spring学习笔记（六）自定义spring-boot-starter（2）
2024-09-24 16:02:14
上篇文章我们主要讲了spring自动装配的原理，我们知道了springboot在启动的时候会自动去读.factories文件，在factories文件中，autoConfiguration对应的就是我们程序启动时自己预加载的类，另外我也提到了另外一个比较核心的注解，即@ConditionOnxxx。详情点击https://blog.csdn.net/qq_41907991/article/details/88704448。
这篇文章我们主要分析下@ConditionOnxxx注解，以及自己实现一个starter。下面开始分析我们的@ConditionOnxxx注解。先看代码：
我们以@ConditionalOnMissingBean这个注解来分析原理：
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnBeanCondition.class)
public @interface ConditionalOnMissingBean {....}很明显，上面的核心注解就是@Conditional注解，我们接下来分析这个注解，直接上代码看效果
package com.study.spring.condition.condition;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
/**
* @Author: dmz
* @Description:
* @Date: Create in 23:16 2019/3/25
*/
public class CatCondition implements Condition {
@Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
return context.getEnvironment().getProperty("what").equals("cat");
}
}
package com.study.spring.condition.condition;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
/**
* @Author: dmz
* @Description:
* @Date: Create in 23:16 2019/3/25
*/
public class DogCondition implements Condition {
@Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
return context.getEnvironment().getProperty("what").equals("dog");
}
}
上面这两个类，是我自定义的两个条件
package com.study.spring.condition.model;
import com.study.spring.condition.condition.CatCondition;
import org.springframework.context.annotation.Conditional;
import org.springframework.stereotype.Component;
/**
* @Author: dmz
* @Description:
* @Date: Create in 23:19 2019/3/25
*/
@Component
@Conditional({CatCondition.class})
public class Cat {
public Cat(){
System.out.println("猫来了，喵喵喵~~");
}
}
package com.study.spring.condition.model;
import com.study.spring.condition.condition.DogCondition;
import org.springframework.context.annotation.Conditional;
import org.springframework.stereotype.Component;
/**
* @Author: dmz
* @Description:
* @Date: Create in 23:18 2019/3/25
*/
@Component
@Conditional({DogCondition.class})
public class Dog {
public Dog(){
System.out.println("dog 来了，汪汪汪~~~");
}
}
主要是为了通过条件控制我们这两个类的加载
what:cat
这是配置文件中的内容
package com.study.spring.condition;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class ConditionApplication {
public static void main(String[] args) {
SpringApplication.run(ConditionApplication.class, args);
}
}
这是启动类
启动程序，可以看到程序打印：
猫来了，喵喵喵~~经过上面的程序我相信大家对这个@conditional注解已经有了一定的了解
接下来我们来实现我们的自定义starter
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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.3.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.study.spring</groupId>
<artifactId>starter</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>myAutoconfig-spring-boot-starter</name>
<description>Demo project for Spring Boot</description>
<packaging>jar</packaging>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure</artifactId>
</dependency>
<!--为了生成spring-configuration-metadata.json-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
整体项目结构如下
package com.study.spring.starter.AutoConfig;
import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
/**
* @author dmz
* @date Create in 22:06 2019/3/23
*/
@Data
@ConfigurationProperties(prefix = "config")
public class Config {
private String name;
private Integer age;
}
package com.study.spring.starter.AutoConfig;
import com.study.spring.starter.service.MyService;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
* @author dmz
* @date Create in 21:24 2019/3/23
*/
@Configuration
@EnableConfigurationProperties(Config.class)
@ConditionalOnClass(MyService.class)
public class MyAutoConfig {
@Bean
@ConditionalOnMissingBean(MyService.class)
public MyService getMyService() {
return new MyService();
}
}
package com.study.spring.starter.service;
import com.study.spring.starter.AutoConfig.Config;
import org.springframework.beans.factory.annotation.Autowired;
/**
* @author dmz
* @date Create in 21:53 2019/3/23
*/
public class MyService {
@Autowired
private Config config;
public void say() {
System.out.println("自定义的starter来了,say:" + config.getName());
}
}
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
*保留启动类，主要是为了执行maven的命令，
* 打包到我们的本地仓库
*/
@SpringBootApplication
public class StarterApplication{
public static void main(String[] args) {
SpringApplication.run(StarterApplication.class, args);
}
}
spring.factories文件如下：
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.study.spring.starter.AutoConfig.MyAutoConfig测试代码如下：
<?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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.3.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.study.spring</groupId>
<artifactId>starter-test</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>starter-test</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<!--引入我们的依赖-->
<dependency>
<groupId>com.study.spring</groupId>
<artifactId>starter</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
启动类：
package com.study.spring.startertest;
import com.study.spring.starter.service.MyService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class StarterTestApplication implements ApplicationRunner {
@Autowired
private MyService myService;
public static void main(String[] args) {
SpringApplication.run(StarterTestApplication.class, args);
}
@Override
public void run(ApplicationArguments args) throws Exception {
myService.say();
}
}
我们在测试项目中加了配置信息
config.name=zhangsan
运行结果如下：
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.3.RELEASE)
2019-03-27 00:09:52.995 INFO 19468 --- [ main] c.s.s.s.StarterTestApplication : Starting StarterTestApplication on DESKTOP-N88SU6M with PID 19468 (C:\Users\dell\Desktop\spring-master\starter-test\target\classes started by dell in C:\Users\dell\Desktop\spring-master)
2019-03-27 00:09:52.999 INFO 19468 --- [ main] c.s.s.s.StarterTestApplication : No active profile set, falling back to default profiles: default
2019-03-27 00:09:53.416 INFO 19468 --- [ main] c.s.s.s.StarterTestApplication : Started StarterTestApplication in 0.722 seconds (JVM running for 1.243)
自定义的starter来了,say:zhangsan
Process finished with exit code 0验证成功~~
项目github地址：https://github.com/daimingzhi/spring.git
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