java - 如何将 spring bean 集成从 XML 转换为基于 Java 注解的 Config

Question

我有这个基于 xml 的配置。但是在我的项目中，我想使用基于 java 注解的配置。如何转换？

 <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
        <property name="host" value="mail.csonth.gov.uk"/>
    </bean>

    <bean id="registrationService" class="com.foo.SimpleRegistrationService">
        <property name="mailSender" ref="mailSender"/>
        <property name="velocityEngine" ref="velocityEngine"/>
    </bean>

    <bean id="velocityEngine" class="org.springframework.ui.velocity.VelocityEngineFactoryBean">
        <property name="velocityProperties">
            <value>
                resource.loader=class
                class.resource.loader.class=org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader
            </value>
        </property>
    </bean>

</beans>

Answer 1

创建一个用 @Configuration (org.springframework.context.annotation.Configuration) 注释的类，并为 XML 文件中的每个 bean 声明创建一个 @此类中的 Bean (org.springframework.context.annotation.Bean) 方法。

@Configuration
public class MyConfiguration {

    @Bean
    public JavaMailSenderImpl mailSender() {
        JavaMailSenderImpl mailSender = new JavaMailSenderImpl();
        mailSender.setHost("mail.csonth.gov.uk");
        return mailSender;
    }

    @Bean
    public SimpleRegistrationService registrationService(JavaMailSenderImpl mailSender, VelocityEngineFactoryBean velocityEngine) {
        SimpleRegistrationService registrationService = new SimpleRegistrationService();
        registrationService.setMailSender(mailSender);
        registrationService.setVelocityEngine(velocityEngine); 
        return registrationService; 
    }

    @Bean
    public VelocityEngineFactoryBean velocityEngine() {
        VelocityEngineFactoryBean velocityEngine = new VelocityEngineFactoryBean();
        Properties velocityProperties = new Properties();
        velocityProperties.put("resource.loader", "class");
        velocityProperties.put("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        velocityEngine.setVelocityProperties(velocityProperties);
        return velocityEngine;
    }
}

此示例假定您的应用程序配置中的其他地方需要 mailSender 和 velocityEngine bean，因为您提供的 XML 配置暗示了这一点。如果不是这种情况，即如果 mailSender 和 velocityEngine bean 仅 需要构建 registrationService bean 那么您不需要将 mailSender() 和 velocityEngine() 方法声明为公共(public)方法，也不需要使用 @Bean 进行注释。

你可以通过以下方式指示Spring读取这个配置类

• 组件扫描，例如@ComponentScan("your.package.name")

• 使用 AnnotationConfigApplicationContext 注册类，例如

     AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
     context.register(MyConfiguration.class);
     context.refresh();