[Java知识库]Spring核心机制——IoC和AOP

Spring核心机制

1 Spring IoC 和 AOP

Spring 框架Java开发的行业标准

Spring 全家桶

Web：Spring Web MVC/Spring MVC、Spring Web Flux

持久层: Spring Data/ Spring DataJPA、Spring Data Redis、Spring Data MongoDB

安全校验: Spring Security

构建工程脚手架:Spring Boot

微服务:Spring Cloud

IoC是Spring全家桶各个功能模块的基础，创建对象的容器。

AOP也是以loC为基础，AOP是面向切面编程，抽象化的面向对象

1、打印日志

2、事务

3、权限处理

1.1 IoC

控制反转，将对象的创建进行反转，常规情况下，对象都是开发者手动创建的，使用loC开发者不再需要创建对象，而是由loC容器根据需求自动创建项目所需要的对象。

不用IoC：所有对象开发者自己创建

使用IoC：对象不用开发者创建，而是交给Spring框架来完成

1.pom.xml

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>5.2.12.RELEASE</version>
</dependency>

引入IoC的环境下

基于XML和基于注解

基于XML：开发者把需要的对象在XML中进行配置，Spring框架读取这个配置文件，根据配置文件的内容来创建对象

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:tx="http://www.springframework.org/schema/beans"
       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
       http://www.springframework.org/schema/aop 
       http://www.springframework.org/schema/aop/spring-aop.xsd
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/tx/spring-tx.xsd">

    <bean class="nuc.edu.springdemo.DataConfig" id="config">
        <property name="driverName" value="Driver"></property>
        <property name="url" value="loaclhost:8080"></property>
        <property name="username" value="root"></property>
        <property name="password" value="654321"></property>
    </bean>
</beans>

package nuc.edu.springdemo;

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

public class Test {
    public static void main(String[] args) {
//        DataConfig dataConfig = new DataConfig();
//        dataConfig.setDriverName("Driver");
//        dataConfig.setUrl("localhost:3306/dbname");
//        dataConfig.setUsername("root");
//        dataConfig.setPassword("123456");

        ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
        System.out.println(context.getBean("config"));

    }
}

基于注解

1、配置类

package nuc.edu.springdemo.configuration;

import nuc.edu.springdemo.DataConfig;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class BeanConfiguration {
    
    @Bean(value = "config")
    public DataConfig dataConfig() {
        DataConfig dataConfig = new DataConfig();
        dataConfig.setDriverName("Driver");
        dataConfig.setUrl("localhost:3306/dbname");
        dataConfig.setUsername("root");
        dataConfig.setPassword("123456");
        return dataConfig;
    }
}

package nuc.edu.springdemo;

import nuc.edu.springdemo.configuration.BeanConfiguration;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] args) {
//        DataConfig dataConfig = new DataConfig();
//        dataConfig.setDriverName("Driver");
//        dataConfig.setUrl("localhost:3306/dbname");
//        dataConfig.setUsername("root");
//        dataConfig.setPassword("123456");

ApplicationContext context = new AnnotationConfigApplicationContext(BeanConfiguration.class);
System.out.println(context.getBean(DataConfig.class));
System.out.println(context.getBean("config"));

当配置类存在多个时，直接使用包名

ApplicationContext context = new AnnotationConfigApplicationContext("nuc.edu.springdemo.configuration");

2、扫包+注解

更简单的方式，不再需要依赖于XML或者配置类，而是直接将bean的创建交给目标类，在目标类添加注解来创建

package nuc.edu.springdemo.ioc;

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

@Data
@Component
public class DataConfig {
    @Value("localhost:3306")
    private String url;
    @Value("Driver")
    private String driverName;
    @Value("root")
    private String username;
    @Value("654123")
    private String password;

}

ApplicationContext context = new AnnotationConfigApplicationContext("nuc.edu.springdemo.ioc");
System.out.println(context.getBean(DataConfig.class));

自动创建对象，完成依赖注入

package nuc.edu.springdemo.ioc;

import lombok.Data;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Data
@Component
public class GlobalConfig {
    @Value("8080")
    private String port;
    @Value("/")
    private String path;
    @Autowired
    private DataConfig dataConfig;
}

