Java 9 揭秘（12. Process API 更新）

一. Process API是什么

Runtime
ProcessBuilder
ProcessBuilder.Redirect
Process
ProcessHandle
ProcessHandle.Info

Process

Runtime

exec()

ProcessBuilder

ProcessBuilder.Redirect

ProcessBuilder

start()

Process

start()

ProcessBuilder

ProcessBuilder

Runtime.exec()

Process

ProcessBuilder

ProcessHandle

ProcessHandle

Process

ProcessHandle

Process

ProcessHandle

Process

ProcessHandle

Process

ProcessHandle

toHandle()

ProcessHandle.Info

ProcessHandle

info()

ProcessHandle.Info

二. 当前进程

ProcessHandle

current()

// Get the handle of the current process
ProcessHandle current = ProcessHandle.current();

ProcessHandle

ProcessHandle

destroy()

destroyForcibly()

IllegalStateException

三. 查询进程状态

ProcessHandle

static Stream<ProcessHandle> allProcesses()

Stream<ProcessHandle> children()

descendants()

static ProcessHandle current()

ProcessHandle

Stream<ProcessHandle> descendants()

children()

boolean destroy()

boolean destroyForcibly()

long getPid()

ProcessHandle.Info info()

boolean isAlive()

ProcessHandle

static Optional<ProcessHandle> of(long pid)

Optional<ProcessHandle>

Optional

CompletableFuture <ProcessHandle> onExit()

CompletableFuture<ProcessHandle>

IllegalStateException

Optional<ProcessHandle> parent()

Optional<ProcessHandle>

boolean supportsNormalTermination()

destroy()

ProcessHandle.Info

ProcessHandle

Process

info()

ProcessHandle.Info

Optional

Optional<String[]> arguments()

Optional<String> command()

Optional<String> commandLine()

command()

arguments()

Optional

command()

arguments()

Optional<Instant> startInstant()

Optional

Optional<Duration> totalCpuDuration()

Optional<String> user()

ProcessHandle

ProcessHandle.Info

// module-info.java
module com.jdojo.process.api {
exports com.jdojo.process.api;
}

CurrentProcessInfo

printInfo()

ProcessHandle

main()

// CurrentProcessInfo.java
package com.jdojo.process.api;
import java.time.Duration;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Arrays;
public class CurrentProcessInfo {
public static void main(String[] args) {
// Get the handle of the current process
ProcessHandle current = ProcessHandle.current();
// Print the process details
printInfo(current);
}
public static void printInfo(ProcessHandle handle) {
// Get the process ID
long pid = handle.getPid();
// Is the process still running
boolean isAlive = handle.isAlive();
// Get other process info
ProcessHandle.Info info = handle.info();
String command = info.command().orElse("");
String[] args = info.arguments()
.orElse(new String[]{});
String commandLine = info.commandLine().orElse("");
ZonedDateTime startTime = info.startInstant()
.orElse(Instant.now())
.atZone(ZoneId.systemDefault());
Duration duration = info.totalCpuDuration()
.orElse(Duration.ZERO);
String owner = info.user().orElse("Unknown");
long childrenCount = handle.children().count();
// Print the process details
System.out.printf("PID: %d%n", pid);
System.out.printf("IsAlive: %b%n", isAlive);
System.out.printf("Command: %s%n", command);
System.out.printf("Arguments: %s%n", Arrays.toString(args));
System.out.printf("CommandLine: %s%n", commandLine);
System.out.printf("Start Time: %s%n", startTime);
System.out.printf("CPU Time: %s%n", duration);
System.out.printf("Owner: %s%n", owner);
System.out.printf("Children Count: %d%n", childrenCount);
}
}

PID: 8692
IsAlive: true
Command: C:\java9\bin\java.exe
Arguments: []
CommandLine:
Start Time: 2016-11-27T12:28:20.611-06:00[America/Chicago]
CPU Time: PT0.296875S
Owner: kishori\ksharan
Children Count: 1

四. 比较进程

ProcessHandle

equals()

