很少寫部落格了，似乎就為了讓自己不斷加深印象來寫部落格啦~ 

遇到的問題 是 spring boot 啟動不起來 問題 是 

Field XXX  that could not be found.

給出的建議Action:

Consider defining a bean of type 'XX ‘ in your configuration.

Spring載入外部Bean兩種方式
將定義在另外一個帶有@Configuration的類中的Bean載入
1. 在Application類中使用@Import指定該類，
2.讓@ComponentScan掃描到該類。

大多數使用的2. 實際上是要在spring boot 初始化前加入該類所在的包 進行掃描

在spring boot 主啟動main函式上面加上預設的 掃描就好

@ComponentScan(basePackageClasses = {"XX", "XX.XX"})

如果想用自己的註解時可以使用SpringBootApplication 進行中間轉化 

自己封裝一個啟動註解時 

public @interface App {
   
    @AliasFor(annotation = SpringBootApplication.class, attribute = "scanBasePackages")
    String[] scanBasePackages() default {};

    @AliasFor(annotation = SpringBootApplication.class, attribute = "scanBasePackageClasses")
    Class<?>[] scanBasePackageClasses() default {};
}
 

要不就直接用

SpringBootApplication

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.springframework.boot.autoconfigure;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.context.TypeExcludeFilter;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.ComponentScan.Filter;
import org.springframework.core.annotation.AliasFor;

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    classes = {TypeExcludeFilter.class}
)}
)
public @interface SpringBootApplication {
    Class<?>[] exclude() default {};

    String[] excludeName() default {};

    @AliasFor(
        annotation = ComponentScan.class,
        attribute = "basePackages"
    )
    String[] scanBasePackages() default {};

    @AliasFor(
        annotation = ComponentScan.class,
        attribute = "basePackageClasses"
    )
    Class<?>[] scanBasePackageClasses() default {};
}