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JSON Viewer: A Sample Application using DBXJSON.pas in Delphi
How to Download and Use DBXJSON.pas in Delphi
Delphi is a powerful programming language and IDE that allows you to create native applications for Windows, Linux, macOS, Android, iOS, and other platforms. One of the features that makes Delphi stand out is its support for JSON, a text-based data interchange format that is widely used on the web and in mobile applications. JSON is simple, lightweight, and easy to read and write.
dbxjson.pas download
In this article, you will learn how to download and use DBXJSON.pas, a unit that provides JSON support for Delphi. You will also learn how to use DBXJSON.pas to parse and generate JSON data, work with JSON objects and arrays, and serialize and deserialize Delphi objects to and from JSON strings.
What is DBXJSON.pas and why is it useful for Delphi programmers?
DBXJSON.pas is a unit that was introduced in Delphi 2010 as part of the DBExpress database driver architecture. It contains classes and methods that allow you to work with JSON data in Delphi. JSON stands for JavaScript Object Notation, and it is a format that represents structured data as a collection of name-value pairs (objects) or a list of values (arrays). JSON is based on the syntax of JavaScript, but it can be used independently from any programming language.
DBXJSON.pas is useful for Delphi programmers because it enables them to:
Read and write JSON data from files, streams, or web services
Create and manipulate JSON objects and arrays in memory
Convert between JSON data and Delphi data types
Serialize and deserialize Delphi objects to and from JSON strings
DBXJSON.pas is compatible with all versions of Delphi from 2010 onwards, including the latest version of RAD Studio. It is also cross-platform, meaning that you can use it to create applications for Windows, Linux, macOS, Android, iOS, and other platforms.
How to download and install DBXJSON.pas in Delphi?
If you have Delphi 2010 or later installed on your computer, you already have DBXJSON.pas available in your library path. You can find it in the following folder:
C:\Program Files (x86)\Embarcadero\Studio\21.0\source\data\dbx\DBXJSON.pas
If you have an older version of Delphi or you want to update DBXJSON.pas to the latest version, you can download it from the official Embarcadero website or from GitHub. Here are the links:
Embarcadero website
GitHub repositoryOnce you have downloaded DBXJSON.pas, you need to add it to your project. You can do this by following these steps:
Open your Delphi project in the IDE
Go to Project > Options > Delphi Compiler > Search path
Add the folder where you saved DBXJSON.pas to the search path
Click OK to save the changes
Go to File > Use Unit and select DBXJSON.pas from the list
Click OK to add the unit to your project
Alternatively, you can simply add the following line to the uses clause of your unit:
uses DBXJSON;
Now you are ready to use DBXJSON.pas in your Delphi code.
How to use DBXJSON.pas to parse and generate JSON data in Delphi?
Parsing and generating JSON data are two common tasks that you may need to perform when working with JSON in Delphi. Parsing JSON data means converting a JSON string or stream into a Delphi object that you can manipulate in memory. Generating JSON data means converting a Delphi object into a JSON string or stream that you can write to a file or send over the network.
DBXJSON.pas provides two pairs of classes that help you with these tasks: TJSONParser and TJSONDocument for parsing, and TJSONBuilder and TJSONWriter for generating. Let's see how they work.
Parsing JSON data with TJSONParser and TJSONDocument
TJSONParser is a class that reads a JSON string or stream and creates a TJSONDocument object that represents the JSON data. TJSONDocument is a class that holds a reference to the root element of the JSON data, which can be either a TJSONObject or a TJSONArray.
