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In computer science, in the context of data storage, serialization (or serialisation) is the process of translating data structures or object state into a format that can be stored (for example, in a file or memory buffer) or transmitted (for example, across a network connection link) and reconstructed later (possibly in a different computer environment).[1] When the resulting series of bits is reread according to the serialization format, it can be used to create a semantically identical clone of the original object. For many complex objects, such as those that make extensive use of references, this process is not straightforward. Serialization of object-oriented objects does not include any of their associated methods with which they were previously linked.
Serialization of Java Objects to XML can be done using XMLEncoder, XMLDecoder. Java Object Serialization feature was introduced in JDK 1.1. Serialization transforms a Java object or graph of Java object into an array of bytes which can be stored in a file or transmitted over a network. Java Serialization Tutorials Java provides a mechanism, called object serialization where an object can be represented as a sequence of bytes that includes the object’s data as well as information about the object’s type and the types of data stored in the object. Java.io.Serializable; java.io.Externalizable; Serializable interface is a marker interface. Which means that you does not have to implement any methods if your class derives from this interface. This is just a marker and the Java runtime, when trying to Serialize the class, will just check for the presence of this interface in the class.
This process of serializing an object is also called marshalling an object in some situations.[1][2] The opposite operation, extracting a data structure from a series of bytes, is deserialization (also called unmarshalling).
Java serialization is the process of converting an object into a stream of bytes so we can do stuff like store it on disk or send it over the network. Deserialization is the reverse process – converting a stream of bytes into an object in memory. A serializable class can declare its own.
Uses[edit]
For some of these features to be useful, architecture independence must be maintained. For example, for maximal use of distribution, a computer running on a different hardware architecture should be able to reliably reconstruct a serialized data stream, regardless of endianness. This means that the simpler and faster procedure of directly copying the memory layout of the data structure cannot work reliably for all architectures. Serializing the data structure in an architecture-independent format means preventing the problems of byte ordering, memory layout, or simply different ways of representing data structures in different programming languages.
Inherent to any serialization scheme is that, because the encoding of the data is by definition serial, extracting one part of the serialized data structure requires that the entire object be read from start to end, and reconstructed. In many applications, this linearity is an asset, because it enables simple, common I/O interfaces to be utilized to hold and pass on the state of an object. In applications where higher performance is an issue, it can make sense to expend more effort to deal with a more complex, non-linear storage organization.
Even on a single machine, primitive pointer objects are too fragile to save because the objects to which they point may be reloaded to a different location in memory. To deal with this, the serialization process includes a step called unswizzling or pointer unswizzling, where direct pointer references are converted to references based on name or position. The deserialization process includes an inverse step called pointer swizzling. Heroquest equipment pdf download.
Since both serializing and deserializing can be driven from common code (for example, the Serialize function in Microsoft Foundation Classes), it is possible for the common code to do both at the same time, and thus, 1) detect differences between the objects being serialized and their prior copies, and 2) provide the input for the next such detection. It is not necessary to actually build the prior copy because differences can be detected on the fly. The technique is called differential execution. This is useful in the programming of user interfaces whose contents are time-varying — graphical objects can be created, removed, altered, or made to handle input events without necessarily having to write separate code to do those things.
Drawbacks[edit]
Serialization breaks the opacity of an abstract data type by potentially exposing private implementation details. Trivial implementations which serialize all data members may violate encapsulation.[2]
To discourage competitors from making compatible products, publishers of proprietary software often keep the details of their programs' serialization formats a trade secret. Some deliberately obfuscate or even encrypt the serialized data. Yet, interoperability requires that applications be able to understand each other's serialization formats. Therefore, remote method call architectures such as CORBA define their serialization formats in detail.
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Many institutions, such as archives and libraries, attempt to future proof their backup archives—in particular, database dumps—by storing them in some relatively human-readable serialized format.
Serialization formats[edit]
The Xerox Network Systems Courier technology in the early 1980s influenced the first widely adopted standard. Sun Microsystems published the External Data Representation (XDR) in 1987.[3]
In the late 1990s, a push to provide an alternative to the standard serialization protocols started: XML was used to produce a human readable text-based encoding. Such an encoding can be useful for persistent objects that may be read and understood by humans, or communicated to other systems regardless of programming language. It has the disadvantage of losing the more compact, byte-stream-based encoding, but by this point larger storage and transmission capacities made file size less of a concern than in the early days of computing. Binary XML had been proposed as a compromise which was not readable by plain-text editors, but was more compact than regular XML. In the 2000s, XML was often used for asynchronous transfer of structured data between client and server in Ajax web applications.
