Amazon DynamoDB Demo

package com.cloudspokes.dynamodb;

@Controller
public class HomeController {

 static AmazonDynamoDBClient dynamoDB;
 private String tableName = "kiva-loans";
 // aws keys
 public static final String ACCESSKEY = "YOURKEY";
 public static final String SECRETKEY = "YOURSECRET";

 public HomeController() {
  try {
 setup();
  } catch (Exception e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
  }
 }

 /**
  * Displays the list of loans from the table
  */
 @RequestMapping(value = "/loans", method = RequestMethod.GET)
 public String loans(Locale locale,
 @RequestParam(value = "keyword", required = false) String keyword,
 Model model) {

  ArrayList<Loan> loans = new ArrayList<Loan>();
  ScanRequest scanRequest = new ScanRequest(tableName);

  if (keyword != null) {
 HashMap<String, Condition> scanFilter = new HashMap<String, Condition>();
 Condition condition = new Condition().withComparisonOperator(
   ComparisonOperator.EQ.toString()).withAttributeValueList(
   new AttributeValue().withS(keyword));
 scanFilter.put("country", condition);
 scanRequest = new ScanRequest(tableName).withScanFilter(scanFilter);
  }
  ScanResult scanResult = dynamoDB.scan(scanRequest);

  for (int i = 0; i < scanResult.getCount(); i++) {
 HashMap<String, AttributeValue> item = (HashMap<String, AttributeValue>) scanResult
   .getItems().get(i);
 Loan loan = new Loan();
 loan.setActivity(item.get("activity").getS());
 loan.setCountry(item.get("country").getS());
 loan.setFunded_amount(Double.parseDouble(item.get("funded_amount")
   .getN()));
 loan.setId(Integer.parseInt(item.get("id").getN()));
 loan.setName(item.get("name").getS());
 loan.setStatus(item.get("status").getS());
 loan.setUse(item.get("use").getS());
 loans.add(loan);
  }

  model.addAttribute("loans", loans);
  return "loans";
 }

 /**
  * Displays a loan item
  */
 @RequestMapping(value = "/show/{id}", method = RequestMethod.GET)
 public String show(@PathVariable String id, Locale locale, Model model) {
  model.addAttribute("loan", getLoan(id));
  return "show";
 }

 /**
  * Displays a form to create a new loan item
  */
 @RequestMapping(value = "/new", method = RequestMethod.GET)
 public String newLoan(Locale locale, Model model) {
  model.addAttribute("loan", new Loan());
  return "new";
 }

 /**
  * Inserts a new loan item into dynamodb
  */
 @RequestMapping(value = "/new", method = RequestMethod.POST)
 public String addLoan(@ModelAttribute("loan") Loan loan,
 BindingResult result) {

  // populate an item with the data to put
  HashMap<String, AttributeValue> item = new HashMap<String, AttributeValue>();
  item.put("id", new AttributeValue().withN(String.valueOf(loan.getId())));
  item.put("activity", new AttributeValue().withS(loan.getActivity()));
  item.put("country", new AttributeValue().withS(loan.getCountry()));
  item.put("funded_amount", new AttributeValue().withN(String
  .valueOf(loan.getFunded_amount())));
  item.put("name", new AttributeValue().withS(loan.getName()));
  item.put("status", new AttributeValue().withS(loan.getStatus()));
  item.put("use", new AttributeValue().withS(loan.getUse()));

  // put the item to the table
  try {
 PutItemRequest req = new PutItemRequest(tableName, item);
 PutItemResult res = dynamoDB.putItem(req);
  } catch (AmazonServiceException ase) {
 System.err.println("Failed to create item in " + tableName);
  }

  return "redirect:show/" + loan.getId();
 }

 /**
  * Displays the item for editing
  */
 @RequestMapping(value = "/edit/{id}", method = RequestMethod.GET)
 public String editLoan(@PathVariable String id, Locale locale, Model model) {
  model.addAttribute("loan", getLoan(id));
  return "edit";
 }

 /**
  * Submits the updates loan data to dynamodb
  */
 @RequestMapping(value = "/edit/{id}", method = RequestMethod.POST)
 public String updateLoan(@PathVariable String id,
 @ModelAttribute("loan") Loan loan, BindingResult result) {

  Key key = new Key().withHashKeyElement(new AttributeValue().withN(id));
  HashMap<String, AttributeValueUpdate> updates = new HashMap<String, AttributeValueUpdate>();

  AttributeValueUpdate update = new AttributeValueUpdate().withValue(
  new AttributeValue(loan.getStatus())).withAction("PUT");
  updates.put("status", update);

