Reputation: 2149

How to use cURL in Java?

I want to use curl in java. Is curl built-in with Java or I have to install it from any 3rd party source to use with Java? If it needs to be separately installed, how can that be done?

Upvotes: 112

Answers (7)

Stevko

Reputation: 4505

Using standard Java libs, I suggest looking at the HttpUrlConnection class http://java.sun.com/javase/6/docs/api/java/net/HttpURLConnection.html

It can handle most of what CURL can do with setting up the connection. What you do with the stream is up to you.

Upvotes: 3

david

Reputation: 518

You can use Runtime to call Curl as @ariane26 said in his response or use java libraries such as HttpClient, HttpURLConnection, jsoup or OkHttp

HttpClient:

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

HttpClient client = HttpClient.newHttpClient();

HttpRequest request = HttpRequest.newBuilder()
    .uri(URI.create("http://example.com"))
    .GET()
    .build();

HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

HttpURLConnection:

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Scanner;

class Main {

    public static void main(String[] args) throws IOException {
        URL url = new URL("http://example.com");
        HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setRequestMethod("GET");

        InputStream responseStream = httpConn.getResponseCode() / 100 == 2
                ? httpConn.getInputStream()
                : httpConn.getErrorStream();
        Scanner s = new Scanner(responseStream).useDelimiter("\\A");
        String response = s.hasNext() ? s.next() : "";
        System.out.println(response);
    }
}

jsoup:

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import org.jsoup.Connection;
import org.jsoup.Jsoup;


class Main {

    public static void main(String[] args) throws IOException {
        Connection.Response response = Jsoup.connect("http://example.com")
            .method(org.jsoup.Connection.Method.GET)
            .ignoreContentType(true)
            .execute();

        System.out.println(response.parse());
    }
}

Okhttp:

import java.io.IOException;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

OkHttpClient client = new OkHttpClient();

Request request = new Request.Builder()
    .url("http://example.com")
    .build();

try (Response response = client.newCall(request).execute()) {
    if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
    response.body().string();
}

Upvotes: 1

ariane26

Reputation: 183

Use Runtime to call Curl. This code works for both Ubuntu and Windows.

String[] commands = new String[] {"curl", "-X", "GET", "http://checkip.amazonaws.com"};
Process process = Runtime.getRuntime().exec(commands);
BufferedReader reader = new BufferedReader(new 
InputStreamReader(process.getInputStream()));
String line;
String response;
while ((line = reader.readLine()) != null) {
    response.append(line);
}

Upvotes: 2

BalusC

Reputation: 1109502

You can make use of java.net.URL and/or java.net.URLConnection.

URL url = new URL("https://stackoverflow.com");

try (BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream(), "UTF-8"))) {
    for (String line; (line = reader.readLine()) != null;) {
        System.out.println(line);
    }
}

Also see the Oracle's simple tutorial on the subject. It's however a bit verbose. To end up with less verbose code, you may want to consider Apache HttpClient instead.

By the way: if your next question is "How to process HTML result?", then the answer is "Use a HTML parser. No, don't use regex for this.".

How to use cURL in Java?

Answers (7)

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