ProcessHandle

ProcessHandle

compareTo()

五. 创建进程

ProcessBuilder

start()

start()

Process

ProcessBuilder

ProcessBuilder pb = new ProcessBuilder()
.command("C:\\java9\\bin\\java.exe",
"--module-path",
"myModulePath",
"--module",
"myModule/className")
.inheritIO();

ProcessBuilder

command()

command()

ProcessBuilder

String

List<String>

inheritIO()

ProcessBuilder

redirectXxx()

start()

// Start a new process
Process newProcess = pb.start();

ProcessBuilder

start()

ProcessBuilder

Process

toHandle()

// Get the process handle
ProcessHandle handle = newProcess.toHandle();

Job

main()

ProcessHandle.current()

// Job.java
package com.jdojo.process.api;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
/**
* An instance of this class is used as a job that sleeps at a
* regular interval up to a maximum duration. The sleep
* interval in seconds can be specified as the first argument
* and the sleep duration as the second argument while running.
* this class. The default sleep interval and sleep duration
* are 5 seconds and 60 seconds, respectively. If these values
* are less than zero, zero is used instead.
*/
public class Job {
// The job sleep interval
public static final long DEFAULT_SLEEP_INTERVAL = 5;
// The job sleep duration
public static final long DEFAULT_SLEEP_DURATION = 60;
public static void main(String[] args) {
long sleepInterval = DEFAULT_SLEEP_INTERVAL;
long sleepDuration = DEFAULT_SLEEP_DURATION;
// Get the passed in sleep interval
if (args.length >= 1) {
sleepInterval = parseArg(args[0], DEFAULT_SLEEP_INTERVAL);
if (sleepInterval < 0) {
sleepInterval = 0;
}
}
// Get the passed in the sleep duration
if (args.length >= 2) {
sleepDuration = parseArg(args[1], DEFAULT_SLEEP_DURATION);
if (sleepDuration < 0) {
sleepDuration = 0;
}
}
long pid = ProcessHandle.current().getPid();
System.out.printf("Job (pid=%d) info: Sleep Interval" +
"=%d seconds, Sleep Duration=%d " +
"seconds.%n",
pid, sleepInterval, sleepDuration);
for (long sleptFor = 0; sleptFor < sleepDuration;
sleptFor += sleepInterval) {
try {
System.out.printf("Job (pid=%d) is going to" +
" sleep for %d seconds.%n",
pid, sleepInterval);
// Sleep for the sleep interval
TimeUnit.SECONDS.sleep(sleepInterval);
} catch (InterruptedException ex) {
System.out.printf("Job (pid=%d) was " +
"interrupted.%n", pid);
}
}
}
/**
* Starts a new JVM to run the Job class.
* @param sleepInterval The sleep interval when the Job
* class is run. It is passed to the JVM as the first
* argument.
* @param sleepDuration The sleep duration for the Job
* class. It is passed to the JVM as the second argument.
* @return The new process reference of the newly launched
* JVM or null if the JVM cannot be launched.
*/
public static Process startProcess(long sleepInterval,
long sleepDuration) {
// Store the command to launch a new JVM in a
// List<String>
List<String> cmd = new ArrayList<>();
// Add command components in order
addJvmPath(cmd);
addModulePath(cmd);
addClassPath(cmd);
addMainClass(cmd);
// Add arguments to run the class
cmd.add(String.valueOf(sleepInterval));
cmd.add(String.valueOf(sleepDuration));
// Build the process attributes
ProcessBuilder pb = new ProcessBuilder()
.command(cmd)
.inheritIO();
String commandLine = pb.command()
.stream()
.collect(Collectors.joining(" "));
System.out.println("Command used:\n" + commandLine);
// Start the process
Process p = null;
try {
p = pb.start();
} catch (IOException e) {
e.printStackTrace();
}
return p;
}
/**
* Used to parse the arguments passed to the JVM, which
* in turn is passed to the main() method.
* @param valueStr The string value of the argument
* @param defaultValue The default value of the argument if
* the valueStr is not an integer.
* @return valueStr as a long or the defaultValue if
* valueStr is not an integer.
*/
private static long parseArg(String valueStr,
long defaultValue) {
long value = defaultValue;
if (valueStr != null) {
try {
value = Long.parseLong(valueStr);
} catch (NumberFormatException e) {
// no action needed
}
}
return value;
}
/**
* Adds the JVM path to the command list. It first attempts
* to use the command attribute of the current process;
* failing that it relies on the java.home system property.
* @param cmd The command list
*/
private static void addJvmPath(List<String> cmd) {
// First try getting the command to run the current JVM
String jvmPath = ProcessHandle.current()
.info()
.command().orElse("");
if(jvmPath.length() > 0) {
cmd.add(jvmPath);
} else {
// Try composing the JVM path using the java.home
// system property
final String FILE_SEPARATOR =
System.getProperty("file.separator");
jvmPath = System.getProperty("java.home") +
FILE_SEPARATOR +  "bin" +
FILE_SEPARATOR + "java";
cmd.add(jvmPath);
}
}
/**
* Adds a module path to the command list.
* @param cmd The command list
*/
private static void addModulePath(List<String> cmd) {
String modulePath =
System.getProperty("jdk.module.path");
if(modulePath != null && modulePath.trim().length() > 0) {
cmd.add("--module-path");
cmd.add(modulePath);
}
}
/**
* Adds class path to the command list.
* @param cmd The command list
*/
private static void addClassPath(List<String> cmd) {
String classPath = System.getProperty("java.class.path");
if(classPath != null && classPath.trim().length() > 0) {
cmd.add("--class-path");
cmd.add(classPath);
}
}
/**
* Adds a main class to the command list. Adds
* module/className or just className depending on whether
* the Job class was loaded in a named module or unnamed
* module
* @param cmd The command list
*/
private static void addMainClass(List<String> cmd) {
Class<Job> cls = Job.class;
String className = cls.getName();
Module module = cls.getModule();
if(module.isNamed()) {
String moduleName = module.getName();
cmd.add("--module");
cmd.add(moduleName + "/" + className);
} else {
cmd.add(className);
}
}
}

Job

startProcess(long sleepInterval，long sleepDuration)

Job

Job

JDK_HOME\bin\java --module-path <module-path> --module com.jdojo.process.api/com.jdojo.process.api.Job <sleepInterval> <sleepDuration>

Job

JDK_HOME\bin\java -class-path <class-path> com.jdojo.process.api.Job <sleepInterval> <sleepDuration>

startProcess()

addJvmPath()

java.home

Job

main()

Job

startProcess()

// Start a process that runs for 15 seconds
Process p = Job.startProcess(5, 15);

CurrentProcessInfo

printInfo()

// Get the handle of the current process
ProcessHandle handle = p.toHandle();
// Print the process details
CurrentProcessInfo.printInfo(handle);

ProcessHandle的onExit()

CompletableFuture<ProcessHandle> future = handle.onExit();
// Print a message when process terminates
future.thenAccept((ProcessHandle ph) -> {
System.out.printf("Job (pid=%d) terminated.%n", ph.getPid());
});

// Wait for the process to terminate
future.get();

future.get()

ProcessHandle

handle

StartProcessTest

Job

main()

// StartProcessTest.java
package com.jdojo.process.api;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
public class StartProcessTest {
public static void main(String[] args) {
// Start a process that runs for 15 seconds
Process p = Job.startProcess(5, 15);
if (p == null) {
System.out.println("Could not create a new process.");
return;
}
// Get the handle of the current process
ProcessHandle handle = p.toHandle();
// Print the process details
CurrentProcessInfo.printInfo(handle);
CompletableFuture<ProcessHandle> future = handle.onExit();
// Print a message when process terminates
future.thenAccept((ProcessHandle ph) -> {
System.out.printf("Job (pid=%d) terminated.%n", ph.getPid());
});
try {
// Wait for the process to complete
future.get();
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
// Print process details again
CurrentProcessInfo.printInfo(handle);
}
}

