DynamoDB PaginatedQueryList空对象引用错误

我得到一个空对象引用错误，当我尝试从我的dynamoDB表这样的查询数据：DynamoDB PaginatedQueryList空对象引用错误

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);

我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*/ 

    }

哪有我解决了我在“PaginatedQueryList”代码行上得到的这个错误：

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

来源

2016-11-21 S bruce

你创建自己DataMapperClass？如果是的话，你可以分享它的代码，请确保它是正确注释的，如http://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapper.html所述。 – dinesh

你是否得到NullPointerException？在上面的代码中我看不到QueryResult。在执行查询或mapper.query后，您是否收到异常？ – notionquest

@notionquest：在AsyncTask的doInBackground（）中执行代码后，我得到java.lang.NullPointerException“null object reference”错误。 –

问题sol VED！

我意识到我没有在我的onCreate（）做到这一点：

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

来源

2016-11-21 16:22:28

DynamoDB PaginatedQueryList空对象引用错误

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