org.kiwiproject.yaml.YamlHelper Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of kiwi Show documentation
Kiwi is a utility library. We really like Google's Guava, and also use Apache Commons. But if they don't have something we need, and we think it is useful, this is where we put it.
There is a newer version: 4.4.0
Show newest version
package org.kiwiproject.yaml;

import static com.google.common.base.Preconditions.checkArgument;
import static java.util.Objects.nonNull;
import static org.kiwiproject.base.KiwiPreconditions.checkArgumentNotBlank;
import static org.kiwiproject.base.KiwiPreconditions.checkArgumentNotNull;

import com.fasterxml.jackson.annotation.JsonView;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
import com.fasterxml.jackson.dataformat.yaml.YAMLGenerator;

import java.util.List;
import java.util.Map;

/**
 * Some utilities to make it easy to work with YAML.
 *
 * @implNote This uses Jackson to perform YAML operations, which in turn uses SnakeYAML, so both of those must
 * be available at runtime.
 */
public class YamlHelper {

    private static final TypeReference> MAP_TYPE_REFERENCE = new TypeReference<>() {
    };

    private final ObjectMapper objectMapper;

    /**
     * Create a new instance using an {@link ObjectMapper} created with a {@link YAMLFactory} to support YAML.
     * In addition, the {@link YAMLFactory} disables the
     * {@link YAMLGenerator.Feature#SPLIT_LINES SPLIT_LINES} feature.
     */
    public YamlHelper() {
        this(new ObjectMapper(newYAMLFactory()));
    }

    private static YAMLFactory newYAMLFactory() {
        return new YAMLFactory().disable(YAMLGenerator.Feature.SPLIT_LINES);
    }

    /**
     * Create a new instance using the given {@link ObjectMapper}, which must support the YAML
     * format. Otherwise it can be configured however you want.
     *
     * @param objectMapper the {@link ObjectMapper} to use
     * @throws IllegalArgumentException if the object mapper is null or does not support YAML
     * @see YAMLFactory#getFormatName()
     * @see YAMLFactory#FORMAT_NAME_YAML
     */
    public YamlHelper(ObjectMapper objectMapper) {
        checkArgumentNotNull(objectMapper, "objectMapper cannot be null");
        var supportedFormat = objectMapper.getFactory().getFormatName();
        checkArgument(YAMLFactory.FORMAT_NAME_YAML.equals(supportedFormat), "ObjectMapper does not support YAML");
        this.objectMapper = objectMapper;
    }

    /**
     * Convert the given object to YAML.
     *
     * @param object the object to convert
     * @return a YAML representation of the given object
     */
    public String toYaml(Object object) {
        return toYaml(object, null);
    }

    /**
     * Convert the given object to YAML using the given {@link JsonView}.
     *
     * @param object   the object to convert
     * @param yamlView the nullable {@link JsonView} class
     * @return a YAML representation of the given object
     */
    public String toYaml(Object object, Class yamlView) {
        var writer = objectMapper.writer();

        if (nonNull(yamlView)) {
            writer = writer.withView(yamlView);
        }

        try {
            return writer.writeValueAsString(object);
        } catch (JsonProcessingException e) {
            throw new RuntimeYamlException(e);
        }
    }

    /**
     * Convert the given YAML into the specified type.
     *
     * @param yaml        the YAML content
     * @param targetClass the type of obejct to convert into
     * @param          the object type
     * @return a new instance of the given type
     * @throws IllegalArgumentException if the YAML is blank or null
     */
    public  T toObject(String yaml, Class targetClass) {
        checkYamlNotBlank(yaml);
        try {
            return objectMapper.readValue(yaml, targetClass);
        } catch (JsonProcessingException e) {
            throw new RuntimeYamlException(e);
        }
    }

    /**
     * Convert the given YAML into an object of type {@code T} using the given {@link TypeReference}.
     *
     * @param yaml       the YAML content
     * @param targetType the {@link TypeReference} representing the target object type
     * @param         the object type
     * @return a new instance of the given type reference
     * @throws IllegalArgumentException if the YAML is blank or null
     */
    public  T toObject(String yaml, TypeReference targetType) {
        checkYamlNotBlank(yaml);
        try {
            return objectMapper.readValue(yaml, targetType);
        } catch (JsonProcessingException e) {
            throw new RuntimeYamlException(e);
        }
    }

    /**
     * Convert the given YAML into a List of objects of type {@code T}.
     *
     * @param yaml           the YAML content
     * @param targetListType the {@link TypeReference} representing the target object type
     * @param             the object type
     * @return a list containing objects of the given type
     * @throws IllegalArgumentException if the YAML is blank or null
     */
    public  List toObjectList(String yaml, TypeReference> targetListType) {
        checkYamlNotBlank(yaml);
        return toObject(yaml, targetListType);
    }

    /**
     * Convert the given YAML into a map with String keys and Object values.
     *
     * @param yaml the YAML content
     * @return the parsed map
     * @throws IllegalArgumentException if the YAML is blank or null
     */
    public Map toMap(String yaml) {
        return toMap(yaml, MAP_TYPE_REFERENCE);
    }

    /**
     * Convert the given YAML into a map with keys of type {@code K} and values of type {@code V}.
     *
     * @param yaml          the YAML content
     * @param targetMapType the {@link TypeReference} representing the target map type
     * @param            the type of keys in the map
     * @param            the type of values in the map
     * @return the parsed map
     * @throws IllegalArgumentException if the YAML is blank or null
     */
    public  Map toMap(String yaml, TypeReference> targetMapType) {
        checkYamlNotBlank(yaml);
        try {
            return objectMapper.readValue(yaml, targetMapType);
        } catch (JsonProcessingException e) {
            throw new RuntimeYamlException(e);
        }
    }

    public void checkYamlNotBlank(String yaml) {
        checkArgumentNotBlank(yaml, "yaml cannot be blank");
    }
}