Java 中的 Java.lang.ProcessBuilder 类
原文:https://www . geesforgeks . org/Java-lang-process builder-class-Java/
此类用于创建操作系统进程。每个流程构建器实例管理一组流程属性。start()方法用这些属性创建一个新的 Process 实例。start()方法可以从同一个实例中重复调用，以创建具有相同或相关属性的新子流程。
- ProcessBuilder 可用于帮助创建操作系统进程。
- 在 JDK 5.0 之前，创建和执行进程的唯一方法是使用 Runtime.exec()方法。
- 它扩展了类对象。
- 此类未同步。
施工方:
-
ProcessBuilder(List 命令):用指定的操作系统程序和参数构造一个进程构建器。
-
process builder(String…command):这将使用指定的操作系统程序和参数构建一个进程构建器。
方法:
1。List command(): 这个方法返回进程构建器的操作系统程序和参数。
Syntax: public List command().
Returns: this process builder's program and its arguments.
Exceptions: NullPointerException - if the argument is null.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating command() method
import java.io.*;
import java.lang.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg) throws IOException
{
// creating list of process
List<String> list = new ArrayList<String>();
list.add("notepad.exe");
// create the process
ProcessBuilder build = new ProcessBuilder(list);
// checking the command i list
System.out.println("command: " + build.command());
}
}
Output
command: [notepad.exe]
2。ProcessBuilder 命令(List 命令):此方法设置进程构建器的操作系统程序和参数。
Syntax: public ProcessBuilder command(List command).
Returns: NA.
Exception: NullPointerException - if the argument is null.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating ProcessBuilder
// command(List<String> command)
import java.io.*;
import java.lang.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg) throws IOException
{
// creating list of process
List<String> list = new ArrayList<String>();
list.add("notepad.exe");
list.add("xyz.txt");
// create the process
ProcessBuilder build = new ProcessBuilder(list);
// checking the command in list
System.out.println("command: " + build.command());
}
}
Output
command: [notepad.exe, xyz.txt]
3。ProcessBuilder 目录(文件目录):此方法设置流程构建器的工作目录。随后由对象的 start()方法启动的子进程将使用它作为它们的工作目录。该参数可能为 null，这意味着使用当前 Java 进程的工作目录，通常是由 system 属性 user.dir 命名的目录，作为子进程的工作目录。
Syntax: public ProcessBuilder directory(File directory).
Returns: this process builder.
Exception: NA.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating directory() method
import java.io.*;
import java.lang.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg) throws IOException
{
// creating list of process
List<String> list = new ArrayList<String>();
list.add("notepad.exe");
list.add("abc.txt");
// creating the process
ProcessBuilder build = new ProcessBuilder(list);
// setting the directory
build.directory(new File("src"));
// checking the directory, on which currently
// working on
System.out.println("directory: "
+ build.directory());
}
}
Output
directory: src
4。Map environment(): 此方法返回流程构建器环境的字符串映射视图。每当创建流程构建器时，环境都会被初始化为当前流程环境的副本。随后由对象的 start()方法启动的子进程将使用这个映射作为它们的环境。
Syntax: public Map environment()
Returns: this process builder's environment
Exception: SecurityException - if a security manager exists
and its checkPermission method doesn't allow access to the process environment.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating environment() method
import java.io.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg) throws IOException
{
// creating the process
ProcessBuilder pb = new ProcessBuilder();
// map view of this process builder's environment
Map<String, String> envMap = pb.environment();
// checking map view of environment
for (Map.Entry<String, String> entry :
envMap.entrySet()) {
// checking key and value separately
System.out.println("Key = " + entry.getKey()
+ ", Value = "
+ entry.getValue());
}
}
}
输出:
Key = PATH, Value = /usr/bin:/bin:/usr/sbin:/sbin
Key = JAVA_MAIN_CLASS_14267, Value = ProcessBuilderDemo
Key = J2D_PIXMAPS, Value = shared
Key = SHELL, Value = /bin/bash
Key = JAVA_MAIN_CLASS_11858, Value = org.netbeans.Main
Key = USER, Value = abhishekverma
Key = TMPDIR, Value = /var/folders/9z/p63ysmfd797clc0468vvy4980000gn/T/
Key = SSH_AUTH_SOCK, Value = /private/tmp/com.apple.launchd.uWvCfYQWBP/Listeners
Key = XPC_FLAGS, Value = 0x0
Key = LD_LIBRARY_PATH, Value = /Library/Java/JavaVirtualMachines
/jdk1.8.0_121.jdk/Contents/Home/jre/lib/
amd64:/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk
/Contents/Home/jre/lib/i386:
Key = __CF_USER_TEXT_ENCODING, Value = 0x1F5:0x0:0x0
Key = Apple_PubSub_Socket_Render, Value = /private/tmp/com.apple.launchd.weuNq4pAfF/Render
Key = LOGNAME, Value = abhishekverma
Key = LC_CTYPE, Value = UTF-8
Key = XPC_SERVICE_NAME, Value = 0
Key = PWD, Value = /
Key = SHLVL, Value = 1
Key = HOME, Value = /Users/abhishekverma
Key = _, Value = /Library/Java/JavaVirtualMachines/
jdk1.8.0_121.jdk/Contents/Home/bin/java
理解上面的输出:输出是子流程构建的地图视图。以上输出因用户而异，完全取决于操作系统和用户。
5。boolean redirecterrortstream():这个方法告诉流程构建器是否合并标准错误和标准输出。如果此属性为真，则由对象的 start()方法随后启动的子进程生成的任何错误输出都将与标准输出合并，以便可以使用 Process.getInputStream()方法读取两者。这使得将错误消息与相应的输出相关联变得更加容易。初始值为假。
Syntax: public boolean redirectErrorStream().