To parse JSON data with TJSONParser and TJSONDocument, you can use the following steps:
Create an instance of TJSONParser and pass the JSON string or stream to its constructor
Call the Parse method of the TJSONParser instance to create a TJSONDocument instance
Use the GetRoot method of the TJSONDocument instance to get the root element of the JSON data
Cast the root element to either TJSONObject or TJSONArray depending on its type
Free the TJSONParser and TJSONDocument instances when you are done with them
Here is an example of parsing a JSON string with TJSONParser and TJSONDocument:
var Parser: TJSONParser; Doc: TJSONDocument; Root: TJSONObject; Name: string; Age: integer; begin // Create a JSON parser and pass the JSON string to it Parser := TJSONParser.Create('"name":"John","age":25'); try // Parse the JSON string and create a JSON document Doc := Parser.Parse; try // Get the root element of the JSON document Root := Doc.GetRoot as TJSONObject; // Get the name and age values from the root object Name := Root.Get('name').JsonValue.Value; Age := StrToInt(Root.Get('age').JsonValue.Value); // Do something with the name and age values ShowMessage(Format('Name: %s, Age: %d', [Name, Age])); finally // Free the JSON document Doc.Free; end; finally // Free the JSON parser Parser.Free; end; end; Generating JSON data with TJSONBuilder and TJSONWriter
TJSONBuilder is a class that allows you to create JSON data in memory by using a fluent interface. TJSONWriter is a class that allows you to write JSON data to a string or a stream by using a TJSONBuilder instance.
To generate JSON data with TJSONBuilder and TJSONWriter, you can use the following steps:
Create an instance of TJSONBuilder and use its methods to create JSON objects and arrays
Create an instance of TJSONWriter and pass the TJSONBuilder instance to its constructor
Call the ToString or ToStream method of the TJSONWriter instance to get the JSON string or stream
Free the TJSONBuilder and TJSONWriter instances when you are done with them
Here is an example of generating a JSON string with TJSONBuilder and TJSONWriter:
var Builder: TJSONBuilder; Writer: TJSONWriter; JSON: string; begin // Create a JSON builder and use its methods to create a JSON object Builder := TJSONBuilder.Create; try Builder.BeginObject .Add('name', 'John') .Add('age', 25) .EndObject; // Create a JSON writer and pass the JSON builder to it Writer := TJSONWriter.Create(Builder); try // Get the JSON string from the JSON writer JSON := Writer.ToString; // Do something with the JSON string ShowMessage(JSON); finally // Free the JSON writer Writer.Free; end; finally // Free the JSON builder Builder.Free; end; end; How to use DBXJSON.pas to work with JSON objects and arrays in Delphi?
JSON objects and arrays are the two main types of elements that make up JSON data. A JSON object is a collection of name-value pairs, where the name is a string and the value can be any JSON data type. A JSON array is a list of values, where each value can be any JSON data type. JSON data types include strings, numbers, booleans, null, objects, and arrays.
DBXJSON.pas provides two pairs of classes that help you work with JSON objects and arrays in Delphi: TJSONObject and TJSONPair for objects, and TJSONArray and TJSONValue for arrays. Let's see how they work.
Accessing JSON object properties with TJSONObject and TJSONPair
TJSONObject is a class that represents a JSON object. It inherits from TJSONValue, which is the base class for all JSON data types. TJSONObject contains a list of TJSONPair instances, which represent the name-value pairs of the object. You can access the properties of a JSON object by using the following methods of TJSONObject:
Get: returns the TJSONPair instance with the given name
GetValue: returns the TJSONValue instance with the given name
Count: returns the number of name-value pairs in the object
GetPairs: returns an array of TJSONPair instances in the object
AddPair: adds a new name-value pair to the object
RemovePair: removes an existing name-value pair from the object
TJSONPair is a class that represents a name-value pair in a JSON object. It has two properties: JsonString and JsonValue, which hold the name and value of the pair respectively. You can access the name and value of a JSON pair by using the following methods of TJSONPair:
GetJsonString: returns the TJSONString instance that represents the name
GetJsonValue: returns the TJSONValue instance that represents the value
ToString: returns a string representation of the pair
Clone: returns a copy of the pair
Here is an example of accessing JSON object properties with TJSONObject and TJSONPair:
var Obj: TJSONObject; Pair: TJSONPair; Name: string; Age: integer; begin // Create a JSON object with some properties Obj := TJSONObject.Create; try Obj.AddPair('name', 'John'); Obj.AddPair('age', TJSONNumber.Create(25)); // Get the name property from the object Pair := Obj.Get('name'); Name := Pair.JsonValue.Value; // Get the age property from the object Pair := Obj.Get('age'); Age := (Pair.JsonValue as TJSONNumber).AsInt; // Do something with the name and age values ShowMessage(Format('Name: %s, Age: %d', [Name, Age])); finally // Free the JSON object Obj.Free; end; end; Iterating over JSON array elements with TJSONArray and TJSONValue
TJSONArray is a class that represents a JSON array. It inherits from TJSONValue, which is the base class for all JSON data types. TJSONArray contains a list of TJSONValue instances, which represent the elements of the array. You can access the elements of a JSON array by using the following methods of TJSONArray:
Get: returns the TJSONValue instance at the given index
GetValue: returns the TJSONValue instance at the given index, casted to a specific type
Count: returns the number of elements in the array
GetItems: returns an array of TJSONValue instances in the array
AddElement: adds a new element to the array
RemoveElement: removes an existing element from the array
TJSONValue is a class that represents any JSON data type. It has a property called Value, which returns a string representation of the value. It also has several methods that allow you to cast the value to a specific type, such as AsString, AsNumber, AsBoolean, AsObject, and AsArray.
