# springboot-learn

**Repository Path**: serain/springboot-learn

## Basic Information

- **Project Name**: springboot-learn
- **Description**: SpringBoot学习交流项目
- **Primary Language**: Java
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2018-09-04
- **Last Updated**: 2020-12-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# SpringBoot示例项目列表
> 所有项目基于SpringBoot2构建

* springboot-introduction

  最简单的一个入门例子

* example

 ExampleService接口及实现

* example-springboot-starter
 
 基于配置文件中某个配置项(在这里是example.service.enabled)启用的方式

* example-springboot-starter-demo
 
 基于配置文件启用的方式,使用示例

* example-annocation-springboot-starter

 基于注解启用的方式



* example-annocation-springboot-starter-demo

 基于配置文件启用的方式,使用示例

* springboot-jpa-with-h2-unit-test
 
 演示springboot如何整合jpa，以及如何使用h2来做单元测试,Swagger接口文档




# 自定义spring-boot-starter之使用注解方式启用

## 定义启用注解
```java
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface EnableExampleService {

}
```

## 自动配置类上加是否存在启用注解
> 关键就是这一句@ConditionalOnBean(annotation = EnableExampleService.class)
```java
@Configuration
@ConditionalOnBean(annotation = EnableExampleService.class)
@ConditionalOnClass(ExampleService.class)
@EnableConfigurationProperties(ExampleServiceProperties.class)
public class ExampleServiceAutoConfiguration {

    @Autowired
    private ExampleServiceProperties exampleServiceProperties;

    private static final String TEXT_TRANSFORM_LOWERCASE = "lowercase";

    private static final String TEXT_TRANSFORM_UPPERCASE = "uppercase";

    @Bean
    @ConditionalOnMissingBean
    public ExampleService exampleService (){
        if(TEXT_TRANSFORM_LOWERCASE.equalsIgnoreCase(exampleServiceProperties.getTextTransform())){
            return new ExampleLowercaseServiceImpl(exampleServiceProperties.getPrefix(),exampleServiceProperties.getSuffix());
        }
        if(TEXT_TRANSFORM_UPPERCASE.equalsIgnoreCase(exampleServiceProperties.getTextTransform())){
            return new ExampleUppercaseServiceImpl(exampleServiceProperties.getPrefix(),exampleServiceProperties.getSuffix());
        }
        throw new IllegalArgumentException("example.service.text-transform only can be one of lowercase or uppercase");
    }
}
```
## resources/META-INF/spring.factories定义好自动化配置类,以便SpringFactoriesLoader加载
```properties
org.springframework.boot.autoconfigure.EnableAutoConfiguration=cn.jaychang.example.ExampleServiceAutoConfiguration
``` 

# 参考资料

https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#using-boot-maven-without-a-parent
https://www.jianshu.com/p/346cac67bfcc
https://docs.spring.io/spring-boot/docs/current/reference/html/configuration-metadata.html