与服务器实例混淆

Question

我有下面的一段代码，它工作正常，没有问题，但我很困惑，如何制作多个实例。每次运行此代码时，我都会得到“有 1 个实例正在运行”

public class HolisticCounter extends HttpServlet {


    private static final long serialVersionUID = 1L;
static int classCount = 0;  // shared by all instances
  int count = 0;              // separate for each servlet
  static Hashtable instances = new Hashtable();  // also shared

  public void doGet(HttpServletRequest req, HttpServletResponse res) 
                               throws ServletException, IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();

    count++;
    out.println("Since loading, this servlet instance has been accessed " +
                count + " times.");

    // Keep track of the instance count by putting a reference to this
    // instance in a Hashtable. Duplicate entries are ignored. 
    // The size() method returns the number of unique instances stored.
    instances.put(this, this);
    out.println("There are currently " + 
                instances.size() + " instances.");

    classCount++;
    out.println("Across all instances, this servlet class has been " +
                "accessed " + classCount + " times.");
  }
}

Answer 1

在绝大多数情况下，每个 条目只有一个 servlet 实例。容器不再需要实例化，因此它为每个请求重用相同的实例。

服务器允许实例化多个，但通常没有理由这样做。