What is the difference between Serialization and Marshaling

Question

I know that in terms of several distributed techniques  such as RPC   the term  quot Marshaling quot  is used but don t understand how it differs from Serialization  Aren t they both transforming objects into series of bits  Related  What is Serialization  What is Object Marshalling

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My vies is  Problem  Object belongs to some process VM  and it s lifetime is the same Serialisation - transform object state into stream of bytes JSON  XML     for saving  sharing  transforming    Marshalling - contains Serialisation   codebase  Usually it used by Remote procedure call RPC  - gt  Java Remote Method Invocation Java RMI  where you are able to invoke a object s method which is hosted on remote Java processes  codebase - is a place or URL to class definition where it can be downloaded by ClassLoader  CLASSPATH About  is as a local codebase JVM - gt  Class Loader - gt  load class definition - gt  class  Very simple diagram for RMI  Serialisation - state Marshalling - state   class definition  Official doc

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Marshaling and serialization are loosely synonymous in the context of remote procedure call  but semantically different as a matter of intent   In particular  marshaling is about getting parameters from here to there  while serialization is about copying structured data to or from a primitive form such as a byte stream   In this sense  serialization is one means to perform marshaling  usually implementing pass-by-value semantics   It is also possible for an object to be marshaled by reference  in which case the data  on the wire  is simply location information for the original object   However  such an object may still be amenable to value serialization   As  Bill mentions  there may be additional metadata such as code base location or even object implementation code

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Think of them as synonyms  both have a producer that sends stuff over to a consumer    In the end fields of instances are written into a byte stream and the other end foes the reverse ands up with the same instances    NB - java RMI also contains support for transporting classes that are missing from the recipient

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My understanding of marshalling is different to the other answers    Serialization   To Produce or rehydrate a wire-format version of an object graph utilizing a convention    Marshalling   To Produce or rehydrate a wire-format version of an object graph by utilizing a mapping file  so that the results can be customized  The tool may start by adhering to a convention  but the important difference is the ability to customize results    Contract First Development   Marshalling is important within the context of contract first development     Its possible to make changes to an internal object graph  while keeping the external interface stable over time  This way all of the service subscribers won t have to be modified for every trivial change   Its possible to map the results across different languages  For example from the property name convention of one language   property name   to another   propertyName

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From the Marshalling  computer science  Wikipedia article   The term  quot marshal quot  is considered to be synonymous with  quot serialize quot  in the Python standard library1  but the terms are not synonymous in the Java-related RFC 2713  To  quot marshal quot  an object means to record its state and codebase s  in such a way that when the marshalled object is  quot unmarshalled quot   a copy of the original object is obtained  possibly by automatically loading the class definitions of the object  You can marshal any object that is serializable or remote  Marshalling is like serialization  except marshalling also records codebases  Marshalling is different from serialization in that marshalling treats remote objects specially   RFC 2713  To  quot serialize quot  an object means to convert its state into a byte stream in such a way that the byte stream can be converted back into a copy of the object   So  marshalling also saves the codebase of an object in the byte stream in addition to its state

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Both do one thing in common - that is serializing an Object  Serialization is used to transfer objects or to store them  But     Serialization  When you serialize an object  only the member data within that object is written to the byte stream  not the code that actually implements the object  Marshalling   Term Marshalling is used when we talk about passing Object to remote objects RMI   In Marshalling Object is serialized member data is serialized    Codebase is attached    So Serialization is part of Marshalling   CodeBase is information that tells the receiver of Object where the implementation of this object can be found  Any program that thinks it might ever pass an object to another program that may not have seen it before must set the codebase  so that the receiver can know where to download the code from  if it doesn t have the code available locally  The receiver will  upon deserializing the object  fetch the codebase from it and load the code from that location

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Marshaling refers to converting the signature and parameters of a function into a single byte array  Specifically for the purpose of RPC   Serialization more often refers to converting an entire object   object tree into a byte array Marshaling will serialize object parameters in order to add them to the message and pass it across the network   Serialization can also be used for storage to disk

