如何获得嵌套字段

Question

我是新的反射，我试图得到一个嵌套字段。总结我有以下类别：

public class Agreement{ 

    private Long id; 

    private String cdAgreement; 

    private Address address; 

    //Constructor getter and setter 

} 

public class Address{ 

    private Long id; 

    private String description; 

    //Constructor getter and setter 

} 

现在我想说明字段，然后我写了这个代码：

Agreement agreement = new Agreement(); 
Class c = agreement.getClass(); 
Field f = c.getDeclaredField("address.descritpion"); 

而不是作品，我得到以下异常：

java.lang.NoSuchFieldException: address.descritpion 
at java.lang.Class.getDeclaredField(Class.java:1948) 

我在哪里做错了？

Answer 1

目前的问题是没有字段的名称为“address.description”（它甚至不是字段的有效名称）。

您必须首先获取地址字段，访问其类并从此处获取嵌套字段。要做到这一点，使用getType()：

Agreement agreement = new Agreement(); 
Class c = agreement.getClass();   // Agreement class 
Field f = c.getDeclaredField("address"); // address field 
Class<?> fieldClass = f.getType();  // class of address field (Address) 
Field nested = fieldClass.getDeclaredField("description"); // description field 

你也可以连接呼叫无局部变量：

Field nested = c.getDeclaredField("address").getType().getDeclaredField("description"); 

Answer 2

必须分解操作。

Agreement agreement = new Agreement(); 
Field fAddress = agreement.getClass().getDeclaredField("address"); 
Address address = (Address)fAddress.get(agreement); 
Field fDescription = address.getClass().getDeclaredField("description"); 
String description = (String)fDescription.get(address);