foreword
Usually we always write some non-business-related public codes in our work. These public codes are usually placed in a module separately. When using springBoot for development, the spring team provides us with many out-of-the-box starters. Then How to create your own starter to encapsulate these public non-business codes
Create starter submodule
First look at the structure of the project
Let's start creating our demo-spring-boot-starter
1. Create properties attribute entity
@ConfigurationProperties(prefix = "spring.demo")
public class DemoProperties {
private String name;
private Integer age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}
2. Create service
public class DemoService {
private final DemoProperties demoProperties;
public DemoService(DemoProperties demoProperties) {
this.demoProperties = demoProperties;
}
public void test(){
System.out.println(this.demoProperties.getName() +"-"+this.demoProperties.getAge());
}
}
3. Create autoConfig
@Configuration
@ConditionalOnClass(DemoProperties.class)
@EnableConfigurationProperties(DemoProperties.class)
public class DemoAutoConfiguration {
private DemoProperties demoProperties;
@Bean
@ConditionalOnMissingBean
public DemoService demoService(){
return new DemoService(demoProperties);
}
}
Here is a brief introduction to the use of several conditional annotations
- @ConditionalOnBean //This bean will only be created when the bean is required to exist
- @ConditionalOnMissingBean //This bean will only be created when the bean does not exist
- @ConditionalOnClass //This bean will only be created when the class exists
- @ConditionalOnMissingClass //The bean will only be created when the class does not exist.
These conditional annotations can control the timing of bean injection, so that when a third party introduces our dependencies, an exception will be thrown because there is no bean or class. After
that , and annotations such as @DependsOn can control the injection order of beans;
4. Create spring.factories and expose autoConfig
After creating the META-INF folder under the resources folder, create spring.factories
org.springframework.boot.autoconfigure.EnableAutoConfiguration= \
com.demo.config.DemoAutoConfiguration
At this point, a custom starter has been created, and then it can be packaged into a jar and used happily.