Spring 了解 YAML 中的属性

Question

Spring 是否放弃 YAML 作为 .properties / .xml 的替代品，因为：

[Spring Developer]：...YAML 已被考虑，但我们认为对空白进行显着计数是一场正在形成的支持噩梦... [参考来自 Spring 论坛]

我相信 YAML 对于属性来说很有意义，我目前正在项目中使用它，但很难以

<property name="productName" value="${client.product.name}" />

时尚的方式注入属性。

我缺少什么，或者我应该创建一个自定义 YamlPropertyPlaceholderConfigurer ？

Answer 1

您引用的论坛帖子来自 dmServer 论坛，而不是 Spring Framework，两者之间几乎没有关系，所以我不会阅读其中的任何内容。

最重要的是，YAML 在 Java 世界中几乎是闻所未闻的，因此添加对它的支持充其量只是一个象征性的姿态（如果你能原谅这个表达的话）。 XML 在 Java 中占据主导地位，尤其是服务器端，因此在 Java 中逆流而上几乎没有什么用处，尤其是对于像 YAML 这样的少数格式。

话虽如此，假设您可以找到适用于 Java 的 YAML 解析器，那么编写您自己的 YamlPropertyPlaceholderConfigurer 应该很容易。

Answer 2

我不知道这是否有点太晚了，但不是 - 您不必实现整个 YamlPropertyPlaceholderConfigurer 相反，您可以简单地创建自定义 PropertiesPersister 并将其添加为可选参数。

这是您的配置的外观

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
        <value>file:///C:/somewhere/site.yaml</value>
    </property>
    <property name="propertiesPersister" ref="persister"></property>
</bean>
<bean id="persister" class="com.foo.utils.YamlPropertiesPersister"></bean>

这是使用 SnakeYaml 的裸机（只读）实现，请随意添加您需要的内容，包括错误处理

public class YamlPropertiesPersister implements PropertiesPersister {
@Override
public void load(Properties props, InputStream is) throws IOException {
    load(props, new InputStreamReader(is));
}

/**
 * We want to traverse map representing Yaml object and each time we find String=String pair we want to
 * save it as Property. As we are going deeper into map we generate compound key as path-like String
 * 
 * @param props
 * @param reader
 * @throws IOException
 * @see org.springframework.util.PropertiesPersister#load(java.util.Properties, java.io.Reader)
 */
@Override
public void load(Properties props, Reader reader) throws IOException {
    Yaml yaml = CollectorUtils.instanceOfYaml();
    Map<String, Object> map = (Map<String, Object>) yaml.load(reader);
    // now we can populate supplied props
    assignProperties(props, map, null);
}

/**
 * @param props
 * @param map
 */
public void assignProperties(Properties props, Map<String, Object> map, String path) {
    for (Entry<String, Object> entry : map.entrySet()) {
        String key = entry.getKey();
        if (StringUtils.isNotEmpty(path))
            key = path + "." + key;
        Object val = entry.getValue();
        if (val instanceof String) {
            // see if we need to create a compound key
            props.put(key, val);
        } else if (val instanceof Map) {
            assignProperties(props, (Map<String, Object>) val, key);
        }
    }
}

@Override
public void store(Properties props, OutputStream os, String header) throws IOException {
    throw new NotImplementedException("Current implementation is a read-only");
}

@Override
public void store(Properties props, Writer writer, String header) throws IOException {
    throw new NotImplementedException("Current implementation is a read-only");
}

@Override
public void loadFromXml(Properties props, InputStream is) throws IOException {
    throw new NotImplementedException("Use DefaultPropertiesPersister if you want to read/write XML");
}

@Override
public void storeToXml(Properties props, OutputStream os, String header) throws IOException {
    throw new NotImplementedException("Use DefaultPropertiesPersister if you want to load/store to XML");
}

@Override
public void storeToXml(Properties props, OutputStream os, String header, String encoding) throws IOException {
    throw new NotImplementedException("Use DefaultPropertiesPersister if you want to read/write XML");
}
}

