{"id":2061,"date":"2011-04-20T17:23:06","date_gmt":"2011-04-20T11:53:06","guid":{"rendered":"http:\/\/JitendraZaa.com\/blog\/?p=2061"},"modified":"2011-04-20T17:23:06","modified_gmt":"2011-04-20T11:53:06","slug":"explain-serialversionuid-in-java","status":"publish","type":"post","link":"https:\/\/www.jitendrazaa.com\/blog\/java\/explain-serialversionuid-in-java\/","title":{"rendered":"Explain serialVersionUID in Java"},"content":{"rendered":"

The serialization <\/a>runtime associates with each serializable class a version number, called a serialVersionUID<\/strong>, 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 the corresponding sender’s class, then deserialization will result in an InvalidClassException<\/strong>. A serializable class can declare its own serialVersionUID explicitly by declaring a field named “serialVersionUID<\/strong>” that must be static, final, and of type long:<\/p>\n

ANY-ACCESS-MODIFIER static final long serialVersionUID = 42L;<\/strong><\/p><\/blockquote>\n

If a serializable class does not explicitly declare a serialVersionUID, then the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class, as described in the Java(TM) Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values, since the<\/span> default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization<\/span>.<\/em> Therefore, to guarantee a consistent serialVersionUID value across different java compiler implementations, a serializable class must declare an explicit serialVersionUID value<\/strong>. It is also strongly advised that explicit serialVersionUID declarations use the private modifier<\/strong> where possible, since such declarations apply only to the immediately declaring class.serialVersionUID fields are not useful as inherited members.<\/p>\n

