Question

我正在将lightcouch用于我的spring boot应用程序，并且我需要能够基于提供的过滤器在CouchDb数据库中查询文档。由于这些过滤器始终可以不同，因此无法使用预设视图。我正在寻找一种可以像下面正常查找一样工作的东西：

public List<MyEntity> getEntities(MyFilter myFilter)
{
   return dbClient.find(resourceFilter, MyEntity.class);
}

myFilter将是一个Map对象，我将根据该地图中提供的某些值来查询文档。可能吗？有没有实现我想要的方法？谢谢

Answer 1

LightCouch内部API允许用户定义的原始HTTP请求针对数据库执行。这可以通过CouchDbClient#executeRequest方法来完成。

我不在Java项目中使用LightCouch，而是将Apache HTTPClient和GSON一起使用。以下示例假定您的本地计算机上安装了CouchDB，并且用户名和密码均为“ admin”。可以很容易地使用CouchDbClient#executeRequest。

mangoSelector方法中的find参数必须符合CouchDB selector syntax。

public class CouchDBAccess {

    private static final String BASE_URL = "http://localhost:5984/";
    private static final Gson GSON = new GsonBuilder().create();

    private final Header[] httpHeaders;

    public CouchDBAccess() {
        this.httpHeaders = new Header[] { //
                new BasicHeader("Accept", "application/json"), //
                new BasicHeader("Content-type", "application/json"), //
                new BasicHeader("Authorization", "Basic " + Base64.getEncoder().encodeToString("admin:admin".getBytes())) //
        };
    }

    FindResult find(String dbName, String mangoSelector) throws IOException {
        try (CloseableHttpClient client = HttpClientBuilder.create().build()) {
            HttpPost httpPost = new HttpPost(BASE_URL + dbName + "/_find");
            httpPost.setHeaders(httpHeaders);
            httpPost.setEntity(new StringEntity(mangoSelector, ContentType.APPLICATION_JSON));
            HttpResponse response = client.execute(httpPost);
            int statusCode = response.getStatusLine().getStatusCode();
            if (statusCode == HttpStatus.SC_OK) {
                return GSON.fromJson(extractContent(response), FindResult.class);
            } else {
                // handle invalid response
            }
        }
    }

    private String extractContent(HttpResponse response) throws IOException {
        StringWriter writer = new StringWriter();
        IOUtils.copy(response.getEntity().getContent(), writer, defaultCharset());
        return writer.toString();
    }
}

class FindResult {
    MyEntity[] docs;
}

相应的jUnit测试方法如下所示：

@Test
public void testFind() throws IOException {
    String mangoSelector = "{\"selector\": {\"Host\": \"local drive\"}}";
    FindResult findResult = couchDBAccess.find("data_1", mangoSelector);

    assertEquals(100, findResult.docs.length); // or whatever you expect
}

Answer 2

LightCouch提供了使用芒果选择器查询CouchDB的方法。

请参见CouchDbClientBase.java

 /**
 * Find documents using a declarative JSON querying syntax.
 * @param <T> The class type.
 * @param jsonQuery The JSON query string.
 * @param classOfT The class of type T.
 * @return The result of the query as a {@code List<T> }
 * @throws CouchDbException If the query failed to execute or the request is invalid.
 */
public <T> List<T> findDocs(String jsonQuery, Class<T> classOfT) { ...

您可以使用Lightcouch通过过滤器查询文档吗？

2 个答案: