dynamodb query filter with optional parameter

Question

In the below code, language filter condition is optional whether it may contains data or null. If it contains null means dynamodb throws some error. How to overcome this ?

Map<String,String> expressionAttributesNames = new HashMap<>(); expressionAttributesNames.put("#Language", "Language");

    Map<String,AttributeValue> expressionAttributeValues = new HashMap<>();
    //expressionAttributeValues.put(":type", new AttributeValue().withS("test1"));
    expressionAttributeValues.put(":name", new AttributeValue().withS("data part"));
    //expressionAttributeValues.put(":key", new AttributeValue().withS("xxx yyy"));
    expressionAttributeValues.put(":language", new AttributeValue().withS(null));
    
    DynamoDBQueryExpression<Sample> queryExpression = new DynamoDBQueryExpression<Sample>()
            .withKeyConditionExpression(keyConditionExpression)
            .withExpressionAttributeNames(expressionAttributesNames)
            .withExpressionAttributeValues(expressionAttributeValues)
            .withFilterExpression("#Language = :language"); List<Sample> tools = mapper.query(Sample.class, queryExpression); 

Exception is,

ExpressionAttributeValues contains invalid value: Supplied AttributeValue is empty, must contain exactly one of the supported datatypes for key :language (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException;

Answer 1

If the language filter expression is optional, you should only include it in the query if the value for language is not null.

.
.
.
if (language != null) {
    queryExpression.withFilterExpression("#Language = :language");
    expressionAttributeValues.put(":language", new AttributeValue().withS(language));
    expressionAttributesNames.put("#Language", "Language");
}

List<Tools> tools = mapper.query(Sample.class, queryExpression);