4

我希望能够执行 .Jar 文件，如果堆空间设置的不够大，它应该使用相同的 .Jar 文件启动一个新的 JVM，但设置更大的堆空间，然后关闭第一个JVM 和 .Jar。

我试过使用 ProcessBuilder，但我无法让它工作。

它必须跨平台工作。

-ONi

4

4 回答 4

6

我找到了解决方案，它可以跨平台工作。要从代码重新启动 JVM，请使用以下命令。这个答案取自我在这里搜索数小时后发现的另一个问题。如果需要，可以在调用此方法后使用 System.exit(0) 来终止启动新进程的 JVM。

public static void startSecondJVM() throws Exception {
    String separator = System.getProperty("file.separator");
    String classpath = System.getProperty("java.class.path");
    String path = System.getProperty("java.home")
            + separator + "bin" + separator + "java";
    ProcessBuilder processBuilder = 
            new ProcessBuilder(path, "-Xmx1024m", "-cp",
            classpath, 
            Main.class.getName());
    Process process = processBuilder.start();
}
于 2011-05-20T23:20:08.220 回答
1

You might try combining these two sources.

MemoryRecoveryTest.java

Makes attempts to recover from an OutOfMemoryError.

/*License - LGPL
<h3>Recovery from an OutOfMemory Error</h3>
<p>The JavaDocs for Error state, in the first sentence..

<blockquote>"An Error is a subclass of Throwable that indicates
serious problems that a reasonable application should
not try to catch."</blockquote>

<p>This advice has led to the fallacy that an OutOfMemoryError
should not be caught and dealt with.But this demo. shows
that it is quite easy to recover to the point of providing
the user with meaningful information, and advice on how to
proceed.

<p>I aim to make my applications 'unreasonable'.;-)
*/

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.JOptionPane;
import javax.swing.JDialog;
import javax.swing.Timer;

import javax.swing.border.EmptyBorder;

import java.util.ArrayList;

/** A demo. showing recovery from an OutOfMemoryError.
Our options once an OOME is encountered are relatively
few, but we can still warn the end user and provide
advice on how to correct the problem.
@author Andrew Thompson */
public class MemoryRecoveryTest {

    public static void main(String[] args) {
        // reserve a buffer of memory
        byte[] buffer = new byte[2^10];
        ArrayList<Object> list = new ArrayList<Object>();
        final JProgressBar memory = new JProgressBar(
            0,
            (int)Runtime.getRuntime().totalMemory());
        ActionListener listener = new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                memory.setValue(
                    (int)Runtime.getRuntime().freeMemory() );
            }
        };
        Timer timer = new Timer(500, listener);
        timer.start();

        JDialog dialog = new JDialog();
        dialog.setTitle("Available Memory");
        JPanel memoryPanel = new JPanel();
        memoryPanel.add(memory);
        memoryPanel.setBorder(new EmptyBorder(25,25,25,25));
        dialog.add( memoryPanel );
        dialog.pack();
        dialog.setLocationRelativeTo(null);
        dialog.setVisible(true);
        dialog.addWindowListener( new WindowAdapter(){
            @Override
            public void windowClosing(WindowEvent we) {
                System.exit(0);
            }
        } );

        // prepare a memory warning panel in advance
        JPanel memoryWarning = new JPanel();
        memoryWarning.add( new JLabel(
            "<HTML><BODY>There is not enough memory to" +
            " complete the task!<BR> Use a variant " +
            " of the application that assigns more memory.") );

        try {
            // do our 'memory intensive' task
            while(true) {
                list.add( new Object() );
            }
        } catch(OutOfMemoryError oome) {
            // provide the VM with some memory 'breathing space'
            // by clearing the buffer
            buffer = null;
            // tell the user what went wrong, and how to fix it
            JOptionPane.showMessageDialog(
                dialog,
                memoryWarning,
                "Out of Memory!",
                JOptionPane.ERROR_MESSAGE);
        }
    }
}

IWantToBeBig.java

Ensures a Process is started with a memory size specified.

import java.awt.EventQueue;
import javax.swing.JOptionPane;
import java.io.File;

class IWantToBeBig {

    public static void main(String[] args) throws Exception {
        if (args.length==0) {
            ProcessBuilder pb = new ProcessBuilder(
                "java",
                "-jar",
                "-Xmx512m",
                "big.jar",
                "anArgument"
                );
            pb.directory(new File("."));
            Process process = pb.start();
            process.waitFor();
            System.out.println("Exit value: " + process.exitValue());
        } else {
            Runnable r = new Runnable() {
                public void run() {
                    JOptionPane.showMessageDialog(
                        null,
                        "Max Memory: " +
                        Runtime.getRuntime().maxMemory() +
                        " bytes.");
                }
            };
            EventQueue.invokeLater(r);
        }
    }
}
于 2011-05-20T23:41:26.467 回答
1

您可以使用初始堆大小启动 java，还可以指定仅在需要时使用的最大堆大小。我不确定您要做什么，但它可能会模仿您想要的行为？

java -Xms256m -Xmx1g -jar myapp.jar

在此示例中，您从 256M 开始，如果应用程序需要更多内存，它将逐渐占用它，直到 1G。

于 2011-05-20T09:40:20.987 回答
0

我会在外部脚本文件中做这种工作 - 用伪代码：

$heap := 128
$ok := true
do {
  exitCode = java -Xmx$heapM -jar myApp.jar
  if (exitCode = OOME) {
    heap += 128
    $ok := false
  }
while(!$ok)

应该始终可以捕获 OOME 并使用自定义代码退出。这种方法存在一个问题 - 如果 $heap 值超过目标系统可能的最大堆空间（例如：在 Win32 系统上为 ~1.4GByte），那么它将不会终止。

注意：这只是问题的答案——通常会分配大量内存和/或解决内存泄漏问题——但我不知道实际的要求/限制

于 2011-05-20T09:39:49.000 回答