edu.memphis.iis.demosurvey

Class DataStoreClient

java.lang.Object

edu.memphis.iis.demosurvey.DataStoreClient

public class DataStoreClient
extends Object

This is a very simple demonstration of an interface to a data store, sometimes called a DAO. Depending on what data you're working with, if you're using something like Spring or Guice, and how large your project is, you might have much more complicated DAO's, you might skip them entirely, or they might be provided by a library. Note that we manually create our DynamoDB client, db, and mapper instances in the constructor. In a large system, we would want to use an Inversion of Control (aka Dependency Injection) pattern. Those instances would be injected by some kind of context object that could vary for unit tests, local workstation debugging, and running in the actual AWS cloud For this simple demo, we are just using some custom logic based on system properties. See the pom.xml for how we set aws.dynamoEndpoint for local Tomcat testing AND the AWS credential properties so that our use of DefaultAWSCredentialsProviderChain works. Note that this class supports auto-creation of all tables listed in the TABLES variable. It also supports automatic key checking (which we use in saveSurvey).

Constructor Summary

Constructors

Constructor and Description
DataStoreClient() Default constructor

Method Summary

Methods

Modifier and Type	Method and Description
void	ensureSchema() Insure that the current database schema is properly loaded.
List<Survey>	findSurveys() Return a list of all surveys.
protected com.amazonaws.services.dynamodbv2.document.DynamoDB	getDB() Simple helper to lazy-create the (low-level) Dynamo DB instance for our current client.
protected com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper	getMapper() Simple helper to lazy-create the (high-level) Dynamo DB mapper instance for our current client.
void	saveSurvey(Survey survey, boolean allowOverwrite) Persist the given survey

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DataStoreClient

public DataStoreClient()

Default constructor

Method Detail

getDB

protected com.amazonaws.services.dynamodbv2.document.DynamoDB getDB()

Simple helper to lazy-create the (low-level) Dynamo DB instance for our current client.

Returns:

valid instance of Dynamo DB

getMapper

protected com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper getMapper()

Simple helper to lazy-create the (high-level) Dynamo DB mapper instance for our current client.

Returns:

valid instance of Dynamo DB Mapper

ensureSchema

public void ensureSchema()

Insure that the current database schema is properly loaded. This example pattern creates a set of tables needed, removes any previously created tables from that set, and then creates any tables left over.

saveSurvey

public void saveSurvey(Survey survey,
              boolean allowOverwrite)

Persist the given survey

Parameters:

survey - the object to save

allowOverwrite - if true, a previous record will overwritten

findSurveys

public List<Survey> findSurveys()

Return a list of all surveys. Note that the underlying implementation of the list is unspecified. Currently we use the AWS SDK's lazy-loading list (which returns a page at a time). There may be delays while iterating over this list, AND this may change in the future

Returns:

a List<> of Survey instances, or a List<> of size 0 if no Survey's are found