Spring IoC 与 Spring DI 详解 | 极客日志

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Spring IoC 与 Spring DI 详解

Spring IoC（控制反转）与 DI（依赖注入）的核心概念。通过对比传统对象创建与容器管理，阐述降低耦合度的优势。讲解 Bean 存储注解（@Controller, @Service 等）及获取方式。分析属性、构造器、Setter 三种依赖注入方式的优缺点，并提供多 Bean 注入冲突的解决方案（@Primary, @Qualifier, @Resource）。

ArchDesign发布于 2026/3/26更新于 2026/5/2833 浏览

一、IoC 与 DI

名词解释：

Spring 是一个装了众多工具对象的 IoC 容器。
IoC 思想：对象交给 Spring 管理，就是 IoC 思想。
IoC：Inversion of Control，控制反转。

控制权反转，需要某个对象时，传统开发模式中需要自己通过 new 创建对象，现在不需要再进行创建，把创建对象的任务交给容器（IoC 容器。Spring 是一个 IoC 容器，所以有时 Spring 也称为 Spring 容器），程序中只需要依赖注入 (Dependency Injection, DI) 就可以了。

1.1 IoC

实现下面的需求：

在传统的实现中，我们将每个模块当成一个类：

public class NewCarExample {
    public static void main(String[] args) {
        Car car = new Car();
        car.run();
    }

    /**
     * 汽车对象
     */
    static class Car {
        private Framework framework;

        public Car() {
            framework = new Framework();
            System.out.println("Car init....");
        }

        public void run() {
            System.out.println("Car run...");
        }
    }

    /**
     * 车身类
     */
    static class Framework {
        private Bottom bottom;

        public Framework() {
            bottom = new ();
            System.out.println();
        }
    }

    
       {
         Tire tire;

          {
            .tire =  ();
            System.out.println();
        }
    }

    
       {
        
          size;

          {
            .size = ;
            System.out.println( + size);
        }
    }
}

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public class IocCarExample {
    public static void main(String[] args) {
        Tire tire = new Tire(20);
        Bottom bottom = new Bottom(tire);
        Framework framework = new Framework(bottom);
        Car car = new Car(framework);
        car.run();
    }

    static class Car {
        private Framework framework;

        public Car(Framework framework) {
            this.framework = framework;
            System.out.println("Car init....");
        }

        public void run() {
            System.out.println("Car run...");
        }
    }

    static class Framework {
        private Bottom bottom;

        public Framework(Bottom bottom) {
            this.bottom = bottom;
            System.out.println("Framework init...");
        }
    }

    static class Bottom {
        private Tire tire;

        public Bottom(Tire tire) {
            this.tire = tire;
            System.out.println("Bottom init...");
        }
    }

    static class Tire {
        private int size;

        public Tire(int size) {
            this.size = size;
            System.out.println("轮胎尺寸：" + size);
        }
    }
}

package com.example.project.controller;

import com.example.project.model.BookInfo;
import com.example.project.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;

@RequestMapping("/book")
@RestController
@Component
public class BookController {
    @Autowired
    private BookService bookService;

    @RequestMapping("/getList")
    public List<BookInfo> getList() {
        return bookService.getList();
    }
}

package com.example.project.service;

import com.example.project.dao.BookDao;
import com.example.project.model.BookInfo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.util.ArrayList;
import java.util.List;

@Component
public class BookService {
    @Autowired
    BookDao bookDao;

    public List<BookInfo> getList() {
        List<BookInfo> books = new ArrayList<>();
        books = bookDao.mockData();
        for (BookInfo book : books) {
            if (book.getStatus() == 1) {
                book.setStatusCN("可借阅");
            } else {
                book.setStatusCN("不可借阅");
            }
        }
        return books;
    }
}

package com.example.project.dao;

import com.example.project.model.BookInfo;
import org.springframework.stereotype.Component;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

@Component
public class BookDao {
    public List<BookInfo> mockData() {
        List<BookInfo> books = new ArrayList<>();
        for (int i = 0; i < 5; i++) {
            BookInfo book = new BookInfo();
            book.setId(i);
            book.setBookName("书籍" + i);
            book.setAuthor("作者" + i);
            book.setCount(i * 5 + 3);
            book.setPrice(new BigDecimal(new Random().nextInt(100)));
            book.setPublish("出版社" + i);
            book.setStatus(1);
            books.add(book);
        }
        return books;
    }
}

package com.example.springioc.controller;

import org.springframework.stereotype.Controller;

@Controller
public class UserController {
    public void hello() {
        System.out.println("Hello");
    }
}

package com.example.springioc.controller;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

@SpringBootApplication
public class SpringIocDemoApplication {
    public static void main(String[] args) {
        // 先获取 Spring 上下文对象
        ApplicationContext context = SpringApplication.run(SpringIocDemoApplication.class, args);
        // 从 Spring 上下文中获取对象
        UserController userController = context.getBean(UserController.class);
        userController.hello();
    }
}

package com.example.springioc.controller;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

