星期六, 4月 30, 2011

Excluding Fields From Serialization and Deserialization

Gson's @Expose

This feature provides a way where you can mark certain fields of your objects to be excluded for consideration for serialization and deserialization to JSON. To use this annotation, you must create Gson by using new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create(). The Gson instance created will exclude all fields in a class that are not marked with @Exposeannotation.

Versioning Support

Multiple versions of the same object can be maintained by using @Since annotation. This annotation can be used on Classes, Fields and, in a future release, Methods. In order to leverage this feature, you must configure your Gson instance to ignore any field/object that is greater than some version number. If no version is set on the Gson instance then it will serialize and deserialize all fields and classes regardless of the version.

public class VersionedClass {
@Since(1.1) private final String newerField;
  @Since(1.0) private final String newField;
private final String field;

public VersionedClass() {
    this.newerField = "newer";
    this.newField = "new";
    this.field = "old";
}
}

VersionedClass versionedObject = new VersionedClass();
Gson gson = new GsonBuilder().setVersion(1.0).create();
String jsonOutput = gson.toJson(someObject);
System.out.println(jsonOutput);System.out.println();
gson = new Gson();
jsonOutput = gson.toJson(someObject);
System.out.println(jsonOutput);

======== OUTPUT ========
{"newField":"new","field":"old"}
{"newerField":"newer","newField":"new","field":"old"}

Compact Vs. Pretty Printing for JSON Output Format

If you like to use the Pretty Print feature, you must configure your Gson instance using the GsonBuilder. The JsonFormatter is not exposed through our public API, so the client is unable to configure the default print settings/margins for the JSON output. For now, we only provide a default JsonPrintFormatter that has default line length of 80 character, 2 character indentation, and 4 character right margin.

The following is an example shows how to configure a Gson instance to use the default JsonPrintFormatter instead of the JsonCompactFormatter:

Gson gson = new GsonBuilder().setPrettyPrinting().create();
String jsonOutput = gson.toJson(someObject);

Apps on Facebook.com

http://developers.facebook.com/docs/guides/canvas/
Building an app on Facebook gives you the opportunity to deeply integrate into the core Facebook experience. Your app can integrate with many aspects of Facebook.com, including the News Feed and Notifications. All of the core Facebook Platform technologies, such as Social Plugins, the Graph API and Platform Dialogs are available to Apps on Facebook.com.

google-gson

http://code.google.com/p/google-gson/

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

There are a few open-source projects that can convert Java objects to JSON. However, most of them require that you place Java annotations in your classes something that you can not do if you do not have access to the source-code. Most also do not fully support the use of Java Generics. Gson considers both of these as very important design goals.

Gson Goals

Provide simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa
Allow pre-existing unmodifiable objects to be converted to and from JSON
Extensive support of Java Generics
Allow custom representations for objects
Support arbitrarily complex objects (with deep inheritance hierarchies and extensive use of generic types)

Gson Documentation

Gson API: Javadocs for the current Gson release
Gson user guide: This guide contains examples on how to use Gson in your code.
Gson Roadmap: Details on upcoming releases
Gson design document: This document discusses issues we faced while designing Gson. It also include a comparison of Gson with other Java libraries that can be used for Json conversion

Please use the google-gson Google Group to discuss Gson, or to post questions.

星期三, 4月 20, 2011

★我在日本受的防災訓練及阪神生存者的防災建議 @ 就醬的營養午餐 :: 痞客邦 PIXNET ::

星期五, 4月 15, 2011

olap4j 1.0.0 was released on April 12, 2011.

This project aims at demonstrating some of the functionality of olap4j. They are not a tutorial, but serve as a source of sample code snippets.

To use, you will need Apache Ant 1.7 or newer. Then simply run "ant" in a terminal where you installed olap4j-demo. It will resolve all dependencies. You can then run the examples. There is also a sample eclipse project included.

http://www.olap4j.org/

http://code.google.com/p/olap4j-demo/

Memory of Jack Wen