Indexing existing relational database like Oracle using elasticsearch

I have created Spring boot integrated with elasticsearch app. Which is now able to create index for my own record which am entering in postman and also am able to search those record with the help of id.

How can i create index for my Oracle DB's record and i want to search those record with the help of id or any other column values of those records.

Please find my existing code below.

Book.java

@JsonInclude(JsonInclude.Include.NON_EMPTY)
public class Book {

    private String id;
    private String title;

    public String getId() {
        return id;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}

ElasticSearchConfiguration.java

@Configuration
public class ElasticSearchConfiguration extends AbstractFactoryBean<RestHighLevelClient> {

    private static final Logger logger = LoggerFactory.getLogger(ElasticSearchConfiguration.class);
    @Value("${spring.data.elasticsearch.cluster-nodes}")
    private String clusterNodes;
    @Value("${spring.data.elasticsearch.cluster-name}")
    private String clusterName;
    private RestHighLevelClient restHighLevelClient;

    @Override
    public void destroy() {
        try {
            if (restHighLevelClient != null) {
                restHighLevelClient.close();
            }
        } catch (final Exception e) {
            logger.error("Error closing ElasticSearch client: ", e);
        }
    }

    @Override
    public Class<RestHighLevelClient> getObjectType() {
        return RestHighLevelClient.class;
    }

    @Override
    public boolean isSingleton() {
        return false;
    }

    @Override
    public RestHighLevelClient createInstance() {
        return buildClient();
    }

    private RestHighLevelClient buildClient() {
        try {
            restHighLevelClient = new RestHighLevelClient(
                    RestClient.builder(
                            new HttpHost("localhost", 9200, "http"),
                            new HttpHost("localhost", 9201, "http")));
        } catch (Exception e) {
            logger.error(e.getMessage());
        }
        return restHighLevelClient;
    }


}

BookController.java

@RestController
@RequestMapping("/books")
public class BookController {

    private BookDao bookDao;

    public BookController(BookDao bookDao) {
        this.bookDao = bookDao;
    }

    @PostMapping
    public Book insertBook(@RequestBody Book book) throws Exception{
        return bookDao.insertBook(book);
    }

    @GetMapping("/{id}")
    public Map<String, Object> getBookById(@PathVariable String id){
        return bookDao.getBookById(id);
    }

    }
}

BookDao.java

@Repository
public class BookDao {

    private final String INDEX = "bookdata";
    private final String TYPE = "books";

    private RestHighLevelClient restHighLevelClient;

    private ObjectMapper objectMapper;

    public BookDao( ObjectMapper objectMapper, RestHighLevelClient restHighLevelClient) {
        this.objectMapper = objectMapper;
        this.restHighLevelClient = restHighLevelClient;
    }

    public Book insertBook(Book book){
        book.setId(UUID.randomUUID().toString());
        Map<String, Object> dataMap = objectMapper.convertValue(book, Map.class);
        IndexRequest indexRequest = new IndexRequest(INDEX, TYPE, book.getId())
                .source(dataMap);
        try {
            IndexResponse response = restHighLevelClient.index(indexRequest);
        } catch(ElasticsearchException e) {
            e.getDetailedMessage();
        } catch (java.io.IOException ex){
            ex.getLocalizedMessage();
        }
        return book;
    }

    public Map<String, Object> getBookById(String id){
        GetRequest getRequest = new GetRequest(INDEX, TYPE, id);
        GetResponse getResponse = null;
        try {
            getResponse = restHighLevelClient.get(getRequest);
        } catch (java.io.IOException e){
            e.getLocalizedMessage();
        }
        Map<String, Object> sourceAsMap = getResponse.getSourceAsMap();
        return sourceAsMap;
    }

    }

}

Maven depencencies

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <!-- Elasticsearch Dependencies -->

    <dependency>
        <groupId>org.elasticsearch</groupId>
        <artifactId>elasticsearch</artifactId>
        <version>6.1.2</version>
    </dependency>

    <dependency>
        <groupId>org.elasticsearch.client</groupId>
        <artifactId>elasticsearch-rest-high-level-client</artifactId>
        <version>6.1.2</version>
    </dependency>

    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.8.2</version>
    </dependency>

    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.8.2</version>
    </dependency>

    <dependency>
        <groupId>org.elasticsearch.client</groupId>
        <artifactId>elasticsearch-rest-client</artifactId>
        <version>6.1.2</version>
    </dependency>

    <dependency>
        <groupId>org.elasticsearch.client</groupId>
        <artifactId>elasticsearch-rest-client-sniffer</artifactId>
        <version>6.1.2</version>
    </dependency>

</dependencies>

Please find my input and output too :

Am inserting record via Postman in the below format :

Input:

 {
    "title": "Java Always",
}

Output :

{
    "id": "be2e497f-585f-4dff-8d07-fbcee1dc1c80",
    "title": "Java Always",
}