Spring笔记 #01# 一个小而生动的IOC例子代码

时间：2022-05-06 20:26:26

例子中仅包含两种类：英雄类Hero和武器类Weapon。

  1. 演示DI：给Hero初始化Weapon
  2. 演示AOP：法师是一个英雄，当他发动攻击的时候需要念咒语，只有咒语正确才能施展魔法。通过定义一个切面来检验咒语的正确性（假设咒语必须要符合某种公共的标准。。。。。）

代码结构：

Spring笔记 #01# 一个小而生动的IOC例子代码

Spring容器的最小可用依赖

  1. Spring的核心是一个IOC容器，包含两个基础模块：context以及bean（必要）
  2. 添加AspectJ相关依赖用于支持AOP（必要）
  3. 添加Log4j依赖方便输出（可选）
<?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>

    <groupId>sample</groupId>

    <artifactId>spring</artifactId>

    <version>1.0-SNAPSHOT</version>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <!-- -source 1.5 中不支持 try-with-resources-->

        <maven.compiler.source>1.8</maven.compiler.source>

        <maven.compiler.target>1.8</maven.compiler.target>

        <!-- Use the latest version whenever possible. -->

        <spring.version>5.1.3.RELEASE</spring.version>

        <log4j.version>2.11.1</log4j.version>

        <aspectj.version>1.9.2</aspectj.version>

    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-beans -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-beans</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->

        <dependency>

            <groupId>org.apache.logging.log4j</groupId>

            <artifactId>log4j-core</artifactId>

            <version>${log4j.version}</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-api -->

        <dependency>

            <groupId>org.apache.logging.log4j</groupId>

            <artifactId>log4j-api</artifactId>

            <version>${log4j.version}</version>

        </dependency>
        <!-- https://mvnrepository.com/artifact/org.aspectj/aspectjrt -->

        <dependency>

            <groupId>org.aspectj</groupId>

            <artifactId>aspectjrt</artifactId>

            <version>${aspectj.version}</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.aspectj/aspectjweaver -->

        <dependency>

            <groupId>org.aspectj</groupId>

            <artifactId>aspectjweaver</artifactId>

            <version>${aspectj.version}</version>

        </dependency>

    </dependencies>

</project>

用XML定义元数据

★主配置文件：

<?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

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

    <import resource="bean/weapons.xml"/>

    <import resource="bean/heroes.xml"/>

</beans>

★子配置文件1：

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"

       xsi:schemaLocation="http://www.springframework.org/schema/beans

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

    <bean id="mySword" class="sample.spring.iocbasis.weapon.Sword"/>

    <bean id="myMagicBook" class="sample.spring.iocbasis.weapon.MagicBook"/>

    <aop:config>

        <aop:aspect ref="myMagicBook">

            <aop:pointcut id="mageAttack"

                          expression="execution(* sample.spring.iocbasis.hero.Mage.attack(String))" />

            <aop:around pointcut-ref="mageAttack" method="magicLimit" />

        </aop:aspect>

    </aop:config>

</beans>

★子配置文件2，IDEA可能会报错说找不到引用，但其实是Ok的。注意不要重复import一个配置文件，这会导致重复定义bean或者切面：

<?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

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

    <bean id="iocWarrior" class="sample.spring.iocbasis.hero.Warrior">

        <constructor-arg ref="mySword" />

    </bean>

    <bean id="iocMage" class="sample.spring.iocbasis.hero.Mage">

        <constructor-arg ref="myMagicBook" />

    </bean>

</beans>

实例化容器&使用容器

★程序入口：

package sample.spring.iocbasis;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import sample.spring.iocbasis.hero.Hero;

import sample.spring.iocbasis.hero.Mage;

import sample.spring.iocbasis.hero.Warrior;

import sample.spring.iocbasis.weapon.MagicBook;

import sample.spring.iocbasis.weapon.Sword;

public class MyTest {

    public static void main(String[] args) {

        System.out.println("===========手动调用setter方法注入=================");

        Warrior warrior = new Warrior();

        warrior.attack(null);

        warrior.setWeapon(new Sword());

        warrior.attack(null);

        System.out.println("===========手动调用构造器方法注入=================");

        Warrior warrior2 = new Warrior(new Sword());

        warrior2.attack(null);

        System.out.println("===========直接从IOC容器中获得事先组装好的对象=================");

        ApplicationContext context = new ClassPathXmlApplicationContext("\\spring\\config.xml");

        Warrior iocWarrior = context.getBean("iocWarrior", Warrior.class);

        iocWarrior.attack(null);

        System.out.println("===========通过动态代理增强方法=================");

