1. Overview

1.概述

In this quick tutorial, we’ll show how to read a YAML properties file using the @PropertySource annotation in Spring Boot.

在这个快速教程中，我们将展示如何使用Spring Boot中的@PropertySource注释来读取YAML属性文件。

2. @PropertySource and YAML Format

2.@PropertySource和YAML格式

Spring Boot has great support for externalized configuration. Also, it’s possible to use different ways and formats to read the properties in the Spring Boot application out-of-the-box.

Spring Boot对外部化配置有很大支持。此外，还可以使用不同的方式和格式来读取Spring Boot应用程序中开箱即用的属性。

However, by default, @PropertySource doesn’t load YAML files. This fact is explicitly mentioned in the official documentation.

然而，默认情况下，@PropertySource不会加载YAML文件。这一事实在官方文档中被明确提及。。

So, if we want to use the @PropertySource annotation in our application, we need to stick with the standard properties files. Or we can implement the missing puzzle piece ourselves!

因此，如果我们想在我们的应用程序中使用@PropertySource注释，我们需要坚持使用标准properties文件。或者我们可以自己实现缺少的那块拼图！。

3. Custom PropertySourceFactory

3.自定义PropertySourceFactory

As of Spring 4.3, @PropertySource comes with the factory attribute. We can make use of it to provide our custom implementation of the PropertySourceFactory, which will handle the YAML file processing.

从Spring 4.3开始，@PropertySource自带factory属性。我们可以利用它来提供我们对PropertySourceFactory的自定义实现，它将处理YAML文件的处理。

This is easier than it sounds! Let’s see how to do this:

这比听起来要容易得多!让我们看看如何做到这一点：

public class YamlPropertySourceFactory implements PropertySourceFactory {

    @Override
    public PropertySource<?> createPropertySource(String name, EncodedResource encodedResource) 
      throws IOException {
        YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
        factory.setResources(encodedResource.getResource());

        Properties properties = factory.getObject();

        return new PropertiesPropertySource(encodedResource.getResource().getFilename(), properties);
    }
}

As we can see, it’s enough to implement a single createPropertySource method.

正如我们所看到的，实现一个单一的createPropertySource方法即可。

In our custom implementation, first, we used the YamlPropertiesFactoryBean to convert the resources in YAML format to the java.util.Properties object.

在我们的自定义实现中，首先，我们使用了YamlPropertiesFactoryBean 将YAML格式的资源转换成java.util.Properties对象。

Then, we simply returned a new instance of the PropertiesPropertySource, which is a wrapper that allows Spring to read the parsed properties.

然后，我们简单地返回了一个新的PropertiesPropertySource的实例，它是一个包装器，允许Spring读取解析的属性。。

4. @PropertySource and YAML in Action

4.@PropertySource和YAML的作用

Let’s now put all the pieces together and see how to use them in practice.

现在让我们把所有的碎片放在一起，看看如何在实践中使用它们。

First, let’s create a simple YAML file – foo.yml:

首先，让我们创建一个简单的YAML文件 – foo.yml。

yaml:
  name: foo
  aliases:
    - abc
    - xyz

Next, let’s create a properties class with @ConfigurationProperties and use our custom YamlPropertySourceFactory:

接下来，让我们用@ConfigurationProperties创建一个属性类，并使用我们自定义的YamlPropertySourceFactory：。

@Configuration
@ConfigurationProperties(prefix = "yaml")
@PropertySource(value = "classpath:foo.yml", factory = YamlPropertySourceFactory.class)
public class YamlFooProperties {

    private String name;

    private List<String> aliases;

    // standard getter and setters
}

And finally, let’s verify that the properties are properly injected:

最后，让我们验证一下属性是否被正确注入。

@RunWith(SpringRunner.class)
@SpringBootTest
public class YamlFooPropertiesIntegrationTest {

    @Autowired
    private YamlFooProperties yamlFooProperties;

    @Test
    public void whenFactoryProvidedThenYamlPropertiesInjected() {
        assertThat(yamlFooProperties.getName()).isEqualTo("foo");
        assertThat(yamlFooProperties.getAliases()).containsExactly("abc", "xyz");
    }
}

5. Conclusion

5.总结

To sum up, in this quick tutorial, we first showed how easy it is to create a custom PropertySourceFactory. After that, we presented how to pass this custom implementation to the @PropertySource using its factory attribute.

总之，在这个快速教程中，我们首先展示了创建一个自定义的PropertySourceFactory是多么简单。之后，我们介绍了如何使用其@PropertySource属性将这个自定义实现传递给。

Consequently, we were able to successfully load the YAML properties file into our Spring Boot application.

因此，我们能够成功地将YAML属性文件加载到我们的Spring Boot应用程序中。

As usual, all the code examples are available over on GitHub.

像往常一样，所有的代码实例都可以在GitHub上找到。