YAMLMapper MismatchedInputException YAML key with periods

Question

Error: com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input

Yaml file:

formatting.template:
  fields:
    - name: birthdate
      type: java.lang.String
      subType: java.util.Date
      lenght: 10

ConfigurationProperties:

@Data
public class FormattingConfigurationProperties {

    private List<Field> fields;

    @Data
    public static class Field {
        private String name;
        private String type;
        private String subType;
        private String lenght;
    }

}

Method to read yaml

private static FormattingConfigurationProperties buildFormattingConfigurationProperties() throws IOException {

    InputStream inputStream = new FileInputStream(new File("./src/test/resources/" + "application_formatting.yaml"));
    
    YAMLMapper mapper = new YAMLMapper();
    mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
    mapper.enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);

    return mapper.readerFor(FormattingConfigurationProperties.class)
                 .at(/formatting/template)
                 .readValue(inputStream);

}

I actually solved it by changing the Yaml file, splitting formatting.template on separate lines:

formatting:
  template:
    fields:
      - name: birthdate
        type: java.lang.String
        subType: java.util.Date
        lenght: 10

This means that is not able to read key with dot (periods (.)). Someone know how to avoid MismatchedInputException, when the prefix is on the same line separated by dot?

Answer 1

You're using the JSON Pointer /formatting/template. This is for nested mappings, as shown in your second YAML file. If you have a condensed key formatting.template, you'll need the JSON Pointer /formatting.template instead.

YAML is perfectly able to read keys with a dot, it just does not do what you think it does. The dot is not a special character in YAML, just part of the content.

You may have worked with Spring which loads YAML files by rewriting them as Properties files, where . is a separator. Since the existing dots are not escaped, for YAML files used with Spring, a dot is the same as nested keys. However when you directly use a YAML loader, such as Jackson, that is not the case.