Updated on 2017-07-11

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https://github.com/spring-projects/spring-framework

https://github.com/spring-projects/spring-boot

Dependency

Spring Doc | Spring API

Spring Boot Doc | Spring Boot API

Spring Security Doc | Spring Security API

Spring Data JPA Doc | Spring Data JPA API

Concept

  • 控制反转（IOC）：应用程序本身不负责依赖对象的创建与维护，而是由外部容器负责管理。
    • 依赖注入（DI）是其实现方式。
    • 依赖对象 通过接口 了解注入对象并 表明依赖关系。（面向接口编程）
    • 作用：负责 创建 对象并 维护 对象之间的依赖关系，使应用对象彼此之间保持 低耦合。
    • 对象解耦。
  • 面向切面编程（AOP）：用另一种编程架构的思想来 补充面向对象编程（OOP）的思想。
    • AOP 进行 提取，OOP 进行 封装。
    • AOP 主要的模块单元是 切面（Aspect），而 OOP 主要的模块单元是 类（Class）。
    • 作用：使诸如日志管理等分散在各个应用对象的 逻辑（横切关注点）模块化为切面。
    • 功能解耦。
  • 装配：Wiring。
  • 感知：Aware。
  • 组件：@Component
    • 控制层：@Controller
    • 业务层：@Service
    • 持久层：@Repository

Configuration

build.gradle.kts

compile("org.springframework:spring-context:+")

compile("org.springframework:spring-aspects:+")

装配方式

组件扫描和自动装配（隐式装配）

soundsystem

CompactDisc
package soundsystem;

public interface CompactDisc {
    void play();
}
MediaPlayer
package soundsystem;

public interface MediaPlayer {
    void play();
}
SgtPeppers
package soundsystem;

import org.springframework.stereotype.Component;

@Component     组件（Java 规范中的 Named 作用与其相同）
public class SgtPeppers implements CompactDisc {
    private final String title = "Sgt. Pepper's Lonely Hearts Club Band";
    private final String artist = "The Beatles";

    @Override
    public void play() {
        System.out.println("Playing " + title + " by " + artist);
    }
}

Bean 名称的缺省值为类名（首字母小写）（@Component）。
CDPlayer
package soundsystem;

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

@Component     组件（Java 规范中的 Named 作用与其相同）
public class CDPlayer implements MediaPlayer {
    private CompactDisc cd;

    @Autowired     自动装配（Java 规范中的 Inject 作用与其相同）
    public CDPlayer(CompactDisc cd) {     构造注入
        this.cd = cd;
    }

    @Override
    public void play() {
        cd.play();
    }
}

AppConfig

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

@Configuration     指示为配置类
@ComponentScan(basePackages = {"soundsystem"})     组件扫描（搜寻其他 Component 和 Configuration）
public class AppConfig {
}

Main

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import soundsystem.CDPlayer;

public class Main {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

        CDPlayer cdPlayer = context.getBean(CDPlayer.class);
        cdPlayer.play();

        context.destroy();
    }
}

----
输出：
Playing Sgt. Pepper's Lonely Hearts Club Band by The Beatles

Java 注解（显式装配）

soundsystem

CompactDisc
package soundsystem;

public interface CompactDisc {
    void play();
}
MediaPlayer
package soundsystem;

public interface MediaPlayer {
    void play();
}
SgtPeppers
package soundsystem;

public class SgtPeppers implements CompactDisc {
    private final String title = "Sgt. Pepper's Lonely Hearts Club Band";
    private final String artist = "The Beatles";

    @Override
    public void play() {
        System.out.println("Playing " + title + " by " + artist);
    }
}
CDPlayer
package soundsystem;

public class CDPlayer implements MediaPlayer {
    private CompactDisc cd;

    public CDPlayer(CompactDisc cd) {
        this.cd = cd;
    }

    @Override
    public void play() {
        cd.play();
    }
}

AppConfig

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import soundsystem.CDPlayer;
import soundsystem.CompactDisc;
import soundsystem.MediaPlayer;
import soundsystem.SgtPeppers;

