Question

我希望能够执行.Jar文件，如果堆空间设置得不够大，它应该启动一个具有相同.Jar文件的新JVM，但设置更大的堆空间，然后关闭第一个JVM和.Jar。

我尝试过使用ProcessBuilder，但我无法让它工作。

它必须跨平台工作。

-ONi

Answer 1

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，可以使用System.exit（0）跟随它，以在调用此方法后终止启动新进程的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();
}

Answer 2

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。我不确定你要做什么，但它可能会模仿你想要的行为？

java -Xms256m -Xmx1g -jar myapp.jar

在这个示例中，您从256M开始，如果应用程序需要更多内存，它将逐步增加，直到1G。

Answer 3

您可以尝试将这两个来源合并。

MemoryRecoveryTest.java

尝试从OutOfMemoryError恢复。

/*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

确保以指定的内存大小启动Process。

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);
        }
    }
}

Answer 4

我会在外部脚本文件中执行此类工作 - 伪代码：

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

Catch OOME并且应该始终可以使用自定义代码退出。这种方法存在一个问题 - 如果$ heap值超过了目标系统可能达到的最大堆空间（例如：Win32系统上的~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/或消除内存泄漏 - 但我不知道实际的要求/限制} < / p>

重新启动具有更大堆空间的JVM

4 个答案:

MemoryRecoveryTest.java

IWantToBeBig.java