kinit -kt /etc/keytabs/keytab kafka/tos_demo@DEMO.TDH 转换为java代码

The `kinit` command is typically used to obtain and cache a Kerberos ticket-granting ticket (TGT) for a user or service principal. The `-kt` option specifies the path to the keytab file containing the service principal's key, and the principal name `kafka/tos_demo@DEMO.TDH` specifies the service principal to use for authentication.

Here is an example Java code snippet that shows how to use the `javax.security.auth.Subject` and `javax.security.auth.login.LoginContext` classes to obtain a Kerberos TGT using a keytab file:

import javax.security.auth.Subject;
import javax.security.auth.login.LoginContext;
import javax.security.auth.login.LoginException;
import java.io.File;

public class KerberosAuthenticator {

    public static void main(String[] args) {
        String keytabPath = "/etc/keytabs/keytab";
        String principalName = "kafka/tos_demo@DEMO.TDH";

        // Set up the Kerberos login configuration
        System.setProperty("java.security.auth.login.config", "/etc/krb5.conf");

        // Create a new subject to hold the Kerberos credentials
        Subject subject = new Subject();

        // Create a new login context using the keytab and principal
        try {
            LoginContext loginContext = new LoginContext("KafkaClient", subject, null,
                    new KeytabPrincipalAuthenticationModule(keytabPath, principalName));
            loginContext.login();
        } catch (LoginException e) {
            System.err.println("Failed to login: " + e.getMessage());
            return;
        }

        // Print out the Kerberos ticket details
        System.out.println("Kerberos ticket granted to:");
        subject.getPrincipals().forEach(System.out::println);
    }

    private static class KeytabPrincipalAuthenticationModule implements javax.security.auth.spi.LoginModule {
        private final String keytabPath;
        private final String principalName;
        private boolean succeeded = false;

        public KeytabPrincipalAuthenticationModule(String keytabPath, String principalName) {
            this.keytabPath = keytabPath;
            this.principalName = principalName;
        }

        @Override
        public void initialize(Subject subject, CallbackHandler callbackHandler,
                               java.util.Map<String, ?> sharedState, java.util.Map<String, ?> options) {
        }

        @Override
        public boolean login() throws LoginException {
            // Create a new Kerberos login configuration based on the specified keytab and principal
            javax.security.auth.login.Configuration config =
                    new javax.security.auth.login.AppConfigurationEntry[] {
                            new javax.security.auth.login.AppConfigurationEntry(
                                    "com.sun.security.auth.module.Krb5LoginModule",
                                    javax.security.auth.login.AppConfigurationEntry.LoginModuleControlFlag.REQUIRED,
                                    java.util.Map.of(
                                            "useKeyTab", "true",
                                            "keyTab", keytabPath,
                                            "principal", principalName,
                                            "storeKey", "true",
                                            "doNotPrompt", "true"
                                    )
                            )
                    };

            // Attempt to authenticate using the keytab and principal
            javax.security.auth.login.LoginContext context =
                    new javax.security.auth.login.LoginContext("", null, null, config);
            context.login();

            // Add the Kerberos credentials to the subject
            succeeded = true;
            subject.getPrivateCredentials().add(context.getTicket());
            return true;
        }

        @Override
        public boolean commit() throws LoginException {
            return succeeded;
        }

        @Override
        public boolean abort() throws LoginException {
            return false;
        }

        @Override
        public boolean logout() throws LoginException {
            subject.getPrivateCredentials().clear();
            return true;
        }
    }
}

This code defines a `K