• Spring 使用指南 ~ 1、Spring 的 IOC 和 DI 简介

    一、IOC && DI

    1、概念介绍

    • IOC：控制反转，即把类的实例化交给 Spring 来管理
    • DI：依赖注入，即通过 Spring 为应用中被 Spring 管理的类实例注入其依赖的实例和其他信息

    2、使用 XML 形式

    1）、构造函数注入
    package com.luo.spring.guides.iocdi.xml.constructorconfusion;

import org.springframework.context.support.GenericXmlApplicationContext;

/**
* @author : archer
* @date : Created in 2022/11/30 14:46
* @description :
*/
public class ConstructorConfusion {

   private String someValue;

   public ConstructorConfusion(String someValue) {
       System.out.println("ConstructorConfusion(String) called");
       this.someValue = someValue;
   }

   public ConstructorConfusion(int someValue) {
       System.out.println("ConstructorConfusion(int) called");
       this.someValue = "Number: " + Integer.toString(someValue);
   }

   public String toString() {
       return someValue;
   }
}


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    app-context-xml.xml

    

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

    <bean id="constructorConfusion"
          class="com.luo.spring.guides.iocdi.xml.constructorconfusion.ConstructorConfusion">
        <constructor-arg type="int">
            <value>90value>
        constructor-arg>
    bean>
beans>


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    测试

    package com.luo.spring.guides.iocdi.xml.constructorconfusion;

import org.springframework.context.support.GenericXmlApplicationContext;

/**
 * @author : archer
 * @date : Created in 2022/11/30 14:51
 * @description :
 */
public class Main {
    public static void main(String... args) {
        GenericXmlApplicationContext ctx = new GenericXmlApplicationContext();
        ctx.load("classpath:iocdi/app-context.xml");
        ctx.refresh();
        ConstructorConfusion cc = (ConstructorConfusion) ctx.getBean("constructorConfusion");
        System.out.println(cc);
        ctx.close();
    }
}


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    输出

    ConstructorConfusion(int) called
    Number: 90

    2）、setter 注入
    package com.luo.spring.guides.iocdi.xml.setter;

public class Dependency {

    @Override
    public String toString() {
        return "Dependency{}";
    }
}

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    package com.luo.spring.guides.iocdi.xml.setter;

public class SetterInjection {

	private Dependency dependency;

	public void setDependency(Dependency dependency) {
		this.dependency = dependency;
	}

	@Override
	public String toString() {
		return dependency.toString();
	}
}

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    app-context-xml.xml

    

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


    <bean id="dependency" class="com.luo.spring.guides.iocdi.xml.setter.Dependency"/>

    <bean id="setterInjection" class="com.luo.spring.guides.iocdi.xml.setter.SetterInjection"
          p:dependency-ref="dependency"/>
beans>

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    测试

    package com.luo.spring.guides.iocdi.xml.setter;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author : archer
 * @date : Created in 2022/11/30 15:22
 * @description :
 */
public class Main {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext
                ("iocdi/injection/setter/app-context-xml.xml");

        SetterInjection mr = ctx.getBean("setterInjection", SetterInjection.class);
        System.out.println(mr);
    }
}


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    输出

    Dependency{}

    3）、字段注入
    package com.luo.spring.guides.iocdi.xml.field;

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

/**
 * Created by iuliana.cosmina on 2/15/17.
 */
public class Inspiration {

	private String lyric = "I can keep the door cracked open, to let light through";

	public Inspiration(){

	}

	public Inspiration(@Value("For all my running, I can understand") String lyric) {
		this.lyric = lyric;
	}

	public String getLyric() {
		return lyric;
	}

	public void setLyric(String lyric) {
		this.lyric = lyric;
	}
}

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    package com.luo.spring.guides.iocdi.xml.field;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;

/**
 * Created by iuliana.cosmina on 2/15/17.
 */
public class Singer {

	@Autowired
	private Inspiration inspirationBean;

	public void sing() {
		System.out.println("... " + inspirationBean.getLyric());
	}
}

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

    <context:component-scan
            base-package="com.luo.spring.guides.iocdi.xml.field"/>

