Esempio: indici secondari globali che utilizzano l'API del documento AWS SDK for Java

Il seguente esempio di codice Java mostra come utilizzare gli indici secondari globali. L'esempio crea una tabella denominata Issues, che può essere utilizzata in un semplice sistema di tracciamento di bug per lo sviluppo di software. La chiave di partizione è IssueId e la chiave di ordinamento è Title. In questa tabella esistono tre indici secondari globali:

• CreateDateIndex: la chiave di partizione è CreateDate e la chiave di ordinamento è IssueId. Oltre alle chiavi di tabella, vengono proiettati nell'indice gli attributi Description e Status.

• TitleIndex: la chiave di partizione è Title e la chiave di ordinamento è IssueId. Non vengono proiettati nell'indice attributi diversi dalle chiavi di tabella.

• DueDateIndex: la chiave di partizione è DueDate; non è presente una chiave di ordinamento. Tutti gli attributi della tabella vengono proiettati nell'indice.

Una volta creata la tabella Issues, il programma carica la tabella con i dati che rappresentano i report sui bug del software. Quindi esegue una query sui dati utilizzando gli indici secondari globali. Infine, il programma elimina la tabella Issues.

Per step-by-step istruzioni su come testare l'esempio seguente, vedereEsempi di codice Java.

Esempio

package com.amazonaws.codesamples.document;

import java.util.ArrayList;
import java.util.Iterator;

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Index;
import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.ItemCollection;
import com.amazonaws.services.dynamodbv2.document.QueryOutcome;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.document.spec.QuerySpec;
import com.amazonaws.services.dynamodbv2.document.utils.ValueMap;
import com.amazonaws.services.dynamodbv2.model.AttributeDefinition;
import com.amazonaws.services.dynamodbv2.model.CreateTableRequest;
import com.amazonaws.services.dynamodbv2.model.GlobalSecondaryIndex;
import com.amazonaws.services.dynamodbv2.model.KeySchemaElement;
import com.amazonaws.services.dynamodbv2.model.KeyType;
import com.amazonaws.services.dynamodbv2.model.Projection;
import com.amazonaws.services.dynamodbv2.model.ProvisionedThroughput;

public class DocumentAPIGlobalSecondaryIndexExample {

    static AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard().build();
    static DynamoDB dynamoDB = new DynamoDB(client);

    public static String tableName = "Issues";

    public static void main(String[] args) throws Exception {

        createTable();
        loadData();

        queryIndex("CreateDateIndex");
        queryIndex("TitleIndex");
        queryIndex("DueDateIndex");

        deleteTable(tableName);

    }

    public static void createTable() {

        // Attribute definitions
        ArrayList<AttributeDefinition> attributeDefinitions = new ArrayList<AttributeDefinition>();

        attributeDefinitions.add(new AttributeDefinition().withAttributeName("IssueId").withAttributeType("S"));
        attributeDefinitions.add(new AttributeDefinition().withAttributeName("Title").withAttributeType("S"));
        attributeDefinitions.add(new AttributeDefinition().withAttributeName("CreateDate").withAttributeType("S"));
        attributeDefinitions.add(new AttributeDefinition().withAttributeName("DueDate").withAttributeType("S"));

        // Key schema for table
        ArrayList<KeySchemaElement> tableKeySchema = new ArrayList<KeySchemaElement>();
        tableKeySchema.add(new KeySchemaElement().withAttributeName("IssueId").withKeyType(KeyType.HASH)); // Partition
                                                                                                           // key
        tableKeySchema.add(new KeySchemaElement().withAttributeName("Title").withKeyType(KeyType.RANGE)); // Sort
                                                                                                          // key

        // Initial provisioned throughput settings for the indexes
        ProvisionedThroughput ptIndex = new ProvisionedThroughput().withReadCapacityUnits(1L)
                .withWriteCapacityUnits(1L);

        // CreateDateIndex
        GlobalSecondaryIndex createDateIndex = new GlobalSecondaryIndex().withIndexName("CreateDateIndex")
                .withProvisionedThroughput(ptIndex)
                .withKeySchema(new KeySchemaElement().withAttributeName("CreateDate").withKeyType(KeyType.HASH), // Partition
                                                                                                                 // key
                        new KeySchemaElement().withAttributeName("IssueId").withKeyType(KeyType.RANGE)) // Sort
                                                                                                        // key
                .withProjection(
                        new Projection().withProjectionType("INCLUDE").withNonKeyAttributes("Description", "Status"));

        // TitleIndex
        GlobalSecondaryIndex titleIndex = new GlobalSecondaryIndex().withIndexName("TitleIndex")
                .withProvisionedThroughput(ptIndex)
                .withKeySchema(new KeySchemaElement().withAttributeName("Title").withKeyType(KeyType.HASH), // Partition
                                                                                                            // key
                        new KeySchemaElement().withAttributeName("IssueId").withKeyType(KeyType.RANGE)) // Sort
                                                                                                        // key
                .withProjection(new Projection().withProjectionType("KEYS_ONLY"));

