IOC

<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>
    <groupId>tszrIOC</groupId>
    <artifactId>IOC</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <!-- 声明项目配置依赖编码格式为 utf-8 -->
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <fastjson.version>1.2.24</fastjson.version>
    </properties>

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-dbcp2</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

logging.level.root=DEBUG
logging.level.org.springframework=DEBUG

package com.springboot.chapter3.pojo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("user")
public class User {
    @Value("1")
    private Long id;
    @Value("user_name_1")
    private String userName;
    @Value("note_1")
    private String note;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note;
    }
}

package com.springboot.chapter3.config;

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

import com.springboot.chapter3.pojo.User;

@Configuration
public class AppConfig {
    @Bean("user")
    public User initUser() {
        User user = new User();
        user.setId(1L);
        user.setUserName("吴裕雄");
        user.setNote("note-1");
        return user;
    }
}

package com.springboot.chapter3.config;

import org.apache.log4j.Logger;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.springboot.chapter3.pojo.User;

public class IoCTest {
    private static Logger log = Logger.getLogger(IoCTest.class);
    public static void main(String[] args){
        @SuppressWarnings("resource")
        ApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
        User user = ctx.getBean(User.class);
        log.info(user.getId());
    }
}