模板方法模式

模板方法模式UML类图

模板方法模式java实现

/**
 * StealingMethod defines skeleton for the algorithm.
 偷窃Method定义了算法的框架。
 */
public abstract class StealingMethod {

  private static final Logger LOGGER = LoggerFactory.getLogger(StealingMethod.class);

  protected abstract String pickTarget();

  protected abstract void confuseTarget(String target);

  protected abstract void stealTheItem(String target);

  /**
   * Steal.
   */
  public void steal() {
    //挑选目标
    var target = pickTarget();
    LOGGER.info("The target has been chosen as {}.", target);
    //迷惑目标
    confuseTarget(target);
    //偷物品
    stealTheItem(target);
  }
}

/**
 * SubtleMethod implementation of {@link StealingMethod}.
 微妙
 */
public class SubtleMethod extends StealingMethod {

  private static final Logger LOGGER = LoggerFactory.getLogger(SubtleMethod.class);

  @Override
  protected String pickTarget() {
      //店主
    return "shop keeper";
  }

  @Override
  protected void confuseTarget(String target) {
      //泪流满面地接近店主，拥抱他！
    LOGGER.info("Approach the {} with tears running and hug him!", target);
  }

  @Override
  protected void stealTheItem(String target) {
      //保持密切联系时，抓住店主的钱包。
    LOGGER.info("While in close contact grab the {}'s wallet.", target);
  }
}

/**
 * HitAndRunMethod implementation of {@link StealingMethod}.
 奔跑
 */
public class HitAndRunMethod extends StealingMethod {

  private static final Logger LOGGER = LoggerFactory.getLogger(HitAndRunMethod.class);

  @Override
  protected String pickTarget() {
      //小妖精的女人
    return "old goblin woman";
  }

  @Override
  protected void confuseTarget(String target) {
      //从后面接近老妖精的女人。
    LOGGER.info("Approach the {} from behind.", target);
  }

  @Override
  protected void stealTheItem(String target) {
      //抓住手提包，快点逃跑！
    LOGGER.info("Grab the handbag and run away fast!");
  }
}

/**
 * Halfling thief uses {@link StealingMethod} to steal.
 */
public class HalflingThief {

  private StealingMethod method;

  public HalflingThief(StealingMethod method) {
    this.method = method;
  }

  public void steal() {
    method.steal();
  }

  public void changeMethod(StealingMethod method) {
    this.method = method;
  }
}

/**
 * Template Method defines a skeleton for an algorithm. The algorithm subclasses provide
 * implementation for the blank parts.
 *
 * <p>In this example {@link HalflingThief} contains {@link StealingMethod} that can be changed.
 * First the thief hits with {@link HitAndRunMethod} and then with {@link SubtleMethod}.
 模板方法定义算法的框架。 算法子类为空白部分提供实现。
<p>在此示例中，{@ link HalflingThief}包含可以更改的{@link StealingMethod}。 首先，小偷用{@link HitAndRunMethod}打，然后用{@link SubtleMethod}打。
 */
public class App {

  /**
   * Program entry point.
   *
   * @param args command line args
   */
  public static void main(String[] args) {
    var thief = new HalflingThief(new HitAndRunMethod());
    thief.steal();
    thief.changeMethod(new SubtleMethod());
    thief.steal();
  }
}

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实际应用案例

复用

• Java IO 类库中InputStream read()
• Java AbstractList addAll()
  扩展
• Java HttpServlet 的 service()
• JUnit TestCase setUp() tearDown()
  回调
• JdbcTemplate