@Autowired 通过类型进行注入，如果需要通过名称取值，通过@Qualifier注解完成名称的映射

package nuc.edu.springdemo.ioc;

import lombok.Data;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Data
@Component
public class GlobalConfig {
    @Value("8080")
    private String port;
    @Value("/")
    private String path;
    @Autowired
    @Qualifier("config")
    private DataConfig dataConfig;
}

package nuc.edu.springdemo.ioc;

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

@Data
@Component("config")
public class DataConfig {
    @Value("localhost:3306")
    private String url;
    @Value("Driver")
    private String driverName;
    @Value("root")
    private String username;
    @Value("654123")
    private String password;
}

1.2AOP

面向切面编程，是一种抽象化的面向对象编程，对面向对象编程的补充，底层使用动态代理机制来实现

打印日志

业务代码和打印日志耦合起来

package nuc.edu.springdemo.aop;

public class CalImpl implements Cal {

    @Override
    public int add(int num1, int num2) {
        System.out.println("add方法的参数是[" + num1 + "," + num2 + "]");
        int result = num1 + num2;
        System.out.println("add方法的结果是" + result);
        return result;
    }

    @Override
    public int sub(int num1, int num2) {
        System.out.println("sub方法的参数是[" + num1 + "," + num2 + "]");
        int result = num1 - num2;
        System.out.println("sub方法的结果是" + result);
        return result;
    }

    @Override
    public int mul(int num1, int num2) {
        System.out.println("mul方法的参数是[" + num1 + "," + num2 + "]");
        int result = num1 * num2;
        System.out.println("mul方法的结果是" + result);
        return result;
    }

    @Override
    public int div(int num1, int num2) {
        System.out.println("div方法的参数是[" + num1 + "," + num2 + "]");
        int result = num1 / num2;
        System.out.println("div方法的结果是" + result);
        return result;
    }
}

计算器方法中，日志和业务混合在一起，AOP要做的就是将日志代码全部抽象出去统一进行处理，计算器方法中只保留核心的业务代码。

做到核心业务和非业务代码的解耦合

1、创建切面类

package nuc.edu.springdemo.aop;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;

import java.util.Arrays;

@Component
@Aspect
public class LoggerAspect {
    @Before("execution(public int nuc.edu.springdemo.aop.CalImpl.*(..))")
    public void before(JoinPoint joinPoint){
        String name = joinPoint.getSignature().getName();
        System.out.println(name+"方法的参数是"+ Arrays.toString(joinPoint.getArgs()));
    }
    @AfterReturning(value = "execution(public int nuc.edu.springdemo.aop.CalImpl.*(..))",returning = "result")
    public void afterReturning(JoinPoint joinPoint,Object result){
        String name = joinPoint.getSignature().getName();
        System.out.println(name+"方法的结果是"+ result);
    }
}

2、实现类添加@Component注解

package nuc.edu.springdemo.aop;

import org.springframework.stereotype.Component;

@Component
public class CalImpl implements Cal {

    @Override
    public int add(int num1, int num2) {
        int result = num1 + num2;
        return result;
    }

    @Override
    public int sub(int num1, int num2) {
        int result = num1 - num2;
        return result;
    }

    @Override
    public int mul(int num1, int num2) {
        int result = num1 * num2;
        return result;
    }

    @Override
    public int div(int num1, int num2) {
        int result = num1 / num2;
        return result;
    }
}

3、配置自动扫包，开启自动生产代理对象

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:tx="http://www.springframework.org/schema/beans"
       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
      http://www.springframework.org/schema/aop
      http://www.springframework.org/schema/aop/spring-aop.xsd
      http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/tx/spring-tx.xsd">
    
        <!--自动扫包-->
    <context:component-scan base-package="nuc.edu.springdemo.aop"></context:component-scan>
        <!--开启自动生成代理-->
    <aop:aspectj-autoproxy></aop:aspectj-autoproxy>
    
</beans>

4、使用

package nuc.edu.springdemo.aop;

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

public class Test {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
        Cal bean = context.getBean(Cal.class);
        System.out.println(bean.add(9, 8));
        System.out.println(bean.sub(9, 8));
        System.out.println(bean.mul(9, 8));
        System.out.println(bean.div(9, 8));
    }
}