        Hero iocMage = context.getBean("iocMage", Hero.class);

        iocMage.attack("hello world.");

        iocMage.attack("hlo worl.");

        System.out.println("===========绕过动态代理=================");

        new Mage(new MagicBook()).attack("hlo worl.");

    }

}

/*

===========手动调用setter方法注入=================

Warrior{no=1}用WoodenStick{}发起了一次攻击。

Warrior{no=1}用Sword{no=1}发起了一次攻击。

===========手动调用构造器方法注入=================

Warrior{no=2}用Sword{no=2}发起了一次攻击。

===========直接从IOC容器中获得事先组装好的对象=================

Warrior{no=3}用Sword{no=3}发起了一次攻击。

===========通过动态代理增强方法=================

Mage{no=1}试图发动一次魔法攻击，准备校验咒语【hello world.】正确性 ...

Mage{no=1}用MagicBook{no=1}发起了一次攻击

Mage{no=1}试图发动一次魔法攻击，准备校验咒语【hlo worl.】正确性 ...

Mage{no=1}的咒语念错了，魔法发动失败 ...

===========绕过动态代理=================

Mage{no=2}用MagicBook{no=2}发起了一次攻击

 */

唯一能看出“第三方依赖痕迹”的类：

package sample.spring.iocbasis.weapon;

import org.apache.logging.log4j.LogManager;

import org.apache.logging.log4j.Logger;

import org.aspectj.lang.ProceedingJoinPoint;

public class MagicBook implements Weapon {

    private static final Logger LOGGER = LogManager.getLogger();

    private static int count = 0;

    private int no = ++count;

    @Override

    public void attack() {

    }

    public void magicLimit(ProceedingJoinPoint jp) {

        try {

            Object obj = jp.getThis();

            String spell = String.valueOf(jp.getArgs()[0]);

            LOGGER.info("{}试图发动一次魔法攻击，准备校验咒语【{}】正确性 ...", obj, spell);

            if ("hello world.".equals(spell)) {

                jp.proceed();

            } else {

                LOGGER.info("{}的咒语念错了，魔法发动失败 ...", obj);

            }

        } catch (Throwable throwable) {

            throwable.printStackTrace();

        }

    }

    @Override

    public String toString() {

        return "MagicBook{" +

                "no=" + no +

                '}';

    }

}

其它类：

package sample.spring.iocbasis.hero;

import org.apache.logging.log4j.LogManager;

import org.apache.logging.log4j.Logger;

import sample.spring.iocbasis.weapon.Weapon;

import sample.spring.iocbasis.weapon.WoodenStick;

public class Warrior implements Hero {

    private static final Logger LOGGER = LogManager.getLogger();

    private static int count = 0;

    private int no = ++count;

    private Weapon weapon;

    public Warrior() {

        weapon = new WoodenStick();

    }

    public Warrior(Weapon weapon) {

        this.weapon = weapon;

    }

    public void setWeapon(Weapon weapon) {

        this.weapon = weapon;

    }

    @Override

    public void attack(String sth) {

        LOGGER.info("{}用{}发起了一次攻击。", this, weapon);

        weapon.attack();

    }

    @Override

    public String toString() {

        return "Warrior{" +

                "no=" + no +

                '}';

    }

}

Warrior.java

package sample.spring.iocbasis.hero;

import org.apache.logging.log4j.LogManager;

import org.apache.logging.log4j.Logger;

import sample.spring.iocbasis.weapon.Weapon;

public class Mage implements Hero {

    private static final Logger LOGGER = LogManager.getLogger();

    private static int count = 0;

    private int no = ++count;

    private Weapon weapon;

    public Mage(Weapon weapon) {

        this.weapon = weapon;

    }

    @Override

    public void attack(String spell) {

        LOGGER.info("{}用{}发起了一次攻击", this, weapon);

    }

    @Override

    public String toString() {

        return "Mage{" +

                "no=" + no +

                '}';

    }

}

Mage.java

package sample.spring.iocbasis.weapon;

public class Sword implements Weapon {

    private static int count = 0;

    private int no = ++count;

    @Override

    public void attack() {

    }

    @Override

    public String toString() {

        return "Sword{" +

                "no=" + no +

                '}';

    }

}

Sword.java

package sample.spring.iocbasis.weapon;

public class WoodenStick implements Weapon {

    @Override

    public void attack() {

    }

    @Override

    public String toString() {

        return "WoodenStick{}";

    }

}

WoodenStick.java

package sample.spring.iocbasis.hero;

public interface Hero {

    void attack(String sth);

}

Hero.java

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