Spring底層機制環(huán)境搭建全過程

更新時間：2024年12月09日 10:50:31 作者：S-X-S

本文介紹了如何創(chuàng)建和使用Spring框架,包括模塊創(chuàng)建、依賴引入、環(huán)境搭建、Bean的生命周期管理、AOP編程以及代碼托管,通過實際操作和代碼示例,詳細講解了Spring的核心概念和功能

Spring底層機制環(huán)境搭建

1.模塊創(chuàng)建和依賴引入

聚合模塊，下面有一個myspring

查看父模塊是否管理了子模塊

myspring模塊引入基本包

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>5.3.8</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aspects</artifactId>
        <version>5.3.8</version>
    </dependency>
</dependencies>

2.進行環(huán)境搭建

目錄概覽

UserController.java

package com.sunxiansheng.myspring.component;

import org.springframework.stereotype.Component;

/**
 * Description: 就是一個Controller組件
 * @Author sun
 * @Create 2024/8/4 13:53
 * @Version 1.0
 */
@Component
public class UserController {
}

UserService.java

package com.sunxiansheng.myspring.component;

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

/**
 * Description: 一個Service組件
 * @Author sun
 * @Create 2024/8/4 13:54
 * @Version 1.0
 */
@Component
public class UserService {

    /**
     * 依賴注入UserDao
     */
    @Autowired
    private UserDao userDao;

    public void add() {
        System.out.println("UserService 調(diào)用了UserDao的add方法");
        userDao.add();
    }

}

UserDao.java

package com.sunxiansheng.myspring.component;

import org.springframework.stereotype.Component;

/**
 * Description: 一個Dao組件
 * @Author sun
 * @Create 2024/8/4 13:53
 * @Version 1.0
 */
@Component
public class UserDao {

    public void add() {
        System.out.println("UserDao add...");
    }

}

AppMain.java

package com.sunxiansheng.myspring;

import com.sunxiansheng.myspring.component.UserController;
import com.sunxiansheng.myspring.component.UserDao;
import com.sunxiansheng.myspring.component.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Description: 啟動類
 * @Author sun
 * @Create 2024/8/4 13:59
 * @Version 1.0
 */
public class AppMain {

    public static void main(String[] args) {
        // 從類路徑下加載beans.xml配置文件
        ApplicationContext ioc = new ClassPathXmlApplicationContext("beans.xml");
        // 從容器中獲取UserController對象，這里獲取兩次，看是否是同一個對象
        UserController userController1 = (UserController) ioc.getBean("userController");
        UserController userController2 = (UserController) ioc.getBean("userController");
        System.out.println("userController1 == userController2 ? " + (userController1 == userController2));
        // 從容器中獲取UserService對象
        UserService userService = (UserService) ioc.getBean("userService");
        System.out.println("userService = " + userService);
        // 從容器中獲取UserDao對象
        UserDao userDao = (UserDao) ioc.getBean("userDao");
        System.out.println("userDao = " + userDao);
    }

}

beans.xml

<?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: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 https://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 配置自動掃描的包 -->
    <context:component-scan base-package="com.sunxiansheng.myspring.component"/>

</beans>

測試

配置UserController.java為多例的，然后測試

UserService調(diào)用add方法，然后測試

引入Bean后置處理器

1.位置

2.MyBeanPostProcessor.java

package com.sunxiansheng.myspring.process;

import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;

/**
 * Description: Bean的后置處理器
 * @Author sun
 * @Create 2024/8/4 14:19
 * @Version 1.0
 */
@Component // 將這個類加入到容器中
public class MyBeanPostProcessor implements BeanPostProcessor {

    /**
     * 在每個Bean的初始化方法之前執(zhí)行
     * @param bean
     * @param beanName
     * @return
     */
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) {
        // 這里可以提前對bean進行一些處理
        System.out.println("postProcessBeforeInitialization..."+beanName+"=>"+bean.getClass());
        return bean;
    }

    /**
     * 在每個Bean的初始化方法之后執(zhí)行
     * @param bean
     * @param beanName
     * @return
     */
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) {
        System.out.println("postProcessAfterInitialization..."+beanName+"=>"+bean.getClass());
        return bean;
    }

}

3.UserService.java 設(shè)置初始化方法

4.beans.xml配置掃描

5.測試

6.注意事項

bean的后置處理器在初始化方法調(diào)用前后執(zhí)行
觸發(fā)時機為單例的第一次getBean和多例的每次getBean，也就是，每個Bean都會經(jīng)過Bean的后置處理器處理

引入AOP

1.目錄

2.SmartAnimal.java

package com.sunxiansheng.myspring.aop;

/**
 * Description: SmartAnimal
 * @Author sun
 * @Create 2024/8/4 14:51
 * @Version 1.0
 */
public interface SmartAnimal {

    public float getSum(float a, float b);

    public float getSub(float a, float b);

