DJSON

DJSON is a JSON implementation for Delphi 7 and Lazarus (FPC).

The objects are memory-managed and auto-constructed in a fluent coding style.

To use in your project just compile the corresponding version.

Using with Delphi 7

• Open the package DJsonD7.dpk and compile.
• The .dcu and .bpl files will be in .\lib\D7\ path.

Using with Lazarus

• Open the package DJsonFPC.lpk and compile.
• The .o and .ppu files will be in .\lib\FPC\<target-cpu>-<target-os>\ path.

Unit tests

There are projects for unit testing the library for both Delphi 7 (using DUnit) and Lazarus (using FPUnit). To execute the tests you need first compile the library, then the test projects.

Examples

The starting point for creating JSON objects is through JSONBuilder, like:

JString := JSONBuilder.BuildString('JSON Test'); // "JSON Test"
JNumber := JSONBuiler.BuildNumber(666); // 666
JBoolean := JSONBuilder.BuildBoolean(true); // true
JNull := JSONBuilder.BuildNull; // null
JArray := JSONBuilder.BuildArray
  .Add('String test')
  .Add(100)
  .Add(false)
  .Build;
// ["String test", 100, false]
JObject := JSONBuilder.BuildObject
  .Add('Library Name', 'DJSON')
  .Add('Version', 1000)
  .Add('Suport FPC', true)
  .Add('Suport D7', true)
  .Build;
// {"Library Name":"DJSON","Version":1000,"Suport FPC":true,"Suport D7": true}

You can check which type the object is using the .ValueType property. The valid values are:

(jsObject, jsArray, jsString, jsNumber, jsBoolean, jsNull)

And you can mix calls to JSONBuilder to build complex JSON objects like:

JCplxObject := JSONBuilder.BuildObject
  .Add('Library', 'DJSON')
  .Add('Version', JSONBuilder.BuildArray
    .Add(1)
    .Add(0)
    .Add(0)
    .Add(0)
    .Build)
  .Build;
// {"Library":"DJSON", "Version":[1,0,0,0]}

You can use the TJSONReader class to parse strings into JSON objects, like:

JObject := TJSONReader.Read('{"Library":"DJSON", "Version":[1,0,0,0]}'); // parse a string directly
JObject := TJSONReader.ReadFromStream(aStream); // Read JSON from a stream
JObject := TJSONReader.ReadFromFile(aFile); // Read JSON from a file

You can write a JSON using the TJSONWriter class, like:

TJSONWriter.WriteToStream(aJSON, aStream);
TJSONWriter.WriteToFile(aJSON, aFile);

To transform a JSON object to string, simple call the ToString() method, like:

MyJSONText := aJSON.ToString;

The simple JSON values (string, number, boolean and null) are accessed using the .Value property, like:

JNumber := JSONBuilder.BuildNumber(666);
MyNumber := JNumber.Value; // MyNumber = 666

The JSON array values are accessed using the default property Element[], like:

JArray := JSONBuilder.BuildArray
  .Add('String test')
  .Add(100)
  .Add(false)
  .Build;
// JArray[0].Value = 'String test'
// JArray.Element[1].Value = 100
// JArray[2].Value = false

The JSON object values are accessed using the default property Member[], like:

JObject := JSONBuilder.BuildObject
  .Add('Library Name', 'DJSON')
  .Add('Version', 1000)
  .Add('Suport FPC', true)
  .Add('Suport D7', true)
  .Build;
// JObject['Library Name'].Value = 'DJSON'
// JObject['Version'].Value = 1000

You can access a specific member by its index in a JSON object using the MemberAt[] property, like:

JObject := JSONBuilder.BuildObject
  .Add('Library Name', 'DJSON')
  .Add('Version', 1000)
  .Add('Suport FPC', true)
  .Add('Suport D7', false)
  .Build;
// JObject.MemberAt[2].Value = true
// JObject.MemberAt[3].Value = false

You can also access the member name or value by its index using NameAt[] and ValueAt[], respectively, like:

JObject := JSONBuilder.BuildObject
  .Add('Library Name', 'DJSON')
  .Add('Version', 1000)
  .Add('Suport FPC', true)
  .Add('Suport D7', false)
  .Build;
// JObject.NameAt[2] = 'Suport FPC'
// JObject.ValueAt[2] = true

Both IJSONArray and IJSONObject have the .Count property which returns the total elements inside the object.

For complex JSON objects, you can access a nested complex element using .AsArray or .AsObject properties, like:

JObject := TJSONReader.Read('{"Library":"DJSON", "Version":[1,0,0,0]}');
// JObject['Version'].AsArray[0].Value = 1
// JObject['Version'].AsArray[1].Value = 0
...

If you like you can use a validation tool to check if the values are considered a valid JSON.

Take a look at the unit test DJsonTests.pas file to see more examples.