null

问题 Is there a setting in hibernate to ignore null values of properties when saving a hibernate object? NOTE In my case I am de-serializing JSON to a Hibernate Pojo via Jackson. The JSON only contains some of the fields of the Pojo. If I save the Pojo the fields that were not in the JSON are null in the Pojo and hibernate UPDATES them. I came accross the setting updateable=false , but this isn't a 100% solution. http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity

问题 I have seen below macro in many topmost header files: #define NULL 0 // C++03 In all over the code, NULL and 0 are used interchangeably. If I change it to. #define NULL nullptr // C++11 Will it cause any bad side effect ? I can think of the only (good) side effect as following usage will become ill-formed; int i = NULL; 回答1: I have seen below macro in topmost header file: You shouldn't have seen that, the standard library defines it in <cstddef> (and <stddef.h> ). And, IIRC, according to the

问题 I once read that having nullable types is an absolute evil. I believe it was in an article written by the very person who created them(in Ada?) I believe this is the article Anyway, so what if by default a language like C# used non-nullable types? How would you replace some of the common idioms in C# or Ruby or any other common language where null is an acceptable value? 回答1: Instead of outright declaring that nullable types are evil, I would posit: most languages graft nullability onto

问题 I'm looking for a way to easily determine if all not None items in a list occur in a single continuous slice. I'll use integers as examples of not None items. For example, the list [None, None, 1, 2, 3, None, None] meets my requirements for continuous integer entries. By contrast, [1, 2, None, None, 3, None] is not continuous, because there are None entries between integers. Some more examples to make this a clear as possible. Continuous : [1, 2, 3, None, None] [None, None, 1, 2, 3] [None, 1,

问题 Both are terms whose type is the intersection of all types (uninhabited). Both can be passed around in code without failing until one attempts to evaluate them. The only difference I can see is that in Java, there is a loophole which allows null to be evaluated for exactly one operation, which is reference equality comparison ( == )--whereas in Haskell undefined can't be evaluated at all without throwing an exception. Is this the only difference? Edit What I'm really trying to get at with

问题 Both are terms whose type is the intersection of all types (uninhabited). Both can be passed around in code without failing until one attempts to evaluate them. The only difference I can see is that in Java, there is a loophole which allows null to be evaluated for exactly one operation, which is reference equality comparison ( == )--whereas in Haskell undefined can't be evaluated at all without throwing an exception. Is this the only difference? Edit What I'm really trying to get at with

问题 In C#, are there any good reasons (other than a better error message) for adding parameter null checks to every function where null is not a valid value? Obviously, the code that uses s will throw an exception anyway. And such checks make code slower and harder to maintain. void f(SomeType s) { if (s == null) { throw new ArgumentNullException("s cannot be null."); } // Use s } 回答1: Yes, there are good reasons: It identifies exactly what is null, which may not be obvious from a

问题 This code stopped doing anything at all after I changed something that I no longer remember #Dash Shell import os import datetime class LocalComputer: pass def InitInformation(): Home = LocalComputer() #Acquires user information if (os.name == "nt"): Home.ComputerName = os.getenv("COMPUTERNAME") Home.Username = os.getenv("USERNAME") Home.Homedir = os.getenv("HOMEPATH") else: Home.ComputerName = os.getenv() Home.Username = os.getenv("USER") Home.Homedir = os.getenv("HOME") return Home def

问题 I am attempting to get one class to return a string from another class, though the return I get is null. I have a set method that works in setting the string in the original class, but when calling the method in my second class, I get a return of null. Here is the first class; public class IceCream { // instance variables - replace the example below with your own private String flavour; public static double price; /** * Constructor for objects of class IceCream */ public IceCream() { //

问题 I am attempting to get one class to return a string from another class, though the return I get is null. I have a set method that works in setting the string in the original class, but when calling the method in my second class, I get a return of null. Here is the first class; public class IceCream { // instance variables - replace the example below with your own private String flavour; public static double price; /** * Constructor for objects of class IceCream */ public IceCream() { //