Spring boot magic Hall: talking about spring boot starter with intelligent tips

Preface

A few months ago, I chatted with Lao Wang from the next group , He said there was a high turnover rate among suppliers of the project , Recently, we have just taken over the development ESB Only two weeks after the subscription publishing interface proposed to quit , And all he could do was smile bitterly and take over the mess in silence .
But happy families are always similar , Unfortunately, I was on the same road as Lao Wang because of the business transformation . The development of interface alone can force a developer to leave his job resolutely , I don't believe in the distortion of human nature , Not to believe is the decline of morality .
Put aside this colorful story , I found that the original project had the following problems ：

No modern dependency management and build tools are used ( Such as Maven, Gradle), Put directly what you depend on Jar The package is stored in the project directory lib Directory , Over time leads to lib There are a lot of useless in the directory Jar package ;
No code version management tools are used to manage code ;
Lack of technical documentation , All rely on the master with apprentice way to teach the use of the framework and development process ;
There are many mechanical configuration items , And later developers can only follow the example to add configuration , It is easy to make mistakes and increase the difficulty of troubleshooting .

For the first two questions , We just need to tease out the necessary dependencies and add Maven or Gradle management , And then escrow to Git that will do .
The latter two can be done through spring-boot-starter Unified management of required dependencies and configurations , Relevant technical documents are attached ; Then simplify the development process through template patterns and annotations , Provide Demo Make it easier to get started .
Finally, the specific business function development can be handed over to the supplier , We can concentrate on process management and acceptance .

This article will focus on sharing spring-boot-starter Development matters , Please sit down and hold on ！

Naming specification

In the custom starter Before that, we have to think about how to name our starter, The official nomenclature is as follows ：

Official starter With spring-boot-starter Name the item as a prefix
Such as ：spring-boot-starter-web
The unofficial ones are spring-boot-starter Name items as suffixes
Such as ：mybatis-spring-boot-starter

Project structure

adopt Spring Initializr or Spring Boot CLI After creating the project structure , take pom.xml The relevant items of the project are revised as follows

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifacId>
<version>2.3.1.RELEASE</version>
<relativePath/>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<!-- Here is the custom Starter The dependencies of -->
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-source-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

stay starter We will define SpringBean Registration configuration and property configuration of , Such as ESB The configuration item of subscription service is

@Configuration
@EnableConfigurationProperties({EsbServerProperties.class})
public class EsbServerConfiguration {
@Bean
public SpringBus springBus(){
return new SpringBus();
}
@Bean
public LoggingFeature loggingFeature(){
return new LoggingFeature();
}
@Bean
public List<JMSConfigFeature> jmsConfigFeatures(EsbServerProperties props) throws JMSException {
List<JMSConfigFeature> features = new ArrayList<>();
/**
* I'm going to use EsbServerProperties Attribute construction of Bean example
*/
return features;
}
}

Property configuration item

// from application.yml Read and bind from the configuration file esb.server.destination Attribute values such as
@Data
@ConfigurationProperties("esb.server")
public class EsbServerProperties {
String destination;
int currConsumers = 1;
String channel;
int ccsid = 1205;
int transportType = 1;
List<String> connectionNameLists;
boolean replyError = false;
String replySuccessText = "Success";
String replyErrorText = "Failure";
}

So far we have completed a basic starter The function of

adopt @ConfigurationProperties Define the starter register bean Set of attributes required when
adopt @Configuration Define the starter Registered bean

But quote the starter How to enable configuration for your project ？ There are actually two ways , They are manual and automatic , We will focus on the auto enable configuration .

Manually enable configuration

The so-called manual configuration is actually in SpringBoot Add a custom annotation to the entry class to enable configuration , For the top EsbServerConfiguration We can customize it EnableESBSrv annotation

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({EsbServerConfiguration.class})
public @interface EnableEsbSrv {
}

And then the entry class @SpringBootApplication Add... Before and after the annotation @EnableEsbSrv that will do .

It's a labor-saving automatic startup configuration

To enable configuration automatically, you just need to pom.xml Introduce the dependent starter, Then enable the application to automatically enable the starter Of @Configuration Annotated classes to register Bean And read property configuration .
And it's all about AutoConfigurationImportSelector Let's do it , And we can @EnableAutoConfiguration or @SpringBootApplication And so on AutoConfigurationImportSelector class , Matching recipes resources/META-INF/spring.factories Realize the function of automatic configuration .
The specific method is ： take EsbServerConfiguration The fully restricted class name of is written in resources/META-INF/spring.factories Of org.springframework.boot.autoconfigure.EnableAutoConfiguration Next , If there are more than one, separate them with commas .

org.springframework.boot.autoconfigure.EnableAutoConfiguration = \
com.john.starter.EsbServerConfiguration,\
com.john.starter.OtherConfiguration

Good and better —— Integrate IDE Smart tips

When the app starts, it will application.yml The corresponding configuration item in is bound to @ConfigurationProperties On the annotated class instance , So for application developers, the daily job is to modify application.yml Configuration item for . but IDE There is also a lack of intelligent tips for configuration items , That would be inefficient . Luckily Spring Boot We have long been provided with good solutions , It is divided into manual and automatic . For the sake of efficiency, it can be automatic, not manual .

Starter Project work

introduce spring-boot-configuration-processor Dependencies ;

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>

if src/resources/META-INF/spring-configuration-metadata.json non-existent , Then perform mvn compile Will generate target/classes/META-INF/spring-configuration-metadata.json;
Copy target/classes/META-INF/spring-configuration-metadata.json To src/resources/META-INF/spring-configuration-metadata.json that will do .

Business system project work

introduce spring-boot-configuration-processor Dependencies ;

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>

IDEA install Spring Assistant plug-in unit , And enable the Enable annotation processing( Check Settings/Build, Execution & Deployment/Compiles/Annotation Processors/Enable annotation processing).

summary

spring-boot-starter It is very suitable for technology accumulation and precipitation of the team , But I want to apply it properly , Not only does it need to go deep Spring Internal principles also need to sort out the business logic . We'll go into it later Spring The kernel thing ！

Please quote from ：https://www.cnblogs.com/fsjoh... —— ^_^ Fat boy John