How to log into Minecraft inside of Eclipse

[Sun_Minecraft]

I was trying to log into Minecraft inside of Eclipse so could try some mods out on servers. 
I’ve tried adding

—username username

And —password password

into the program arguments but in the console it shows that the argument password is being ignored and I’m not logged in.

Does anyone know any other way to log into my Minecraft Account inside of Eclipse?

[Luis_ST]

this is no longer possible with a Mojang Account,
irrc you need to use the access token form the Launcher

also why do you want to login in dev environment?
there is no reason to be logged in

Edited March 5, 2022 by Luis_ST

[Sun_Minecraft]

Ok Good to know thanks for the information.

[Koolade446]

On 3/5/2022 at 8:28 AM, Luis_ST said:

this is no longer possible with a Mojang Account,
irrc you need to use the access token form the Launcher

also why do you want to login in dev environment?
there is no reason to be logged in

This isn't true HOWEVER its super complicated to do and you have to change the command every time. 

Below is a code snippet from a custom minecraft launcher I'm working on so there may be some unnecessary steps focus mainly on the HTTP connections, request types, and request bodys/url endpoints. Forewarning this is incredibly complicated and i would advise against it. If you need to test your mod on a server just put it in offline mode.
 

Spoiler

public static void signUserIn() throws Exception {	
        String content;
        JSONObject playerJson = new JSONObject();
        if (AppUtils.accountsStatus == 1) {
            SignInFrame sif = new SignInFrame().showSignIn();
            while (sif.code == null) {
                Thread.sleep(1);
            }

            content = String.format(
                    "client_id=%s" +
                            "&code=%s" +
                            "&grant_type=authorization_code" +
                            "&redirect_uri=%s",
                    "[Redacted]", //You'll need to regester an app with Azure to get this code
                    sif.code,
                    "https://login.live.com/oauth20_desktop.srf"
            );
        } else {
            content = String.format(
                    "client_id=%s" +
                            "&refresh_token=%s" +
                            "&grant_type=refresh_token" +
                            "&redirect_uri=%s",
                    "[Redacted]",
                    AppUtils.accountsInfo.getJSONObject(AppUtils.activeAccount).getString("refresh_token"),
                    "https://login.live.com/oauth20_desktop.srf"
            );
        }

        CloseableHttpClient client = HttpClients.createDefault();

        HttpPost msaLogin = new HttpPost("https://login.live.com/oauth20_token.srf");
        msaLogin.setEntity(new StringEntity(content, ContentType.APPLICATION_FORM_URLENCODED));

        CloseableHttpResponse msaResponse = client.execute(msaLogin);
        JSONObject msaResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(msaResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        content = String.format(
                "{" +
                        "\"Properties\": {" +
                        "\"AuthMethod\": \"RPS\"," +
                        "\"SiteName\": \"user.auth.xboxlive.com\"," +
                        "\"RpsTicket\": \"d=%s\"" +
                        "}," +
                        "\"RelyingParty\": \"http://auth.xboxlive.com\"," +
                        "\"TokenType\": \"JWT\"" +
                        "}",
                msaResponseJSON.getString("access_token")
        );

        HttpPost xblLogin = new HttpPost("https://user.auth.xboxlive.com/user/authenticate");
        xblLogin.setEntity(new StringEntity(content, ContentType.APPLICATION_JSON));
        xblLogin.setHeader(HttpHeaders.ACCEPT, "application/json");

        CloseableHttpResponse xblResponse = client.execute(xblLogin);
        JSONObject xblResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(xblResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        content = String.format(
                "{\n" +
                        "\"Properties\": {" +
                        "\"SandboxId\": \"RETAIL\"," +
                        "\"UserTokens\": [" +
                        "\"%s\"" +
                        "]" +
                        "}," +
                        "\"RelyingParty\": \"rp://api.minecraftservices.com/\"," +
                        "\"TokenType\": \"JWT\"" +
                        "}",
                xblResponseJSON.getString("Token")
        );

        HttpPost xstsPost = new HttpPost("https://xsts.auth.xboxlive.com/xsts/authorize");
        xstsPost.setEntity(new StringEntity(content, ContentType.APPLICATION_JSON));
        xstsPost.setHeader(new BasicHeader(HttpHeaders.ACCEPT, "application/json"));

