如何将spring bean集成从XML转换为基于Java注释的Config

Question

I have this xml based configuration. But in my project I want to use java annotation based configuration. How to do the conversion?

 <?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

Create a class annotated with @Configuration ( org.springframework.context.annotation.Configuration ) and for each bean declaration in your XML file create a @Bean ( org.springframework.context.annotation.Bean ) method within this class.

@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;
    }
}

This example assumes that the mailSender and velocityEngine beans are required elsewhere in your application config since this is implied by the XML config you supplied. If this is not the case ie if the mailSender and velocityEngine beans are only required to construct the registrationService bean then you do not need to declare the mailSender() and velocityEngine() methods as public nor do you need to annotate then with @Bean .

You can instruct Spring to read this configuration class by

• Component scanning eg @ComponentScan("your.package.name")

• Registering the class with an AnnotationConfigApplicationContext eg

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

Answer 2

Answer of @glitch was helpful but I got an error at below line.

velocityEngine.setVelocityProperties("resource.loader=class", "class.resource.loader.class=org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");

How ever I fixed that. Find below is the full implementation

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.mail.javamail.JavaMailSenderImpl;
import com.vlclabs.adsops.service.SendEmailServiceImpl;
import org.springframework.ui.velocity.VelocityEngineFactoryBean;

import java.util.Properties;

@Configuration
public class EmailConfiguration {

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

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