@SpringBootApplication
public class SpringIocDemoApplication {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(SpringIocDemoApplication.class, args);
        UserController bean1 = context.getBean(UserController.class);
        bean1.hello();
        UserController bean2 = (UserController) context.getBean("userController");
        bean2.hello();
        UserController bean3 = context.getBean("userController", UserController.class);
        bean3.hello();
    }
}

package com.example.springioc.service;

import org.springframework.stereotype.Service;

@Service
public class UserService {
    void print() {
        System.out.println("do Service");
    }
}

package com.example.springioc.service;

import org.springframework.stereotype.Repository;

@Repository
public class UserRepository {
    void print() {
        System.out.println("do Repository");
    }
}

package com.example.springioc.service;

import org.springframework.stereotype.Component;

@Component
public class UserComponent {
    void print() {
        System.out.println("do Component");
    }
}

package com.example.springioc.service;

import org.springframework.context.annotation.Configuration;

@Configuration
public class UserConfiguration {
    void print() {
        System.out.println("do Configuration");
    }
}

package com.example.springioc.controller;

import com.example.springioc.model.User;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Controller;

@Controller
public class UserController {
    @Bean
    public User user() {
        return new User("zhangsan", 11);
    }

    public void hello() {
        System.out.println("Hello");
    }
}

package com.example.springioc.controller;

import com.example.springioc.model.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

@SpringBootApplication
public class SpringIocDemoApplication {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(SpringIocDemoApplication.class, args);
        User bean1 = (User) context.getBean("user");
        System.out.println(bean1.getName());
    }
}

package com.example.springioc.controller;

import com.example.springioc.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;

@Controller
public class UserController {
    @Autowired
    private UserService us;

    public void hello() {
        System.out.println("Hello");
        us.print();
    }
}

package com.example.springioc;

import com.example.springioc.controller.UserController;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

@SpringBootApplication
public class SpringIocDemoApplication {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(SpringIocDemoApplication.class, args);
        UserController bean = context.getBean(UserController.class);
        bean.hello();
    }
}

package com.example.springioc.controller;

import com.example.springioc.service.UserService;
import org.springframework.stereotype.Controller;

@Controller
public class UserController {
    private UserService us;

    public UserController(UserService us) {
        this.userService = us;
    }

    public void hello() {
        System.out.println("Hello");
        us.print();
    }
}

package com.example.springioc.controller;

import com.example.springioc.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;

@Controller
public class UserController {
    private UserService us;

    @Autowired
    public void setUserService(UserService us) {
        this.us = us;
    }

    public void hello() {
        System.out.println("Hello");
        us.print();
    }
}

package com.example.springioc.service;

import com.example.springioc.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Primary;
import org.springframework.stereotype.Service;

@Service
public class UserService {
    @Bean
    public User u1(String name) {
        return new User(name, 11);
    }

    @Bean
    public User u2() {
        return new User("lisi", 18);
    }

    @Bean
    public String name() {
        return "zhangsan";
    }

    public void print() {
        System.out.println("do Service");
    }
}

package com.example.springioc.controller;

import com.example.springioc.model.User;
import jakarta.annotation.Resource;
import org.springframework.stereotype.Controller;

@Controller
public class UserController {
    @Resource(name = "u1")
    private User user;

    public void hello() {
        System.out.println("Hello");
        System.out.println(user.toString());
    }
}

@Bean
@Primary
public String name() {
    return "zhangsan";
}

@Autowired
@Qualifier("u1")
private User user;

@Resource(name = "u2")
private User user;

Spring IoC 与 Spring DI 详解

一、IoC 与 DI

1.1 IoC

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1.2 DI

二、IoC 与 DI 的使用

三、IoC 详解

3.1 Bean 的存储

3.2 @Controller（控制器存储）

3.3 获取 Bean 对象

3.4 @Service（服务存储）

3.5 @Repository（仓库存储）

3.6 @Component（组件存储）

3.7 @Configuration（配置存储）

3.8 五大注解区别

3.9 方法注解 @Bean

四、Spring 扫描路径

五、DI 详解

5.1 属性注入 @Autowired

5.2 构造方法注入

5.3 setter 方法注入

5.4 @Autowired 注解问题及解决

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Spring IoC 与 Spring DI 详解

一、IoC 与 DI

1.1 IoC

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1.2 DI

二、IoC 与 DI 的使用

三、IoC 详解

3.1 Bean 的存储

3.2 @Controller（控制器存储）

3.3 获取 Bean 对象

3.4 @Service（服务存储）

3.5 @Repository（仓库存储）

3.6 @Component（组件存储）

3.7 @Configuration（配置存储）

3.8 五大注解区别

3.9 方法注解 @Bean

四、Spring 扫描路径

五、DI 详解

5.1 属性注入 @Autowired

5.2 构造方法注入

5.3 setter 方法注入

5.4 @Autowired 注解问题及解决

微信扫一扫，关注极客日志

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