C:\java9\bin\java.exe --module-path
C:\Java9Revealed\com.jdojo.process.api\build\classes --class-path
C:\Java9Revealed\com.jdojo.process.api\build\classes --module
com.jdojo.process.api/com.jdojo.process.api.Job 5 15
PID: 10928
IsAlive: true
Command: C:\java9\bin\java.exe
Arguments: []
CommandLine:
Start Time: 2016-11-28T13:43:28.318-06:00[America/Chicago]
CPU Time: PT0S
Owner: kishori\ksharan
Children Count: 1
Job (pid=10928) info: Sleep Interval=5 seconds, Sleep Duration=15 seconds.
Job (pid=10928) is going to sleep for 5 seconds.
Job (pid=10928) is going to sleep for 5 seconds.
Job (pid=10928) is going to sleep for 5 seconds.
Job (pid=10928) terminated.
PID: 10928
IsAlive: false
Command:
Arguments: []
CommandLine:
Start Time: 2016-11-28T13:43:28.318-06:00[America/Chicago]
CPU Time: PT0.359375S
Owner: kishori\ksharan
Children Count: 0

六. 获取进程句柄

Process

toHandle()

ProcessHandle

ProcessHandle

static Optional<ProcessHandle> of(long pid)
static ProcessHandle current()
Optional<ProcessHandle> parent()
Stream<ProcessHandle> children()
Stream<ProcessHandle> descendants()
static Stream<ProcessHandle> allProcesses()

of()

Optional<ProcessHandle>

Optional

// Get the process handle of the process with the pid of 1234
Optional<ProcessHandle> handle = ProcessHandle.of(1234L);

current()

parent()

Optional

children()

descendants()

allProcesses()

System.out.printf("All processes PIDs:%n");
ProcessHandle.allProcesses()
.map(ph -> ph.getPid())
.sorted()
.forEach(System.out::println);

// ProcessStats.java
package com.jdojo.process.api;
import java.time.Duration;
import java.time.Instant;
public class ProcessStats {
public static void main(String[] args) {
System.out.printf("Longest CPU User Process:%n");
ProcessHandle.allProcesses()
.max(ProcessStats::compareCpuTime)
.ifPresent(CurrentProcessInfo::printInfo);
System.out.printf("%nLongest Running Process:%n");
ProcessHandle.allProcesses()
.max(ProcessStats::compareStartTime)
.ifPresent(CurrentProcessInfo::printInfo);
}
public static int compareCpuTime(ProcessHandle ph1,
ProcessHandle ph2) {
return ph1.info()
.totalCpuDuration()
.orElse(Duration.ZERO)
.compareTo(ph2.info()
.totalCpuDuration()
.orElse(Duration.ZERO));
}
public static int compareStartTime(ProcessHandle ph1,
ProcessHandle ph2) {
return ph1.info()
.startInstant()
.orElse(Instant.now())
.compareTo(ph2.info()
.startInstant()
.orElse(Instant.now()));
}
}

Longest CPU User Process:
PID: 10696
IsAlive: true
Command: C:\Program Files (x86)\Google\Chrome\Application\chrome.exe
Arguments: []
CommandLine:
Start Time: 2016-11-28T10:12:08.537-06:00[America/Chicago]
CPU Time: PT14M26.5S
Owner: kishori\ksharan
Children Count: 0
Longest Running Process:
PID: 0
IsAlive: false
Command:
Arguments: []
CommandLine:
Start Time: 2016-11-29T13:18:22.262776600-06:00[America/Chicago]
CPU Time: PT0S
Owner: Unknown
Children Count: 127

七. 终止进程

ProcessHandle

Process

destroy()

destroyForcibly()

destroy()

destroyForcibly()

isAlive()

destroy()

destroyForcibly()

IllegalStateException

ProcessHandle

supportsNormalTermination()

Process

Process

onExit()

CompletableFuture<Process>

ProcessHandle

onExit()

CompletableFuture<ProcessHandle>

八. 管理进程权限

FilePermission(cmd,"execute")

cmd

cmd

FilePermission("<<ALL FILES>>","execute")

