Java实现内存共享
Java实现内存共享
Java内存共享就是对同一段内存的读写;用来进行进程之间的通信。
首先是写的代码:
- package com.sharememory.test;
- import java.io.IOException;
- import java.io.RandomAccessFile;
- import java.nio.MappedByteBuffer;
- import java.nio.channels.FileChannel;
- import java.nio.channels.FileLock;
- public class WriteMemory {
- String fileName = "shm.lock";
- RandomAccessFile raFile;
- FileChannel fc;
- int iSize = 1024;
- MappedByteBuffer mapBuf;
- int iMode;
- public WriteMemory() {
- try {
- init();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- public void init() throws Exception {
- raFile = new RandomAccessFile(fileName, "rw");
- fc = raFile.getChannel();
- mapBuf = fc.map(FileChannel.MapMode.READ_WRITE, 0, iSize);
- }
- public void clearBuffer() {
- // 清除文件内容
- for (int i = 0; i < 1024; i++) {
- mapBuf.put(i, (byte) 0);
- }
- }
- public void putBuffer() throws Exception{
- for (int i = 65; i < 91; i++) {
- int index = i - 63;
- int flag = mapBuf.get(0); // 可读标置第一个字节为 0
- if (flag != 0) { // 不是可写标示 0,则重复循环,等待
- i--;
- continue;
- }
- mapBuf.put(0, (byte) 1); // 正在写数据,标志第一个字节为 1
- mapBuf.put(1, (byte) (index)); // 写数据的位置
- System.out.println("程序 WriteShareMemory:"
- + System.currentTimeMillis() + ":位置:" + index + " 写入数据:"
- + (char) i);
- mapBuf.put(index, (byte) i);// index 位置写入数据
- mapBuf.put(0, (byte) 2); // 置可读数据标志第一个字节为 2
- Thread.sleep(513);
- }
- }
- public boolean getLock() {
- FileLock lock = null;
- try {
- lock = fc.tryLock();
- } catch (IOException e) {
- e.printStackTrace();
- }
- if (lock == null) {
- return false;
- } else {
- return true;
- }
- }
- public static void main(String[] args) {
- // TODO Auto-generated method stub
- WriteMemory map = new WriteMemory();
- if (map.getLock()) {
- try {
- map.putBuffer();
- } catch (Exception e) {
- e.printStackTrace();
- }
- } else {
- System.out.println("can't get lock");
- }
- }
- }
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