作为额外的好处 - 这是我创建 Yaml 实例的方式

    public static Yaml instanceOfYaml() {
    DumperOptions options = new DumperOptions();
    options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK);
    options.setDefaultScalarStyle(ScalarStyle.DOUBLE_QUOTED);
    final Yaml yaml = new Yaml(new Loader(), new Dumper(options), new Resolver() {
        /**
         * @see org.yaml.snakeyaml.resolver.Resolver#addImplicitResolvers()
         */
        @Override
        protected void addImplicitResolvers() {
            addImplicitResolver(Tag.BOOL, BOOL, "yYnNtTfFoO");
            // disable resolving of floats and integers
            // addImplicitResolver(Tags.FLOAT, FLOAT, "-+0123456789.");
            // addImplicitResolver(Tag.INT, INT, "-+0123456789");
            addImplicitResolver(Tag.MERGE, MERGE, "<");
            addImplicitResolver(Tag.NULL, NULL, "~nN\0");
            addImplicitResolver(Tag.NULL, EMPTY, null);
            addImplicitResolver(Tag.TIMESTAMP, TIMESTAMP, "0123456789");
            addImplicitResolver(Tag.VALUE, VALUE, "=");
        }
    });
    return yaml;
}

您也可以在 我的博客

Answer 3

对于使用 Spring 3.1 的用户，您可以注册 Yaml PropetySource。 SnakeYaml代码来自Bostone代码（感谢），适应了Spring 3.1的新PropertySource系统。

import com.google.common.base.Preconditions;
import org.springframework.core.env.PropertiesPropertySource;
import org.springframework.core.io.Resource;
import org.springframework.util.StringUtils;
import org.yaml.snakeyaml.Dumper;
import org.yaml.snakeyaml.DumperOptions;
import org.yaml.snakeyaml.DumperOptions.ScalarStyle;
import org.yaml.snakeyaml.Loader;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.nodes.Tag;
import org.yaml.snakeyaml.resolver.Resolver;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

/**
 * @author Sebastien Lorber <i>([email protected])</i>
 */
public class YamlPropertiesSource extends PropertiesPropertySource {


  public YamlPropertiesSource(String name, Resource yamlResource) {
    super(name, getPropertySource(yamlResource) );
  }

  private static Properties getPropertySource(Resource yamlResource) {
    Preconditions.checkArgument(yamlResource != null,"no yaml resource provided");
    try {
      InputStream is = yamlResource.getInputStream();
      Properties properties = new Properties();
      load(properties, is);
      return properties;
    } catch ( Exception e ) {
      throw new IllegalStateException("Can't get PropertySource from YAML resource=" + yamlResource,e);
    }
  }

  private static void load(Properties props, InputStream is) throws IOException {
    load(props, new InputStreamReader(is));
  }

  private static void load(Properties props, Reader reader) throws IOException {
    Yaml yaml = instanceOfYaml();
    @SuppressWarnings("unchecked")
    Map<String, Object> map = (Map<String, Object>) yaml.load(reader);
    // now we can populate supplied props
    assignProperties(props, map, null);
  }

  private static void assignProperties(Properties props, Map<String, Object> map, String path) {
    for (Entry<String, Object> entry : map.entrySet()) {
      String key = entry.getKey();
      if ( StringUtils.hasLength(path) )
        key = path + "." + key;
      Object val = entry.getValue();
      if (val instanceof String) {
        // see if we need to create a compound key
        props.put(key, val);
      } else if (val instanceof Map) {
        assignProperties(props, (Map<String, Object>) val, key);
      }
    }
  }

  public static Yaml instanceOfYaml() {
    DumperOptions options = new DumperOptions();
    options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK);
    options.setDefaultScalarStyle(ScalarStyle.DOUBLE_QUOTED);
    final Yaml yaml = new Yaml(new Loader(), new Dumper(options), new Resolver() {
      /**
       * @see org.yaml.snakeyaml.resolver.Resolver#addImplicitResolvers()
       */
      @Override
      protected void addImplicitResolvers() {
        addImplicitResolver(Tag.BOOL, BOOL, "yYnNtTfFoO");
        // disable resolving of floats and integers
        // addImplicitResolver(Tags.FLOAT, FLOAT, "-+0123456789.");
        // addImplicitResolver(Tag.INT, INT, "-+0123456789");
        addImplicitResolver(Tag.MERGE, MERGE, "<");
        addImplicitResolver(Tag.NULL, NULL, "~nN\0");
        addImplicitResolver(Tag.NULL, EMPTY, null);
        addImplicitResolver(Tag.TIMESTAMP, TIMESTAMP, "0123456789");
        addImplicitResolver(Tag.VALUE, VALUE, "=");
      }
    });
    return yaml;
  }

}

请注意，这也是受到 ResourcePropertySource 的启发，它加载 ISO 8859-1 字符集中的属性。我为此打开了一个错误： SPR-10096

