java内部类转化问题

错误示范(伪代码)：

@Data
public class User {

	private String userName;

	private String addr;

	private int age;

	private List girlfriends = new ArrayList<>();
	
	@Data
	public class Girlfriend {

		private String girlName;

		private int girlAge;

		private String girlAddr;
	}
}
	

然后我在调用这个接口insert的时候就报错了：
JSON parse error: Cannot construct instance of com.drm.entity.User$Girlfriend (although at least one Creator exists): can only instantiate non-static inner class by using default, no-argument constructor; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of com.drm.entity.User$Girlfriend (although at least one Creator exists): can only instantiate non-static inner class by using default, no-argument constructor\n at [Source: (PushbackInputStream); line: 5, column: 7] (through reference chain: com.drm.entity.User[“girlfriends”]->java.util.ArrayList[0])
产生原因：在进行绑定的时候是采用的静态类调用方式创建内部类实例
解决方法：把内部类置为static即可；
伪代码：

@Data
public class User {

	private String userName;

	private String addr;

	private int age;

	private List girlfriends = new ArrayList<>();
	
	@Data
	public static class Girlfriend {

		private String girlName;

		private int girlAge;

		private String girlAddr;
	}
}