BigDecimal is stored in string in spring data MongoDB

Question

@Document(collection = "loanDetails")
class LoanDetails {
    @Transient
    public static final String COLLECTION_NAME = "loanDetails
    @Id
    String id

    String loanId
    String loanUUID
    String loanStatus
    Date loanDateCreated
    Date loanLastUpdated
    BigDecimal loanAmount //Stores in String
}

I declared a class LoanDetails and a field with BigDecimal type loanAmount in it Whenever i saved some data in this collection

It get stores as a string in mongo db database
while getting the records from database i am getting the error of Failed to decode 'LoandDetails'. Decoding 'loanAmount' errored with: readDecimal can only be called when CurrentBSONType is DECIMAL128, not when CurrentBSONType is STRING.

I tried to add annotation over loanAmount field

@Field(targetType = Decimal128) // This also throws error does not contain targetType attribute attached screenshot for the same
BigDecimal loanAmount

Add a [java] tag to the question for proper syntax highlighting. — Alexey Veleshko, Dec 28 '21 at 12:15
Does this answer your question? [Spring Data MongoDB BigDecimal support](https://stackoverflow.com/questions/37950296/spring-data-mongodb-bigdecimal-support) — Valijon, Dec 28 '21 at 15:47
No @Valijon I tried @Field(targetType = Decimal128) but it did not worked — chaitanya gupta, Dec 29 '21 at 05:35

Valijon · Answer 1 · 2022-01-04T13:35:15.727

1

Probably, you need to drop / migrate your already created loanDetails, since the loanAmount field is persisted as String.

By adding @Field(targetType = FieldType.DECIMAL128) to your loanAmount field it should work.

import org.springframework.data.mongodb.core.mapping.FieldType;
...

@Field(targetType = FieldType.DECIMAL128)
BigDecimal loanAmount;
...

public LoanDetails() {
    loanAmount = new BigDecimal(21.905334472656250);
}
...
 
template.save(loan);

template.find(new Query(), org.bson.Document.class, "loanDetails").forEach(l -> {
    System.out.println(l.get("loanAmount").getClass().getName() + " " + l.get("loanAmount"));   
});
//org.bson.types.Decimal128 21.90533447265625
    
template.findAll(LoanDetails.class).forEach(l -> {
    System.out.println(l.loanAmount.getClass().getName() + " " + l.loanAmount); 
});
//java.math.BigDecimal 21.90533447265625

If you get Conversion to Decimal128 would require inexact rounding of XXX

Note: The Decimal128 type only supports up to 34 digits of precision. (Generally, "precision" = total # of digits, while "scale" = # of decimal digits). Whereas a Java BigDecimal can go higher. So, before saving to the DB, you need to round the BigDecimal value (e.g. use BigDecimal.setScale()) method.

BigDecimalConverter issue | Decimal128

edited Jan 04 '22 at 13:35

answered Dec 30 '21 at 11:23

Valijon

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i mentioned in my question that i tried this @Field(targetType = FieldType.DECIMAL128) but this not work the error is "does not contain targetType attribute" – chaitanya gupta Jan 03 '22 at 03:58
@chaitanyagupta read carefully my answer, you need to drop your already persisted data in order to make it work. – Valijon Jan 03 '22 at 07:35
yes i understand but it is that error i restricting my code to compile as Intellij IDE – chaitanya gupta Jan 03 '22 at 07:47
@chaitanyagupta Update your question with screenshot please, with the error. The solution works perfectly in Eclipse IDE. – Valijon Jan 03 '22 at 16:25
Question is Updated. – chaitanya gupta Jan 04 '22 at 13:27
@chaitanyagupta Seems wrong import https://docs.spring.io/spring-data/mongodb/docs/current/api/org/springframework/data/mongodb/core/mapping/FieldType.html#DECIMAL128 – Valijon Jan 04 '22 at 13:34
import is correct import org.springframework.data.mongodb.core.mapping.Field – chaitanya gupta Jan 05 '22 at 12:38
import org.springframework.data.mongodb.core.mapping.Field does not contain FieldType – chaitanya gupta Jan 05 '22 at 12:38

score 0 · Answer 2 · answered Nov 10 '22 at 05:50

You can register a custom converted in mongo config

@Configuration        
public class MongoConfig
{

    @Bean
    public CustomConversions customConversions()
    {
        return new MongoCustomConversions(Arrays.asList(
                new BigDecimalToDocumentWritingConverter()
            ));
    }
}

And do the conversion there

public class BigDecimalToDocumentWritingConverter implements Converter<BigDecimal, String> {

    @Override
    public String convert(@Nullable BigDecimal amount) {
        if (amount == null) return null;
        return String.valueOf(amount.doubleValue());
    }
}

BigDecimal is stored in string in spring data MongoDB

2 Answers2