Implementation:SeleniumHQ Selenium DevTools Command

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

Overview

The Command class is a generic container representing a Chrome DevTools Protocol (CDP) command, encapsulating the method name, parameters, and a response mapper function.

Description

Command<X> models a single CDP command that can be sent to the browser through the DevTools session. Each command carries a method name (e.g., "Page.navigate"), an immutable map of parameters, and a Function<JsonInput, X> mapper used to deserialize the JSON response into the expected return type X. The class also supports a sendsResponse flag to handle edge-case CDP commands that do not return a response, via the doesNotSendResponse() factory method.

Usage

Use Command when constructing CDP commands to send via a DevTools session. In most cases, commands are created by the auto-generated CDP domain classes (e.g., Network.enable()), but custom commands can be constructed directly for unsupported or experimental CDP methods.

Code Reference

Source Location

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

Signature

public class Command<X> {

  public Command(String method, Map<String, Object> params)
  public Command(String method, Map<String, Object> params, Type typeOfX)
  public Command(String method, Map<String, Object> params, Function<JsonInput, X> mapper)

  public String getMethod()
  public Map<String, Object> getParams()
  public boolean getSendsResponse()
  public Command<X> doesNotSendResponse()
}

Import

import org.openqa.selenium.devtools.Command;

I/O Contract

Constructor Parameters

Parameter	Type	Required	Description
method	String	Yes	The CDP method name (e.g., "Page.navigate")
params	Map<String, Object>	Yes	The command parameters as key-value pairs
typeOfX	java.lang.reflect.Type	No	The type to deserialize the response into (defaults to Object.class)
mapper	Function<JsonInput, X>	No	Custom function to deserialize the JSON response

Return Values

Method	Return Type	Description
getMethod()	String	The CDP method name
getParams()	Map<String, Object>	Immutable copy of command parameters
getSendsResponse()	boolean	Whether the command expects a response from the browser
doesNotSendResponse()	Command<X>	Returns a new Command instance flagged as not expecting a response

Usage Examples

// Creating a command with a type-based mapper
Command<String> navigateCommand = new Command<>(
    "Page.navigate",
    Map.of("url", "https://example.com"),
    String.class
);

// Creating a command with a custom mapper
Command<Boolean> customCommand = new Command<>(
    "Emulation.setDeviceMetricsOverride",
    Map.of("width", 1024, "height", 768, "mobile", false),
    input -> input.read(Boolean.class)
);

// Sending a command via DevTools session
DevTools devTools = ((HasDevTools) driver).getDevTools();
devTools.createSession();
devTools.send(navigateCommand);

// Handling a command that does not send a response
Command<Void> fireAndForget = new Command<>(
    "SomeMethod",
    Map.of()
).doesNotSendResponse();

Related Pages

• DevTools Event -- companion class for CDP event subscriptions
• DevTools ConverterFunctions -- utility functions for building response mappers
• Separation of Concerns -- Command encapsulates method, params, and response mapping in a single object
• Immutability -- parameter maps are defensively copied via Map.copyOf()