composite-build-usage-example

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package by.andd3dfx.templateapp.validators;
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import by.andd3dfx.templateapp.dto.ArticleUpdateDto;
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import javax.validation.ConstraintValidator;
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import javax.validation.ConstraintValidatorContext;
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import java.lang.reflect.Field;
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public class OnlyOneFieldModifiedValidator implements ConstraintValidator<OnlyOneFieldModified, ArticleUpdateDto> {
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    @Override
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    public boolean isValid(ArticleUpdateDto articleUpdateDto, ConstraintValidatorContext context) {
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        int count = 0;
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        ArticleUpdateDto.class.getDeclaredFields();
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        for (Field field : ArticleUpdateDto.class.getDeclaredFields()) {
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            try {
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                final boolean isAccessible = field.canAccess(articleUpdateDto);
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                field.setAccessible(true);
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                final Object o = field.get(articleUpdateDto);
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                if (o != null) {
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                    count++;
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                }
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                field.setAccessible(isAccessible);
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            } catch (IllegalAccessException e) {
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                e.printStackTrace();
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            }
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        }
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        return count == 1;
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    }
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}
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