新闻资讯
仅需四步,写一个 Spring Boot Starter
引言
只要你用 Spring boot,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。
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.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/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:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure-processor</artifactId>
<optional>true</optional>
</dependency>
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。
不熟悉 Spring Boot 基础的可以看下这个仓库:https://github.com/javastacks/spring-boot-best-practice
第二步写自动配置逻辑
各种condition
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。
不熟悉 Spring Boot 基础的可以看下这个仓库:https://github.com/javastacks/spring-boot-best-practice
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。基础知识不熟悉的可以关注公众号Java技术栈回复boot获取一份完整教程。
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\
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
本内容属于网络转载,文中涉及图片等内容如有侵权,请联系编辑删除
回复列表