【Spring】学习笔记08-JavaConfig

JavaConfig是Spring的一个子项目,在Spring4之后,

 

POJO类

package com.wang.POJO;

import lombok.Data;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
@Data
public class User {
    @Value("王广元")
    private String name;
}

@Compomemt注解说明当前User类被Spring容器接管了,注册到了容器中

 

JavaConfig类

package com.wang.config;

import com.wang.POJO.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ImportResource;

//当前类也会被Spring容器托管,注册到容器中,因为它本身就是一个@Component
//@Configuration代表这是一个配置类,就和我们之前看的beans.xml一样
//@Configuration
//@ComponentScan("com.wang")
@ImportResource("com.wang.POJO.User")
public class wangConfig {
    //注册一个bean,就相当于我们之前写的一个bean标签
    //这个方法的名字,就相当于bean标签中的id属性
    //这个方法的返回值,就相当于bean标签中的class属性
    @Bean("user")
    //可以使用@Bean("bean_name")来指定bean id
    public User getUser(){
        return new User();
    }
}

我们查看当前@Configuration注解的源码,发现它本身也是被@Compoment注解,同样也会被Spring容器托管

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Configuration {

    /**
     * Explicitly specify the name of the Spring bean definition associated with the
     * {@code @Configuration} class. If left unspecified (the common case), a bean
     * name will be automatically generated.
     * <p>The custom name applies only if the {@code @Configuration} class is picked
     * up via component scanning or supplied directly to an
     * {@link AnnotationConfigApplicationContext}. If the {@code @Configuration} class
     * is registered as a traditional XML bean definition, the name/id of the bean
     * element will take precedence.
     * @return the explicit component name, if any (or empty String otherwise)
     * @see AnnotationBeanNameGenerator
     */
    @AliasFor(annotation = Component.class)
    String value() default "";

    /**
     * Specify whether {@code @Bean} methods should get proxied in order to enforce
     * bean lifecycle behavior, e.g. to return shared singleton bean instances even
     * in case of direct {@code @Bean} method calls in user code. This feature
     * requires method interception, implemented through a runtime-generated CGLIB
     * subclass which comes with limitations such as the configuration class and
     * its methods not being allowed to declare {@code final}.
     * <p>The default is {@code true}, allowing for 'inter-bean references' within
     * the configuration class as well as for external calls to this configuration's
     * {@code @Bean} methods, e.g. from another configuration class. If this is not
     * needed since each of this particular configuration's {@code @Bean} methods
     * is self-contained and designed as a plain factory method for container use,
     * switch this flag to {@code false} in order to avoid CGLIB subclass processing.
     * <p>Turning off bean method interception effectively processes {@code @Bean}
     * methods individually like when declared on non-{@code @Configuration} classes,
     * a.k.a. "@Bean Lite Mode" (see {@link Bean @Bean's javadoc}). It is therefore
     * behaviorally equivalent to removing the {@code @Configuration} stereotype.
     * @since 5.2
     */
    boolean proxyBeanMethods() default true;

}