Getters needed for ignored properties

[maroony]

I'm wondering that I have to write getters for ignored properties. Here's an working example:

import java.io.IOException;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.databind.MappingIterator;
import com.fasterxml.jackson.dataformat.csv.CsvMapper;
import com.fasterxml.jackson.dataformat.csv.CsvSchema;
import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;

@JsonPropertyOrder({
    "text",
    "ignored",
    "number"
})
@JsonIgnoreProperties(ignoreUnknown = true)
public class Example {

  private String text;
  private Integer number;

  @JsonCreator()
  public Example(String text, Integer number) {
    this.text = text;
    this.number = number;
  }

  public String getText() {
    return text;
  }

  public Integer getNumber() {
    return number;
  }

  // jackson needed getter
  public Object getIgnored() {
    return null;
  }

  public static void main(String[] args) throws IOException {

    CsvMapper csvMapper = new CsvMapper();
    csvMapper.registerModule(new ParameterNamesModule());
    CsvSchema csvSchema = csvMapper.schemaFor(Example.class);

    String value = "foo, ignoredValue, 123";

    MappingIterator<Example> iterator = csvMapper.readerFor(Example.class)
        .with(csvSchema)
        .readValues(value);

    var nextValue = iterator.next();

    System.out.println(nextValue.getText() + ", " + nextValue.getNumber());

  }
}

If you delete the getter getIgnored(), the following exception will be thrown:

Exception in thread "main" com.fasterxml.jackson.databind.RuntimeJsonMappingException: Cannot deserialize value of type `java.lang.Integer` from String "ignoredValue": not a valid `java.lang.Integer` value
 at [Source: (StringReader); line: 1, column: 5] (through reference chain: Example["number"])
        at com.fasterxml.jackson.databind.MappingIterator._handleMappingException(MappingIterator.java:416)
        at com.fasterxml.jackson.databind.MappingIterator.next(MappingIterator.java:201)
        at Example.main(Example.java:55)
Caused by: com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `java.lang.Integer` from String "ignoredValue": not a valid `java.lang.Integer` value
 at [Source: (StringReader); line: 1, column: 5] (through reference chain: Example["number"])
        at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67)
        at com.fasterxml.jackson.databind.DeserializationContext.weirdStringException(DeserializationContext.java:1958)
        at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdStringValue(DeserializationContext.java:1245)
        at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseInteger(StdDeserializer.java:848)
        at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseInteger(StdDeserializer.java:827)
        at com.fasterxml.jackson.databind.deser.std.NumberDeserializers$IntegerDeserializer.deserialize(NumberDeserializers.java:531)
        at com.fasterxml.jackson.databind.deser.std.NumberDeserializers$IntegerDeserializer.deserialize(NumberDeserializers.java:506)
        at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:545)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeWithErrorWrapping(BeanDeserializer.java:570)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeUsingPropertyBased(BeanDeserializer.java:440)
        at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1493)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:348)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:185)
        at com.fasterxml.jackson.databind.MappingIterator.nextValue(MappingIterator.java:283)
        at com.fasterxml.jackson.databind.MappingIterator.next(MappingIterator.java:199)
        ... 1 more

Is this expected behavior? Is there something I can do to omit writing these getters?

What's also interesting: You got a different exception when the ignored column is the last:

import java.io.IOException;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.databind.MappingIterator;
import com.fasterxml.jackson.dataformat.csv.CsvMapper;
import com.fasterxml.jackson.dataformat.csv.CsvSchema;
import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;

@JsonPropertyOrder({
    "text",
    "number",
    "ignored"
})
@JsonIgnoreProperties(ignoreUnknown = true)
public class Example2 {

  private String text;
  private Integer number;

  @JsonCreator()
  public Example2(String text, Integer number) {
    this.text = text;
    this.number = number;
  }

  public String getText() {
    return text;
  }

  public Integer getNumber() {
    return number;
  }

  // jackson needed getter
  public Object getIgnored() {
    return null;
  }

  public static void main(String[] args) throws IOException {

    CsvMapper csvMapper = new CsvMapper();
    csvMapper.registerModule(new ParameterNamesModule());
    CsvSchema csvSchema = csvMapper.schemaFor(Example2.class);

    String value = "foo, 123, ignoredValue";

