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LowLevelQuery.java

/** * Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * This file is licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. A copy of * the License is located at * * http://aws.amazon.com/apache2.0/ * * This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR * CONDITIONS OF ANY KIND, either express or implied. See the License for the * specific language governing permissions and limitations under the License. */ package com.amazonaws.codesamples.lowlevel; import java.text.SimpleDateFormat; import java.util.Date; import java.util.HashMap; import java.util.Map; import com.amazonaws.auth.profile.ProfileCredentialsProvider; import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient; import com.amazonaws.services.dynamodbv2.model.AttributeValue; import com.amazonaws.services.dynamodbv2.model.ComparisonOperator; import com.amazonaws.services.dynamodbv2.model.Condition; import com.amazonaws.services.dynamodbv2.model.QueryRequest; import com.amazonaws.services.dynamodbv2.model.QueryResult; public class LowLevelQuery { static AmazonDynamoDBClient client = new AmazonDynamoDBClient(new ProfileCredentialsProvider()); static String tableName = "Reply"; public static void main(String[] args) throws Exception { String forumName = "Amazon DynamoDB"; String threadSubject = "DynamoDB Thread 1"; findRepliesForAThread(forumName, threadSubject); findRepliesForAThreadSpecifyOptionalLimit(forumName, threadSubject); findRepliesInLast15DaysWithConfig(forumName, threadSubject); findRepliesPostedWithinTimePeriod(forumName, threadSubject); findRepliesUsingAFilterExpression(forumName, threadSubject); } private static void findRepliesForAThread(String forumName, String threadSubject) { String replyId = forumName + "#" + threadSubject; Condition partitionKeyCondition = new Condition().withComparisonOperator(ComparisonOperator.EQ) .withAttributeValueList(new AttributeValue().withS(replyId)); Map<String, Condition> keyConditions = new HashMap<String, Condition>(); keyConditions.put("Id", partitionKeyCondition); QueryRequest queryRequest = new QueryRequest().withTableName(tableName).withKeyConditions(keyConditions); QueryResult result = client.query(queryRequest); for (Map<String, AttributeValue> item : result.getItems()) { printItem(item); } } private static void findRepliesForAThreadSpecifyOptionalLimit(String forumName, String threadSubject) { Map<String, AttributeValue> lastEvaluatedKey = null; do { QueryRequest queryRequest = new QueryRequest().withTableName(tableName) .withKeyConditions(makeReplyKeyConditions(forumName, threadSubject)).withLimit(1) .withExclusiveStartKey(lastEvaluatedKey); QueryResult result = client.query(queryRequest); for (Map<String, AttributeValue> item : result.getItems()) { printItem(item); } lastEvaluatedKey = result.getLastEvaluatedKey(); } while (lastEvaluatedKey != null); } private static void findRepliesInLast15DaysWithConfig(String forumName, String threadSubject) { long twoWeeksAgoMilli = (new Date()).getTime() - (15L * 24L * 60L * 60L * 1000L); Date twoWeeksAgo = new Date(); twoWeeksAgo.setTime(twoWeeksAgoMilli); SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"); String twoWeeksAgoStr = df.format(twoWeeksAgo); Condition sortKeyCondition = new Condition().withComparisonOperator(ComparisonOperator.GT.toString()) .withAttributeValueList(new AttributeValue().withS(twoWeeksAgoStr)); Map<String, Condition> keyConditions = makeReplyKeyConditions(forumName, threadSubject); keyConditions.put("ReplyDateTime", sortKeyCondition); QueryRequest queryRequest = new QueryRequest().withTableName(tableName).withKeyConditions(keyConditions) .withProjectionExpression("Message, ReplyDateTime, PostedBy"); QueryResult result = client.query(queryRequest); for (Map<String, AttributeValue> item : result.getItems()) { printItem(item); } } private static void findRepliesPostedWithinTimePeriod(String forumName, String threadSubject) { long startDateMilli = (new Date()).getTime() - (15L * 24L * 60L * 60L * 1000L); long endDateMilli = (new Date()).getTime() - (5L * 24L * 60L * 60L * 1000L); java.text.SimpleDateFormat df = new java.text.SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"); String startDate = df.format(startDateMilli); String endDate = df.format(endDateMilli); Condition sortKeyCondition = new Condition().withComparisonOperator(ComparisonOperator.BETWEEN.toString()) .withAttributeValueList(new AttributeValue().withS(startDate), new AttributeValue().withS(endDate)); Map<String, Condition> keyConditions = makeReplyKeyConditions(forumName, threadSubject); keyConditions.put("ReplyDateTime", sortKeyCondition); QueryRequest queryRequest = new QueryRequest().withTableName(tableName).withKeyConditions(keyConditions) .withProjectionExpression("Message, ReplyDateTime, PostedBy"); QueryResult result = client.query(queryRequest); for (Map<String, AttributeValue> item : result.getItems()) { printItem(item); } } private static void findRepliesUsingAFilterExpression(String forumName, String threadSubject) { Map<String, Condition> keyConditions = makeReplyKeyConditions(forumName, threadSubject); Map<String, AttributeValue> expressionAttributeValues = new HashMap<String, AttributeValue>(); expressionAttributeValues.put(":val", new AttributeValue().withS("User B")); QueryRequest queryRequest = new QueryRequest().withTableName(tableName).withKeyConditions(keyConditions) .withFilterExpression("PostedBy = :val").withExpressionAttributeValues(expressionAttributeValues) .withProjectionExpression("Message, ReplyDateTime, PostedBy"); QueryResult result = client.query(queryRequest); for (Map<String, AttributeValue> item : result.getItems()) { printItem(item); } } private static void printItem(Map<String, AttributeValue> attributeList) { for (Map.Entry<String, AttributeValue> item : attributeList.entrySet()) { String attributeName = item.getKey(); AttributeValue value = item.getValue(); System.out.println(attributeName + " " + (value.getS() == null ? "" : "S=[" + value.getS() + "]") + (value.getN() == null ? "" : "N=[" + value.getN() + "]") + (value.getB() == null ? "" : "B=[" + value.getB() + "]") + (value.getSS() == null ? "" : "SS=[" + value.getSS() + "]") + (value.getNS() == null ? "" : "NS=[" + value.getNS() + "]") + (value.getBS() == null ? "" : "BS=[" + value.getBS() + "] \n")); } } /** * A simple helper function that returns a KeyCondition map filled in with * the partition key equality condition for a the Reply example table, given * a forumName and threadSubject. */ private static Map<String, Condition> makeReplyKeyConditions(String forumName, String threadSubject) { String replyId = forumName + "#" + threadSubject; Condition partitionKeyCondition = new Condition().withComparisonOperator(ComparisonOperator.EQ) .withAttributeValueList(new AttributeValue().withS(replyId)); Map<String, Condition> keyConditions = new HashMap<String, Condition>(); keyConditions.put("Id", partitionKeyCondition); return keyConditions; } }

Sample Details

Service: dynamodb

Last tested:

Author: AWS

Type: full-example

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