Spring boot query by example with nested object

Question

I have 2 entities: field and crop. Field looks like this:

public class Field {
  private Integer id;
  private String name;

  @ManyToOne
  @JoinColumn(name = "crop")
  private Crop crop;
}

public class Crop {
  private Integer id;
  private String name;
}

I want to query by example the exact field I get in a request.

public class FieldRequest {
  String name;
  Integer cropId;
}

My service looks like this:

public Optional<Field> getField(FieldRequest request) {
  Field fieldExample = Field.builder()
  .name(request.name)
  .crop(Crop.builder()
    .id(request.cropId)
    .build())
  .build();

  fieldRepository.findOne(Example.of(fieldExample, ExampleMatcher.matching()
        .withIncludeNullValues()
        .withIgnorePaths("id")
        .withMatcher("crop.id", ExampleMatcher.GenericPropertyMatcher::exact
        );
}

my problem is that the query that being created ignores the crop and returns the wrong field. How can I make the query to search by the crop id (I don't care about the crop name), I tried with and without the "Crop.id" matcher.

Answer 1

The .withIncludeNullValues() method allows you to include null values in your example query.

Therefore the crop.name field is also added to the query.

You can follow 2 ways: you can ignore the field with .withIgnorePaths("crop.name") or don't use .withIncludeNullValues() at all.

Example 1:

fieldRepository.findOne(
        Example.of(
                fieldExample,
                ExampleMatcher
                        .matching()
                        .withIncludeNullValues()
                        .withIgnorePaths("id")
                        .withIgnorePaths("crop.name")
                        .withMatcher("crop.id", 
                                ExampleMatcher.GenericPropertyMatcher::exact)
        )
);

Example 2:

fieldRepository.findOne(
        Example.of(
                fieldExample,
                ExampleMatcher
                        .matching()
                        .withIgnorePaths("id")
                        .withMatcher("crop.id", 
                                ExampleMatcher.GenericPropertyMatcher::exact)
        )
);