    MappingIterator<Example2> iterator = csvMapper.readerFor(Example2.class)
        .with(csvSchema)
        .readValues(value);

    var nextValue = iterator.next();

    System.out.println(nextValue.getText() + ", " + nextValue.getNumber());
  }
}

If you now delete the getter getIgnored(), the following exception will be thrown:

Exception in thread "main" com.fasterxml.jackson.databind.RuntimeJsonMappingException: Too many entries: expected at most 2 (value #2 (12 chars) "ignoredValue")
 at [Source: (StringReader); line: 1, column: 9]
        at com.fasterxml.jackson.databind.MappingIterator._handleMappingException(MappingIterator.java:416)
        at com.fasterxml.jackson.databind.MappingIterator.next(MappingIterator.java:201)
        at Example2.main(Example2.java:56)
Caused by: com.fasterxml.jackson.dataformat.csv.CsvReadException: Too many entries: expected at most 2 (value #2 (12 chars) "ignoredValue")
 at [Source: (StringReader); line: 1, column: 9]
        at com.fasterxml.jackson.dataformat.csv.CsvReadException.from(CsvReadException.java:25)
        at com.fasterxml.jackson.dataformat.csv.CsvParser._reportCsvMappingError(CsvParser.java:1421)
        at com.fasterxml.jackson.dataformat.csv.CsvParser._handleExtraColumn(CsvParser.java:1163)
        at com.fasterxml.jackson.dataformat.csv.CsvParser._handleNextEntry(CsvParser.java:1030)
        at com.fasterxml.jackson.dataformat.csv.CsvParser.nextToken(CsvParser.java:758)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeUsingPropertyBased(BeanDeserializer.java:442)
        at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1493)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:348)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:185)
        at com.fasterxml.jackson.databind.MappingIterator.nextValue(MappingIterator.java:283)
        at com.fasterxml.jackson.databind.MappingIterator.next(MappingIterator.java:199)
        ... 1 more

Jackson-Version: 2.17.1

[JooHyukKim]

1. There is separate repo for csv format repository and ParamNameModules repo.
2. Ignore unknown option literally means it ignores any undeclared property. Getter may or may not be related?

[maroony]

I really don't know, if this is specific to CSV. So I opened the issue here. Feel free to move it to a better place.

[maroony]

I'm using version 2.17.0 for all jackson dependencies.

[maroony]

Just updated to version 2.17.1: same behavior.

[JooHyukKim]

Did it ever work? like in other version?
Most probably it's csv format related, so not jackson-databind issue.

You may try asking over at Stackoverflow (or similar) first or inquire over at jackson-dataformats-text repo.
But mind that usage inquiry should be asked vis Github Discussions, not Issue

[maroony]

I didn't see this working before. I started a discussion in jackson-dataformats-text.

[yihtserns]

Seems related to FasterXML/jackson-dataformat-csv#82. Has there been any new enhancement to better support such use case since then?

(Credit: https://stackoverflow.com/a/56067713)

[cowtowncoder]

It definitely looks like CSV specific; I will transfer.

Ok so... in general with ignoreUnknown = true it should not be necessary to have getter or setter for ignored property.

However. For generating CsvSchema there has to be something indicating what is in position, and this might be the source of problem. If you built CsvSchema manually, or it was created from header line, things might work better.
But if using CsvMapper.schemaFor() I think matching property is indeed needed.

[maroony]

Thanks for pointing this out. Header lines are usually not usable in my case, because the CSV files are delivered from external sources. Manually building the CsvSchema feels like a lot of extra work for files with hundreds of columns. Looking forward to an improvement:-)

[JooHyukKim]

Looking forward to an improvement:-)

Contributions are welcome also! 😆

[cowtowncoder]

Also: ideas of how this could work: as things are, I am not sure how this could be made to work.

But I have to say I am also surprised by the exception as that would suggest decoder did actually know about the property mapping from column.

Test needs some tweaks to be used here (need to get rid of parameter module), but that should be doable. So the first thing we could do is add a failing test based on code included here. And yes, PRs are welcome (even just for failing test)!

[maroony]

I added a second example to my issue description where I put the ignoredValue to the last column. Now there is a different exception. Maybe this is also interesting for you.