  // update the item to the table
  try {
 UpdateItemRequest req = new UpdateItemRequest(tableName, key,
   updates);
 UpdateItemResult res = dynamoDB.updateItem(req);
  } catch (AmazonServiceException ase) {
 System.err.println("Failed to update item: " + ase.getMessage());
  }

  return "redirect:../show/" + id;
 }

 /**
  * Fetches loan data from Kiva an inserts it into dynamodb
  */
 @RequestMapping(value = "/loadData", method = RequestMethod.GET)
 public String loadData(Locale locale, Model model) {

  // delete all of the current loans
  deleteAllLoans();

  // make the REST call to kiva
  DefaultHttpClient httpClient = new DefaultHttpClient();
  HttpGet getRequest = new HttpGet(
  "http://api.kivaws.org/v1/loans/newest.json");
  getRequest.addHeader("accept", "application/json");
  HttpResponse response;
  String payload = "";

  try {
 response = httpClient.execute(getRequest);

 if (response.getStatusLine().getStatusCode() != 200) {
  throw new RuntimeException("Failed : HTTP error code : "
  + response.getStatusLine().getStatusCode());
 }

 BufferedReader br = new BufferedReader(new InputStreamReader(
   (response.getEntity().getContent())));
 payload = br.readLine();
  } catch (ClientProtocolException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
  } catch (IOException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
  }

  JSONObject json = (JSONObject) JSONSerializer.toJSON(payload);
  // get the array of loans
  JSONArray loans = json.getJSONArray("loans");

  for (int i = 0; i < loans.size(); ++i) {
 JSONObject loan = loans.getJSONObject(i);
 // populate an item with the data to put
 HashMap<String, AttributeValue> item = new HashMap<String, AttributeValue>();
 item.put("id", new AttributeValue().withN(loan.getString("id")));
 item.put("name", new AttributeValue().withS(loan.getString("name")));
 item.put("status",
   new AttributeValue().withS(loan.getString("status")));
 item.put("funded_amount",
   new AttributeValue().withN(loan.getString("funded_amount")));
 item.put("activity",
   new AttributeValue().withS(loan.getString("activity")));
 item.put("use", new AttributeValue().withS(loan.getString("use")));
 item.put("country", new AttributeValue().withS(loan.getJSONObject(
   "location").getString("country")));

 try {
  PutItemRequest req = new PutItemRequest(tableName, item);
  PutItemResult res = dynamoDB.putItem(req);
  System.out.println("Put result: " + res);
 } catch (AmazonServiceException ase) {
  System.err.println("Failed to create item in " + tableName);
 }

  }

  httpClient.getConnectionManager().shutdown();

  return "redirect:loans";
 }

 /**
  * Displays the home page
  */
 @RequestMapping(value = "/", method = RequestMethod.GET)
 public String home(Locale locale, Model model) {
  return "home";
 }

 /**
  * Fetches a specific loan item
  */
 private Loan getLoan(String id) {
  Key key = new Key().withHashKeyElement(new AttributeValue().withN(id));
  GetItemRequest req = new GetItemRequest(tableName, key);
  GetItemResult res = dynamoDB.getItem(req);
  HashMap<String, AttributeValue> item = (HashMap<String, AttributeValue>) res
  .getItem();

  Loan loan = new Loan();
  loan.setActivity(item.get("activity").getS());
  loan.setCountry(item.get("country").getS());
  loan.setFunded_amount(Double.parseDouble(item.get("funded_amount")
  .getN()));
  loan.setId(Integer.parseInt(item.get("id").getN()));
  loan.setName(item.get("name").getS());
  loan.setStatus(item.get("status").getS());
  loan.setUse(item.get("use").getS());
  return loan;
 }

 /**
  * Deletes all items from dynamodb
  */
 private void deleteAllLoans() {
  ScanRequest scanRequest = new ScanRequest(tableName);
  ScanResult scanResult = dynamoDB.scan(scanRequest);
  for (int i = 0; i < scanResult.getItems().size(); i++) {
 HashMap<String, AttributeValue> item = (HashMap<String, AttributeValue>) scanResult
   .getItems().get(i);
 try {
  Key key = new Key()
  .withHashKeyElement(new AttributeValue("id"))
  .withHashKeyElement(item.get("id"));
  DeleteItemRequest request = new DeleteItemRequest(tableName,
  key);
  DeleteItemResult result = dynamoDB.deleteItem(request);
  System.out.println("Result: " + result);
 } catch (AmazonServiceException ase) {
  System.err.println("Failed to delete item in " + tableName);
 }
  }
 }

 private void setup() throws Exception {
  BasicAWSCredentials creds = new BasicAWSCredentials(ACCESSKEY,
  SECRETKEY);
  dynamoDB = new AmazonDynamoDBClient(creds);
  dynamoDB.setEndpoint("http://dynamodb.us-east-1.amazonaws.com");
 }

}