Question

我有一个Context类，它是一个在运行时逐渐填充的键值对。

我想创建需要上下文中某些值的对象实例。

例如：

public interface Task
{
    void execute();
}

public interface UiService
{
    void moveToHomePage();
}

public class UiServiceImpl implements UiService
{
    public UiService(@ContexParam("username") String username, @ContexParam("username") String password)
    {
        login(username, password);
    }

    public void navigateToHomePage() {}

    private void login(String username, String password) 
    {
        //do login
    }
}

public class GetUserDetailsTask implements Task
{
    private ContextService context;

    @Inject
    public GetUserDetailsTask(ContextService context)
    {
        this.context = context;
    }

    public void execute()
    {
        Console c = System.console();
        String username = c.readLine("Please enter your username: ");
        String password = c.readLine("Please enter your password: ");
        context.add("username", username);
        context.add("password", password);
    }
}

public class UseUiServiceTask implements Task
{
    private UiService ui;

    @Inject
    public UseUiServiceTask(UiService uiService)

    public void execute()
    {
        ui.moveToHomePage();
    }
}

我希望能够使用Guice创建UseUiServiceTask的实例。我如何实现这一目标？

Answer 1

您的数据就是：数据。除非在获得模块之前定义数据，否则不要注入数据，并且应用程序的其余部分保持不变。

public static void main(String[] args) {
  Console c = System.console();
  String username = c.readLine("Please enter your username: ");
  String password = c.readLine("Please enter your password: ");

  Guice.createInjector(new LoginModule(username, password));
}

如果您希望在注射开始后检索数据，则不应尝试将其注入。那么你应该做的就是在所需的任何地方注入你的ContextService和/或调用回调，但我更喜欢回调而不必集中维护数据。

public class LoginRequestor {
  String username, password;
  public void requestCredentials() {
    Console c = System.console();
    username = c.readLine("Please enter your username: ");
    password = c.readLine("Please enter your password: ");
  }
}

public class UiServiceImpl implements UiService {
  @Inject LoginRequestor login;
  boolean loggedIn;

  public void navigateToHomePage() {
    checkLoggedIn();
  }
  private void checkLoggedIn() {
    if (loggedIn) {
      return;
    }
    login.requestCredentials();
    String username = login.getUsername();
    String password = login.getPassword();
    // Do login
    loggedIn = ...;
  }
}

使用Guice注入在运行时生成的值

1 个答案: