- 1 year ago
How does Java actually spawn a process by ProcessBuilder on Windows platform?
In Java, the ProcessBuilder
class is used to create and manage operating system processes. When you invoke ProcessBuilder
to spawn a process on the Windows platform, it internally relies on the underlying operating system mechanisms to create and manage the process.
Under the hood, the ProcessBuilder
class utilizes the CreateProcess
function from the Windows API to start a new process. Here's a high-level overview of the process creation steps on Windows:
Create the command-line string: You provide the command-line arguments and executable path to the
ProcessBuilder
constructor or by using thecommand()
andarguments()
methods.Create a
ProcessBuilder
instance: After setting the command-line arguments, you create an instance of theProcessBuilder
class.Start the process: To start the process, you call the
start()
method on theProcessBuilder
instance. This method internally calls theCreateProcess
function to launch the new process.Prepare the
STARTUPINFO
andPROCESS_INFORMATION
structures: Before invokingCreateProcess
, theProcessBuilder
class prepares the necessary data structures, including theSTARTUPINFO
andPROCESS_INFORMATION
structures, which contain information about the new process.Call
CreateProcess
: Finally, theCreateProcess
function is called, passing in the necessary parameters, such as the executable path, command-line arguments, process attributes, and handles for standard input, output, and error.Create the new process: The
CreateProcess
function creates a new process using the specified executable and command-line arguments. It also sets up the standard input, output, and error handles as specified.Return the
Process
object: Once the new process is created, theProcessBuilder
class creates aProcess
object that represents the newly spawned process and returns it to the Java application. ThisProcess
object provides methods for interacting with the process, such as reading from or writing to its input/output streams or waiting for the process to complete.
By using the Windows API function CreateProcess
, the Java ProcessBuilder
class facilitates process creation and management on the Windows platform. The underlying Windows operating system takes care of the low-level details of process creation and execution based on the provided command-line arguments and configuration.