Java進程通信

1. 管道（Pipe）：管道可用於具備親緣關係進程間的通訊，容許一個進程和另外一個與它有共同祖先的進程之間進行通訊。
   建立子進程Java有兩種方式

   //第一種
   Runtime rt = Runtime.getRuntime(); 
   Process process = rt.exec("java -jar app2.jar"); 
   //第二種
   ProcessBuilder pb = new ProcessBuilder("java", "-jar","app2.jar"); 
   Process p = pb.start(); 

   第二種方式操做更方便，實例以下。
   父進程App.class

   try{
   	ProcessBuilder pb=new ProcessBuilder("java -jar app2.jar".split(" "));
   	pb.directory(new File("e:/temp/clean_day/jar/"));
   	//標準錯誤和輸入流合併爲輸入流
   	pb.redirectErrorStream(true);
   	//建立子進程
   	Process p=pb.start();
   	
   	//使用Process的輸入流接收子進程發送的消息
   	BufferedReader br=new BufferedReader(new InputStreamReader(p.getInputStream()));
   	//使用Process的輸出流向子進程發送消息，並把PrintWriter設置爲自動flush.
   	PrintWriter wr=new PrintWriter(new OutputStreamWriter(p.getOutputStream()),true);
   	String lineStr;
   	while((lineStr=br.readLine())!=null){
   		System.out.println("收到子進程的消息："+lineStr);
   		//向子進程發送消息
   		wr.println(System.currentTimeMillis());
   	}
   	wr.close();
   	br.close();
   }catch(Exception ex){
   	System.out.println(ex.getMessage());
   }

   子進程App2.class

   try{
   	System.out.println("子進程啓動成功");
   	System.out.println(System.currentTimeMillis());
   	
   	//利用標準輸入來接收父進程發送的消息
   	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   	String lineStr;
   	while ((lineStr = br.readLine()) != null) {
   		System.out.println("child\t"+lineStr);	
   	}
   	br.close();
   }catch(Exception ex){
   	System.out.println(ex.getMessage());
   }

2. (非進程，而是線程)PipedInputStream、PipedOutStream、PipedReader、PipedWriter管道流

   public class App {
   
   	public static void main(String[] args) {
   		PpWriter wr=new PpWriter();
   		PpReader rd=new PpReader(wr);
   
   		Thread wrth=new Thread(wr);
   		wrth.start();
   		
   		Thread rdth=new Thread(rd);
   		rdth.start();
   	}
   }
   
   /**
    * 管道寫
    * App.java:Temp
    * 2015年3月26日
    * @author kevin.zhai(韓旭)
    */
   class PpWriter implements Runnable{
   	private PipedWriter pipedWriter;
   	
   	public PpWriter(){
   		this.pipedWriter=new PipedWriter();
   	}
   	
   	@Override
   	public void run() {
   		try {
   			while(true){
   				//由於讀使用了readline，所以這裏要換行
   				String sendStr=System.currentTimeMillis()+"\r\n";
   				this.pipedWriter.write(sendStr);
   				System.out.println("父發送："+sendStr);
   				Thread.sleep(1000);
   			}
   		} catch (IOException | InterruptedException e) {
   			e.printStackTrace();
   		}
   	}
   
   	public PipedWriter getPipedWriter() {
   		return pipedWriter;
   	}
   }
   
   /**
    * 管道讀
    * App.java:Temp
    * 2015年3月26日
    * @author kevin.zhai(韓旭)
    */
   class PpReader implements Runnable{
   	private PipedReader pipedReader;
   	
   	public PpReader(PpWriter ppWriter){
   		try {
   			//讀須要先和寫創建鏈接，不然報異常：Pipe not connected
   			this.pipedReader=new PipedReader(ppWriter.getPipedWriter());
   		} catch (IOException e) {
   			e.printStackTrace();
   		}
   	}
   	@Override
   	public void run() {
   		
   		try(BufferedReader br=new BufferedReader(this.pipedReader)){
   			while(true){
   				System.out.println("子接收："+br.readLine());
   			}
   		} catch (IOException e) {
   			e.printStackTrace();
   		}
   	}
   }