import com.mojang.authlib.UserAuthentication; //导入依赖的package包/类
/**
 * Attempts to login with the specified username and password.
 * If the login is successful then a session will be created. If
 * not, {@code null} will be returned
 *
 * @return A valid session, if able to login, otherwise {@code null}
 */
@Override
public Session build() {
    UserAuthentication auth = new YggdrasilAuthenticationService(this.proxy, "").createUserAuthentication(Agent.MINECRAFT);
    auth.setUsername(this.username);
    auth.setPassword(this.password);

    try {
        auth.logIn();
    } catch (AuthenticationException e) {
        return null;
    }

    GameProfile profile = auth.getSelectedProfile();
    return new Session(profile.getName(), profile.getId().toString(), auth.getAuthenticatedToken(), "MOJANG");
}
 

import com.mojang.authlib.UserAuthentication; //导入依赖的package包/类
@Override
public UserAuthentication getUserAuthentication() {
    return this.userAuthentication;
}
 

import com.mojang.authlib.UserAuthentication; //导入依赖的package包/类
public UserAuthentication createUserAuthentication(Proxy proxy) {
    return new YggdrasilAuthenticationService(
                    proxy,
                    UUID.randomUUID().toString()
    ).createUserAuthentication(agent);
}
 

import com.mojang.authlib.UserAuthentication; //导入依赖的package包/类
/**
 * Creates a new Mojang user authentication instance using the given proxy.
 * @param proxy Proxy to use.
 * @return User authentication instance.
 */
public UserAuthentication createUserAuthentication(Proxy proxy);
 

import com.mojang.authlib.UserAuthentication; //导入依赖的package包/类
public UserAuthentication getUserAuthentication();