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ddb-write-read-example-01

Description​

This example's purpose is to support the LocalStack on using the platform with Java AWS applications.

Prerequisites​

Run LocalStack​

Create table​

awslocal dynamodb create-table \
    --table-name person \
    --attribute-definitions AttributeName=id,AttributeType=S \
    --key-schema AttributeName=id,KeyType=HASH \
    --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

Project Structure​

.
├── pom.xml
├── README.md
└── src
    └── main
        ├── java
        │   └── v2
        │       └── dynamodb
        │           ├── DynamoDBService.java
        │           ├── PersonBirthdateConverter.java
        │           └── Person.java
        └── resources

pom.xml​

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>cloud.localstack</groupId>
  <artifactId>ddb-write-read-example-01</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
    <exec.cleanupDaemonThreads>false</exec.cleanupDaemonThreads>
  </properties>

  <dependencies>
    <dependency>
      <groupId>software.amazon.awssdk</groupId>
      <artifactId>dynamodb-enhanced</artifactId>
    </dependency>
    <dependency>
      <groupId>software.amazon.awssdk</groupId>
      <artifactId>dynamodb</artifactId>
    </dependency>
  </dependencies>

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>software.amazon.awssdk</groupId>
        <artifactId>bom</artifactId>
        <version>2.20.47</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>
</project>

Person.java​

package v2.dynamodb;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbBean;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbConvertedBy;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbPartitionKey;

@DynamoDbBean
public class Person {

  private String id;
  private String name;
  private Date birthdate;

  @DynamoDbPartitionKey
  public String getId() {
    return id;
  }

  public void setId(String id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  @DynamoDbConvertedBy(PersonBirthdateConverter.class)
  public Date getBirthdate() {
    return birthdate;
  }

  public void setBirthdate(Date birthdate) {
    this.birthdate = birthdate;
  }

  public String getBirthdateAsString() {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    return sdf.format(birthdate);
  }

  public void setBirthdateFromString(String birthdateStr) throws ParseException {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    this.birthdate = sdf.parse(birthdateStr);
  }

  @Override
  public String toString() {
    return "Person{" +
        "id='" + id + '\'' +
        ", name='" + name + '\'' +
        ", birthdate=" + birthdate +
        '}';
  }
}

DynamoDBService.java​

package v2.dynamodb;

import java.net.URI;
import java.text.ParseException;
import software.amazon.awssdk.auth.credentials.AwsBasicCredentials;
import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider;
import software.amazon.awssdk.auth.credentials.StaticCredentialsProvider;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbTable;
import software.amazon.awssdk.enhanced.dynamodb.Key;
import software.amazon.awssdk.enhanced.dynamodb.TableSchema;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;

public class DynamoDBService {

  // credentials that can be replaced with real AWS values
  private static final String ACCESS_KEY = "test";
  private static final String SECRET_KEY = "test";
  private static String TABLE_NAME = "person";
  private static AwsCredentialsProvider credentials = StaticCredentialsProvider.create(
      AwsBasicCredentials.create(ACCESS_KEY, SECRET_KEY));

  // create the dynamoDB client using the credentials and specific region
  private static Region region = Region.US_EAST_1;

  // create a dynamoDB client
  private static DynamoDbClient dynamoDbClient = DynamoDbClient.builder()
      .region(region)
      .credentialsProvider(
          credentials)
      .endpointOverride(URI.create("https://localhost.localstack.cloud:4566"))
      .build();

  public static void main(String[] args) throws ParseException {
    String personId1 = "100012356";

    addEntryToDynamoDB(personId1);

    readEntryFromDynamoDB(personId1);
  }

  private static void readEntryFromDynamoDB(String personId) {
    try {

      DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
          .dynamoDbClient(dynamoDbClient)
          .build();
      DynamoDbTable<Person> table = enhancedClient.table(TABLE_NAME,
          TableSchema.fromBean(Person.class));

      Person person = table.getItem(Key.builder().partitionValue(personId).build());

      // do something with the person object
      if (person != null) {
        System.out.println("Retrieved Person: " + person);
      } else {
        System.out.println("Person with ID " + personId + " not found.");
      }
    } catch (DynamoDbException exception) {
      System.out.println("Something happened: " + exception.getMessage());
    }
  }

  private static void addEntryToDynamoDB(String personID) throws ParseException {
    try {
      DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
          .dynamoDbClient(dynamoDbClient)
          .build();

      // create the Person object
      Person person = new Person();
      person.setId(personID);
      person.setName("John Doe");
      person.setBirthdateFromString("1979-01-01");

      // use the enhanced client to interact with the table
      DynamoDbTable<Person> table = enhancedClient.table(TABLE_NAME,
          TableSchema.fromBean(Person.class));
      table.putItem(person);

      System.out.println("Entry added successfully!");
    } catch (DynamoDbException exception) {
      System.out.println("An error occurred: " + exception.getMessage());
    }
  }
}

Running and Testing​

mvn clean package
mvn exec:java -Dexec.mainClass="v2.dynamodb.DynamoDBService"

Output:​

Entry added successfully!
Retrieved Person: Person{id='100012356', name='John Doe', birthdate=Mon Jan 01 00:00:00 CET 1979}
awslocal dynamodb get-item --consistent-read \
    --table-name person \
    --key '{ "id": {"S": "100012356"}}'

Output:​

{
    "Item": {
        "name": {
            "S": "John Doe"
        },
        "birthdate": {
            "S": "1979-01-01"
        },
        "id": {
            "S": "100012356"
        }
    }
}
awslocal dynamodb execute-statement --statement "SELECT * FROM person"

Output:​

{
    "Items": [
        {
            "name": {
                "S": "John Doe"
            },
            "birthdate": {
                "S": "1979-01-01"
            },
            "id": {
                "S": "100012356"
            }
        }
    ]
}

Source Code​

https://github.com/ZbCiok/zjc-examples/tree/main/aws/aws/dynamodb/ddb-write-read-example-01