@Configuration     指示为配置类（用于定义 Bean）
public class AppConfig {
    @Bean     指示该方法返回 Bean 对象并在容器中注册
    public CompactDisc sgtPeppers() {
        return new SgtPeppers();
    }

    @Bean     指示该方法返回 Bean 对象并在容器中注册
    public MediaPlayer cdPlayer(CompactDisc cd) {     从容器中获取依赖对象
        return new CDPlayer(cd);     并注入（装配）
    }
}

Bean 名称的缺省值为方法名（@Bean）。

Main

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import soundsystem.CDPlayer;

public class Main {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

        CDPlayer cdPlayer = context.getBean(CDPlayer.class);
        cdPlayer.play();

        context.destroy();
    }
}

----
输出：
Playing Sgt. Pepper's Lonely Hearts Club Band by The Beatles

XML 文件（显式装配）

soundsystem

CompactDisc
package soundsystem;

public interface CompactDisc {
    void play();
}
MediaPlayer
package soundsystem;

public interface MediaPlayer {
    void play();
}
SgtPeppers
package soundsystem;

public class SgtPeppers implements CompactDisc {
    private final String title = "Sgt. Pepper's Lonely Hearts Club Band";
    private final String artist = "The Beatles";

    @Override
    public void play() {
        System.out.println("Playing " + title + " by " + artist);
    }
}
CDPlayer
package soundsystem;

public class CDPlayer implements MediaPlayer {
    private CompactDisc cd;

    public CDPlayer(CompactDisc cd) {
        this.cd = cd;
    }

    @Override
    public void play() {
        cd.play();
    }
}

Main

import org.springframework.context.support.GenericXmlApplicationContext;
import soundsystem.CDPlayer;

public class Main {
    public static void main(String[] args) {
        GenericXmlApplicationContext context = new GenericXmlApplicationContext("123.xml");

        CDPlayer cdPlayer = context.getBean(CDPlayer.class);
        cdPlayer.play();

        context.destroy();
    }
}

----
输出：
Playing Sgt. Pepper's Lonely Hearts Club Band by The Beatles

123.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC
        "-//SPRING//DTD BEAN 2.0//EN"
        "http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
    <bean id="sgtPeppers" class="soundsystem.SgtPeppers"/>     声明 Bean 并指定名称

    <bean class="soundsystem.CDPlayer">     声明 Bean，缺省名称为 "soundsystem.CDPlayer#0"
        <constructor-arg ref="sgtPeppers"/>     强制依赖的注入可使用构造方法（构造注入）
        ----
        <property name="cd" ref="sgtPeppers"/>     可选依赖的注入可使用 Setter（设值注入）
        对应 Setter：
        public void setCd(CompactDisc cd) {
            this.cd = cd;
        }
    </bean>
</beans>

混合使用

cd-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC
        "-//SPRING//DTD BEAN 2.0//EN"
        "http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
    <bean class="soundsystem.SgtPeppers"/>
</beans>

PlayerConfig

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import soundsystem.CDPlayer;
import soundsystem.CompactDisc;
import soundsystem.MediaPlayer;

@Configuration     指示为配置类
public class PlayerConfig {
    @Bean
    public MediaPlayer cdPlayer(CompactDisc cd) {
        return new CDPlayer(cd);
    }
}

AppConfig

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.ImportResource;

@Configuration
@Import(PlayerConfig.class)     导入 Java 注解
@ImportResource("cd-config.xml")     导入 XML 文件
public class AppConfig {
}

Main

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import soundsystem.CDPlayer;

public class Main {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

        CDPlayer cdPlayer = context.getBean(CDPlayer.class);
        cdPlayer.play();

        context.destroy();
    }
}

----
输出：
Playing Sgt. Pepper's Lonely Hearts Club Band by The Beatles