SEVERE: servlet [ProfileServlet]的Servlet.service()在路径为[/Homework]的上下文中引发异常java.lang.NumberFormatException:空

Question

我得到了这个异常，但我不知道为什么。它说它的一个数字格式异常为空。我看过其他关于这个问题的帖子，但是他们都没有解决我的问题。我的配置文件类是一个简单的类，它有id、用户名、姓氏、年龄和带有setter和getter的favTeam，以及一个构造函数。有人知道为什么会这样吗？

我的Servlet

public ProfileServlet() {
    super();
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
HashMap<Integer, Profile> team = new HashMap<Integer, Profile>();

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
{
    response.setContentType("application/json; charset=UTF-8");
    //String requestUrl = request.getRequestURI();
    PrintWriter out = response.getWriter(); 

    Profile test = new Profile();
    int id;

    test = team.get(id = Integer.parseInt(request.getParameter("ID")));

    if(test != null)
    {
        out.println("ID: " + test.getId());
        out.println("name: " + test.getUsername());
        out.println("lastname: " + test.getLastname());
        out.println("age: " + test.getAge());
        out.println("favTeam: " + test.getFavTeam());
    }
    else
    {
        //ERROR

    }
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
{
    String id = request.getParameter("id");
    String age  = request.getParameter("id");

    int x = 0;
    if(id!=null){
      try{
        x = Integer.parseInt(id);
       }catch(Exception e){
       }

    }

    String username = request.getParameter("username");
    String lastname = request.getParameter("lastname");
    String favTeam = request.getParameter("favTeam");

    int numage = 0;
    if(id!=null){
      try{
        numage = Integer.parseInt(age);
       }catch(Exception e){
       }

    }

    Profile profile = new Profile(x,username,lastname,favTeam,numage);

    team.put(profile.getId(),profile);

}

}

我的.xml

 <display-name>Homework</display-name>

  <servlet>
    <servlet-name>ProfileServlet</servlet-name>
    <servlet-class>ntrut.ProfileServlet</servlet-class>
  </servlet>

  <servlet-mapping>
      <servlet-name>ProfileServlet</servlet-name>
      <url-pattern>/profile</url-pattern>
  </servlet-mapping>

  </web-app>

Answer 1

错误似乎出现在您的下面一行中。

Integer.parseInt(request.getParameter("ID"))

确保从request.getParameter("ID")返回的值是一个数字，

您可以尝试在此行之前打印request.getParameter("ID")的值吗？您将看到它不是一个数字值。

Answer 2

我为解决这个问题所做的就是我在doPost中所做的事情。我不得不在我的doGet中对request.getParameter做同样的事情

 String id = request.getParameter("id");

    int x = 0;
    if(id!=null){
      try{
        x = Integer.parseInt(id);
       }catch(Exception e){
       }

    }

    test = team.get(x);