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). Chilkat2 Java

import com.chilkatsoft.chilkat2.AuthAws;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.JsonObject;
import com.chilkatsoft.chilkat2.Rest;
import com.chilkatsoft.chilkat2.StringBuilder;

public class ChilkatExample {

    public static void main(String[] args) {
        Rest rest = new Rest();

        // 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

        AuthAws authAws = new AuthAws();
        authAws.setAccessKey("AWS_ACCESS_KEY");
        authAws.setSecretKey("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.setRegion("us-west-2");
        authAws.setServiceName("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;
        try {
            rest.connect("dynamodb.us-west-2.amazonaws.com", port, bTls, bAutoReconnect);
        } catch (ChilkatException e) {
            System.out.println("ConnectFailReason: " + rest.getConnectFailReason());
            System.out.println(e.getLastErrorText());
            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"
        // }

        JsonObject json = new JsonObject();
        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");

        StringBuilder sbRequestBody = new StringBuilder();
        json.emitSb(sbRequestBody);
        StringBuilder sbResponseBody = new StringBuilder();
        try {
            rest.fullRequestSb("POST", "/", sbRequestBody, sbResponseBody);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        int respStatusCode = rest.getResponseStatusCode();
        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.getResponseHeader());
            System.out.println("Response Body:");
            System.out.println(sbResponseBody.getAsString());
            return;
        }

        JsonObject jsonResponse = new JsonObject();
        jsonResponse.loadSb(sbResponseBody);

        jsonResponse.setEmitCompact(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.setI(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;
        }
    }
}