Returns: this process builder's redirectErrorStream property.
Exception: NA.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating redirectErrorStream() method
import java.io.*;
import java.lang.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg) throws IOException
{
// creating list of commands
List list = new ArrayList();
list.add("notepad.exe");
list.add("xyz.txt");
// creating the process
ProcessBuilder build = new ProcessBuilder(list);
// checking if error stream is redirected
System.out.println(build.redirectErrorStream());
}
}
输出:
false
6。ProcessBuilder redirectErrorStream(布尔 redirectErrorStream): 此方法设置此进程生成器的 redirectErrorStream 属性。如果此属性为真，则由该对象的 start()方法随后启动的子进程生成的任何错误输出都将与标准输出合并，以便可以使用 Process.getInputStream()方法读取两者。这使得将错误消息与相应的输出相关联变得更加容易。初始值为假。
Syntax: public ProcessBuilder redirectErrorStream(boolean redirectErrorStream).
Returns: this process builder.
Exception: NA.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating redirectErrorStream(boolean
// redirectErrorStream) method
import java.io.*;
import java.lang.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg) throws IOException
{
// creating list of commands
List list = new ArrayList();
list.add("notepad.exe");
list.add("xyz.txt");
// creating the process
ProcessBuilder build = new ProcessBuilder(list);
// redirecting error stream
build.redirectErrorStream(true);
// checking if error stream is redirected
System.out.println(build.redirectErrorStream());
}
}
输出:
true
流程启动():此方法使用流程构建器的属性启动一个新流程。新进程将调用由目录()给定的工作目录中的命令()给定的命令和参数，进程环境由环境()给定。此方法检查该命令是否是有效的操作系统命令。哪些命令有效取决于系统，但至少命令必须是非空字符串的非空列表。如果有一个安全管理器，它的 checkExec 方法是用这个对象的命令数组的第一个组件作为参数来调用的。这可能会导致引发安全异常。
Syntax: public Process start().
Returns: a new Process object for managing the subprocess.
Exception: NullPointerException - If an element of the command list is null
IndexOutOfBoundsException - If the command is an empty list (has size 0).
SecurityException - If a security manager exists
and its checkExec method doesn't allow creation of the subprocess.
IOException - If an I/O error occurs.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating start() method
import java.io.*;
import java.lang.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg) throws IOException
{
// creating list of commands
List<String> commands = new ArrayList<String>();
commands.add("ls"); // command
commands.add("-l"); // command
commands.add(
"/Users/abhishekverma"); // command in Mac OS
// creating the process
ProcessBuilder pb = new ProcessBuilder(commands);
// startinf the process
Process process = pb.start();
// for reading the output from stream
BufferedReader stdInput
= new BufferedReader(new InputStreamReader(
process.getInputStream()));
String s = null;
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
}
}
输出:
total 0
drwxr-xr-x 10 abhishekverma staff 340 Jun 20 02:24 AndroidStudioProjects
drwx------@ 22 abhishekverma staff 748 Jun 20 03:00 Desktop
drwx------@ 7 abhishekverma staff 238 Apr 29 22:03 Documents
drwx------+ 27 abhishekverma staff 918 Jun 20 03:01 Downloads
drwx------@ 65 abhishekverma staff 2210 Jun 18 20:48 Library
drwx------+ 3 abhishekverma staff 102 Mar 28 13:08 Movies
drwx------+ 4 abhishekverma staff 136 Apr 8 04:51 Music
drwxr-xr-x 4 abhishekverma staff 136 Jun 19 15:01 NetBeansProjects
drwx------+ 5 abhishekverma staff 170 Apr 10 09:46 Pictures
drwxr-xr-x+ 6 abhishekverma staff 204 Jun 18 20:45 Public
-rw-r--r-- 1 abhishekverma staff 0 Apr 15 19:23 newreactjs.jsx
process builder inherio():将子进程标准 I/O 的源和目标设置为与当前 Java 进程相同。
Syntax: public ProcessBuilder inheritIO().
Returns: this process builder.
Exception: NA.
Java 语言(一种计算机语言，尤用于创建网站)
// Java code illustrating inheritIO() method
import java.io.*;
import java.lang.*;
import java.util.*;
class ProcessBuilderDemo {
public static void main(String[] arg)
throws IOException, InterruptedException
{
ProcessBuilder pb = new ProcessBuilder(
"echo", "Hello GeeksforGeeks\n"
+ "This is ProcessBuilder Example");
pb.inheritIO();
Process process = pb.start();
process.waitFor();
}
}
输出:
Hello GeeksforGeeks
This is ProcessBuilder Example
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