Prompt Title: Export Elasticsearch Data: Spring Batch

To export data from Elasticsearch alias using SQL query and store it into a CSV file using Spring Batch, we can follow these steps: 1. Configure Elasticsearch client and SQL plugin dependencies in the Spring Batch project. 2. Define the SQL query to retrieve data from Elasticsearch alias. 3. Create a Spring Batch job with a single step that reads data from Elasticsearch using the SQL query, processes it and writes it to a CSV file. 4. Configure the job with appropriate parameters such as chunk size, thread pool size, and batch size to optimize the performance. Here's a sample code to illustrate this approach: 1. Dependencies ```xml <dependency> <groupId>org.springframework.data</groupId> <artifactId>spring-data-elasticsearch</artifactId> <version>${spring-data-elasticsearch.version}</version> </dependency> <dependency> <groupId>org.xbib</groupId> <artifactId>elasticsearch-sql</artifactId> <version>${elasticsearch-sql.version}</version> </dependency> ``` 2. SQL Query ```sql SELECT * FROM index_alias WHERE field1 = 'value1' ``` 3. Spring Batch Job ```java @Bean public Job exportDataJob() { return jobBuilderFactory.get("exportDataJob") .start(exportDataStep()) .build(); } @Bean public Step exportDataStep() { return stepBuilderFactory.get("exportDataStep") .<Map<String, Object>, Map<String, Object>>chunk(10000) .reader(elasticsearchItemReader()) .processor(dataProcessor()) .writer(csvFileItemWriter()) .taskExecutor(taskExecutor()) .throttleLimit(20) .build(); } @Bean public ElasticsearchItemReader<Map<String, Object>> elasticsearchItemReader() { ElasticsearchItemReader<Map<String, Object>> reader = new ElasticsearchItemReader<>(); reader.setQuery(sqlQuery()); reader.setClient(elasticsearchClient()); reader.setPageSize(1000); return reader; } @Bean public ItemProcessor<Map<String, Object>, Map<String, Object>> dataProcessor() { return item -> item; // No processing needed } @Bean public FlatFileItemWriter<Map<String, Object>> csvFileItemWriter() { FlatFileItemWriter<Map<String, Object>> writer = new FlatFileItemWriter<>(); writer.setResource(new FileSystemResource("data.csv")); writer.setLineAggregator(new MapToCsvLineAggregator()); return writer; } @Bean public TaskExecutor taskExecutor() { ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor(); taskExecutor.setCorePoolSize(10); taskExecutor.setMaxPoolSize(20); taskExecutor.setQueueCapacity(100); return taskExecutor; } @Bean public SQLQuery sqlQuery() { return new SQLQuery("SELECT * FROM index_alias WHERE field1 = 'value1'"); } @Bean public Client elasticsearchClient() { Settings settings = Settings.builder() .put("cluster.name", "elasticsearch") .build(); TransportClient client = new PreBuiltTransportClient(settings); client.addTransportAddress(new TransportAddress(InetAddress.getByName("localhost"), 9300)); return client; } ``` 4. MapToCsvLineAggregator ```java public class MapToCsvLineAggregator implements LineAggregator<Map<String, Object>> { private static final String CSV_SEPARATOR = ","; @Override public String aggregate(Map<String, Object> map) { StringBuilder sb = new StringBuilder(); for (Object value : map.values()) { if (sb.length() > 0) { sb.append(CSV_SEPARATOR); } sb.append(escapeCsvValue(value));