引言
只要你用Springboot,一定会用到各种spring-boot-starter。其实写一个spring-boot-starter
,仅需4步。下面我们就写一个starter,它将实现,在日志中打印方法执行时间。
第一步 创建maven项目
在使用spring-boot-starter,会发现,有的项目名称是 XX-spring-boot-starter,有的是
spring-boot-starter-XX,这个项目的名称有什么讲究呢?
从springboot官方文档摘录如下:
“Do not start your module names with spring-boot, even if you use a different Maven groupId. We may offer official support for the thing you auto-configure in the future.
As a rule of thumb, you should name a combined module after the starter.
从这段话可以看出spring-boot-starter命名的潜规则。
命名潜规则
spring-boot-starter-XX是springboot官方的starter
XX-spring-boot-starter是第三方扩展的starter
打印方法执行时间的功能,需要用到aop,咱们的项目就叫做
aspectlog-spring-boot-starter吧。
项目的pom文件如下:
<?xml version='1.0' encoding='UTF-8'?>
<project xmlns='http://maven./POM/4.0.0'
xmlns:xsi='http://www./2001/XMLSchema-instance'
xsi:schemaLocation='http://maven./POM/4.0.0 http://maven./xsd/maven-4.0.0.xsd'>
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>aspectlog-spring-boot-starter</artifactId>
<version>1.0.2</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.15.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
</project>
关于spring-boot-configuration-processor的说明,引自springBoot官方文档:
“Spring Boot uses an annotation processor to collect the conditions on auto-configurations in a metadata file ( META-INF/spring-autoconfigure-metadata.properties ). If that file is present, it is used to eagerly filter auto-configurations that do not match, which will improve startup time. It is recommended to add the following dependency in a module that contains auto-configurations:
org.springframework.boot
spring-boot-autoconfigure-processor
true
简单说就是:写starter时,在pom中配置spring-boot-autoconfigure-processor,在编译时会自动收集配置类的条件,写到一个META-INF/spring-autoconfigure-metadata.properties中。
第二步写自动配置逻辑
各种condition
类型 | 注解 | 说明 |
---|
Class Conditions类条件注解 | @ConditionalOnClass | 当前classpath下有指定类才加载 |
@ConditionalOnMissingClass | 当前classpath下无指定类才加载 |
|
Bean ConditionsBean条件注解 | @ConditionalOnBean | 当期容器内有指定bean才加载 |
@ConditionalOnMissingBean | 当期容器内无指定bean才加载 |
|
Property Conditions环境变量条件注解(含配置文件) | @ConditionalOnProperty | prefix 前缀name 名称havingValue 用于匹配配置项值matchIfMissing 没找指定配置项时的默认值 |
ResourceConditions 资源条件注解 | @ConditionalOnResource | 有指定资源才加载 |
Web Application Conditionsweb条件注解 | @ConditionalOnWebApplication | 是web才加载 |
@ConditionalOnNotWebApplication | 不是web才加载 |
|
SpEL Expression Conditions | @ConditionalOnExpression | 符合SpEL 表达式才加载 |
本次我们就选用@ConditionalOnProperty。即配置文件中有aspectLog.enable=true,才加载我们的配置类。
下面开始写自动配置类
2.1.定义AspectLog注解,该注解用于标注需要打印执行时间的方法。
package com.shanyuan.autoconfiguration.aspectlog;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* class_name: ScheduleManage
* describe: 用于控制定时任务的开启与关闭
* 对应切面
* creat_user: wenl
* creat_time: 2018/11/10 18:45
**/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface AspectLog {
}
2.2定义配置文件对应类
package com.shanyuan.autoconfiguration.aspectlog;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties('aspectLog')
public class AspectLogProperties {
private boolean enable;
public boolean isEnable() {
return enable;
}
public void setEnable(boolean enable) {
this.enable = enable;
}
}
2.3定义自动配置类
package com.shanyuan.autoconfiguration.aspectlog;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.autoconfigure.condition.*;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.core.PriorityOrdered;
@Aspect
@EnableAspectJAutoProxy(exposeProxy = true, proxyTargetClass = true)
@Configuration
@ConditionalOnProperty(prefix = 'aspectLog', name = 'enable',
havingValue = 'true', matchIfMissing = true)
public class AspectLogAutoConfiguration implements PriorityOrdered {
protected Logger logger = LoggerFactory.getLogger(getClass());
@Around('@annotation(com.shanyuan.autoconfiguration.aspectlog.AspectLog) ')
public Object isOpen(ProceedingJoinPoint thisJoinPoint)
throws Throwable {
//执行方法名称
String taskName = thisJoinPoint.getSignature()
.toString().substring(
thisJoinPoint.getSignature()
.toString().indexOf(' '),
thisJoinPoint.getSignature().toString().indexOf('('));
taskName = taskName.trim();
long time = System.currentTimeMillis();
Object result = thisJoinPoint.proceed();
logger.info('method:{} run :{} ms', taskName,
(System.currentTimeMillis() - time));
return result;
}
@Override
public int getOrder() {
//保证事务等切面先执行
return Integer.MAX_VALUE;
}
}
配置类简要说明:
@ConditionalOnProperty(prefix = 'aspectLog', name = 'enable',havingValue = 'true', matchIfMissing = true)
当配置文件有aspectLog.enable=true
时开启,如果配置文件没有设置aspectLog.enable
也开启。
第三步META-INF/spring.factories
META-INF/spring.factories
是spring的工厂机制,在这个文件中定义的类,都会被自动加载。多个配置使用逗号分割,换行用\
如果有兴趣可以查看这2篇blog:
2.@Enable
驱动原理(设置连接)
3.@EnableAutoConfiguration
处理逻辑(设置连接)
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.shanyuan.autoconfiguration.aspectlog.AspectLogAutoConfiguration
第四步打包测试
这是我们最终的目录结构
在IDEA中,进行mvn intall
打包完成后,在其他项目中的pom中引入进行测试
参考资料
- https://docs./spring-boot/docs/2.1.15.RELEASE/reference/html/boot-features-developing-auto-configuration.html#boot-features-custom-starter