Azure JSON shared library for Java

Azure JSON provides shared primitives, abstractions, and helpers for JSON.

Getting started

Prerequisites

A Java Development Kit (JDK), version 8 or later.

Include the package

<dependency>
  <groupId>com.azure</groupId>
  <artifactId>azure-json</artifactId>
  <version>1.5.0</version>
</dependency>

Key concepts

JsonSerializable

JsonSerializable is used to define how an object is JSON serialized and deserialized using stream-style serialization where the object itself manages the logic for how it's handled. The interface provides an instance-based toJson API that handles writing the object to a JsonWriter and a static fromJson API which implementations must provide to define how to create an object by reading from a JsonReader, if an implementation isn't provided UnsupportedOperationException will be thrown.

JsonToken

JsonToken is a basic enum that indicates the current state in a JSON stream.

JsonReader

JsonReader provides both basic, reading primitive and boxed primitive types, and convenience, reading arrays, maps, and objects, APIs for reading JSON. JsonReader is provided to allow for any underlying JSON parser to implement it, such as Jackson or GSON, as long as the implementation passes the tests provided by this package's test-jar (JsonReaderContractTests).

JsonReader doesn't progress forward in the JSON stream until nextToken is called, meaning that JsonReader.getInt could be called indefinitely returning the same integer without error until nextToken progresses the JSON stream forward.

JsonReader allows for type conversion between JSON types, such as trying to convert a JSON string to a number or vice versa, and for commonly used nonstandard JSON values, such as NaN, Infinity, +Infinity, and -Infinity.

JsonReader doesn't take ownership of the JSON input source and therefore doesn't close any resources if the JSON is provided using an InputStream or Reader.

Nesting Limits

JsonReader's generic readUntyped API tracks how deeply nested the object being read is. If the nesting passes the threshold of 1000, IllegalStateException is thrown to prevent StackOverflowError.

JsonWriter

JsonWriter provides both basic, writing primitives and boxed primitive types, and convenience, writing arrays, maps, and objects, APIs for writing JSON. JsonWriter is provided to allow for any underlying JSON writer to implement it, such as Jackson or GSON, as long as the implementation passes the tests provided by the package's test-jar (JsonWriterContractTests).

JsonWriter allows for commonly used nonstandard JSON values, such as NaN, Infinity, +Infinity, and -Infinity, to be written using writeNumberField or writeRawValue.

JsonWriter doesn't write null byte[], Boolean, Number, or String values when written as a field, writeBinaryField, writeBooleanField, writeNumberField, or writeStringField, if a null field needs to be written use writeNullField.

JsonWriter must be periodically flushed to ensure content written to it's flushed to the underlying container type, generally an OutputStream or Writer. Failing to flush may result in content being lost. Closing the JsonWriter flushes content, so it's best practice to use JsonWriter in a try-with-resources block where the JsonWriter is closed once it's finished being used.

JsonWriter doesn't take ownership of the JSON output source and therefore doesn't close any resources if the JSON is being written to an OutputSteam or Writer.

JSON State Management

To ensure that the JSON being written is valid, JsonWriter maintains the state of the JSON using JsonWriteContext and on each attempt to write it validates whether the operation is valid. The implementation of JsonWriter must ensure state is tracked correctly, for example when nothing has been written the JSON state must be ROOT and ROOT doesn't allow for JSON field names to be written.

JsonProvider

JsonProvider is a service provider interface that allows for JsonReaders and JsonWriters to be created using implementations found on the classpath. JsonProvider can also create the default implementations that are provided by this package if an implementation isn't found on the classpath.

JsonOptions

JsonOptions contains configurations that must be respected by all implementations of JsonReaders and JsonWriters. At this time, there's only one configuration for determining whether non-numeric numbers, NaN, Infinity, +Infinity, and -Infinity are supported in JSON reading and writing with a default setting of true, that non-numeric numbers are allowed.

Providing an SPI implementation

JsonReader and JsonWriter are service provider interfaces used by JsonProvider and JsonProviders to enable implementations to be loaded from the class path. The Azure JSON package provides a default implementation that is used if one can't be found on the class path. To provide a custom implementation, implement JsonReader, JsonWriter, and JsonProvider in your own package and indicate that the package provides an instance of JsonProvider. To ensure that your implementations are correct, include the test scoped dependency of Azure JSON and extend the JsonReaderContractTests, JsonWriterContractTests, and JsonProviderContractTests. These tests outline all basic contract requirements set forth by JsonReader, JsonWriter, and JsonProvider and testing a few complex scenarios to provide validation of any implementation.

Examples

Check out the samples README for in-depth examples on how to use Azure JSON.

Troubleshooting

If you encounter any bugs, please file issues via GitHub Issues or checkout StackOverflow for Azure Java SDK.

Next steps

Get started with Azure libraries that are built using Azure Core.

Contributing

For details on contributing to this repository, see the contributing guide.

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request