Spring更简单的读取和存储对象

1.存储对象

通过注解来替代配置，依然需要配置扫描包的类对象

1.配置扫描路径

<?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:content="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">
    <content:component-scan base-package="com.bean">
    </content:component-scan>
    <!--    <bean id="user" class="com.bit.beans.User"></bean>-->
</beans>

注册扫描的包

<content:component-scan base-package="com.bean">
    </content:component-scan>

2.添加注解存储Bean对象

有两种注解类型可以实现：

类注解：@Controller、@Service、@Repository、@Component、@Configuration。
⽅法注解：@Bean。

package com.bean;

import org.springframework.stereotype.Controller;

/**
 * Created by 伦敦看日出
 * Description:通过@Controller注解将对象存储到Spring中
 * User: yyt
 * Date: 2023-04-22
 * Time: 15:22
 */
@Controller
public class User {
    public String sayHi(String name) {
        return name + ": spring-bean";
    }
}

启动类App

import com.bean.User;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;

public class App {
    public static void main(String[] args) {
        // 1.获取Spring上下文对象，指定Spring的配置文件
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
        // 2.加载某个bean
        User user = (User) context.getBean("user");
        // 3.调用相应的方法
        System.out.println(user.sayHi("Java"));
    }
}

3.为什么要这么多注解

让程序员看到类注解可以直接了解当前类的用途

⽐如：

@Controller：表示的是业务逻辑层；
@Servie：服务层；
@Repository：持久层；
@Configuration：配置层。

在这里插入图片描述

@Controller / @Service / @Repository / @Configuration 等注解是 @Component 的“⼦类”

4.注意Bean的命名

bean一般都是使用大驼峰命名，读取的时候首字母小写，但是遇到前两个字母都大写的时候就不能将首字母小写，而是要将两字母都大写。

在这里插入图片描述

5.方法注解

@Bean方法注解是添加到方法上，需要搭配类注解一起使用

A. 创建User对象

package com.bean;

import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Controller;

public class User {
    private int id;
    private String name;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

B. 添加注解

package com.bean;

import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Controller;

@Controller
public class Users {
    @Bean
    public User user1() {
        User user = new User();
        user.setId(1);
        user.setName("Bean");
        return user;
    }
}

C. 获取bean对象中的user1

import com.bean.User;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;

public class App {
    public static void main(String[] args) {
        // 1.获取Spring上下文对象，指定Spring的配置文件
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
        // 2.加载某个bean
        User user = (User) context.getBean("user1");
        // 3.调用相应的方法
        System.out.println(user.toString());
    }

}

在这里插入图片描述

6.重命名Bean

@Bean(name = {"u1","u2"})
@Bean({"u1","u2"}) // name= 可以省略

2.获取Bean对象(对象装配)

对象装配（对象注⼊）的实现⽅法以下 3 种

属性注⼊
构造⽅法注⼊
Setter 注⼊

1.属性注⼊

属性注⼊是使⽤ @Autowired 实现的，将 Service 类注⼊到 Controller 类中。

Service 类代码：

package com.bean.service;

import com.bean.User;
import org.springframework.stereotype.Service;

import javax.xml.ws.ServiceMode;

@Service
public class UserService {
    public User getUser(int id) {
        User user = new User();
        user.setId(1);
        user.setName("spring");
        return user;
    }
}

Controller 类代码：

package com.bean.Controller;

import com.bean.User;
import com.bean.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;

@Controller
public class UserController {
    // 注入方法1：属性注入
    @Autowired
    private UserService service;
    public User getUser(int id) {
        return service.getUser(id);
    }
}

获取 Controller中的getUser方法：

package com.bean;

import com.bean.Controller.UserController;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class ControllerTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
        UserController userController = context.getBean(UserController.class);
        System.out.println(userController.getUser(1).toString());
    }
}

输出：

User{id=1, name=‘Bean’}

2.构造方法注入(推荐)

@Controller
public class UserController2 {
    private UserService userService;
    @Autowired
    public UserController2(UserService userService) {
        this.userService = userService;
    }
    public User getUser(int id) {
        return userService.getUser(id);
    }
}

3.Setter注入

@Controller
public class UserController3 {
    private UserService userService;
    @Autowired
    public void setUserService(UserService userService) {
        this.userService = userService;
    }
    public User getUser(int id) {
        return userService.getUser(id);
    }
}