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Here s more specific examples of both   Serialization Example    include  lt stdio h gt   include  lt stdlib h gt   include  lt stdint h gt   typedef struct       char value 11     SerializedInt32   SerializedInt32 SerializeInt32 int32 t x         SerializedInt32 result       itoa x  result value  10        return result     int32 t DeserializeInt32 SerializedInt32 x         int32 t result       result   atoi x value        return result     int main int argc  char   argv            int x         SerializedInt32 data      int32 t result       x   -268435455       data   SerializeInt32 x       result   DeserializeInt32 data        printf  x    s  n   data value        return result      In serialization  data is flattened in a way that can be stored and unflattened later   Marshalling Demo    MarshalDemoLib cpp    include  lt iostream gt   include  lt string gt   extern  C    declspec dllexport  void  StdCoutStdString void  s        std  string  str    std  string   s      std  cout  lt  lt   str     extern  C    declspec dllexport  void  MarshalCStringToStdString char  s        std  string  str new std  string s         std  cout  lt  lt   string was successfully constructed  n        return str     extern  C    declspec dllexport  void DestroyStdString void  s        std  string  str  std  string   s       delete str       std  cout  lt  lt   string was successfully destroyed  n        MarshalDemo c    include  lt Windows h gt   include  lt stdio h gt   include  lt stdlib h gt   include  lt stdint h gt   int main int argc  char   argv        void  myStdString       LoadLibrary  MarshalDemoLib         myStdString     void      char    GetProcAddress           GetModuleHandleA  MarshalDemoLib             MarshalCStringToStdString          Hello  World  n           void     void    GetProcAddress           GetModuleHandleA  MarshalDemoLib             StdCoutStdString         myStdString          void     void    GetProcAddress           GetModuleHandleA  MarshalDemoLib             DestroyStdString         myStdString           In marshaling  data does not necessarily need to be flattened  but it needs to be transformed to another alternative representation  all casting is marshaling  but not all marshaling is casting   Marshaling doesn t require dynamic allocation to be involved  it can also just be transformation between structs  For example  you might have a pair  but the function expects the pair s first and second elements to be other way around  you casting memcpy one pair to another won t do the job because fst and snd will get flipped    include  lt stdio h gt   typedef struct       int fst      int snd    pair1   typedef struct       int snd      int fst    pair2   void pair2 dump pair2 p        printf   d  d n   p fst  p snd      pair2 marshal pair1 to pair2 pair1 p        pair2 result      result fst   p fst      result snd   p snd      return result     pair1 given    3  7    int main int argc  char   argv            pair2 dump marshal pair1 to pair2 given         return 0      The concept of marshaling becomes especially important when you start dealing with tagged unions of many types  For example  you might find it difficult to get a JavaScript engine to print a  c string  for you  but you can ask it to print a wrapped c string for you  Or if you want to print a string from JavaScript runtime in a Lua or Python runtime  They are all strings  but often won t get along without marshaling   An annoyance I had recently was that JScript arrays marshal to C  as    ComObject   and has no documented way to play with this object  I can find the address of where it is  but I really don t know anything else about it  so the only way to really figure it out is to poke at it in any way possible and hopefully find useful information about it  So it becomes easier to create a new object with a friendlier interface like Scripting Dictionary  copy the data from the JScript array object into it  and pass that object to C  instead of JScript s default array    test js   var x   new ActiveXObject  Dmitry YetAnotherTestObject YetAnotherTestObject     x send  1  2  3  4      YetAnotherTestObject cs  using System  using System Runtime InteropServices   namespace Dmitry YetAnotherTestObject        Guid  C612BD9B-74E0-4176-AAB8-C53EB24C2B29    ComVisible true       public class YetAnotherTestObject               public void send object x                        System Console WriteLine x GetType   Name                          above prints    ComObject   which is somewhat of a black box from the point of view of C     Another interesting concept is that you might have the understanding how to write code  and a computer that knows how  to execute instructions  so as a programmer  you are effectively marshaling the concept of what you want the computer to do from your brain to the program image  If we had good enough marshallers  we could just think of what we want to do change  and the program would change that way without typing on the keyboard  So  if you could have a way to store all the physical changes in your brain for the few seconds where you really want to write a semicolon  you could marshal that data into a signal to print a semicolon  but that s an extreme

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Basics First  Byte Stream - Stream is sequence of data  Input stream - reads data from source  Output stream - writes data to desitnation   Java Byte Streams are used to perform input output byte by byte 8bits at a time   A byte stream is suitable for processing raw data like binary files  Java Character Streams are used to perform input output 2 bytes at a time  because Characters are stored using Unicode conventions in Java with 2 bytes for each character  Character stream is useful when we process read write  text files   RMI Remote Method Invocation  - an API that provides a mechanism to create distributed application in java  The RMI allows an object to invoke methods on an object running in another JVM     Both Serialization and Marshalling are loosely used as synonyms  Here are few differences   Serialization - Data members of an object is written to binary form or Byte Stream and then can be written in file memory database etc   No information about data-types can be retained once object data members are written to binary form      Marshalling - Object is serialized to byte stream in binary format  with data-type   Codebase attached and then passed Remote Object RMI   Marshalling will transform the data-type into a predetermined naming convention so that it can be reconstructed with respect to the initial data-type     So Serialization is part of Marshalling   CodeBase is information that tells the receiver of Object where the implementation of this object can be found  Any program that thinks it might ever pass an object to another program that may not have seen it before must set the codebase  so that the receiver can know where to download the code from  if it doesn t have the code available locally  The receiver will  upon deserializing the object  fetch the codebase from it and load the code from that location   Copied from  Nasir answer   Serialization is almost like a stupid memory-dump of the memory used by the object s   while Marshalling stores information about custom data-types   In a way  Serialization performs marshalling with implematation of pass-by-value because no information of data-type is passed  just the primitive form is passed to byte stream   Serialization may have some issues related to big-endian  small-endian if the stream is going from one OS to another if the different OS have different means of representing the same data  On the other hand  marshalling is perfectly fine to migrate between OS because the result is a higher-level representation

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Marshalling is the rule to tell compiler how the data will be represented on another environment system  For example      MarshalAs UnmanagedType ByValTStr  SizeConst   260   public string cFileName   MarshalAs UnmanagedType ByValTStr  SizeConst   14   public string cAlternateFileName    as you can see two different string values represented as different value types   Serialization will only convert object content  not representation  will stay same  and obey rules of serialization   what to export or no   For example  private values will not be serialized  public values yes and object structure will stay same

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Marshalling is usually between relatively closely associated processes  serialization does not necessarily have that expectation   So when marshalling data between processes  for example  you may wish to merely send a REFERENCE to potentially expensive data to recover  whereas with serialization  you would wish to save it all  to properly recreate the object s  when deserialized

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I think that the main difference is that Marshalling supposedly also involves the codebase  In other words  you would not be able to marshal and unmarshal an object into a state-equivalent instance of a different class     Serialization just means that you can store the object and reobtain an equivalent state  even if it is an instance of another class   That being said  they are typically synonyms

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Marshaling uses Serialization process actually but the major difference is that it in Serialization only data members and object itself get serialized not signatures  but in Marshalling Object   code base its implementation  will also get transformed into bytes   Marshalling is the process to convert java object to xml objects using JAXB so that it can be used in web services

[serialization] What is the difference between Serialization and Marshaling?

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