一、注解基本使用介绍

二、环境

三、代码实现

四、简化上述代码

五、注解

六、Bean添加别名

一、注解基本使用介绍

使用annotation注释替换之前较为复杂的spring.xml管理代码的方式。

二、环境

1.Pom

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.7.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.7.RELEASE</version>
    </dependency>
    <!--单元测试-->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>

三、代码实现

1.代码

（1）Bean1类

package com.spring.ioc;

/**
 * Created by Administrator on 2019/10/26.
 */
public class Bean1 {
}

（2）MyConfiguration类（相当于之前的spring.xml文件）

package com.spring.ioc;

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Bean;
/**
 * Created by Administrator on 2019/10/26.
 */
@Configuration
public class MyConfiguration {
    @Bean(value = "bean1")
    public Bean1 bean1(){
        return new Bean1();
    }
}

2.测试

package com.spring.ioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Created by Administrator on 2019/10/26.
 */
public class testCode {
    @Test
    public void test(){
        ApplicationContext context=new AnnotationConfigApplicationContext(MyConfiguration.class);
        //bean1
        Bean1 bean1=context.getBean("bean1",Bean1.class);
        System.out.println("bean1 = " + bean1);


    }
}

结果：

bean1 = com.spring.ioc.Bean1@36f0f1be

四、简化上述代码

1.MyConfiguration.class类
在配置文件上面添加ComponentScan注解，扫描指定包下面的实例对象

package com.spring.ioc;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Bean;
/**
 * Created by Administrator on 2019/10/26.
 */
@Configuration
@ComponentScan(value = "com.spring.ioc")
public class MyConfiguration {

}

2.Bean1.class类
添加@Component注解，说明是一个交由spring管理的Bean对象。备注：value可以指定对应id，默认id是方法的Bean的第一个字母小写。

package com.spring.ioc;

import org.springframework.stereotype.Component;

/**
 * Created by Administrator on 2019/10/26.
 */
@Component(value = "bean2")
public class Bean1 {
}

3.测试代码

package com.spring.ioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Created by Administrator on 2019/10/26.
 */
public class testCode {
    @Test
    public void test(){
        ApplicationContext context=new AnnotationConfigApplicationContext(MyConfiguration.class);
        //bean1
        Bean1 bean1=context.getBean("bean2",Bean1.class);
        System.out.println("bean1 = " + bean1);


    }
}

结果

bean1 = com.spring.ioc.Bean1@2145433b

五、注解

1.@Controller：被标注在Controller层
2.@Service：被标注在Service层
3.@Repository：被标注在Dao层
4.@component：通用型注解

六、Bean添加别名

1.修改配置文件
只能用比较复杂的注入方式

package com.spring.ioc;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Bean;
/**
 * Created by Administrator on 2019/10/26.
 */
@Configuration
//@ComponentScan(value = "com.spring.ioc")
public class MyConfiguration {

    @Bean(value = {"bean2","bean3"})
    public Bean1 bean1(){
        return new Bean1();
    }
}

2.Bean1类

package com.spring.ioc;

import org.springframework.stereotype.Component;

/**
 * Created by Administrator on 2019/10/26.
 */
//@Component(value = "bean2")
public class Bean1 {
}

4.测试代码

package com.spring.ioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Created by Administrator on 2019/10/26.
 */
public class testCode {
    @Test
    public void test(){
        ApplicationContext context=new AnnotationConfigApplicationContext(MyConfiguration.class);
        //bean1
        Bean1 bean1=context.getBean("bean2",Bean1.class);
        System.out.println("bean1 = " + bean1);

        //bean3
        Bean1 bean3=context.getBean("bean3",Bean1.class);
        System.out.println("bean3 = " + bean3);
    }
}

测试代码

bean1 = com.spring.ioc.Bean1@36f0f1be
bean3 = com.spring.ioc.Bean1@36f0f1be