    <bean id="singer" class="com.luo.spring.guides.iocdi.xml.field.Singer"/>

    <bean id="inspiration" class="com.luo.spring.guides.iocdi.xml.field.Inspiration"/>


beans>

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    测试

    package com.luo.spring.guides.iocdi.xml.field;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author : archer
 * @date : Created in 2022/11/30 20:46
 * @description :
 */
public class Main {

    public static void main(String... args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("iocdi/injection/field/app-context-xml.xml");
        Singer singer = ctx.getBean("singer", Singer.class);

        Singer singerBean = ctx.getBean(Singer.class);
        System.out.println(singer == singerBean);
        singerBean.sing();
        singer.sing();
    }
}

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    输出

    true
    … I can keep the door cracked open, to let light through
    … I can keep the door cracked open, to let light through

    4）、查找方法注入
    • 这种方式性能较差，当有其他方式替代时，请使用其他方式
    package com.luo.spring.guides.iocdi.lookup.xml;

/**
 * Created by iuliana.cosmina on 2/20/17.
 */
public class Singer {
    private String lyric = "I played a quick game of chess with the salt and pepper shaker";

    public void sing() {
//        System.out.println(lyric);
    }
}

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    package com.luo.spring.guides.iocdi.lookup.xml;

public interface DemoBean {
    Singer getMySinger();
    void doSomething();
}

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    package com.luo.spring.guides.iocdi.lookup.xml;

public abstract class AbstractLookupDemoBean implements DemoBean {
    public abstract Singer getMySinger();

    @Override
    public void doSomething() {
        getMySinger().sing();
    }
}

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    package com.luo.spring.guides.iocdi.lookup.xml;

public class StandardLookupDemoBean implements DemoBean {

	private Singer mySinger;

	public void setMySinger(Singer mySinger) {
		this.mySinger = mySinger;
	}

	@Override
	public Singer getMySinger() {
		return this.mySinger;
	}

	@Override
	public void doSomething() {
		mySinger.sing();
	}
}

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<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
        http://www.springframework.org/schema/beans/spring-beans.xsd">

<bean id="singer" class="com.luo.spring.guides.iocdi.lookup.xml.Singer"  scope="prototype"/>

<bean id="abstractLookupBean" class="com.luo.spring.guides.iocdi.lookup.xml.AbstractLookupDemoBean">
    <lookup-method name="getMySinger" bean="singer"/>
bean>

<bean id="standardLookupBean" class="com.luo.spring.guides.iocdi.lookup.xml.StandardLookupDemoBean">
    <property name="mySinger" ref="singer"/>
bean>
beans>

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    测试

    package com.luo.spring.guides.iocdi.lookup.xml;

import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.util.StopWatch;

/**
 * @author : archer
 * @date : Created in 2022/12/1 11:23
 * @description :
 */
public class Main {

    public static void main(String... args) {
        GenericXmlApplicationContext ctx = new GenericXmlApplicationContext();
        ctx.load("classpath:iocdi/injection/lookup/app-context-xml.xml");
        ctx.refresh();

        DemoBean abstractBean = ctx.getBean("abstractLookupBean", DemoBean.class);
        DemoBean standardBean = ctx.getBean("standardLookupBean", DemoBean.class);

        displayInfo("abstractLookupBean", abstractBean);
        displayInfo("standardLookupBean", standardBean);

        ctx.close();
    }

    public static void displayInfo(String beanName, DemoBean bean) {
        Singer singer1 = bean.getMySinger();
        Singer singer2 = bean.getMySinger();

        System.out.println("[" + beanName + "]: Singer Instances the Same?  "
                + (singer1 == singer2));

        StopWatch stopWatch = new StopWatch();
        stopWatch.start("lookupDemo");

        for (int x = 0; x < 100000; x++) {
            Singer singer = bean.getMySinger();
            singer.sing();
        }

        stopWatch.stop();
        System.out.println("100000 gets took " + stopWatch.getTotalTimeMillis() + " ms");
    }
}

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    输出

    [abstractLookupBean]: Singer Instances the Same? false
    100000 gets took 561 ms
    [standardLookupBean]: Singer Instances the Same? true
    100000 gets took 1 ms

