Ejemplo: índices secundarios globales que utilizan la API de documentos de AWS SDK for Java

En el siguiente ejemplo de código Java se muestra cómo usar índices secundarios globales. En el ejemplo se crea una tabla denominada Issues, que puede utilizarse en un sistema sencillo de seguimiento de errores con fines de desarrollo de software. La clave de partición es IssueId y la de ordenación, Title. Hay tres índices secundarios globales en esta tabla:

• CreateDateIndex: la clave de partición es CreateDate y la de ordenación IssueId. Además de las claves de tabla, se proyectan en el índice los atributos Description y Status.

• TitleIndex: la clave de partición es Title y la de ordenación IssueId. No se proyecta en el índice ningún otro atributo excepto las claves de tabla.

• DueDateIndex: la clave de partición es DueDate y no hay clave de ordenación. Todos los atributos de la tabla se proyectan en el índice.

Una vez que se ha creado la tabla Issues, el programa carga la tabla con datos que representan informes de errores de software. A continuación, consulta los datos utilizando los índices secundarios globales. Por último, el programa elimina la tabla Issues.

Para obtener instrucciones paso a paso para probar el siguiente ejemplo, consulte Ejemplos de código Java.

ejemplo

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);
    }

}