@SpringBootApplication之@SpringBootConfiguration

原创转载请注明出处：https://www.cnblogs.com/agilestyle/p/14900455.html

@SpringBootApplication 是一个复合注解，包括

• @SpringBootConfiguration


• @EnableAutoConfiguration


• @ComponentScan

@SpringBootConfiguration 源码

可以看出@SpringBootConfiguration 其实就是一个 @Configuration，标注当前类是配置类。

从Spring3.0开始，@Configuration 用于定义配置类，可替换xml 配置文件，被注解的类内部包含一个或多个@Bean 注解的方法，这些方法将会被AnnotationConfigApplicationContext 或AnnotationConfigWebApplicationContext 类进行扫描，并且构建bean 定义，初始化Spring 容器。

@Configuration 标注在类上，等价于Spring 的xml 配置文件中的

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd">

使用@Configuration 配置Spring 并加载Spring容器

Project Directory

Maven Dependency

4.0.0

org.springframework.boot
spring-boot-starter-parent
2.3.12.RELEASE


org.fool
hellospring
1.0-SNAPSHOT

8
8



org.springframework.boot
spring-boot-starter-web

org.springframework.boot
spring-boot-maven-plugin




View Code

SRC

MockUserBean.java

package org.fool.spring.configuration;
public class MockUserBean {
private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "MockUserBean{" +
"username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}

MockUserService.java

package org.fool.spring.configuration;
public class MockUserService {
public MockUserBean findUser() {
MockUserBean mockUserBean = new MockUserBean();
mockUserBean.setUsername("administrator");
mockUserBean.setPassword("administrator");
return mockUserBean;
}
}

AppConfiguration.java

package org.fool.spring.configuration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class AppConfiguration {
public AppConfiguration() {
System.out.println("AppConfiguration init...");
}
@Bean
public MockUserBean userBean() {
MockUserBean mockUserBean = new MockUserBean();
mockUserBean.setUsername("admin");
mockUserBean.setPassword("admin");
return mockUserBean;
}
@Bean
public MockUserService userService() {
return new MockUserService();
}
}

Note: 带有@Bean 的注解方法会返回一个对象，该对象会被注册到Spring IoC 容器中。

MainTest.java

package org.fool.spring.configuration;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class MainTest {
public static void main(String[] args) {
ApplicationContext cOntext= new AnnotationConfigApplicationContext(AppConfiguration.class);
MockUserBean mockUserBean = context.getBean(MockUserBean.class);
MockUserService mockUserService = context.getBean(MockUserService.class);
System.out.println(mockUserBean);
System.out.println(mockUserService.findUser());
}
}

Run

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