Java

DynamoDB - Query

See more Amazon DynamoDB Examples

The Query operation finds items based on primary key values. You can query any table or secondary index that has a composite primary key (a partition key and a sort key). Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    CkRest rest = new CkRest();

    // Implements the following CURL command:

    // curl -X POST https://dynamodb.us-west-2.amazonaws.com/ \
    //   -H "Accept-Encoding: identity" \
    //   -H "Content-Type: application/x-amz-json-1.0" \
    //   -H "Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=<Headers>, Signature=<Signature>" \
    //   -H "X-Amz-Date: <Date>" \
    //   -H "X-Amz-Target: DynamoDB_20120810.Query" \
    //   -d '{
    //     "TableName": "Reply",
    //     "IndexName": "PostedBy-Index",
    //     "Limit": 3,
    //     "ConsistentRead": true,
    //     "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
    //     "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
    //     "ExpressionAttributeValues": {
    //         ":v1": {"S": "Amazon DynamoDB#DynamoDB Thread 1"},
    //         ":v2a": {"S": "User A"},
    //         ":v2b": {"S": "User C"}
    //     },
    //     "ReturnConsumedCapacity": "TOTAL"
    // }'

    // Use the following online tool to generate REST code from a CURL command
    // Convert a cURL Command to REST Source Code

    CkAuthAws authAws = new CkAuthAws();
    authAws.put_AccessKey("AWS_ACCESS_KEY");
    authAws.put_SecretKey("AWS_SECRET_KEY");
    // Don't forget to change the region to your particular region. (Also make the same change in the call to Connect below.)
    authAws.put_Region("us-west-2");
    authAws.put_ServiceName("dynamodb");
    // SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
    rest.SetAuthAws(authAws);

    // URL: https://dynamodb.us-west-2.amazonaws.com/
    boolean bTls = true;
    int port = 443;
    boolean bAutoReconnect = true;
    success = rest.Connect("dynamodb.us-west-2.amazonaws.com",port,bTls,bAutoReconnect);
    if (success != true) {
        System.out.println("ConnectFailReason: " + rest.get_ConnectFailReason());
        System.out.println(rest.lastErrorText());
        return;
        }

    // Note: The above code does not need to be repeatedly called for each REST request.
    // The rest object can be setup once, and then many requests can be sent.  Chilkat will automatically
    // reconnect within a FullRequest* method as needed.  It is only the very first connection that is explicitly
    // made via the Connect method.

    // Use this online tool to generate code from sample JSON:
    // Generate Code to Create JSON

    // The following JSON is sent in the request body.

    // {
    //   "TableName": "Reply",
    //   "IndexName": "PostedBy-Index",
    //   "Limit": 3,
    //   "ConsistentRead": true,
    //   "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
    //   "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
    //   "ExpressionAttributeValues": {
    //     ":v1": {
    //       "S": "Amazon DynamoDB#DynamoDB Thread 1"
    //     },
    //     ":v2a": {
    //       "S": "User A"
    //     },
    //     ":v2b": {
    //       "S": "User C"
    //     }
    //   },
    //   "ReturnConsumedCapacity": "TOTAL"
    // }

    CkJsonObject json = new CkJsonObject();
    json.UpdateString("TableName","Reply");
    json.UpdateString("IndexName","PostedBy-Index");
    json.UpdateInt("Limit",3);
    json.UpdateBool("ConsistentRead",true);
    json.UpdateString("ProjectionExpression","Id, PostedBy, ReplyDateTime");
    json.UpdateString("KeyConditionExpression","Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b");
    json.UpdateString("ExpressionAttributeValues.:v1.S","Amazon DynamoDB#DynamoDB Thread 1");
    json.UpdateString("ExpressionAttributeValues.:v2a.S","User A");
    json.UpdateString("ExpressionAttributeValues.:v2b.S","User C");
    json.UpdateString("ReturnConsumedCapacity","TOTAL");

    rest.AddHeader("Content-Type","application/x-amz-json-1.0");
    rest.AddHeader("X-Amz-Target","DynamoDB_20120810.Query");
    rest.AddHeader("Accept-Encoding","identity");

    CkStringBuilder sbRequestBody = new CkStringBuilder();
    json.EmitSb(sbRequestBody);
    CkStringBuilder sbResponseBody = new CkStringBuilder();
    success = rest.FullRequestSb("POST","/",sbRequestBody,sbResponseBody);
    if (success != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    int respStatusCode = rest.get_ResponseStatusCode();
    System.out.println("response status code = " + respStatusCode);
    if (respStatusCode >= 400) {
        System.out.println("Response Status Code = " + respStatusCode);
        System.out.println("Response Header:");
        System.out.println(rest.responseHeader());
        System.out.println("Response Body:");
        System.out.println(sbResponseBody.getAsString());
        return;
        }

    CkJsonObject jsonResponse = new CkJsonObject();
    jsonResponse.LoadSb(sbResponseBody);

    jsonResponse.put_EmitCompact(false);
    System.out.println(jsonResponse.emit());

    // Sample JSON response:
    // (Sample code for parsing the JSON response is shown below)

    // {
    //   "ConsumedCapacity": {
    //     "CapacityUnits": 1,
    //     "TableName": "Reply"
    //   },
    //   "Count": 2,
    //   "Items": [
    //     {
    //       "ReplyDateTime": {
    //         "S": "2015-02-18T20:27:36.165Z"
    //       },
    //       "PostedBy": {
    //         "S": "User A"
    //       },
    //       "Id": {
    //         "S": "Amazon DynamoDB#DynamoDB Thread 1"
    //       }
    //     },
    //     {
    //       "ReplyDateTime": {
    //         "S": "2015-02-25T20:27:36.165Z"
    //       },
    //       "PostedBy": {
    //         "S": "User B"
    //       },
    //       "Id": {
    //         "S": "Amazon DynamoDB#DynamoDB Thread 1"
    //       }
    //     }
    //   ],
    //   "ScannedCount": 2
    // }

    // Sample code for parsing the JSON response...
    // Use the following online tool to generate parsing code from sample JSON:
    // Generate Parsing Code from JSON

    String ReplyDateTimeS;
    String PostedByS;
    String IdS;

    int ConsumedCapacityCapacityUnits = jsonResponse.IntOf("ConsumedCapacity.CapacityUnits");
    String ConsumedCapacityTableName = jsonResponse.stringOf("ConsumedCapacity.TableName");
    int Count = jsonResponse.IntOf("Count");
    int ScannedCount = jsonResponse.IntOf("ScannedCount");
    int i = 0;
    int count_i = jsonResponse.SizeOfArray("Items");
    while (i < count_i) {
        jsonResponse.put_I(i);
        ReplyDateTimeS = jsonResponse.stringOf("Items[i].ReplyDateTime.S");
        PostedByS = jsonResponse.stringOf("Items[i].PostedBy.S");
        IdS = jsonResponse.stringOf("Items[i].Id.S");
        i = i+1;
        }
  }
}