How to provide a dynamic index name in Spring Data Elasticsearch using SpEL

In Spring Data Elasticsearch – at the time of writing, version 4.0 is the current version – the name of an index is normally defined by the @Document annotation on the entity class. For the following examples let’s assume we want to write some log entries to Elasticsearch with our application. We use the following entity:

@Document(indexName = "log")
public class LogEntity {
    @Id
    private String id = UUID.randomUUID().toString();

    @Field(type = FieldType.Text)
    private String text;

    @Field(name = "log-time", type = FieldType.Date, format = DateFormat.basic_date_time)
    private ZonedDateTime logTime = ZonedDateTime.now();

    public String getId() {
        return id;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public ZonedDateTime getLogTime() {
        return logTime;
    }

    public void setLogTime(ZonedDateTime logTime) {
        this.logTime = logTime;
    }
}

Here the index name is the fixed name log.

it is possible to use a dynamically defined name for an index by using Spring Expression Language SpEL. Important: We need to use a SpEL template expression, that is an expression enclosed in #{}. This allows for the following setups:

Use a value from the application configuration

Let’s assume we have the following entry in the application.properties file:

index.prefix=test

We then use this code

@Document(indexName = "#{@environment.getProperty('index.prefix')}-log")

and the index name to use changes to test-log.

Use a value provided by a static method of some class

The second example shows how to call a static function to get a dynamic value. We use the following definition to add the current date to the index name:

@Document(indexName = "log-#{T(java.time.LocalDate).now().toString()}")

Currently this would provide an index name of log-2020-07-28.

Use a value provided by a Spring bean

For the third case we provide a bean that will give us a dynamically created string to be used as part of the index name.

@Component
public class LogIndexNameProvider {

    public String timeSuffix() {
        return LocalTime.now().truncatedTo(ChronoUnit.MINUTES).toString().replace(':', '-');
    }
}

This bean, named logIndexNameProvider, can return a String that contains the current time as hh-mm (I would not use this for naming indices, but this is just an example).

Changing the definition to

@Document(indexName = "log-#{@logIndexNameProvider.timeSuffix()}")

will now create index names like log-08-25 or log-22-07.

Of course we can mix all of these together: add a prefix from the configuration, append the current date.

Important notice:

The evaluation of SpEL for index names is only done for the index names defined in the @Document annotation. It is not done for index names that are passed as a IndexCoordinates parameter in the different methods of the ElasticsearchOperations or IndexOperations interfaces. If it were allowed on these, it would be easy to set up a scenario, where an expression is read from some outside source. And then someone might send something like "log-#{T(java.lang.Runtime).getRuntime().exec(new String[]{'/bin/rm', '/tmp/somefile'})}" which will not provide an index name, but delete files on your computer.

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