Contoh: Operasi CRUD menggunakan AWS SDK for Java document API

Contoh kode berikut menunjukkan operasi CRUD pada item Amazon DynamoDB. Contohnya membuat item, mengambilnya, melakukan berbagai pembaruan, dan akhirnya menghapus item tersebut.

catatan

SDK untuk Java juga menyediakan model persistensi objek, memungkinkan Anda memetakan kelas sisi klien ke tabel DynamoDB. Pendekatan ini dapat mengurangi jumlah kode yang harus Anda tulis. Untuk informasi selengkapnya, lihat Java 1.x: DynamoDBMapper.

catatan

Contoh kode ini mengasumsikan bahwa Anda telah memuat data ke DynamoDB untuk akun Anda dengan mengikuti petunjuk di bagian Membuat tabel dan memuat data untuk contoh kode di DynamoDB.

Untuk step-by-step instruksi untuk menjalankan contoh berikut, lihatContoh kode Java.

package com.amazonaws.codesamples.document;

import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.document.DeleteItemOutcome;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.document.UpdateItemOutcome;
import com.amazonaws.services.dynamodbv2.document.spec.DeleteItemSpec;
import com.amazonaws.services.dynamodbv2.document.spec.UpdateItemSpec;
import com.amazonaws.services.dynamodbv2.document.utils.NameMap;
import com.amazonaws.services.dynamodbv2.document.utils.ValueMap;
import com.amazonaws.services.dynamodbv2.model.ReturnValue;

public class DocumentAPIItemCRUDExample {

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

    static String tableName = "ProductCatalog";

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

        createItems();

        retrieveItem();

        // Perform various updates.
        updateMultipleAttributes();
        updateAddNewAttribute();
        updateExistingAttributeConditionally();

        // Delete the item.
        deleteItem();

    }

    private static void createItems() {

        Table table = dynamoDB.getTable(tableName);
        try {

            Item item = new Item().withPrimaryKey("Id", 120).withString("Title", "Book 120 Title")
                    .withString("ISBN", "120-1111111111")
                    .withStringSet("Authors", new HashSet<String>(Arrays.asList("Author12", "Author22")))
                    .withNumber("Price", 20).withString("Dimensions", "8.5x11.0x.75").withNumber("PageCount", 500)
                    .withBoolean("InPublication", false).withString("ProductCategory", "Book");
            table.putItem(item);

            item = new Item().withPrimaryKey("Id", 121).withString("Title", "Book 121 Title")
                    .withString("ISBN", "121-1111111111")
                    .withStringSet("Authors", new HashSet<String>(Arrays.asList("Author21", "Author 22")))
                    .withNumber("Price", 20).withString("Dimensions", "8.5x11.0x.75").withNumber("PageCount", 500)
                    .withBoolean("InPublication", true).withString("ProductCategory", "Book");
            table.putItem(item);

        } catch (Exception e) {
            System.err.println("Create items failed.");
            System.err.println(e.getMessage());

        }
    }

    private static void retrieveItem() {
        Table table = dynamoDB.getTable(tableName);

        try {

            Item item = table.getItem("Id", 120, "Id, ISBN, Title, Authors", null);

            System.out.println("Printing item after retrieving it....");
            System.out.println(item.toJSONPretty());

        } catch (Exception e) {
            System.err.println("GetItem failed.");
            System.err.println(e.getMessage());
        }

    }

    private static void updateAddNewAttribute() {
        Table table = dynamoDB.getTable(tableName);

        try {

            UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("Id", 121)
                    .withUpdateExpression("set #na = :val1").withNameMap(new NameMap().with("#na", "NewAttribute"))
                    .withValueMap(new ValueMap().withString(":val1", "Some value"))
                    .withReturnValues(ReturnValue.ALL_NEW);

            UpdateItemOutcome outcome = table.updateItem(updateItemSpec);

            // Check the response.
            System.out.println("Printing item after adding new attribute...");
            System.out.println(outcome.getItem().toJSONPretty());

        } catch (Exception e) {
            System.err.println("Failed to add new attribute in " + tableName);
            System.err.println(e.getMessage());
        }
    }

    private static void updateMultipleAttributes() {

        Table table = dynamoDB.getTable(tableName);

        try {

            UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("Id", 120)
                    .withUpdateExpression("add #a :val1 set #na=:val2")
                    .withNameMap(new NameMap().with("#a", "Authors").with("#na", "NewAttribute"))
                    .withValueMap(
                            new ValueMap().withStringSet(":val1", "Author YY", "Author ZZ").withString(":val2",
                                    "someValue"))
                    .withReturnValues(ReturnValue.ALL_NEW);

            UpdateItemOutcome outcome = table.updateItem(updateItemSpec);

            // Check the response.
            System.out.println("Printing item after multiple attribute update...");
            System.out.println(outcome.getItem().toJSONPretty());

        } catch (Exception e) {
            System.err.println("Failed to update multiple attributes in " + tableName);
            System.err.println(e.getMessage());

        }
    }

    private static void updateExistingAttributeConditionally() {

        Table table = dynamoDB.getTable(tableName);

        try {

            // Specify the desired price (25.00) and also the condition (price =
            // 20.00)

            UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("Id", 120)
                    .withReturnValues(ReturnValue.ALL_NEW).withUpdateExpression("set #p = :val1")
                    .withConditionExpression("#p = :val2").withNameMap(new NameMap().with("#p", "Price"))
                    .withValueMap(new ValueMap().withNumber(":val1", 25).withNumber(":val2", 20));

            UpdateItemOutcome outcome = table.updateItem(updateItemSpec);

            // Check the response.
            System.out.println("Printing item after conditional update to new attribute...");
            System.out.println(outcome.getItem().toJSONPretty());

        } catch (Exception e) {
            System.err.println("Error updating item in " + tableName);
            System.err.println(e.getMessage());
        }
    }

    private static void deleteItem() {

        Table table = dynamoDB.getTable(tableName);

        try {

            DeleteItemSpec deleteItemSpec = new DeleteItemSpec().withPrimaryKey("Id", 120)
                    .withConditionExpression("#ip = :val").withNameMap(new NameMap().with("#ip", "InPublication"))
                    .withValueMap(new ValueMap().withBoolean(":val", false)).withReturnValues(ReturnValue.ALL_OLD);

            DeleteItemOutcome outcome = table.deleteItem(deleteItemSpec);

            // Check the response.
            System.out.println("Printing item that was deleted...");
            System.out.println(outcome.getItem().toJSONPretty());

        } catch (Exception e) {
            System.err.println("Error deleting item in " + tableName);
            System.err.println(e.getMessage());
        }
    }
}