        CloseableHttpResponse xstsResponse = client.execute(xstsPost);
        JSONObject xstsResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(xstsResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        content = String.format(
                "{" +
                        "\"identityToken\" : \"XBL3.0 x=%s;%s\"," +
                        "\"ensureLegacyEnabled\" : true" +
                        "}",
                xstsResponseJSON.getJSONObject("DisplayClaims").getJSONArray("xui").getJSONObject(0).getString("uhs"),
                xstsResponseJSON.getString("Token")
        );

        HttpPost mctPost = new HttpPost("https://api.minecraftservices.com/authentication/login_with_xbox");
        mctPost.setEntity(new StringEntity(content, ContentType.APPLICATION_JSON));

        CloseableHttpResponse mctResponse = client.execute(mctPost);
        JSONObject mctResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(mctResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        HttpGet mcGet = new HttpGet("https://api.minecraftservices.com/minecraft/profile");
        mcGet.setHeader(new BasicHeader(HttpHeaders.AUTHORIZATION, String.format(
                "Bearer %s",
                mctResponseJSON.getString("access_token")
        )));
        CloseableHttpResponse mcResponse = client.execute(mcGet);
        JSONObject mcResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(mcResponse.getEntity().getContent())).lines().collect(Collectors.joining()));
        System.out.println(mcResponseJSON.toString());

        JSONObject playerInfo = new JSONObject();
        playerInfo.put("refresh_token", msaResponseJSON.getString("refresh_token"));
        playerInfo.put("ms_id", mctResponseJSON.getString("username"));
        for (Object sk : mcResponseJSON.getJSONArray("skins")) {
            JSONObject skj = ((JSONObject) sk);
            if (skj.getString("state").equalsIgnoreCase("active")) {
                playerInfo.put("skin_url", skj.getString("url"));
                break;
            }
        }
        playerInfo.put("user_name", mcResponseJSON.getString("name"));
        AppUtils.accountsInfo.put(mcResponseJSON.getString("id"), playerInfo);
        AppUtils.accountsInfo.put("active_account", mcResponseJSON.getString("id"));
        AppUtils.activeAccount = mcResponseJSON.getString("id");
        AppUtils.accountsStatus = 0;
        AppUtils.updateSkinImage();
    }

    public static void signSecondaryUserIn() throws Exception {
        String content;
        JSONObject playerJson = new JSONObject();
        SignInFrame sif = new SignInFrame().showSignIn();
        while (sif.code == null) {
            Thread.sleep(1);
        }

        content = String.format(
                "client_id=%s" +
                        "&code=%s" +
                        "&grant_type=authorization_code" +
                        "&redirect_uri=%s",
                "60ea6a7c-d173-43bd-97af-8b8ea1108a31",
                sif.code,
                "https://login.live.com/oauth20_desktop.srf"
        );

        CloseableHttpClient client = HttpClients.createDefault();

        HttpPost msaLogin = new HttpPost("https://login.live.com/oauth20_token.srf");
        msaLogin.setEntity(new StringEntity(content, ContentType.APPLICATION_FORM_URLENCODED));

        CloseableHttpResponse msaResponse = client.execute(msaLogin);
        JSONObject msaResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(msaResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        content = String.format(
                "{" +
                        "\"Properties\": {" +
                        "\"AuthMethod\": \"RPS\"," +
                        "\"SiteName\": \"user.auth.xboxlive.com\"," +
                        "\"RpsTicket\": \"d=%s\"" +
                        "}," +
                        "\"RelyingParty\": \"http://auth.xboxlive.com\"," +
                        "\"TokenType\": \"JWT\"" +
                        "}",
                msaResponseJSON.getString("access_token")
        );

        HttpPost xblLogin = new HttpPost("https://user.auth.xboxlive.com/user/authenticate");
        xblLogin.setEntity(new StringEntity(content, ContentType.APPLICATION_JSON));
        xblLogin.setHeader(HttpHeaders.ACCEPT, "application/json");

        CloseableHttpResponse xblResponse = client.execute(xblLogin);
        JSONObject xblResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(xblResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        content = String.format(
                "{\n" +
                        "\"Properties\": {" +
                        "\"SandboxId\": \"RETAIL\"," +
                        "\"UserTokens\": [" +
                        "\"%s\"" +
                        "]" +
                        "}," +
                        "\"RelyingParty\": \"rp://api.minecraftservices.com/\"," +
                        "\"TokenType\": \"JWT\"" +
                        "}",
                xblResponseJSON.getString("Token")
        );

        HttpPost xstsPost = new HttpPost("https://xsts.auth.xboxlive.com/xsts/authorize");
        xstsPost.setEntity(new StringEntity(content, ContentType.APPLICATION_JSON));
        xstsPost.setHeader(new BasicHeader(HttpHeaders.ACCEPT, "application/json"));

