http如何在java中构造curl XHEAD请求

Question

我正在使用elasticsearch Java API，并试图进行一个curl调用，以确定我的索引中是否存在文档This是在命令行中执行的方式。从这里的帖子中可以看出，我应该使用HttpURLConnection java类或ApacheHttpClient来用java发送curl请求。 我的要求应该是：

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，但答案并不是那么解释性的——因此我不确定如何为curl head请求配置请求参数。到目前为止，我复制了Ashay的this答案，但它不起作用

有没有人在elasticsearch的java API中发送curl调用，并能解释怎么做

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

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()));

另外，这个索引的文档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

以下片段可能是一个起点

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());
        });

使用带有默认elasticsearch安装的requestURL = "http://localhost:9200";将返回

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

添加也许你可以尝试以下类似的步骤。根据你的需要修改它们。也许你可以跳过第一步

索引某物

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

从命令行查询它

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
}}

使用上述Java代码片段进行查询

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

取决于你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