    3、使用注解形式

    1）、构造函数注入
    package com.luo.spring.guides.iocdi.annotation.constructorconfusion;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.stereotype.Service;

@Service("constructorConfusion")
public class ConstructorConfusion {

	private String someValue;

	public ConstructorConfusion(String someValue) {
		System.out.println("ConstructorConfusion(String) called");
		this.someValue = someValue;
	}

	@Autowired
	public ConstructorConfusion(@Value("90") int someValue) {
		System.out.println("ConstructorConfusion(int) called");
		this.someValue = "Number: " + Integer.toString(someValue);
	}

	public String toString() {
		return someValue;
	}
}


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    app-context-annotation.xml

    

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

    <context:component-scan 
          base-package="com.luo.spring.guides.iocdi.annotation"/>

    <bean id="message" class="java.lang.String"
          c:_0="I hope that someone gets my message in a bottle"/>

    <bean id="message2" class="java.lang.String"
          c:_0="I know I won't be injected :("/>
beans>

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    测试

    package com.luo.spring.guides.iocdi.annotation.constructorconfusion;

import org.springframework.context.support.GenericXmlApplicationContext;

/**
 * @author : archer
 * @date : Created in 2022/11/30 14:51
 * @description :
 */
public class Main {
    public static void main(String... args) {
        GenericXmlApplicationContext ctx = new GenericXmlApplicationContext();
        ctx.load("classpath:iocdi/app-context-annotation.xml");
        ctx.refresh();

        ConstructorConfusion cc = (ConstructorConfusion) ctx.getBean("constructorConfusion");
        System.out.println(cc);
        ctx.close();
    }
}


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    输出

    ConstructorConfusion(int) called
    Number: 90

    2）、setter 注入
    package com.luo.spring.guides.iocdi.annotation.setter;

import org.springframework.stereotype.Component;

@Component("dependency")
public class Dependency {

    @Override
    public String toString() {
        return "Dependency{}";
    }
}

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    package com.luo.spring.guides.iocdi.annotation.setter;

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

@Component("setterInjection")
public class SetterInjection {

	private Dependency dependency;

	@Autowired
	public void setDependency(Dependency dependency) {
		this.dependency = dependency;
	}

	@Override
	public String toString() {
		return dependency.toString();
	}
}


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    配置类

    package com.luo.spring.guides.iocdi.annotation.setter;

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

/**
 * @author : archer
 * @date : Created in 2022/11/30 15:32
 * @description :
 */
@ComponentScan(basePackages = {"com.luo.spring.guides.iocdi.annotation"})
@Configuration
public class SetterInjectionConfiguration {
}

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    测试

    package com.luo.spring.guides.iocdi.annotation.setter;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * @author : archer
 * @date : Created in 2022/11/30 15:33
 * @description :
 */
public class Main {
    public static void main(String... args) {
        ApplicationContext ctx = new AnnotationConfigApplicationContext
                (SetterInjectionConfiguration.class);
        SetterInjection mr = ctx.getBean("setterInjection", SetterInjection.class);
        System.out.println(mr);
    }
}

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    输出

    Dependency{}

    3）、字段注入
    package com.luo.spring.guides.iocdi.annotation.field;

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

/**
 * Created by iuliana.cosmina on 2/15/17.
 */
@Service("singer")
public class Singer {

	@Autowired
	private Inspiration inspirationBean;

	public void sing() {
		System.out.println("... " + inspirationBean.getLyric());
	}
}


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    package com.luo.spring.guides.iocdi.annotation.field;

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

/**
 * Created by iuliana.cosmina on 2/15/17.
 */
@Component
public class Inspiration {

	private String lyric = "I can keep the door cracked open, to let light through";

	public Inspiration(@Value("For all my running, I can understand") String lyric) {
		this.lyric = lyric;
	}

	public String getLyric() {
		return lyric;
	}

	public void setLyric(String lyric) {
		this.lyric = lyric;
	}
}

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    测试

    package com.luo.spring.guides.iocdi.annotation.field;

import com.luo.spring.guides.iocdi.annotation.InjectionConfiguration;
import com.luo.spring.guides.iocdi.annotation.setter.SetterInjection;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;

