Implementation:SeleniumHQ Selenium DevTools ConverterFunctions

Knowledge Sources	SeleniumHQ_Selenium Selenium Documentation
Domains	WebDriver, DevTools_Protocol
Last Updated	2026-02-12 00:00 GMT

Overview

The ConverterFunctions class provides static utility methods for creating JSON-to-object mapper functions used by CDP Command and Event instances to extract values from DevTools Protocol responses.

Description

ConverterFunctions is a utility class containing factory methods that produce Function<JsonInput, X> instances. These mappers are designed to parse CDP JSON response objects, extracting a specific named key and converting it to a desired Java type. The class provides three factory methods:

• map(String keyName, Type typeOfX) -- extracts a key from a JSON object and deserializes it using a java.lang.reflect.Type.
• map(String keyName, Function<JsonInput, X> read) -- extracts a key from a JSON object and applies a custom reader function.
• empty() -- handles CDP responses that return an empty JSON object ({}), returning null.

Both map overloads iterate through all keys of the JSON object, matching on the specified key name and skipping all others.

Usage

Use ConverterFunctions when building custom CDP commands or events that need to extract specific values from JSON response objects. These utilities are used extensively by the auto-generated CDP domain classes to define response mappers for commands and events.

Code Reference

Source Location

• Repository: SeleniumHQ_Selenium
• File: java/src/org/openqa/selenium/devtools/ConverterFunctions.java

Signature

public class ConverterFunctions {

  public static <X> Function<JsonInput, @Nullable X> map(String keyName, Type typeOfX)
  public static <X> Function<JsonInput, @Nullable X> map(String keyName, Function<JsonInput, @Nullable X> read)
  public static Function<JsonInput, @Nullable Void> empty()
}

Import

import org.openqa.selenium.devtools.ConverterFunctions;

I/O Contract

Method: map(String keyName, Type typeOfX)

Parameter	Type	Required	Description
keyName	String	Yes	The JSON object key to extract from the response
typeOfX	java.lang.reflect.Type	Yes	The Java type to deserialize the key's value into

Returns	Description
Function<JsonInput, @Nullable X>	A mapper function that extracts and deserializes the named key from a JSON object; returns null if the key is not found

Method: map(String keyName, Function read)

Parameter	Type	Required	Description
keyName	String	Yes	The JSON object key to extract from the response
read	Function<JsonInput, @Nullable X>	Yes	A custom function to read and convert the JSON value

Returns	Description
Function<JsonInput, @Nullable X>	A mapper function that finds the named key and applies the custom reader; returns null if the key is not found

Method: empty()

Returns	Description
Function<JsonInput, @Nullable Void>	A mapper function that consumes an empty JSON object and returns null

Usage Examples

// Extract a String value from a CDP response by key name
Function<JsonInput, String> sessionIdMapper =
    ConverterFunctions.map("sessionId", String.class);

// Use the mapper in a Command
Command<String> attachCommand = new Command<>(
    "Target.attachToTarget",
    Map.of("targetId", targetId, "flatten", true),
    ConverterFunctions.map("sessionId", String.class)
);

// Use with a custom reader function for complex types
Function<JsonInput, MyType> customMapper =
    ConverterFunctions.map("result", input -> {
        // Custom deserialization logic
        return new MyType(input.read(String.class));
    });

// Use empty() for commands that return no meaningful data
Command<Void> enableCommand = new Command<>(
    "Network.enable",
    Map.of(),
    ConverterFunctions.empty()
);

Related Pages

• DevTools Command -- uses converter functions as response mappers
• DevTools Event -- uses converter functions as event payload mappers
• Factory Method -- static factory methods produce mapper functions
• Single Responsibility -- isolates JSON-to-object mapping logic from command/event definitions