To iterate over JSON array elements with TJSONArray and TJSONValue, you can use a for loop or a for-in loop. Here is an example of iterating over a JSON array with a for loop:
var Arr: TJSONArray; Val: TJSONValue; Str: string; I: integer; begin // Create a JSON array with some elements Arr := TJSONArray.Create; try Arr.AddElement(TJSONString.Create('Hello')); Arr.AddElement(TJSONNumber.Create(42)); Arr.AddElement(TJSONTrue.Create); // Iterate over the array elements with a for loop for I := 0 to Arr.Count - 1 do begin // Get the element at the current index Val := Arr.Get(I); // Get the string representation of the element Str := Val.Value; // Do something with the string value ShowMessage(Str); end; finally // Free the JSON array Arr.Free; end; end;
Here is an example of iterating over a JSON array with a for-in loop:
var Arr: TJSONArray; Val: TJSONValue; Str: string; begin // Create a JSON array with some elements Arr := TJSONArray.Create; try Arr.AddElement(TJSONString.Create('Hello')); Arr.AddElement(TJSONNumber.Create(42)); Arr.AddElement(TJSONTrue.Create); // Iterate over the array elements with a for-in loop for Val in Arr do begin // Get the string representation of the element Str := Val.Value; // Do something with the string value ShowMessage(Str); end; finally // Free the JSON array Arr.Free; end; end; How to use DBXJSON.pas to work with JSON serialization and deserialization in Delphi?
JSON serialization and deserialization are two advanced features that allow you to convert between Delphi objects and JSON strings. Serialization means converting a Delphi object into a JSON string that represents its state and properties. Deserialization means converting a JSON string into a Delphi object that restores its state and properties.
DBXJSON.pas provides two methods that help you with these features: TJson.ObjectToJsonString and TJson.JsonToObject. Let's see how they work.
Serializing Delphi objects to JSON strings with TJson.ObjectToJsonString
TJson.ObjectToJsonString is a class method that takes a Delphi object as a parameter and returns a JSON string that represents the object. The object can be any class that is registered with the RTTI (Run-Time Type Information) system, such as TPersistent, TComponent, or any custom class that has the $M+ directive.
To serialize Delphi objects to JSON strings with TJson.ObjectToJsonString, you can use the following steps:
Create an instance of the class that you want to serialize
Set the values of the properties that you want to include in the JSON string
Call the TJson.ObjectToJsonString method and pass the object instance as a parameter
Get the JSON string from the return value of the method
Free the object instance when you are done with it
Here is an example of serializing a Delphi object to a JSON string with TJson.ObjectToJsonString:
type // A custom class that has the $M+ directive TPerson = class private FName: string; FAge: integer; public property Name: string read FName write FName; property Age: integer read FAge write FAge; end; var Person: TPerson; JSON: string; begin // Create an instance of the custom class Person := TPerson.Create; try // Set the values of the properties Person.Name := 'John'; Person.Age := 25; // Serialize the object to a JSON string JSON := TJson.ObjectToJsonString(Person); // Do something with the JSON string ShowMessage(JSON); finally // Free the object Person.Free; end; end; Deserializing JSON strings to Delphi objects with TJson.JsonToObject
TJson.JsonToObject is a class method that takes a JSON string as a parameter and returns a Delphi object that represents the string. The object can be any class that is registered with the RTTI (Run-Time Type Information) system, such as TPersistent, TComponent, or any custom class that has the $M+ directive.
