DynamoDBのPaginatedQueryList nullオブジェクト参照エラー

Question

私はこのような私のDynamoDBのテーブルからデータを照会しようとすると、私はnullオブジェクト参照エラーが表示されます。

mapper = new DynamoDBMapper(ddbClient); 

DataMapperClass dataMapperClass = new DataMapperClass(); 
dataMapperClass.setHash("theHashValueIset"); 

String queryString = String.valueOf("theRangeValueIset"); 

Condition rangeKeyCondition = new Condition() 
    .withComparisonOperator(ComparisonOperator.BEGINS_WITH.toString()) 
    .withAttributeValueList(new AttributeValue().withS(queryString.toString())); 

DynamoDBQueryExpression <DataMapperClass> queryExpression = new DynamoDBQueryExpression<DataMapperClass>() 
    .withHashKeyValues(dataMapperClass) 
    .withRangeKeyCondition("rangeAttributeOnTable", rangeKeyCondition) 
    .withConsistentRead(false); 

PaginatedQueryList<DataMapperClass> result = mapper.query(DataMapperClass.class, queryExpression); 

マイDataMapperClass.class：

@DynamoDBTable(tableName = "myTableName") 
    public class DataMapperClass { 

    private String hash;//based on a set of categories I chose 
    private String objectID; //auto generated 


    //Hash 
    @DynamoDBHashKey(attributeName = "hashNameOnMyTable") 
    public String getHash() { return hash; } 
    public void setHash(String hash) { this.hash = hash;} 


    //ObjectID 
    @DynamoDBRangeKey(attributeName = "rangeAttributeOnTable") 
    @DynamoDBAutoGeneratedKey 
    public String getObjectID() {return objectID;} 
    public void setObjectID(String objectID) { this.objectID = objectID; } 

    /* other @DynamoDBAttribute*/ 

    } 

どのようにすることができます私はこのエラーを解決し、「PaginatedQueryList」コード行に行きます：

Attempt to invoke interface method 'com.amazonaws.services.dynamodbv2.model.QueryResult com.amazonaws.services.dynamodbv2.AmazonDynamoDB.query(com.amazonaws.services.dynamodbv2.model.QueryRequest)' on a null object reference 

Answer 1

問題sol ved！

ddbClient = new AmazonDynamoDBClient(identityManager.getCredentialsProvider());