第七章 Thread-Per-Message

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背景介绍：每一个消息一个线程，forexample ：ThreadLocal from jdk1.2 java.lang.ThreadLocal

使用场景：客户端送达的请求，由主线程来接收。而实际处理该请求，则交给其他线程负责，主线程回到继续等待其他客户端请求的状态，此时主线程会结束，然后其他线程

继续处理请求

public class Host {    private final Helper helper = new Helper();    public void request(final int count, final char c) {        System.out.println("    request(" + count + ", " + c + ") BEGIN");        new Thread() {//每次请求建立新线程处理数据            public void run() {                helper.handle(count, c);            }        }.start();        System.out.println("    request(" + count + ", " + c + ") END");    }}public class Helper {    public void handle(int count, char c) {        System.out.println("        handle(" + count + ", " + c + ") BEGIN");        for (int i = 0; i < count; i++) {            slowly();            System.out.print(c);        }        System.out.println("");        System.out.println("        handle(" + count + ", " + c + ") END");    }    private void slowly() {        try {            Thread.sleep(100);        } catch (InterruptedException e) {        }    }}

public class ThreadPerMessage {    public static void main(String args[]) {        System.out.println("BEGIN");        Object obj = new Object();        Blackhole.enter(obj);        System.out.println("END");    }}class Blackhole {    public static void enter(Object obj) {        System.out.println("Step 1");        magic(obj);        System.out.println("Step 2");        synchronized (obj) {            System.out.println("Step 3 (never reached here)");          }    }    //用新线程反复获取obj锁定    public static void magic(final Object obj) {          Thread thread = new Thread() {      // inner class            public void run() {                synchronized (obj) { // 在此取得obj的锁定                    synchronized (this) {                        this.setName("Locked"); // 不设置的话，magic方法跳不出来                        this.notifyAll();       // 通知已经取得obj的锁定  让thread解除锁定                    }                    /*try {                        this.join();//等待主线程结束，但是主线程卡死在obj上                    } catch (InterruptedException e) {                    }*/                    while (true) {//导致主线程永远得不到obj                        // 无穷循环                    }                }            }        };                synchronized (thread) {            thread.setName("");            thread.start(); // 线程的启动            // Guarded Suspension模式            while (thread.getName().equals("")) {                try {                    thread.wait(); //  等待新的线程取得obj的锁定                } catch (Exception e) {                }            }        }    }}

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