To deserialize JSON strings to Delphi objects with TJson.JsonToObject, you can use the following steps:
Create a variable of the class type that you want to deserialize
Assign the JSON string to the variable
Call the TJson.JsonToObject method and pass the variable as a parameter
Get the object instance from the return value of the method
Use the properties and methods of the object instance as needed
Free the object instance when you are done with it
Here is an example of deserializing a JSON string to a Delphi object with TJson.JsonToObject:
type // A custom class that has the $M+ directive TPerson = class private FName: string; FAge: integer; public property Name: string read FName write FName; property Age: integer read FAge write FAge; end; var Person: TPerson; JSON: string; begin // Assign the JSON string to a variable JSON := '"name":"John","age":25'; // Deserialize the JSON string to an object Person := TJson.JsonToObject(JSON); try // Use the properties and methods of the object ShowMessage(Format('Name: %s, Age: %d', [Person.Name, Person.Age])); finally // Free the object Person.Free; end; end;
Conclusion
In this article, you have learned how to download and use DBXJSON.pas, a unit that provides JSON support for Delphi. You have also learned how to use DBXJSON.pas to parse and generate JSON data, work with JSON objects and arrays, and serialize and deserialize Delphi objects to and from JSON strings.
DBXJSON.pas is a powerful and versatile unit that can help you create cross-platform applications that can communicate with web services, databases, and other systems that use JSON as a data interchange format. It can also help you simplify and optimize your code by using JSON as a serialization format for your objects.
If you want to learn more about DBXJSON.pas and its features, you can check out the following resources:
DBXJSON.pas documentation
DBXJSON.pas examples
DBXJSON.pas blog posts
FAQs
What are the advantages of using JSON over XML in Delphi?
Some of the advantages of using JSON over XML in Delphi are:
JSON is simpler and more concise than XML, which makes it easier to read and write
JSON is more compatible with JavaScript and other web technologies, which makes it more suitable for web development
JSON has better performance than XML, which makes it faster to parse and generate
JSON has native support in Delphi since version 2010, which makes it easier to use
What are the differences between DBXJSON.pas and other JSON libraries for Delphi?
Some of the differences between DBXJSON.pas and other JSON libraries for Delphi are:
DBXJSON.pas is part of the official Delphi library, which means it is maintained and updated by Embarcadero
DBXJSON.pas uses RTTI (Run-Time Type Information) to serialize and deserialize objects, which means it can handle complex types and inheritance
DBXJSON.pas uses a fluent interface to create JSON data in memory, which means it is more readable and expressive
DBXJSON.pas supports both UTF-8 and UTF-16 encoding for JSON strings, which means it can handle different character sets
How to handle errors and exceptions when using DBXJSON.pas in Delphi?
To handle errors and exceptions when using DBXJSON.pas in Delphi, you can use the following techniques:
Use try-except blocks to catch and handle any exceptions that may occur when calling the methods of DBXJSON.pas
Use the IsValid method of TJSONValue to check if a JSON value is valid before using it
Use the TryGetValue method of TJSONObject to check if a JSON object has a property with a given name before accessing it
Use the TryGet method of TJSONArray to check if a JSON array has an element at a given index before accessing it
Use the TryParse and TryObjectToJsonString methods of TJson to check if a JSON string can be parsed or serialized without raising an exception
Here is an example of handling errors and exceptions with DBXJSON.pas in Delphi:
var Parser: TJSONParser; Doc: TJSONDocument; Root: TJSONObject; Name: string; Age: integer; begin // Create a JSON parser and pass an invalid JSON string to it Parser := TJSONParser.Create('{"name":"Joh