(proxyBeanMethods=false)
public class ConfC {
public ConfC(){
System.out.println("ConfC构造方式执行...");
}
}
spring.factories
执行结果
2023-02-24 13:52:42.244 INFO 16748 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2023-02-24 13:52:42.245 INFO 16748 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.46]
2023-02-24 13:52:42.299 INFO 16748 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2023-02-24 13:52:42.299 INFO 16748 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 513 ms
2023-02-24 13:52:42.394 INFO 16748 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
ConfB构造方式执行...
2023-02-24 13:52:42.875 INFO 16748 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2023-02-24 13:52:42.920 INFO 16748 --- [ main] test.MyStarterApplication : Started MyStarterApplication in 1.392 seconds (JVM running for 2.02)
可以看到只有ConfB加载成功。
结论：使用@AutoConfigureBefore、@AutoConfigureAfter中的类必须在spring.factories中指定才行
不能控制加载顺序
那么再换种思路，不在spring.factories中指定，但是使用@Configuration注解让springboot启动时自动扫描到来处理呢，试一下
ConfA
@Configuration(proxyBeanMethods=false)
public class ConfA {
public ConfA(){
System.out.println("ConfA构造方式执行...");
}
}
ConfB
@AutoConfigureAfter(ConfA.class)
@AutoConfigureBefore(ConfC.class)
@Configuration(proxyBeanMethods=false)
public class ConfB {
public ConfB(){
System.out.println("ConfB构造方式执行...");
}
}
ConfC
@Configuration(proxyBeanMethods=false)
public class ConfC {
public ConfC(){
System.out.println("ConfC构造方式执行...");
}
}
项目结构
spring.factories
将conf包放到了test包下，这样springboot的启动类就能自动扫描到ConfA、ConfB、ConfC了
执行结果
2023-02-24 13:54:38.107 INFO 27784 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2023-02-24 13:54:38.107 INFO 27784 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.46]
2023-02-24 13:54:38.161 INFO 27784 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2023-02-24 13:54:38.161 INFO 27784 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 515 ms
ConfA构造方式执行...
ConfC构造方式执行...
2023-02-24 13:54:38.257 INFO 27784 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
ConfB构造方式执行...
2023-02-24 13:54:38.741 INFO 27784 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2023-02-24 13:54:38.797 INFO 27784 --- [ main] test.MyStarterApplication : Started MyStarterApplication in 1.41 seconds (JVM running for 2.025)
可以看到ConfA、ConfB、ConfC没有按照指定的顺序进行加载
结论：
将 ConfA、ConfB、ConfC 添加到 spring.factories 中。在保证不会被扫描包自动扫描到的范围内的情况下才能够保证指定顺序的加载
总结
- 自定义 starter 中spring.factories 中指定的配置类，要避免被自动扫描到才行
- @ComponetScan 也就是自动扫描能扫描到的范围下的配置类，会立即初始化，所以这三个配置类的加载顺序也就无法保证了。
- spring.factories 中的指定的配置类是不需要 @Configuration 注解的，如果要配置@Configuration 注解，要配置成@Configuration(proxyBeanMethods = false)
