java - 如何在 java 中制定 curl -XHEAD 请求

Question

我正在使用 elasticsearch Java API 并尝试进行 curl 调用以查明我的索引中是否存在文档。 This是如何在命令行中完成的。据我从这里的帖子可以看出，我应该使用 HttpURLConnection java 类或 apache httpclient 在 java 中发送 curl 请求。我的请求应该是这样的:

curl -i -XHEAD http://localhost:9200/indexName/mappingName/docID。

关于如何通过 java 发送 curl 请求实际上有很多问题，但答案并没有那么解释 - 因此我不确定如何为 curl head 请求配置请求参数。到目前为止，我已经转载了this来自 Ashay 的回答，但它不起作用。

有没有人在 elasticsearch 的 java API 中发送 curl 调用并且可以解释如何做？

这是我的代码，我得到的错误是“java.net.MalformedURLException:无协议(protocol)”

import org.apache.commons.codec.binary.Base64;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

String encodedURL = URLEncoder.encode(new StringBuilder()
    .append("http://").append(serverName).append(":9200/") // elasticsearch port
    .append(indexName).append("/").append(mappingName).append("/")
    .append(url).toString(), "UTF-8"); // docID is a url
System.out.print("encodedURL : " + encodedURL + "\n");

URL url = new URL(new StringBuilder().append(encodedURL).toString());
System.out.print("url "+ url.toString() + "\n");

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("X-Requested-With", "Curl");
connection.setRequestMethod("HEAD");

String userpass = new StringBuilder().append(username).append(":").append(password).toString();
String basicAuth = new StringBuilder().append("Basic ").append(new String(new Base64().encode(userpass.getBytes()))).toString();
connection.setRequestProperty("Authorization", basicAuth);
String inputLine;
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));

附言该索引的文档 ID 是 URL，这就是为什么我需要对它们进行编码。另一方面，我不确定是否应该对完整的 http 请求进行编码。

Answer 1

以下片段可以作为起点。

String serverName = "localhost";
String indexName = "index_name";
String mappingName = "mapping_name";
String docId = "FooBarId";

String username = "JohnDoe";
String password = "secret";

String requestURL = String.format("http://%s:9200/%s/%s/%s",
        serverName,
        indexName,
        mappingName,
        docId
);
System.out.println("requestURL: " + requestURL);

URL url = new URL(requestURL);
System.out.println("URL: " + url);

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("X-Requested-With", "Curl");
connection.setRequestMethod("HEAD");

String credentials = username + ":" + password;

Base64.Encoder encoder = Base64.getEncoder();
String basicAuth = "Basic " + encoder.encodeToString(credentials.getBytes());

connection.setRequestProperty("Authorization", basicAuth);

connection.getHeaderFields()
        .entrySet()
        .forEach((Entry<String, List<String>> t) -> {
            System.out.printf("%-20s : %s%n", t.getKey(), t.getValue());
        });

在默认的 elasticsearch 安装中使用 requestURL = "http://localhost:9200"; 会返回

requestURL: http://localhost:9200
URL: http://localhost:9200
null                 : [HTTP/1.1 200 OK]
Content-Length       : [0]
Content-Type         : [text/plain; charset=UTF-8]

添加 也许您可以尝试类似于以下步骤的操作。根据您的需要修改它们。也许您可以跳过第一步。

索引一些东西

curl -XPUT "http://localhost:9200/books/book/1" -d'
{
    "title": "The Hitchhikers Guide to the Galaxy",
    "author": "Douglas Adams",
    "year": 1978
}'

从命令行查询

curl -X GET http://localhost:9200/books/book/1

输出

{"_index":"books","_type":"book","_id":"1","_version":1,"found":true,"_source":
{
    "title": "The Hitchhikers Guide to the Galaxy",
    "author": "Douglas Adams",
    "year": 1978
}}

使用上面的 Java 片段查询

String serverName = "localhost";
String indexName = "books";
String mappingName = "book";
String docId = "1";
String requestURL = String.format("http://%s:9200/%s/%s/%s",
        serverName,
        indexName,
        mappingName,
        docId
);
System.out.println("requestURL: " + requestURL);
URL url = new URL(requestURL);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.getHeaderFields()
        .entrySet()
        .forEach((Entry<String, List<String>> t) -> {
            System.out.printf("%-20s : %s%n", t.getKey(), t.getValue());
        });
try (InputStream inputStream = connection.getInputStream()) {
    for (int i = inputStream.read(); i > -1; i = inputStream.read()) {
        System.out.print((char) i);
    }
}

输出

requestURL: http://localhost:9200/books/book/1
null                 : [HTTP/1.1 200 OK]
Content-Length       : [184]
Content-Type         : [application/json; charset=UTF-8]
{"_index":"books","_type":"book","_id":"1","_version":1,"found":true,"_source":
{
    "title": "The Hitchhikers Guide to the Galaxy",
    "author": "Douglas Adams",
    "year": 1978
}}

该示例使用默认的 elasticsearch 安装。

取决于您真正想要实现的目标。您最好使用 elasticsearch TransportClient。

import java.net.InetAddress;
import org.elasticsearch.action.get.GetRequestBuilder;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.client.Client;
import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.transport.InetSocketTransportAddress;

public class GetDemo {

    public static void main(String[] args) throws Exception {
        InetAddress hostAddr = InetAddress.getByName("localhost");
        InetSocketTransportAddress socketAddr =
                new InetSocketTransportAddress(hostAddr, 9300);
        try (Client client = TransportClient.builder().build()
                .addTransportAddress(socketAddr)) {
            GetRequestBuilder request = client.prepareGet("books", "book", "1");
            GetResponse response = request.execute().actionGet();
            response.getSource()
                    .forEach((k, v) -> System.out.printf("%-6s: %s%n", k, v));
        }
    }
}

输出

...
year  : 1978
author: Douglas Adams
title : The Hitchhikers Guide to the Galaxy