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《Springboot极简教程》使用@SpringBootApplication annotation

小沙坨 2022-06-09 阅读 199

许多Spring Boot开发人员总是使用@Configuration,@EnableAutoConfiguration和@ComponentScan来标注它们的主类。 由于这些注释经常一起使用(特别是如果您遵循上述最佳实践),Spring Boot提供了一个方便的@SpringBootApplication替代方法。

@SpringBootApplication注释相当于同时使用@Configuration,@EnableAutoConfiguration和@ComponentScan及其默认属性(重复注解,SpringBoot是怎么处理的?):

package com.example.myproject;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
/* same as */
//@Configuration
//@EnableAutoConfiguration
//@ComponentScan
public class Application {

public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}

}

NOTE

@SpringBootApplication alias 关联了注解: @EnableAutoConfiguration和@ComponentScan的属性。

源码:

/*
* Copyright 2012-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package org.springframework.boot.autoconfigure;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

/**
* Indicates a {@link Configuration configuration} class that declares one or more
* {@link Bean @Bean} methods and also triggers {@link EnableAutoConfiguration
* auto-configuration} and {@link ComponentScan component scanning}. This is a convenience
* annotation that is equivalent to declaring {@code @Configuration},
* {@code @EnableAutoConfiguration} and {@code @ComponentScan}.
*
* @author Phillip Webb
* @since 1.2.0
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Configuration
@EnableAutoConfiguration
@ComponentScan
public @interface SpringBootApplication {

/**
* Exclude specific auto-configuration classes such that they will never be applied.
* @return the classes to exclude
*/
Class<?>[] exclude() default {};

}

所以说,你也可以直接自己定于注解,来封装一些常用的注解。

package com.restfiddle;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

/**
* Created by jack on 2017/3/23.
*
* @author jack
* @date 2017/03/23
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Configuration
@EnableAutoConfiguration
@ComponentScan
public @interface RestBoot {
Class<?>[] exclude() default {};
}

代码中可以这样用:

/*
* Copyright 2014 Ranjan Kumar
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.restfiddle;

import org.springframework.boot.SpringApplication;

/**
* 应用入口类 main函数
*/

//@Configuration
//@EnableAutoConfiguration
//@ComponentScan({"com.restfiddle"})
//@SpringBootApplication
@RestBoot
public class RestFiddleApplication {

public RestFiddleApplication() {
}

public static void main(String[] args) throws Exception {
SpringApplication.run(RestFiddleApplication.class, args);
}

}



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