@PropertySource 支持 yml 文件

前言

项目开发中经常需要加载外部资源文件，@PropertySource给我们提供了极大的便利。但是@PropertySource目前不支持 yml 文件的解析，由于 yml 结构清晰等优点，使用频率也会越来越高。

源码解读

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repeatable(PropertySources.class)
public @interface PropertySource {

    /**
     * Indicate the name of this property source. If omitted, a name will
     * be generated based on the description of the underlying resource.
     * @see org.springframework.core.env.PropertySource#getName()
     * @see org.springframework.core.io.Resource#getDescription()
     */
    String name() default "";

    /**
     * Indicate the resource location(s) of the properties file to be loaded.
     * 
Both traditional and XML-based properties file formats are supported
     * — for example, {@code "classpath:/com/myco/app.properties"}
     * or {@code "file:/path/to/file.xml"}.
     * 
Resource location wildcards (e.g. **/*.properties) are not permitted;
     * each location must evaluate to exactly one {@code .properties} resource.
     * 
${...} placeholders will be resolved against any/all property sources already
     * registered with the {@code Environment}. See {@linkplain PropertySource above}
     * for examples.
     * 
Each location will be added to the enclosing {@code Environment} as its own
     * property source, and in the order declared.
     */
    String[] value();

    /**
     * Indicate if failure to find the a {@link #value() property resource} should be
     * ignored.
     * 
{@code true} is appropriate if the properties file is completely optional.
     * Default is {@code false}.
     * @since 4.0
     */
    boolean ignoreResourceNotFound() default false;

    /**
     * A specific character encoding for the given resources, e.g. "UTF-8".
     * @since 4.3
     */
    String encoding() default "";

    /**
     * Specify a custom {@link PropertySourceFactory}, if any.
     * 
By default, a default factory for standard resource files will be used.
     * @since 4.3
     * @see org.springframework.core.io.support.DefaultPropertySourceFactory
     * @see org.springframework.core.io.support.ResourcePropertySource
     */
    Class factory() default PropertySourceFactory.class;
}

注意 factory 这个属性，作为解析资源文件的工厂类，默认实现是 DefaultPropertySourceFactory：

public class DefaultPropertySourceFactory implements PropertySourceFactory {

    @Override
    public PropertySource createPropertySource(@Nullable String name, EncodedResource resource) throws IOException {
        return (name != null ? new ResourcePropertySource(name, resource) : new ResourcePropertySource(resource));
    }
}

编码实现

我们只需要自定义一个工厂类 ResourceFactory，继承这个 default 工厂，重写 createPropertySource即可：

public class ResourceFactory extends DefaultPropertySourceFactory {

    @Override
    public PropertySource createPropertySource(String name, EncodedResource resource) throws IOException {
        String sourceName = (name == null) ? resource.getResource().getFilename() : name;
        assert sourceName != null;
        if (sourceName.endsWith(".yml") || sourceName.endsWith(".yaml")) {
            YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
            factory.setResources(resource.getResource());
            factory.afterPropertiesSet();
            Properties properties = factory.getObject();
            assert properties != null;
            return new PropertiesPropertySource(sourceName, properties);
        }
        return super.createPropertySource(name, resource);
    }
}

新建测试文件 sso.yml：

sso:
  url: "http://www.baidu.com"
  name: sso-service

结合 @ConfigurationProperties实现 sso 配置类注入：

@Data
@Component
@ConfigurationProperties("sso")
@PropertySource(value = "classpath:sso.yml", factory = ResourceFactory.class)
public class Sso {

    private String url;
    private String name;

    @PostConstruct
    public void test(){
        System.out.println(this);
    }
}

test 方法作为测试输出当前信息：

Sso(url=http://www.baidu.com, name=sso-service)