Example demonstrating the use of serialVersionUID :<\/p>\n

\npackage com.G2.Serialization;\n\nimport java.io.FileOutputStream;\nimport java.io.IOException;\nimport java.io.ObjectOutputStream;\nimport java.io.Serializable;\n\nclass Demo1 implements Serializable {\n\n\tpublic Demo1() {\n\t}\n}\n\npublic class ExternizationDemo {\n\tpublic static void main(String[] args) throws IOException, ClassNotFoundException {\n\t\tDemo1 b1 = new Demo1();\n\n\t\tObjectOutputStream o = new ObjectOutputStream(new FileOutputStream("Demo1.srz"));\n\t\to.writeObject(b1);\n\t\to.close();\n\n\t}\n}\n<\/pre>\n
Above program will run perfectly. now add one more parameter in above class and lets try below example.<\/p>\n
\npackage com.G2.Serialization;\n\nimport java.io.FileInputStream;\nimport java.io.IOException;\nimport java.io.ObjectInputStream;\nimport java.io.Serializable;\n\nclass Demo1 implements Serializable {\n\tString NeedOfSerial = "Very imp";\n\tpublic Demo1() {\n\t}\n}\n\npublic class ExternizationDemo {\n\tpublic static void main(String[] args) throws IOException, ClassNotFoundException {\n\t\tDemo1 b1 = new Demo1();\n\n\t\t ObjectInputStream in = new ObjectInputStream(new\n\t\t FileInputStream("Demo1.srz"));\n\t\t b1 = (Demo1) in.readObject();\n\t\t System.out.println(" --- Object recovered --- ");\n\n\t}\n}\n<\/pre>\n
Output will be something like below message :<\/p>\n
Exception in thread “main” java.io.InvalidClassException: com.G2.Serialization.Demo1; local class incompatible: stream classdesc serialVersionUID = -9110957255177458835, local class serialVersionUID = 4792304913344431293
\nat java.io.ObjectStreamClass.initNonProxy(Unknown Source)
\nat java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
\nat java.io.ObjectInputStream.readClassDesc(Unknown Source)
\nat java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
\nat java.io.ObjectInputStream.readObject0(Unknown Source)
\nat java.io.ObjectInputStream.readObject(Unknown Source)
\nat com.G2.Serialization.ExternizationDemo.main(ExternizationDemo.java:26)<\/p><\/blockquote>\n
By adding below line in class Demo1, above problem will be resolved.<\/p>\n
private static final long serialVersionUID = 998985689L;<\/strong><\/p><\/blockquote>\n
value of serialVersionUID can be anything unique to the class.<\/p>\n","protected":false},"excerpt":{"rendered":"
What is serialVersionUID and what is its need ?<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"jz_research_post":"","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[3],"tags":[329],"class_list":["post-2061","post","type-post","status-publish","format-standard","hentry","category-java","tag-java"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":1612,"url":"https:\/\/www.jitendrazaa.com\/blog\/java\/serialization-marshalling-deflating-in-java\/","url_meta":{"origin":2061,"position":0},"title":"Serialization \/ Marshalling \/ Deflating in JAVA","author":"Jitendra","date":"March 9, 2011","format":false,"excerpt":"Concept of Serialization \/ Marshalling \/ Deflating in JAVA","rel":"","context":"In "JAVA"","block_context":{"text":"JAVA","link":"https:\/\/www.jitendrazaa.com\/blog\/category\/java\/"},"img":{"alt_text":"Serialization ,Marshalling ,deflating, DeSerialization ,UnMarshalling ,inflating","src":"https:\/\/i0.wp.com\/jitendrazaa.com\/blog\/wp-content\/uploads\/2011\/03\/Serialization-Marshalling-deflating-DeSerialization-UnMarshalling-inflating.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":2049,"url":"https:\/\/www.jitendrazaa.com\/blog\/java\/explain-externalizable-in-java\/","url_meta":{"origin":2061,"position":1},"title":"Explain Externalizable in Java","author":"Jitendra","date":"April 20, 2011","format":false,"excerpt":"Explain Externalizable in Java","rel":"","context":"In "JAVA"","block_context":{"text":"JAVA","link":"https:\/\/www.jitendrazaa.com\/blog\/category\/java\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":2017,"url":"https:\/\/www.jitendrazaa.com\/blog\/java\/java-j2ee-interview-questions-1\/","url_meta":{"origin":2061,"position":2},"title":"Java – J2EE Interview Questions – 1","author":"Jitendra","date":"April 15, 2011","format":false,"excerpt":"JAVA - J2EE Interview Questions - 1, JAVA - J2EE Interview Questions - 1,custom tag JSP, Externalization , serialVersionUID, difference between interface and abstract class, iterate HashMap","rel":"","context":"In "JAVA"","block_context":{"text":"JAVA","link":"https:\/\/www.jitendrazaa.com\/blog\/category\/java\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":3050,"url":"https:\/\/www.jitendrazaa.com\/blog\/salesforce\/my-favorite-top-10-features-of-winter-13-release-salesforce\/","url_meta":{"origin":2061,"position":3},"title":"My Favorite Top 10 Features of Winter 13 release – Salesforce","author":"Jitendra","date":"August 24, 2012","format":false,"excerpt":"Dear Friends, I am very excited to write this article about the cool Winter 13 features which i have added in My List. There are lots of lots of new features added in this release and i have made the list of my top 10 favorite features. Yesterday Salesforce published\u2026","rel":"","context":"In "Salesforce"","block_context":{"text":"Salesforce","link":"https:\/\/www.jitendrazaa.com\/blog\/category\/salesforce\/"},"img":{"alt_text":"Salesforce Winter 13 Release Notes","src":"https:\/\/i0.wp.com\/jitendrazaa.com\/blog\/wp-content\/uploads\/2012\/08\/Salesforce-Winter-13-Release-Notes-300x212.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":700,"url":"https:\/\/www.jitendrazaa.com\/blog\/java\/interface\/","url_meta":{"origin":2061,"position":4},"title":"Interface in JAVA","author":"Jitendra","date":"August 2, 2010","format":false,"excerpt":"Explains the usage and benefits of interface in JAVA.","rel":"","context":"In "JAVA"","block_context":{"text":"JAVA","link":"https:\/\/www.jitendrazaa.com\/blog\/category\/java\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":3411,"url":"https:\/\/www.jitendrazaa.com\/blog\/salesforce\/apex-interview-question-salesforce-part-16\/","url_meta":{"origin":2061,"position":5},"title":"Apex Interview Question \u2013 Salesforce – Part 16","author":"Jitendra","date":"July 28, 2013","format":false,"excerpt":"151. Give Sample Code Snippet of Apex that that will show that how Parent and Child record can be inserted in Single Statement ? Ans : It can be done with help of External Id. 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