從Apache駱駝路線的分頁API中讀取

Question

如何從分頁的REST API端點或使用Apache Camel DSL一次讀取“ K”項/記錄的JDBC SQL查詢中讀取？ 贊賞是否有一個干凈的例子。

提前致謝。

Answer 1

我已經使用loopDoWhile dsl完成了此操作：

from("direct:start").loopDoWhile(stopLoopPredicate())
                        .to("bean:restAPIProcessor")
                        .to("bean:dataEnricherBean")
                     .end();

stopLoopPredicate（）在這里：

public Predicate stopLoopPredicate() {
        Predicate stopLoop = new Predicate() {
            @Override
            public boolean matches(Exchange exchange) {
                return exchange.getIn().getBody() != null && !exchange.getIn().getBody().toString().equalsIgnoreCase("stopLoop");
            }
        };
        return stopLoop;
    }

restAPIProcessor是在其中進行REST API調用的Processor的實現。

用於處理分頁的邏輯是在restAPIProcessor中實現的，當實際的REST API返回空響應“ stopLoop”時，會將其設置為交換出路由的主體。 效果很好。 這是RestAPIProcessor的代碼：

public class RestAPIProcessor implements Processor {

    @Inject
    private RestTemplate restTemplate;

    private static final int LIMIT = 100;

    private static final String REST_API = "<REST API URL>";

    @Override
    public void process(Exchange exchange) throws Exception {
        Integer offset = (Integer) exchange.getIn().getHeader("offset");
        Integer count = (Integer) exchange.getIn().getHeader("count");

        if (offset == null) offset = 0;
        if (count == null) count = 0;

        String response = "";
        Map<String,Object> body = new LinkedHashMap<>();
        body.put("offset",offset++);
        body.put("limit",LIMIT);
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        HttpEntity<?> entity = new HttpEntity<Object>(body,headers);
        ResponseEntity<String> countResponseEntity = restTemplate.exchange(REST_API, HttpMethod.POST,entity,String.class);
        response = countResponseEntity.getBody();
        count += LIMIT;
        if (response == null || response.isEmpty()) {
            exchange.getIn().setBody("stopLoop");
            exchange.getOut().setHeaders(exchange.getIn().getHeaders());
        } else {
            exchange.getIn().setHeader("count", count);
            exchange.getIn().setHeader("offset", offset);
            exchange.getOut().setHeaders(exchange.getIn().getHeaders());
            exchange.getOut().setBody(response);
        }
    }
}