@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 <beans></beans>

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    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">

    <bean id="..." class="...">  
        <!-- collaborators and configuration for this bean go here -->
    </bean>

    <bean id="..." class="...">
        <!-- collaborators and configuration for this bean go here -->
    </bean>

    <!-- more bean definitions go here -->

</beans>

 

使用@Configuration 配置Spring 并加载Spring容器

Project Directory

 

Maven Dependency

<?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>2.3.12.RELEASE</version>
        <relativePath/>
    </parent>

    <groupId>org.fool</groupId>
    <artifactId>hellospring</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

 

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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