Spring註解開發

<?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

        https://www.springframework.org/schema/beans/spring-beans.xsd

        http://www.springframework.org/schema/context

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

    <!--註解支援-->

    <context:annotation-config/>

</beans>

bean註冊到Spring容器中

applicationContext.xml新增包掃描註解

<?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

        https://www.springframework.org/schema/beans/spring-beans.xsd

        http://www.springframework.org/schema/context

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

    <!--註解支援-->

    <context:annotation-config/>

    <!--指定要掃描的包，包下的註解就會生效-->

    <context:component-scan base-package="com.qing"/>

</beans>

實體類添加註解@Component

package com.qing.dao;

import org.springframework.stereotype.Component;

@Component

public class User {

    private String name;

}

import com.qing.dao.User;

import org.junit.jupiter.api.Test;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {

    @Test

    public void test01(){

        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        User user = context.getBean("user", User.class);

        System.out.println(user.getName());

    }

}

User實體類被Spring管理，通過@Component註解註冊到Spring容器中

屬性注入

屬性添加註解@Value("張三丰")

package com.qing.pojo;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.stereotype.Component;

@Component

public class User {

    @Value("張三丰")

    private String name;

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

import com.qing.pojo.User;

import org.junit.jupiter.api.Test;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {

    @Test

    public void test01(){

        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        User user = context.getBean("user", User.class);

        System.out.println(user.getName());

    }

}

@Component的衍生註解

在web開發中，會按照MVC三層架構分層，分別使用註解，但他們的作用和@Component註解是一樣的，都是將類註冊到spring容器中，只是為了標記分層使用不同的註解

dao層 @Repository

package com.qing.dao;

import org.springframework.stereotype.Repository;

@Repository

public class UserDao {

}

service層 @Service

package com.qing.service;

import org.springframework.stereotype.Service;

@Service

public class UserService {

}

controller層 @Controller

package com.qing.controller;

import org.springframework.stereotype.Controller;

@Controller

public class UserController {

}

自動裝配

作用域

單例@Scope("singleton") 原型@Scope("prototype")

package com.qing.pojo;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.context.annotation.Scope;

import org.springframework.stereotype.Component;

@Component

@Scope("singleton")

//@Scope("prototype")

public class User {

    @Value("張三丰")

    private String name;

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

xml與註解區別

@Configuration 不使用Spring的xml配置，完全Java來做

JavaConfig是Spring的一個子專案，在Spring4之後，它成為了一個核心功能

新增配置類

@Configuration代表這是一個配置類

package com.qing.config;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

import org.springframework.context.annotation.Import;

// @Configuration代表這是一個配置類，相當於applicationContext.xml

@Configuration

// @ComponentScan 掃描包下註解

@ComponentScan("com.qing.pojo")

// @Import 匯入其他配置類

@Import(QingConfig2.class)

public class QingConfig {

}

實體類添加註解

package com.qing.pojo;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.stereotype.Component;

@Component

public class User {

    @Value("張三丰")

    private String name;

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

測試

import com.qing.config.QingConfig;

import com.qing.pojo.User;

import org.junit.jupiter.api.Test;

import org.springframework.context.ApplicationContext;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class MyTest {

    @Test

    public void test01(){

        // 通過AnnotationConfigApplicationContext獲取容器，通過配置類的class載入

        ApplicationContext context = new AnnotationConfigApplicationContext(QingConfig.class);

        User user = context.getBean("user", User.class);

        System.out.println(user.getName());

    }

}