The serializable class
VaadintestprojectApplication does not
declare a static final
serialVersionUID field of type long
- What does this statement mean? I get
an error for this.
- What does serizlizable ...
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Possible Duplicate:
Why should I bother about serialVersionUID?
I was examining the Struts2 validation documentation. Even here it is defined:
private static final long serialVersionUID ...
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Whenever I am trying to compute serialversionUID from the command prompt, I am getting "Exception in thread "main" java.lang.NoClassDefFoundError: javax.servlet.http.HttpServletRequest".
classpath is set correctly.I have j2ee.jar in my classpath.
Can anyone help me ... |
As part of debugging an application, I noticed that Field.getDeclaredFields() returns some synthetic fields, including a serialVersionUID field in a class extending an interface, although none extend Serializable.
Why does the compiler ... |
Suren, The serialVersionUID allows you to explicitly specify the value of something called a stream unique identifier (SUID) that's normally calculated by Java's serialization mechanism. You're never required to define the serialVersionUID field, but you may find it useful sometimes. The SUID value (either one you explicitly define or one that's calculated at run time) of a class is included with ... |
Hi, I came to know that " The identifier that is part of all classes is maintained in a field called serialVersionUID." But I am not able to access this field directly (say through a print statement, like System.out.println(serialVersionUID); ). So where is this value stored ? Also, i didnt find it in the class file when i opened it with ... |
On the warning about a serialiable class not having an id, Eclipse offers 3 quick fixes: Add default serial version ID Add generated serial version ID Add @SuppressWarnings to class Of the first 2, is one always better, if not when is one better? About the last option, it seems wrong to me to ignore any warning. Ia this not the ... |
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When a object is deserialized , first it checks that class compatibility with the class available to the classloader at the instance of deserialization.This is done by comparing the serialversionID of the class that is there with the serialized data to that of the serialversionID class which would be used for deserialization. It might happen that class used for creating the ... |
I usually add an Eclipse-generated serialVersionUID to all classes which implement Serializable. However this value stays the same after I modify the class, which breaks the reliability of the deserialization which uses this variable. Is there a way to insure that this variable gets updated every time there's a significant change to the class -- preferably something automatic through Eclipse which ... |
It needs to be a long. You can make one up. Incompatible versions of the same class should have different values. If you make a change to a class that would alter the way it would be serialized [i.e., add a field], you should change the UID. If you need to find the uid of an existing class you can use ... |
So I'm doing some object serialization that will be passed between different JVMs on our networks here. I've been looking around, and I can't find basic information on what I'm supposed to add the serialVersionUID to. Obviously, a class that implements Serializable that's going to be serialized is a candidate for adding an explicit serialVersionUID. But what if I have the ... |
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Hi Amrithraj, You do the following to understand serialVersionUID. 1- Serialize instances of your class. 2- Change the class definition, add method(s), remove member variables or add 3- Try to deserialize the instances you serialized in the step 1 You will get InvalidClassException because while serialization takes place, some information about your class in also saved as part of serialization. OK! ... |
The serialVersionUID should be specific to every class, but it doesn't have to be (many people 'cheat' and just define it as 1L). Subclasses should get their own serialVersionUID. The serialVersionUID is specific to a class, not an object, since they are static. I don't think it matters if two different classes have the same serialVersionUID, since it is used in ... |
The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID than that of ... |
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The idea of the SUIDis that when you have two instances of the same class with the same SUID, the JVM assumes they are from the same class object. If you have different SUIDs, the JVM may assume they are from different versions of the class, and the objects may not be de-serialized. And I agree it is very peculiar to ... |
I am aware of the importance of serialVersionUID from the docs in sun website and google searches. My question still remains unanswered, maybe I was not clear. It is mentioned that the basic purpose of the serialVersionUID field is to allow the JVM to compare incoming serialized objects to the local definition of the class, to ensure that no changes have ... |
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i was reading an article today and it said it is important to give serialVersionUID variable to your class which we think will be required to serialize. My question are given below 1.) what will be the problem we will face if we do not give serialVersionUID in our serialized java class (i know java will create one for us if ... |
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A quick question I was wondering if anyone had an answer to. When setting the serialVersionUID in a class is there any benefit to setting it to any particular value? You can generate a value for the serialVersionUID. IDE's like Eclipse will do this for you. Where the generated value is based on the structure of the class just like Java ... |
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so I'm coding up my own event using Eclipse (for pretty much the first time), and it gives me a warning of The serializable class CaptureEvent does not declare a static final serialVersionUID field of type long now ... first I notice that it's a warning, not an error. second, after looking up stuff on the api, it appears that the ... |
The serialVersionID is needed to identify the version of a particular class during serialisation and deserialisation. Not including it in any Serializable class yields a compiler warning depending on the strictness settings for the compiler, as it can lead to problems (not all changes to a class warrant a new class version, thus a new serialVersionID, and you might want to ... |
It seems like its there to easily find out if a new version of a class is deserialized, but from what i know of RMI, RMI doesnt let you use the wrong version any way. so what does it do exactly? how is the behaviour changed if you dont inclide it? should you change it every time you change the class? ... |
Take a look at the API [http://java.sun.com/javase/6/docs/api/java/io/Serializable.html] To allow subtypes of non-serializable classes to be serialized, the subtype may assume responsibility for saving and restoring the state of the supertype's public, protected, and (if accessible) package fields. The subtype may assume this responsibility only if the class it extends has an accessible no-arg constructor to initialize the class's state. It is ... |
I have a simple utility that doesn't implement serialisable but does import a package that does. When it is run it reads in a properties file which has an attribute that tells it what host to run against. When this is set to localhost it works fine. However, when I point it to another server on the network it gives: java.io.InvalidClassException: ... |
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Blank boys I ask you an aid a lot important. I am realizing a written graphical application in java. Until a sure point when I compiled it went well tuto. To improviso when the plan has grown and the compilations they have become more frequent are introduces 23 warning very to you of the type: has not definition of serialVersionUID. Turning ... |
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I am a beginner in serializable classes and could not find the answers to my questions when searching all forums. With JBuilder 2007 I received warning messages that my serializable classes do not declare a static final serialVersionUID field of type long. I have 3 questions: 1) Can I just declare the serialVersionUIDs in an arbitrary way such as: private static ... |