您可以将此属性源添加到您的应用程序中语境。这也可以在单元测试中完成：

public class PropertySourceContextLoader extends GenericXmlContextLoader {
    @Override
    protected void loadBeanDefinitions(GenericApplicationContext context,MergedContextConfiguration mergedConfig) {
        PropertySource<String> ps = new MyPropertySource();
        context.getEnvironment().getPropertySources().addLast(ps);
        super.loadBeanDefinitions(context, mergedConfig);
    }
}

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(loader = PropertySourceContextLoader.class, locations = { "classpath:/spring-application-context.xml" })
public class SpringBasedTest {
         ..........
}

Answer 4

对于像我这样完全彻底的傻瓜，他们对作者实际上在做什么的了解为零，但无论如何都需要这样做......这就是我如何让它发挥作用。但不知道如何弃用 instanceOfYaml() 。
另一件事是，我的 Spring Boot Eclipse 项目从标记为 .yml 的文件读取，而不是从 .yaml 读取

import org.springframework.util.PropertiesPersister;
import org.springframework.util.StringUtils;
import org.yaml.snakeyaml.Dumper;
import org.yaml.snakeyaml.DumperOptions;
import org.yaml.snakeyaml.DumperOptions.ScalarStyle;
import org.yaml.snakeyaml.Loader;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.nodes.Tag;
import org.yaml.snakeyaml.resolver.Resolver;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

public class YamlPropertiesPersister implements PropertiesPersister {
    @Override
    public void load(Properties props, InputStream is) throws IOException {
        load(props, new InputStreamReader(is));
    }

    /**
     * We want to traverse map representing Yaml object and each time we will find String:String value pair we want to
     * save it as Property. As we are going deeper into map we generate a compound key as path-like String
     *
     * @param props
     * @param reader
     * @throws IOException
     * @see org.springframework.util.PropertiesPersister#load(java.util.Properties, java.io.Reader)
     */
    @Override
    public void load(Properties props, Reader reader) throws IOException {
        Yaml yaml = instanceOfYaml();
        Map<String, Object> map = (Map<String, Object>) yaml.load(reader);
        // now we can populate supplied props
        assignProperties(props, map, null);
    }

    /**
     * @param props
     * @param map
     */
    public void assignProperties(Properties props, Map<String, Object> map, String path) {
        for (Entry<String, Object> entry : map.entrySet()) {
            String key = entry.getKey();
            if (!StringUtils.isEmpty(path))
                key = path + "." + key;
            Object val = entry.getValue();
            if (val instanceof String) {
                // see if we need to create a compound key
                props.put(key, val);
            } else if (val instanceof Map) {
                assignProperties(props, (Map<String, Object>) val, key);
            }
        }
    }

    @Override
    public void store(Properties props, OutputStream os, String header) throws IOException {
        throw new UnsupportedOperationException("Current implementation is a read-only");
    }

    @Override
    public void store(Properties props, Writer writer, String header) throws IOException {
        throw new UnsupportedOperationException("Current implementation is a read-only");
    }

    @Override
    public void loadFromXml(Properties props, InputStream is) throws IOException {
        throw new UnsupportedOperationException("Use DefaultPropertiesPersister if you want to read/write XML");
    }

    @Override
    public void storeToXml(Properties props, OutputStream os, String header) throws IOException {
        throw new UnsupportedOperationException("Use DefaultPropertiesPersister if you want to load/store to XML");
    }

    @Override
    public void storeToXml(Properties props, OutputStream os, String header, String encoding) throws IOException {
        throw new UnsupportedOperationException("Use DefaultPropertiesPersister if you want to read/write XML");
    }


    public static Yaml instanceOfYaml() {
        DumperOptions options = new DumperOptions();
        options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK);
        options.setDefaultScalarStyle(ScalarStyle.DOUBLE_QUOTED);
        final Yaml yaml = new Yaml(new Loader(), new Dumper(options), new Resolver() {
            /**
             * @see org.yaml.snakeyaml.resolver.Resolver#addImplicitResolvers()
             */
            @Override
            protected void addImplicitResolvers() {
                addImplicitResolver(Tag.BOOL, BOOL, "yYnNtTfFoO");
                // disable resolving of floats and integers
                // addImplicitResolver(Tags.FLOAT, FLOAT, "-+0123456789.");
                // addImplicitResolver(Tag.INT, INT, "-+0123456789");
                addImplicitResolver(Tag.MERGE, MERGE, "<");
                addImplicitResolver(Tag.NULL, NULL, "~nN\0");
                addImplicitResolver(Tag.NULL, EMPTY, null);
                addImplicitResolver(Tag.TIMESTAMP, TIMESTAMP, "0123456789");
                addImplicitResolver(Tag.VALUE, VALUE, "=");
            }
        });
        return yaml;
    }
}