Spring 框架中的属性注入

Question

我在使用 Spring MVC 向 bean 注入值时遇到问题。

这是我对 Spring 的部分配置：

<beans>
    <!-- Enable Annotation based configuration -->
    <context:annotation-config />

    <!-- MailGun.org Authentication -->
    <bean class="com.example.something.util.MailSender">
        <property name="smtpHost" value="smtp.mailgun.org" />
        <property name="smtpUsername" value="USERNAME_HERE" />
        <property name="smtpPassWord" value="PASSWORD_HERE" />
    </bean>
</beans>

这是要注入的 bean：

package com.example.something.util;

@Component
public class MailSender {
    public void sendMail(String recipient, String subject, String text) {
        System.out.println(smtpHost);
    }

    @Autowired
    private String smtpHost;
}

为了对此进行测试，我创建了一个测试类：

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:test-spring-context.xml"})
public class MailSenderTest {
    @Test
    public void testSendMail() {
        MailSender sender = new MailSender();
        sender.sendMail("zjhzxhz@gmail.com", "Mail From MailGun", "This is a test mail");
    }
}

当我运行这个测试用例时，出现异常：

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.lang.String com.example.something.util.MailSender.smtpHost; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [java.lang.String] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:561)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 41 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [java.lang.String] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1308)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1054)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:949)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:533)
    ... 43 more

有什么问题吗？请帮我。谢谢！

Answer 1

您不需要 smtpHost 上的 @Autowired，如果您从 Spring 上下文中获取 MailSender bean，它应该已经被填充。你没有，因为用 new MailSender() 实例化它完全绕过 Spring 。相反，您应该使用 context.getBean(MailSender.class).

Spring 框架中的属性注入

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inject