如何使用Elastic的High Level Rest Client获取所有索引？

Question

我想要一种不错的，快速且简便的方法，使用其Java REST客户端在elasticsearch中获取所有索引。目前，我可以通过抓住他们的较低级别的客户端来做到这一点，如下所示：

public void fetchIndices() throws IOException {
    List<String> indices = null;

    RestClient restClient = client.getLowLevelClient();
    Response response = null;
    try {
        response = restClient.performRequest("GET", "/_cat/indices?v");
    } catch (IOException e) {
        LOGGER.log(Level.WARNING, e.toString(), e);
    }

    InputStream inputStream = null;
    if (response != null) {
        try {
            inputStream = response.getEntity().getContent();
        } catch (IOException e) {
            LOGGER.log(Level.WARNING, e.toString(), e);
        }
    }

    if (inputStream != null) {
        InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

        indices = new ArrayList<>();
        String line;
        while ((line = bufferedReader.readLine()) != null) {
            // Get tokens with no whitespace
            String[] tokens = line.split("\\s+");
            for (String token : tokens) {
                // TODO - make the startsWith() token configurable
                if (token.startsWith(SOME_TOKEN)) {
                    LOGGER.log(Level.INFO, "Found elasticsearch index " + token);
                    indices.add(token);
                    break;
                }
            }
        }
    }

    // Only update if we got data back from our REST call
    if (indices != null) {
        this.indices = indices;
    }
}

本质上，我只是按照他们的文档中的建议将其称为/_cat/indices?v端点。这可以正常工作，但是我想知道是否有使用Java API的更好的方法。我似乎无法在他们当前的API中找到方法，但想知道是否有人知道我不知道的东西。必须使用s和各个s并不一定很糟糕，而只是想清理hacky字符串解析。InputStreamReader

Answer 1

从Elasticsearch 6.4.0开始，您可以使用以下方法检索所有索引：

    GetIndexRequest request = new GetIndexRequest().indices("*");
    GetIndexResponse response = client.indices().get(request, RequestOptions.DEFAULT);
    String[] indices = response.getIndices();

Answer 2

目前，高级REST客户端不支持此功能。您可以继续_cat/indices使用低级客户端调用API，但尝试添加&format=json查询字符串参数。这样，您将获得相同的信息，但格式为JSON，这使得解析起来容易得多（例如，使用Jackson库）：

List<String> indices = null;

RestClient restClient = client.getLowLevelClient();
Response response = null;
try {
    response = restClient.performRequest("GET", "/_cat/indices?v&format=json");
} catch (IOException e) {
    LOGGER.log(Level.WARNING, e.toString(), e);
}

// parse the JSON response
List<Map<String, String>> list = null;
if (response != null) {
    String rawBody = EntityUtils.toString(response.getEntity());
    TypeReference<List<HashMap<String, String>>> typeRef = new TypeReference<List<HashMap<String, String>>>() {};
    list = mapper.readValue(rawBody, typeRef);
}

// get the index names
if (list != null) {
    indices = list.stream()
        .map(x -> x.get("index"))
        .collect(Collectors.toList());
}

// Only update if we got data back from our REST call
if (indices != null) {
    this.indices = indices;
}

注意：这是高级REST客户端的路线图：https : //github.com/elastic/elasticsearch/issues/27205