transient

问题 Can a transient field in a class be obtained using reflection? (using getDeclaredField(..) ) 回答1: Yes , It is a normal field. You can check whether it is transient by: Modifier.isTransient(field.getModifiers()); transient : A keyword in the Java programming language that indicates that a field is not part of the serialized form of an object. When an object is serialized, the values of its transient fields are not included in the serial representation, while the values of its non-transient

问题 In a java class java.util.Locale, I find that the keyword transient marked a method. public final class Locale implements Cloneable, Serializable { private static class LocaleNameGetter implements sun.util.LocaleServiceProviderPool.LocalizedObjectGetter { public transient String getObject(LocaleNameProvider localenameprovider, Locale locale, String s, Object aobj[]) { if(!$assertionsDisabled && aobj.length != 2) throw new AssertionError(); int i = ((Integer)aobj[0]).intValue(); String s1 =

问题 I'm trying to persist Maps of properties as single JSON-encoded columns, as shown in this question. The problem I'm having is that apparently transient properties cannot be set in the default map constructor . Given any transient field: class Test { //... String foo static transients = ['foo'] } It seems that the map constructor (which Grails overrides in various ways) simply discards transient fields: groovy:000> t = new Test(foo:'bar') ===> Test : (unsaved) groovy:000> t.foo ===> null While

问题 Say for example I have an Entity called Tasks with an Attribute called date and a UITableView populating this Tasks Entity . This is what I currently see: 7-Dec-14 09:30 7-Dec-14 11:00 7-Dec-14 13:30 7-Dec-14 16:00 Now lets pretend the current time is actually 7-Dec-14 12:00 so the first 2 rows have passed but the second 2 rows are in the future. I want to split these into Groups within the UITableView . I've found I can create a Transient Property on the Entity as follows: var dateGroup:

问题 As for the subject title: Why is it legal to declare a transient variable in a non serializable class? What would the use be? 回答1: The transient access modifier can be seen by code other than the serialization mechanism, and is used by some object databases to mark a data field as not persistent. Aside from that, there isn't any harm in allowing this. 回答2: Because also other serialization forms that don't requirier Serializable are able to make use of it too. 回答3: How about if a subclass

问题 Is there a simple way to specify if a field should be transient or not in Java with reflection, similar to how a field's accessibility flag can be set with setAccessible()? 回答1: Reflection itself cannot alter code. Java Agents should allow you to rewrite the class as it is loaded. You can use reflection to alter serialPersistentFields if it exists (unlikely), before the serialisation mechanism caches the class data. You could use reflection in a highly version specific way to alter the data

问题 I'm trying to develop a timetable app. I have TableViewController which shows the classes on current day. In viewDidLoad( ) I fetch the classes with NSFetchedResultsController: let fetchRequest = NSFetchRequest(entityName: "Lessons") let predicate = NSPredicate(format: "startsday = '\(dateFormatter.stringFromDate(NSDate()))'", NSDate()) fetchRequest.predicate = predicate let sortDescriptorStarts = NSSortDescriptor(key: "starts", ascending: true) let sortDescriptorTitle = NSSortDescriptor(key:

问题 What difference does it make if a transient attribute in core data is set to optional or non optional. Normally when you set an entity to being optional, it allows the entity owning that attribute to be stored with that attribute set to null. But in the case of transient attributes they aren't actually stored. So does setting a transient property to optional do anything? Do you need to set a transient attribute to optional if it is calculated using an optional non-transient property? Any

问题 What difference does it make if a transient attribute in core data is set to optional or non optional. Normally when you set an entity to being optional, it allows the entity owning that attribute to be stored with that attribute set to null. But in the case of transient attributes they aren't actually stored. So does setting a transient property to optional do anything? Do you need to set a transient attribute to optional if it is calculated using an optional non-transient property? Any

问题 I have JPA entities where some properties are annotated with @Transient . Should I use these properties in equals/hashCode/toString methods? My first thought is NO but I don't know why. Tips? Ideas? Explanations? 回答1: The case of toString() is different, you can do whatever you want with toString() so I will only cover equals() (and hashCode() ). First, the rule: if you want to store an object in a List , Map or a Set then it is a requirement that equals and hashCode are implemented so they