}

3.SmartDog.java

package com.sunxiansheng.myspring.aop;

import org.springframework.stereotype.Component;

/**
 * Description: SmartDog
 * @Author sun
 * @Create 2024/8/4 14:51
 * @Version 1.0
 */
@Component // 交給Spring容器管理
public class SmartDog implements SmartAnimal {

    @Override
    public float getSum(float a, float b) {
        System.out.println("SmartDog...getSum...res=" + (a + b));
        return a + b;
    }

    @Override
    public float getSub(float a, float b) {
        System.out.println("SmartDog...getSub...res=" + (a - b));
        return a - b;
    }
}

4.SmartAnimalAspect.java

package com.sunxiansheng.myspring.aop;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.Signature;
import org.aspectj.lang.annotation.*;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;

import java.util.Arrays;

/**
 * Description: 切面類
 * @Author sun
 * @Create 2024/8/4 14:53
 * @Version 1.0
 */
@Component // 交給Spring容器管理
@Aspect // 標(biāo)注這是一個切面類
public class SmartAnimalAspect {

    /**
     * @param joinPoint 保存了要切入的方法的信息
     * @Before 前置通知
     * execution（。。。） 切入表達式，表明要切入的方法，格式：格式：訪問修飾符+返回類型 全類名 方法名（參數(shù)類型）
     */
    @Before(value = "execution(public float com.sunxiansheng.myspring.aop.SmartDog.getSub(float, float))")
    public void before(JoinPoint joinPoint) {
        // 獲取方法簽名
        Signature signature = joinPoint.getSignature();
        System.out.println("方法執(zhí)行開始-日志-方法名-" + signature.getName()
                + "-參數(shù)" + Arrays.asList(joinPoint.getArgs()));
        // 還可以獲取目標(biāo)對象，這樣就可以反射進行任何操作了
        SmartDog target = (SmartDog) joinPoint.getTarget();
        System.out.println("目標(biāo)對象-" + target.getClass());
    }

    /**
     * @param joinPoint 保存了要切入的方法的信息
     * @AfterReturning 返回通知
     */
    @AfterReturning(value = "execution(public float com.sunxiansheng.myspring.aop.SmartDog.getSub(float, float))")
    public void afterReturning(JoinPoint joinPoint) {
        Signature signature = joinPoint.getSignature();
        System.out.println("方法執(zhí)行正常結(jié)束-日志-方法名-" + signature.getName());
    }

    /**
     * @param joinPoint
     * @AfterThrowing 異常通知
     */
    @AfterThrowing(value = "execution(public float com.sunxiansheng.myspring.aop.SmartDog.getSub(float, float))")
    public void throwing(JoinPoint joinPoint) {
        Signature signature = joinPoint.getSignature();
        System.out.println("方法出現(xiàn)異常-日志-方法名-" + signature.getName());
    }

    /**
     * @param joinPoint
     * @After 后置通知
     */
    @After(value = "execution(public float com.sunxiansheng.myspring.aop.SmartDog.getSub(float, float))")
    public void after(JoinPoint joinPoint) {
        Signature signature = joinPoint.getSignature();
        System.out.println("方法最終執(zhí)行完畢-日志-方法名-" + signature.getName());
    }

    /**
     * 環(huán)繞通知
     * @param joinPoint
     * @return
     * @throws Throwable
     */
    @Around("execution(public float com.sunxiansheng.myspring.aop.SmartDog.getSub(float, float))")
    public Object logMethodExecution(ProceedingJoinPoint joinPoint) throws Throwable {
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();

        // 獲取方法信息
        String methodName = signature.getMethod().getName();
        String className = signature.getDeclaringType().getSimpleName();

        System.out.println("環(huán)繞通知 method " + className + "." + methodName);

        // 獲取目標(biāo)對象
        Object targetObject = joinPoint.getTarget();
        // 環(huán)繞通知獲取目標(biāo)對象
        System.out.println("環(huán)繞通知獲取目標(biāo)對象：" + targetObject);

        try {
            // 前置通知：環(huán)繞通知獲取參數(shù)
            System.out.println("環(huán)繞通知獲取參數(shù)：" + Arrays.asList(joinPoint.getArgs()));
            Object result = joinPoint.proceed();  // 執(zhí)行目標(biāo)方法
            // 返回通知：環(huán)繞通知獲取結(jié)果
            System.out.println("環(huán)繞通知獲取結(jié)果：" + result);
            return result;
        } catch (Exception e) {
            // 異常通知
            throw e;
        } finally {
            // 最終通知
            System.out.println("環(huán)繞通知 method " + className + "." + methodName);
        }
    }

}

5.beans.xml開啟aop注解并掃描aop包