从私有静态嵌套类调用方法

Question

我有一个不太好的遗留代码涉及使用私有静态类的方法我想知道是否可以调用此类中的方法。我正在为此编写测试。 如果这是一种方法，我知道可以通过反射来完成，但它不是。

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

我相信您正在寻找创建私有内部类的实例？如果是这种情况，此链接已经为您提供了解决方案： Instantiate private inner class with java reflection

您可以像这样访问 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();

}

因为你的内部类是静态的，试试这个：

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));