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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