        CloseableHttpResponse xstsResponse = client.execute(xstsPost);
        JSONObject xstsResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(xstsResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        content = String.format(
                "{" +
                        "\"identityToken\" : \"XBL3.0 x=%s;%s\"," +
                        "\"ensureLegacyEnabled\" : true" +
                        "}",
                xstsResponseJSON.getJSONObject("DisplayClaims").getJSONArray("xui").getJSONObject(0).getString("uhs"),
                xstsResponseJSON.getString("Token")
        );

        HttpPost mctPost = new HttpPost("https://api.minecraftservices.com/authentication/login_with_xbox");
        mctPost.setEntity(new StringEntity(content, ContentType.APPLICATION_JSON));

        CloseableHttpResponse mctResponse = client.execute(mctPost);
        JSONObject mctResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(mctResponse.getEntity().getContent())).lines().collect(Collectors.joining()));

        HttpGet mcGet = new HttpGet("https://api.minecraftservices.com/minecraft/profile");
        mcGet.setHeader(new BasicHeader(HttpHeaders.AUTHORIZATION, String.format(
                "Bearer %s",
                mctResponseJSON.getString("access_token")
        )));
        CloseableHttpResponse mcResponse = client.execute(mcGet);
        JSONObject mcResponseJSON = new JSONObject(new BufferedReader(new InputStreamReader(mcResponse.getEntity().getContent())).lines().collect(Collectors.joining()));
        System.out.println(mcResponseJSON.toString());

        JSONObject playerInfo = new JSONObject();
        playerInfo.put("refresh_token", msaResponseJSON.getString("refresh_token"));
        playerInfo.put("ms_id", mctResponseJSON.getString("username"));
        for (Object sk : mcResponseJSON.getJSONArray("skins")) {
            JSONObject skj = ((JSONObject) sk);
            if (skj.getString("state").equalsIgnoreCase("active")) {
                playerInfo.put("skin_url", skj.getString("url"));
                break;
            }
        }
        playerInfo.put("user_name", mcResponseJSON.getString("name"));
        AppUtils.accountsInfo.put(mcResponseJSON.getString("id"), playerInfo);
        AppUtils.accountsInfo.put("active_account", mcResponseJSON.getString("id"));
        AppUtils.activeAccount = mcResponseJSON.getString("id");
        AppUtils.accountsStatus = 0;
        AppUtils.updateSkinImage();

Sif is a JavaFX panel with Microsoft website embedded into it:

public class SignInFrame extends JFrame {

    WebEngine we;
    public String code;
    WebView wv;

    public SignInFrame showSignIn() throws Exception {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        this.setSize(450, 500);
        this.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
        this.setLocationRelativeTo(null);
        this.setVisible(true);
        this.setTitle("Sign in to minecraft");
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                super.windowClosing(e);

                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException classNotFoundException) {
                    classNotFoundException.printStackTrace();
                }
                JOptionPane.showMessageDialog(new JFrame(), "You must sign in to continue", "Sign In", JOptionPane.WARNING_MESSAGE);

            }
        });


        String redirectUrl = URLEncoder.encode("https://login.live.com/oauth20_desktop.srf", StandardCharsets.UTF_8);
        URL url = new URL("https://login.live.com/oauth20_authorize.srf?client_id=[Redacted]&response_type=code&redirect_uri=" + redirectUrl + "&scope=XboxLive.signin%20offline_access");

        JFXPanel jfxPanel = new JFXPanel();
        this.add(jfxPanel);
        Platform.runLater(() -> {
            Platform.setImplicitExit(true);
            wv = new WebView();
            we = wv.getEngine();
            we.setJavaScriptEnabled(true);
            Scene sc = new Scene(wv);
            jfxPanel.setScene(sc);
            we.load(url.toString());


            we.locationProperty().addListener((obs, oldLocation, newLocation)->{
                if (newLocation.contains("https://login.live.com/oauth20_desktop.srf")) {
                    code = newLocation.split("code=")[1].split("&")[0];
                    this.dispose();
                }
            });
        });

        return this;
    }
}

Learn more about API authentication here: https://mojang-api-docs.netlify.app/authentication/msa.html

 

[Luis_ST]

there is a easier way to to that, but again there is no reason to be logged in in Dev

Edit: if someone knows how, this is the explanation

Edited March 28, 2022 by Luis_ST