        // DueDateIndex
        GlobalSecondaryIndex dueDateIndex = new GlobalSecondaryIndex().withIndexName("DueDateIndex")
                .withProvisionedThroughput(ptIndex)
                .withKeySchema(new KeySchemaElement().withAttributeName("DueDate").withKeyType(KeyType.HASH)) // Partition
                                                                                                              // key
                .withProjection(new Projection().withProjectionType("ALL"));

        CreateTableRequest createTableRequest = new CreateTableRequest().withTableName(tableName)
                .withProvisionedThroughput(
                        new ProvisionedThroughput().withReadCapacityUnits((long) 1).withWriteCapacityUnits((long) 1))
                .withAttributeDefinitions(attributeDefinitions).withKeySchema(tableKeySchema)
                .withGlobalSecondaryIndexes(createDateIndex, titleIndex, dueDateIndex);

        System.out.println("Creating table " + tableName + "...");
        dynamoDB.createTable(createTableRequest);

        // Wait for table to become active
        System.out.println("Waiting for " + tableName + " to become ACTIVE...");
        try {
            Table table = dynamoDB.getTable(tableName);
            table.waitForActive();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void queryIndex(String indexName) {

        Table table = dynamoDB.getTable(tableName);

        System.out.println("\n***********************************************************\n");
        System.out.print("Querying index " + indexName + "...");

        Index index = table.getIndex(indexName);

        ItemCollection<QueryOutcome> items = null;

        QuerySpec querySpec = new QuerySpec();

        if (indexName == "CreateDateIndex") {
            System.out.println("Issues filed on 2013-11-01");
            querySpec.withKeyConditionExpression("CreateDate = :v_date and begins_with(IssueId, :v_issue)")
                    .withValueMap(new ValueMap().withString(":v_date", "2013-11-01").withString(":v_issue", "A-"));
            items = index.query(querySpec);
        } else if (indexName == "TitleIndex") {
            System.out.println("Compilation errors");
            querySpec.withKeyConditionExpression("Title = :v_title and begins_with(IssueId, :v_issue)")
                    .withValueMap(
                            new ValueMap().withString(":v_title", "Compilation error").withString(":v_issue", "A-"));
            items = index.query(querySpec);
        } else if (indexName == "DueDateIndex") {
            System.out.println("Items that are due on 2013-11-30");
            querySpec.withKeyConditionExpression("DueDate = :v_date")
                    .withValueMap(new ValueMap().withString(":v_date", "2013-11-30"));
            items = index.query(querySpec);
        } else {
            System.out.println("\nNo valid index name provided");
            return;
        }

        Iterator<Item> iterator = items.iterator();

        System.out.println("Query: printing results...");

        while (iterator.hasNext()) {
            System.out.println(iterator.next().toJSONPretty());
        }

    }

    public static void deleteTable(String tableName) {

        System.out.println("Deleting table " + tableName + "...");

        Table table = dynamoDB.getTable(tableName);
        table.delete();

        // Wait for table to be deleted
        System.out.println("Waiting for " + tableName + " to be deleted...");
        try {
            table.waitForDelete();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void loadData() {

        System.out.println("Loading data into table " + tableName + "...");

        // IssueId, Title,
        // Description,
        // CreateDate, LastUpdateDate, DueDate,
        // Priority, Status

        putItem("A-101", "Compilation error", "Can't compile Project X - bad version number. What does this mean?",
                "2013-11-01", "2013-11-02", "2013-11-10", 1, "Assigned");

        putItem("A-102", "Can't read data file", "The main data file is missing, or the permissions are incorrect",
                "2013-11-01", "2013-11-04", "2013-11-30", 2, "In progress");

        putItem("A-103", "Test failure", "Functional test of Project X produces errors", "2013-11-01", "2013-11-02",
                "2013-11-10", 1, "In progress");

        putItem("A-104", "Compilation error", "Variable 'messageCount' was not initialized.", "2013-11-15",
                "2013-11-16", "2013-11-30", 3, "Assigned");

        putItem("A-105", "Network issue", "Can't ping IP address 127.0.0.1. Please fix this.", "2013-11-15",
                "2013-11-16", "2013-11-19", 5, "Assigned");

    }

    public static void putItem(

            String issueId, String title, String description, String createDate, String lastUpdateDate, String dueDate,
            Integer priority, String status) {

        Table table = dynamoDB.getTable(tableName);

        Item item = new Item().withPrimaryKey("IssueId", issueId).withString("Title", title)
                .withString("Description", description).withString("CreateDate", createDate)
                .withString("LastUpdateDate", lastUpdateDate).withString("DueDate", dueDate)
                .withNumber("Priority", priority).withString("Status", status);

        table.putItem(item);
    }

}