Exception when trying to use DynamoDBMapper: no mapping for HASH key - database

Question

I have a DynamoDB table with a primary key (id : integer) and secondary key (dateTo : String). I've made a Class that utilizes DynamoDBMapper:
#DynamoDBTable(tableName="MyItems"
public class MyItemsMapper {
private int id;
private String dateTo;
private String name;
#DynamoDBHashKey(attributeName="id")
public void setId(int id) { this.id = id; }
public int getId() { return id; }
#DynamoDBAttribute(attributeName="dateTo")
public void setDateTo(String dateTo) { this.dateTo = dateTo; }
public String getDateTo() { return dateTo; }
#DynamoDBAttribute(attributeName="name")
public void setName(String name { this.name = name; }
public String getName() { return name; }
public boolean saveItem(MyItemsMapper item) {
try {
DynamoDBMapper mapper = new DynamoDBMapper(client); //<-- This connects to the DB. This works fine.
item.setId(generateUniqueNumber()); //<-- This generates a unique integer. Also seems to work fine.
mapper.save(item);
logger.info("Successfully saved item. See info below.");
logger.info(item.toString());
return true;
} catch (Exception e) {
logger.error("Exception while trying to save item: " + e.getMessage());
e.printStackTrace();
return false;
}
}
}
I then have a manager class that uses the bean above, like so:
public class MyManager {
public boolean recordItem(
int id,
String dateTo,
String name,
) {
MyItemsMapper myItemsMapper = new MyItemsMapper();
myItemsMapper.setId(id);
myItemsMapper.setDateTo(dateTo);
myItemsMapper.setName(name);
myItemsMapper.saveItem(myItemsMapper);
}
}
I am running the manager class in a JUnit test:
public class MyManagerTest {
#Test
public void saveNewItemTest() {
MyManager myManager = new MyManager();
myManager.recordItem(1234567, "2018-01-01", "Anthony");
}
}
When I use the saveItem method above via my manager by running my JUnit test, I get the following error:
com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException: MyItemsMapper; no mapping for HASH key
Not really sure what it's pertaining to, as I definitely have a primary key for my table and my secondary key always has a value as well.
How do I get this to work?
More Info:
It's worth noting that I can record data into my DynamoDB table via the Item object. If I do the below, my data gets recorded into the database:
DynamoDB dynamoDB = new DynamoDBClient().connectToDynamoDB(); //<--
Connection. Works fine.
Table table = dynamoDB.getTable("MyItems");
item.withPrimaryKey("id", 1234567);
item.withString("dateTo", "2018-01-01");
item.withString("name", "Anthony");
PutItemOutcome outcome = table.putItem(item);
However, I'm trying to use DynamoDBMapper because I'm reading that it is a more organized, better way to access data.

Answer 1

Im not sure if this is causing the problem, but you are creating the myItemsMapper object, then passing a reference to this object to itself.
I would suggest removing your saveItem method. The MyItemsMapper class should be a plain old java object. Then make MyManager like this
public class MyManager {
public boolean recordItem(
int id,
String dateTo,
String name,
) {
MyItemsMapper myItemsMapper = new MyItemsMapper();
myItemsMapper.setId(id);
myItemsMapper.setDateTo(dateTo);
myItemsMapper.setName(name);
DynamoDBMapper mapper = new DynamoDBMapper(client);
mapper.save(myItemsMapper);
}
}
If you particularly want to keep the saveItem method make it like this
public boolean saveItem() {
try {
DynamoDBMapper mapper = new DynamoDBMapper(client);
mapper.save(this);
logger.info("Successfully saved item. See info below.");
logger.info(this.toString());
return true;
} catch (Exception e) {
logger.error("Exception while trying to save item: " + e.getMessage());
e.printStackTrace();
return false;
}
}
And then in MyManager do
MyItemsMapper myItemsMapper = new MyItemsMapper();
myItemsMapper.setId(id);
myItemsMapper.setDateTo(dateTo);
myItemsMapper.setName(name);
myItemsMapper.saveItem();