在官方文檔中, Spring官方建議咱們正確使用「default」 包,將Main Application Class放置在「default」 包下。推薦結構以下:html
com +- example +- myapplication +- Application.java | +- customer | +- Customer.java | +- CustomerController.java | +- CustomerService.java | +- CustomerRepository.java | +- order +- Order.java +- OrderController.java +- OrderService.java +- OrderRepository.java
在這個結構的基礎上,Main函數強烈建議放置在com.example.myapplication這個"default" 包路徑下。這種狀況下,Main方法的類只須要以下書寫便可:java
package com.example.myapplication; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
這個結構有什麼好處呢?能夠看到上面啓動類中,類上面只有一個註解@SpringBootApplication
,這個註解提供了多個能力。請看下面的代碼:spring
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) }) public @interface SpringBootApplication {...}
官方文檔對@SpringBootApplication
有作比較詳細的介紹,點這裏查看。bootstrap
@EnableAutoConfiguration
: 開啓自動配置。@ComponentScan
: 開啓包路徑掃描,默認狀況下會掃描當前包和子包的@Service
, @Controller
,@Component
等註解。@Configuration
: 容許在上下文中註冊其餘的Bean或者導入其餘配置類。強調Main Class必定要放在「default」 包下,就是由於只有這樣,@ComponentScan
才能掃描到全部的註解。springboot
再看@SpringBootApplication
的內容代碼,使用@SpringBootApplication
的屬性exclude
,excludeName
,scanBasePackages
, scanBasePackageClasses
, nameGenerator
, proxyBeanMethods
就能夠完成@EnableAutoConfiguration
, @ComponentScan
以及@Configuration
的屬性自定義。app
/** * Exclude specific auto-configuration classes such that they will never be applied. * @return the classes to exclude */ @AliasFor(annotation = EnableAutoConfiguration.class) Class<?>[] exclude() default {}; /** * Exclude specific auto-configuration class names such that they will never be * applied. * @return the class names to exclude * @since 1.3.0 */ @AliasFor(annotation = EnableAutoConfiguration.class) String[] excludeName() default {}; /** * Base packages to scan for annotated components. Use {@link #scanBasePackageClasses} * for a type-safe alternative to String-based package names. * <p> * <strong>Note:</strong> this setting is an alias for * {@link ComponentScan @ComponentScan} only. It has no effect on {@code @Entity} * scanning or Spring Data {@link Repository} scanning. For those you should add * {@link org.springframework.boot.autoconfigure.domain.EntityScan @EntityScan} and * {@code @Enable...Repositories} annotations. * @return base packages to scan * @since 1.3.0 */ @AliasFor(annotation = ComponentScan.class, attribute = "basePackages") String[] scanBasePackages() default {}; /** * Type-safe alternative to {@link #scanBasePackages} for specifying the packages to * scan for annotated components. The package of each class specified will be scanned. * <p> * Consider creating a special no-op marker class or interface in each package that * serves no purpose other than being referenced by this attribute. * <p> * <strong>Note:</strong> this setting is an alias for * {@link ComponentScan @ComponentScan} only. It has no effect on {@code @Entity} * scanning or Spring Data {@link Repository} scanning. For those you should add * {@link org.springframework.boot.autoconfigure.domain.EntityScan @EntityScan} and * {@code @Enable...Repositories} annotations. * @return base packages to scan * @since 1.3.0 */ @AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses") Class<?>[] scanBasePackageClasses() default {}; /** * The {@link BeanNameGenerator} class to be used for naming detected components * within the Spring container. * <p> * The default value of the {@link BeanNameGenerator} interface itself indicates that * the scanner used to process this {@code @SpringBootApplication} annotation should * use its inherited bean name generator, e.g. the default * {@link AnnotationBeanNameGenerator} or any custom instance supplied to the * application context at bootstrap time. * @return {@link BeanNameGenerator} to use * @see SpringApplication#setBeanNameGenerator(BeanNameGenerator) * @since 2.3.0 */ @AliasFor(annotation = ComponentScan.class, attribute = "nameGenerator") Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class; /** * Specify whether {@link Bean @Bean} methods should get proxied in order to enforce * bean lifecycle behavior, e.g. to return shared singleton bean instances even in * case of direct {@code @Bean} method calls in user code. This feature requires * method interception, implemented through a runtime-generated CGLIB subclass which * comes with limitations such as the configuration class and its methods not being * allowed to declare {@code final}. * <p> * The default is {@code true}, allowing for 'inter-bean references' within the * configuration class as well as for external calls to this configuration's * {@code @Bean} methods, e.g. from another configuration class. If this is not needed * since each of this particular configuration's {@code @Bean} methods is * self-contained and designed as a plain factory method for container use, switch * this flag to {@code false} in order to avoid CGLIB subclass processing. * <p> * Turning off bean method interception effectively processes {@code @Bean} methods * individually like when declared on non-{@code @Configuration} classes, a.k.a. * "@Bean Lite Mode" (see {@link Bean @Bean's javadoc}). It is therefore behaviorally * equivalent to removing the {@code @Configuration} stereotype. * @since 2.2 * @return whether to proxy {@code @Bean} methods */ @AliasFor(annotation = Configuration.class) boolean proxyBeanMethods() default true;
Spring Boot官方推薦的工程結構在大部分狀況下都適用,用這個結構也是最保險的。若是有特殊狀況,務必要記得配置@ComponentScan
的包路徑。dom