ProcessHandle

RuntimePermission("manageProcess")

// ManageProcessPermission.java
package com.jdojo.process.api;
import java.util.concurrent.ExecutionException;
public class ManageProcessPermission {
public static void main(String[] args) {
// Get the process count
long count = ProcessHandle.allProcesses().count();
System.out.printf("Process Count: %d%n", count);
// Start a new process
Process p = Job.startProcess(1, 3);
try {
p.toHandle().onExit().get();
} catch (InterruptedException | ExecutionException e) {
System.out.println(e.getMessage());
}
// Install a security manager
SecurityManager sm = System.getSecurityManager();
if(sm == null) {
System.setSecurityManager(new SecurityManager());
System.out.println("A security manager is installed.");
}
// Get the process count
try {
count = ProcessHandle.allProcesses().count();
System.out.printf("Process Count: %d%n", count);
} catch(RuntimeException e) {
System.out.println("Could not get a " +
"process count: " + e.getMessage());
}
// Start a new process
try {
p = Job.startProcess(1, 3);
p.toHandle().onExit().get();
} catch (InterruptedException | ExecutionException |
RuntimeException e) {
System.out.println("Could not start a new " +
"process: " + e.getMessage());
}
}
}

ManageProcessPermission

C:\Java9Revealed>java --module-path
C:\Java9Revealed\com.jdojo.process.api\build\classes --module
com.jdojo.process.api/com.jdojo.process.api.ManageProcessPermission

Command used:
C:\java9\bin\java.exe --module-path
C:\Java9Revealed\com.jdojo.process.api\build\classes --module
com.jdojo.process.api/com.jdojo.process.api.Job 1 3
Job (pid=6320) info: Sleep Interval=1 seconds, Sleep Duration=3 seconds.
Job (pid=6320) is going to sleep for 1 seconds.
Job (pid=6320) is going to sleep for 1 seconds.
Job (pid=6320) is going to sleep for 1 seconds.
A security manager is installed.
Could not get a process count: access denied ("java.lang.RuntimePermission" "manageProcess")
Could not start a new process: access denied ("java.lang.RuntimePermission" "manageProcess")

Job

grant {
permission java.lang.RuntimePermission "manageProcess";
permission java.io.FilePermission "C:\\java9\\bin\\java.exe", "execute";
permission java.util.PropertyPermission "jdk.module.path", "read";
permission java.util.PropertyPermission "java.class.path", "read";
};

ManageProcessPermission

Process Count: 133
Command used:
C:\java9\bin\java.exe --module-path
C:\Java9Revealed\com.jdojo.process.api\build\classes --module
com.jdojo.process.api/com.jdojo.process.api.Job 1 3
Job (pid=3108) info: Sleep Interval=1 seconds, Sleep Duration=3 seconds.
Job (pid=3108) is going to sleep for 1 seconds.
Job (pid=3108) is going to sleep for 1 seconds.
Job (pid=3108) is going to sleep for 1 seconds.
A security manager is installed.
Process Count: 133
Command used:
C:\java9\bin\java.exe --module-path
C:\Java9Revealed\com.jdojo.process.api\build\classes --module
com.jdojo.process.api/com.jdojo.process.api.Job 1 3
Job (pid=3684) info: Sleep Interval=1 seconds, Sleep Duration=3 seconds.
Job (pid=3684) is going to sleep for 1 seconds.
Job (pid=3684) is going to sleep for 1 seconds .
Job (pid=3684) is going to sleep for 1 seconds.

九. 总结

ProcessHandle

Runtime

ProcessBuilder

ProcessBuilder.Redirect

Process

ProcessHandle

ProcessHandle.Info

Runtime

exec()

ProcessBuilder

start()

Runtime

exec()

ProcessBuilder.Redirect

Process

ProcessHandle

ProcessHandle.Info

Process

ProcessHandle

info()

toHandle()

ProcessHandle

ProcessHandle

onExit()

CompletableFuture<ProcessHandle>