私有靜態嵌套類的調用方法

Question

我有一個不太好的舊代碼，涉及使用私有靜態類的方法，我想知道是否可以調用此類中的方法。 我正在為此編寫測試。 我知道，如果這是一種方法，則可以通過反射來完成，但事實並非如此。

public class FiscalReport implements Report
    {
   private void readProductValueClass()
  {
   Connection dbc = null;
   Statement st = null;
   ResultSet rs = null;
   String q = null;
  try
  {
  dbc = db.getConnection();
  dbc.setAutoCommit(false);
  st = dbc.createStatement();

  routerClassMap = new HashMap();

  q = "SELECT * FROM sales_report";

  rs = st.executeQuery(q);
  while(rs.next())
  {
    ProductValueClassrc = new ProductValueClass(); // <---this new class 
                                                  //   is where it gets called...
   .....

  }

  private static class ProductValueClass
  {
    public String name;
    public String emp;
    public String sale;
    public String option;
    public String value;
    public Query q;
    public Query qr
    public Query sql;

    public String toString()
    {
      return
      "[" +
      name + ", " +
      emp + ", " +
      sale + ", " +
      option + ", " +
      values +
      "]";
    }

    public Query query()
    {
    return q.add(q(notEqual(qr)? null: sql));
    }
  }
}

Answer 1

我相信您正在尋找創建私有內部類的實例嗎？ 如果是這種情況，此鏈接已經為您提供了一個解決方案： 使用Java反射實例化私有內部類

您可以像這樣訪問ProductValueClass的方法：

try {
    //creating parent object
    Object parent=new FiscalReport();

    //creating inner class object
    Class<?> innerClass=Class.forName("FiscalReport$ProductValueClass");

    //inner object must know type of outer class
    Constructor<?> constructor=innerClass.getDeclaredConstructor(FiscalReport.class);

    //private inner class has private default constructor
    constructor.setAccessible(true);
    //inner object must know about its outer object
    Object child = constructor.newInstance(parent);

    //invoking method on inner class object
    Method method = innerClass.getDeclaredMethod("wantedMethod",new Class<?>[]{});
    method.setAccessible(true);//in case of unaccessible method
    method.invoke(child,new Object[]{});

} catch (ClassNotFoundException | NoSuchMethodException | SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();

}

由於您的內部類是靜態的，請嘗試以下操作：

Class<?> clazz = Class.forName("FiscalReport$ProductValueClass");
Object c = clazz.newInstance();

Class<?> productValueClass = c.getClass();
Method toStringMethod = productValueClass.getMethod("toString", new Class<?>[] {});
toStringMethod.setAccessible(true);
System.out.println(toStringMethod.invoke(c));