Example usage for com.amazonaws.services.dynamodbv2.model PutItemRequest setConditionExpression

Introduction

In this page you can find the example usage for com.amazonaws.services.dynamodbv2.model PutItemRequest setConditionExpression.

Prototype

public void setConditionExpression(String conditionExpression) 

Source Link

Document

A condition that must be satisfied in order for a conditional PutItem operation to succeed.

Usage

From source file:com.vitembp.embedded.configuration.CloudConfigSync.java

License:Open Source License

/**
 * Registers the device's ID to the database.
 * @throws IOException //from  w  w w  .  j  ava2s .  c om
 */
private static void registerDevice() throws IOException {
    // get configuration string
    String config;
    try {
        config = SystemConfig.getConfig().writeToString();
    } catch (XMLStreamException ex) {
        throw new IOException("Could not generate configuration string.", ex);
    }

    // add holds data to store in table.
    Map<String, AttributeValue> itemToSet = new HashMap<>();
    PutItemRequest pir = new PutItemRequest();
    pir.setConditionExpression("attribute_not_exists(ID)");
    // add the system ID
    itemToSet.put("ID", new AttributeValue(SystemConfig.getConfig().getSystemUUID().toString()));
    itemToSet.put("CONFIG", new AttributeValue(config));
    itemToSet.put("UPDATED", new AttributeValue(Boolean.toString(false)));
    pir.setTableName("DEVICES");
    pir.setItem(itemToSet);

    try {
        CloudConfigSync.client.putItem(pir);
        CloudConfigSync.deviceRegistered = true;
        LOGGER.info("Device successfully registered.");
    } catch (ConditionalCheckFailedException e) {
        CloudConfigSync.deviceRegistered = true;
        LOGGER.debug("Device already registered.");
    } catch (ResourceNotFoundException e) {
        LOGGER.error("The database does not contain the device index table.", e);
    } catch (AmazonServiceException e) {
        LOGGER.error("Exception occurred writing to database.", e);
    }
}

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