Java の HttpClient の使い方 (Post)

次のページを参考にしました。
Java HTTP通信のサンプル(HttpClient)

Ubuntu 21.04 で確認しました。

Http_post.java

// -----------------------------------------------------------------------
/*
    Http_post.java

                Jul/30/2020
*/
// -----------------------------------------------------------------------
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpStatus;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

// -----------------------------------------------------------------------
class Uri_get {

    static String uri_post_proc(String uri,List<NameValuePair> params)
        {
        String res = "";

        Charset charset = StandardCharsets.UTF_8;

        CloseableHttpClient httpclient = HttpClients.createDefault();

        HttpPost request = new HttpPost(uri);

        System.out.println
            ("requestの実行　「" + request.getRequestLine() + "」");

        CloseableHttpResponse response = null;

        try {
            request.setEntity(new UrlEncodedFormEntity(params));
            response = httpclient.execute(request);

            int status = response.getStatusLine().getStatusCode();
            System.out.println("HTTPステータス:" + status);
            //HTTPステータス:200

            if (status == HttpStatus.SC_OK){

                res = EntityUtils.toString(response.getEntity(),charset);
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                if (httpclient != null) {
                    httpclient.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    return res;
    }
}

// -----------------------------------------------------------------------
public class Http_post
{
    public static void main(String[] args)
    {
    String uri = "https://httpbin.org/post";        
    List<NameValuePair> params = new ArrayList<>();
    params.add(new BasicNameValuePair("user","jiro"));
    params.add(new BasicNameValuePair("password","123456"));

    String res = Uri_get.uri_post_proc(uri,params);
    System.out.println(res);
    }
}

// -----------------------------------------------------------------------

Makefile

LIB=/usr/share/java
HTTPCLIENT_JAR=.:$(LIB)/httpclient-4.5.13.jar:$(LIB)/httpcore-4.4.14.jar
Http_post.class: Http_post.java
    javac -cp $(HTTPCLIENT_JAR) Http_post.java
clean:
    rm -f *.class

実行コマンド

LIB=/usr/share/java
HTTPCLIENT_JAR=.:$LIB/httpclient-4.5.13.jar:$LIB/httpcore-4.4.14.jar:$LIB/commons-logging-1.2.jar
#
java -cp $HTTPCLIENT_JAR Http_post

実行結果

equestの実行　「POST https://httpbin.org/post HTTP/1.1」
HTTPステータス:200
{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "password": "123456", 
    "user": "jiro"
  }, 
  "headers": {
    "Accept-Encoding": "gzip,deflate", 
    "Content-Length": "25", 
    "Content-Type": "application/x-www-form-urlencoded", 
    "Host": "httpbin.org", 
    "User-Agent": "Apache-HttpClient/4.5.13 (Java/11.0.11)", 
    "X-Amzn-Trace-Id": "Root=1-5f227120-343daab017c55220a4835cd0"
  }, 
  "json": null, 
  "origin": "219.126.139.62", 
  "url": "https://httpbin.org/post"
}

同じことを curl で実行すると

$ curl -X POST https://httpbin.org/post -d 'user=jiro&password=123456'
{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "password": "123456", 
    "user": "jiro"
  }, 
  "headers": {
    "Accept": "*/*", 
    "Content-Length": "25", 
    "Content-Type": "application/x-www-form-urlencoded", 
    "Host": "httpbin.org", 
    "User-Agent": "curl/7.68.0", 
    "X-Amzn-Trace-Id": "Root=1-5f227156-cc1deef43116e768265ffeb8"
  }, 
  "json": null, 
  "origin": "219.126.139.62", 
  "url": "https://httpbin.org/post"
}

Get のサンプルはこちらです。
Java の HttpClient の使い方 (Get)