自定义Spring Boot Starter

SpringBoot SpringBoot Starter
下面定义一个starter，它将实现，在日志中打印方法执行时间。

1、创建Maven项目

项目命名规则

:::info spring-boot-starter-XX是springboot官方的starter
XX-spring-boot-starter是第三方扩展的starter :::

项目的pom依赖文件

<?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>com.fcant</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

2、写自动配置逻辑

各种condition

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

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
 **/
@Target(ElementType.METHOD)@ Retention(RetentionPolicy.RUNTIME)
public@ interface AspectLog {}

2.2定义配置文件对应类

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

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.fcant.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。

3、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.fcant.autoconfiguration.aspectlog.AspectLogAutoConfiguration

4、执行打包测试

使用 mvn intall 命令对工程进行打包

mvn intall

打包完成后，在其他项目中的pom中引入进行测试