JSON is a lighter plain-text alternative to XML which is also commonly used for client-server communication in web applications. JSON is based on JavaScript syntax, but is supported in other programming languages as well.
YAML, is similar to JSON and includes features that make it more powerful for serialization, more 'human friendly,' and potentially more compact. These features include a notion of tagging data types, support for non-hierarchical data structures, the option to structure data with indentation, and multiple forms of scalar data quoting.
The property list format is a human-readable serialization format used in NeXTSTEP, GNUstep, and macOSCocoa.
For large volume scientific datasets, such as satellite data and output of numerical climate, weather, or ocean models, specific binary serialization standards have been developed, e.g. HDF, netCDF and the older GRIB.
For a comparison of Data Serialization Formats see: Comparison of, and Java then handles serialization internally. There are no serialization methods defined on the
Serializable interface, but a serializable class can optionally define methods with certain special names and signatures that if defined, will be called as part of the serialization/deserialization process. The language also allows the developer to override the serialization process more thoroughly by implementing another interface, the Externalizable interface, which includes two special methods that are used to save and restore the object's state. There are three primary reasons why objects are not serializable by default and must implement the Serializable interface to access Java's serialization mechanism. Firstly, not all objects capture useful semantics in a serialized state. For example, a Thread object is tied to the state of the current JVM. There is no context in which a deserialized Thread object would maintain useful semantics. Secondly, the serialized state of an object forms part of its classes' compatibility contract. Maintaining compatibility between versions of serializable classes requires additional effort and consideration. Therefore, making a class serializable needs to be a deliberate design decision and not a default condition. Lastly, serialization allows access to non-transient private members of a class that are not otherwise accessible. Classes containing sensitive information (for example, a password) should not be serializable nor externalizable. The standard encoding method uses a recursive graph-based translation of the object's class descriptor and serializable fields into a byte stream. Primitives as well as non-transient, non-static referenced objects are encoded into the stream. Each object that is referenced by the serialized object via a field that is not marked as transient must also be serialized; and if any object in the complete graph of non-transient object references is not serializable, then serialization will fail. The developer can influence this behavior by marking objects as transient, or by redefining the serialization for an object so that some portion of the reference graph is truncated and not serialized. Java does not use constructor to serialize objects. It is possible to serialize Java objects through JDBC and store them into a database.[8] While Swing components do implement the Serializable interface, they are not guaranteed to be portable between different versions of the Java Virtual Machine. As such, a Swing component, or any component which inherits it, may be serialized to a byte stream, but it is not guaranteed that this will be re-constitutable on another machine.
See also[edit]References[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Serialization&oldid=920444879'
Active5 months ago
I need to serialize some objects to a JSON and send to a WebService. How can I do it using the org.json library? Or I'll have to use another one? Here is the class I need to serialize:
I only put the variables and the constructor of the class but it also have the getters and setters. So if anyone can help please
AurA
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7 Answers
Easy way to do it without annotations is to use Gson library
Simple as that:
Tombart
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BitmanBitman
The quickest and easiest way I've found to Json-ify POJOs is to use the Gson library. This blog post gives a quick overview of using the library.
ryanbatemanryanbateman
You make the http request
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You read the Buffer
Create a JSONObject and pass the result string to the constructor:
Parse the json results to your desired variables:
Do not forget to import:
Carlos LanderasCarlos Landeras
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GSON is easy to use and has relatively small memory footprint. If you loke to have even smaller footprint, you can grab:
Which is tiny wrapper around stripped down GSON libraries for just POJOs
Konstantin PribludaKonstantin Pribluda
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The 'reference' Java implementation by Sean Leary is here on github. Make sure to have the latest version - different libraries pull in versions buggy old versions from 2009.
Java EE 7 has a JSON API in
javax.json , see the Javadoc. From what I can tell, it doesn't have a simple method to marshall any object to JSON, you need to construct a JsonObject or a JsonArray .
But I assume the other libraries like GSON will have adapters to create objects implementing those interfaces.
Ondra ŽižkaOndra Žižka
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One can use the Jackson library as well.
Simply do this:
nasprasnaspras
Java Serialize Class Object
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After JAVAEE8 published , now you can use the new JAVAEE API JSON-B (JSR367)
Maven dependency :
Here is some code snapshot :
JSON-P is also updated to 1.1 and more easy to use. JSON-P 1.1 (JSR374)
Maven dependency :
Here is the runnable code snapshot :
wodongwodong
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