1. Java Config

Java Config enables developers to configure Spring framework beans and dependencies with plain-old Java objects. By using Java Config, developers can avoid the use of XML configuration files and instead write configuration logic directly in Java classes. This can lead to more readable, maintainable, and flexible code.

package cn.tulingxueyuan;

import cn.tulingxueyuan.beans.MyImportBeanDefinitionRegistrar;
import cn.tulingxueyuan.beans.MyImportSelector;
import cn.tulingxueyuan.beans.Role;
import cn.tulingxueyuan.beans.User;
import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.*;
// 用户标记一个spring配置类,之前是根据xml启动spring上下文
// 相当于 xml文件  <beans></beans>
@Configuration
@ComponentScan(basePackages = "cn.tulingxueyuan")   //== <context:component-scan base-package="cn.tulingxueyuan" >
// 使用@PropertySource 引入外部属性资源文件
@PropertySource("classpath:db.properties")
/* @Import
  1 导入其他的配置类@Import(SecondJavaConfig.class)
  2.导入类注册为Bean @Import(Role.class)
  3.导入ImportSelector实现类，可以注册多个bean@Import(MyImportSelector.class)
  4.刀肉ImportBeanDefinitionRegistrar实现类，可以注册多个BeanDefinition
*/
@Import(MyImportBeanDefinitionRegistrar.class)
public class IoCJavaConfig {

/*
<bean class="com.alibaba.druid.pool.DruidDataSource" id="dataSource">
        <property name="username" value="${mysql.username}"></property>
        <property name="password" value="${mysql.password}"></property>
        <property name="url"  value="${mysql.url}"></property>
        <property name="driverClassName" value="${mysql.driverClassName}"></property>
    </bean>
*/
    @Value("${mysql.username}")
    private String name;
    @Value("${mysql.password}}")
    private String password;
    @Value("${mysql.url}")
    private String url;
    @Value("${mysql.driverClassName}")
    private String driverClassName;

    /**
     *  可以将一个类的实例(可以干预Bean实例化过程),注册为一个Bean
     *  会自动将返回值作为Bean的类型    将方法名作为bean的名字
     *  @Bean(name = "dd") 设置bean的名字及别名（替换）
     *  <bean class="com.alibaba.druid.pool.DruidDataSource" id="dataSource">
     *  @Bean(initMethod = "",destroyMethod = "") = <bean class="xx" id="xx" init-method="initByConfig" destroy-method="destroyByConfig"></bean>

     怎么去自动依赖外部Bean:直接在方法里面写上需要依赖的参数即可,不需要写@Autowired
    怎么去自动依赖内部Bean：直接调用方法即可
     */
    @Bean(name = {"dataSource","dd"})
    //@Scope("prototype")  //作用域
    public DruidDataSource dataSource(Role role){
        DruidDataSource dataSource=new DruidDataSource();
        dataSource.setName(name);
        dataSource.setPassword(password);
        dataSource.setUrl(url);
        dataSource.setDriverClassName(driverClassName);
        System.out.println(user3());

        return  dataSource;
    }

    @Bean
    public User user3(){
        System.out.print("new user");
        return new User();
    }
}

1.2 Four ways to Inject a class into IOC (Inversion of Control) container

1. xml:<bean>
2. @Component (@Controller,@Service,@Repository)
3. @Bean
4. @Import

2. Spring AOP

Spring Boot AOP - javatpoint

2.1 Spring AOP

Spring AOP (Aspect-Oriented Programming) is a powerful tool for separating cross-cutting concerns in an application. With AOP, developers can define aspects that can be applied to multiple points in the application's codebase. This allows developers to modularize and encapsulate cross-cutting concerns, such as logging and security, and apply them consistently throughout the application.

AOP can be used for various purposes such as logging, transaction management, security, and more. It allows developers to separate concerns that cut across multiple classes and methods, making the code more modular and easier to maintain.

2.2 Proxy

AOP使用代理实现。代理分为静态代理和动态代理:

2.2.1 静态代理