CODEWITHSUNDEEP
javaspringamazon-web-servicesspring-bootamazon-dynamodb
Clancinio
Clancinio

Reputation: 942

Querying a table in DynamoDB table that contains a specific String

So, I have this scanExpression that returns a list of Blogs depending on the query passed in.

When I pass in the query string "Java", for example, it will return the Blog "Starting out with Java".

But, if I pass the query string "Java tutorials", nothing is returned. So basically, I want blogs to be returns that contain the words "Java" or "Tutorial".

  public List<BlogDetailsEntity> searchBlogs(String query) {
    try {
      DynamoDBScanExpression scanExpression = new DynamoDBScanExpression();
      scanExpression.addFilterCondition("title", new Condition()
              .withComparisonOperator(ComparisonOperator.CONTAINS)
              .withAttributeValueList(new AttributeValue().withS(query.toLowerCase())));
      return dynamoDBMapper.scan(BlogDetailsEntity.class, scanExpression);
    } catch (Exception ex) {
      log.error("failed to get blogs > " + query);
    }
    return null;
  }

Upvotes: 2

Views: 2571

Answers (1)

smac2020
smac2020

Reputation: 10704

To query DynamoDB data, you should look at using the AWS SDK for Java V2 API and the Enhanced Client. Your code is the older version 1 and the Amazon SDK team recommends V2.

The AWS SDK for Java 2.x is a major rewrite of the version 1.x code base. It’s built on top of Java 8+ and adds several frequently requested features. These include support for non-blocking I/O and the ability to plug in a different HTTP implementation at run time.

More about the Enhanced Client here:

Map items in DynamoDB tables

Using the Enhanced Client, you can use Expression objects to get a result set that you want. To see different ways to retrieve data by using V2 and the Enhanced Client, see this code example.

https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/javav2/example_code/dynamodb/src/main/java/com/example/dynamodb/EnhancedScanRecordsWithExpression.java

If you are not familiar with the AWS Java V2 API, see this doc topic in the Java V2 Developer Guide:

Get started with the AWS SDK for Java 2.x

Using DynamoDB V2 API, you can perform your use case. Given this table.

enter image description here

I can pull up records where the word issue is in title using this Java code:

AttributeValue attVal = AttributeValue.builder()
        .s("issue")
        .build();

Map<String, AttributeValue> myMap = new HashMap<>();
           myMap.put(":val1", attVal);

Map<String, String> myExMap = new HashMap<>();
        myExMap.put("#title", "title");

Expression expression = Expression.builder()
         .expressionValues(myMap)
         .expressionNames(myExMap)
         .expression("contains(#title, :val1)")
         .build();

   ScanEnhancedRequest enhancedRequest = ScanEnhancedRequest.builder()
         .filterExpression(expression)
         .limit(15)
         .build();

   // Get items in the Issues table.
   Iterator<Issues> results = table.scan(enhancedRequest).items().iterator();
   while (results.hasNext()) {
            Issues issue = results.next();
            System.out.println("The record description is " + issue.getDescription());
            System.out.println("The record title is " + issue.getTitle());
     }

Also - I noticed that you tagged Spring BOOT. To learn how to write a Spring BOOT web app that uses the DynamoDB API V2, see:

Creating the DynamoDB web application item tracker

Upvotes: 4

Related Questions