/**
 * @author : archer
 * @date : Created in 2022/11/30 20:46
 * @description :
 */
public class Main {

    public static void main(String... args) {
        ApplicationContext ctx = new AnnotationConfigApplicationContext
                (InjectionConfiguration.class);
        Singer singer = ctx.getBean("singer", Singer.class);

        Singer singerBean = ctx.getBean(Singer.class);
        System.out.println(singer == singerBean);
        singerBean.sing();
        singer.sing();
    }
}

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    输出

    ConstructorConfusion(int) called
    true
    … For all my running, I can understand
    … For all my running, I can understand

    4）、查找方法注入
    • 这种方式性能较差，当有其他方式替代时，请使用其他方式
    package com.luo.spring.guides.iocdi.lookup.annotation;

import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

/**
 * Created by iuliana.cosmina on 2/20/17.
 */
@Component("singer")
@Scope("prototype")
public class Singer {
    private String lyric = "I played a quick game of chess with the salt and pepper shaker";

    public void sing() {
        // commented to avoid console pollution
        //System.out.println(lyric);
    }
}

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    package com.luo.spring.guides.iocdi.lookup.annotation;

public interface DemoBean {
    Singer getMySinger();
    void doSomething();
}

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    package com.luo.spring.guides.iocdi.lookup.annotation;

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

@Component("abstractLookupBean")
public class AbstractLookupDemoBean implements DemoBean {
    @Lookup("singer")
    public Singer getMySinger() {
        return null; // This implementation will be overridden by dynamically generated subclass
    }

    @Override
    public void doSomething() {
        getMySinger().sing();
    }
}

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    package com.luo.spring.guides.iocdi.lookup.annotation;

import org.springframework.stereotype.Component;

import javax.annotation.Resource;

@Component("standardLookupBean")
public class StandardLookupDemoBean implements DemoBean {

	private Singer mySinger;

//	@Autowired
//	@Qualifier("singer")
	@Resource(name = "singer")
	public void setMySinger(Singer mySinger) {
		this.mySinger = mySinger;
	}

	@Override
	public Singer getMySinger() {
		return this.mySinger;
	}

	@Override
	public void doSomething() {
		mySinger.sing();
	}
}

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    测试

    package com.luo.spring.guides.iocdi.lookup.annotation;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.util.StopWatch;

/**
 * @author : archer
 * @date : Created in 2022/12/1 12:04
 * @description :
 */
public class Main {

    @Configuration
    @ComponentScan(basePackages = {"com.luo.spring.guides.iocdi.lookup.annotation"})
    public static class LookupConfig {}

    public static void main(String... args) {
        GenericApplicationContext ctx = new AnnotationConfigApplicationContext(LookupConfig.class);
        //Arrays.stream(ctx.getBeanDefinitionNames()).forEach(s-> System.out.println(s));

        DemoBean abstractBean = ctx.getBean("abstractLookupBean", DemoBean.class);
        DemoBean standardBean = ctx.getBean("standardLookupBean", DemoBean.class);


        displayInfo("abstractLookupBean", abstractBean);
        displayInfo("standardLookupBean", standardBean);

        ctx.close();
    }

    public static void displayInfo(String beanName, DemoBean bean) {
        Singer singer1 = bean.getMySinger();
        Singer singer2 = bean.getMySinger();

        System.out.println("[" + beanName + "]: Singer Instances the Same?  "
                + (singer1 == singer2));

        StopWatch stopWatch = new StopWatch();
        stopWatch.start("lookupDemo");

        for (int x = 0; x < 100000; x++) {
            Singer singer = bean.getMySinger();
            singer.sing();
        }

        stopWatch.stop();
        System.out.println("100000 gets took " + stopWatch.getTotalTimeMillis() + " ms");
    }
}

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    输出

    [abstractLookupBean]: Singer Instances the Same? false
    100000 gets took 575 ms
    [standardLookupBean]: Singer Instances the Same? true
    100000 gets took 1 ms

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  • 原文地址：https://blog.csdn.net/lxz352907839/article/details/128118380