java - 如何获取嵌套字段

Question

我是反射的新手，我正在尝试获取嵌套字段。总结我有以下类(class):

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

}

现在我想获取描述字段，然后我写了这段代码:

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

但不起作用，我得到以下异常:

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

我哪里做错了？

Answer 1

当前的问题是没有字段具有名称“address.description”(它甚至不是字段的有效名称)。

您必须先获取地址字段，访问它的类，然后从那里获取嵌套字段。为此，请使用 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

你也可以在没有局部变量的情况下链接调用:

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