jmeter源码---核心JMeterEngine

概述

JMeterEngine接口被运行Jmeter的测试类实现，此接口共8个方法，其中无参stopTest()是调用的stopTest(boolean now)，也可说是7个方法

• void configure(HashTree testPlan);
• void runTest() throws JMeterEngineException;
• default void stopTest(){stopTest(true);}
• void stopTest(boolean now);
• void reset();
• void setProperties(Properties p);
• void exit();
• boolean isActive();

介绍

configure(HashTree testPlan)

HashTree是JMeter执行测试依赖的数据结构，configure在执行测试之前进行配置测试数据。可以参考接口JMeterEngine的实现类StandardJMeterEngine

public void configure(HashTree testTree) {
    // Is testplan serialised?
    SearchByClass<TestPlan> testPlan = new SearchByClass<>(TestPlan.class);
    testTree.traverse(testPlan);
    Object[] plan = testPlan.getSearchResults().toArray();
    if (plan.length == 0) {
        throw new RuntimeException("Could not find the TestPlan class!");
    }
    TestPlan tp = (TestPlan) plan[0];
    serialized = tp.isSerialized();
    tearDownOnShutdown = tp.isTearDownOnShutdown();
    active = true;
    test = testTree;
}

从HashTree中解析出TestPlan, 获取TestPlan的serialized和tearDownOnShutdown并保存为local属性，同时把整个HashTree也保存到local。

    /** Thread Groups run sequentially */
    private volatile boolean serialized = false;

    /** tearDown Thread Groups run after shutdown of main threads */
    private volatile boolean tearDownOnShutdown = false;

StandardJMeterEngine依赖线程组ThreadGroup, 一个测试中可能会有多个线程组，如果serialized为true，则StandardJMeterEngine会串行的去执行这些线程组，每启动一个ThreadGroup主线程都会等它结束；否则就并行执行所有的线程组。
tearDownOnShutdown与PostThreadGroup配合使用的，这个Special Thread Group专门用来做清理工作

/**
 * PostThreadGroup is a special type of ThreadGroup that can be used for
 * performing actions at the end of a test for cleanup and such.
 */
public class PostThreadGroup extends ThreadGroup {
    private static final long serialVersionUID = 240L;
}

如果在HashTree配置中有PostThreadGroup，那么在主线程组(ThreadGroup)执行完之后，StandardJMeterEngine检查tearDownOnShutdown属性，若该属性值true就启动PostThreadGroup。

runTest()

调用该方法用来执行测试。参考StandardJMeterEngine的实现

public void runTest() throws JMeterEngineException {
    if (host != null) {
        long now = System.currentTimeMillis();
        System.out.println("Starting the test on host " + host + " @ " + new Date(now) + " (" + now + ")"); 
    }
    try {
        Thread runningThread = new Thread(this, "StandardJMeterEngine");
        runningThread.start();
    } catch (Exception err) {
        stopTest();
        throw new JMeterEngineException(err);
    }
}

启动一个线程并触发它的run()方法，若报异常则调用stopTest()，抛出JMeterEngineException。

stopTest(boolean now)

停止测试，若now为true则停止动作立即执行；若为false则停止动作缓刑，它会等待当前正在执行的测试至少执行完一个iteration。

public synchronized void stopTest(boolean now) {
    shutdown = !now;
    Thread stopThread = new Thread(new StopTest(now));
    stopThread.start();
}

private class StopTest implements Runnable{……}

stopTest()

public synchronized void stopTest() {
    stopTest(true);
}

reset()

重置。在StandardJMeterEngine中就是直接调用stopTest(true).

public void reset() {
    if (running) {
        stopTest();
    }
}

setProperties(Properties p)

设置属性，可以将额外的配置文件通过该方法添加进去。它会保存在JMeterUtils中，该类保存了JMeterEngine runtime所需要的所有配置参数。

public void setProperties(Properties p) {
    log.info("Applying properties " + p);
    JMeterUtils.getJMeterProperties().putAll(p);
}

exit()

是为Remote Test准备的，如果当前的测试是从一个客户端的JMeter执行远程JMeterEngine的remote samples，则应该调用该exit()方法来关闭远程的测试.被RemoteJMeterEngineImpl.rexit()调用和exitAfterTest为真时被notifyTestListenersOfEnd()调用 ;

public void exit() {
    ClientJMeterEngine.tidyRMI(log); 
    if (REMOTE_SYSTEM_EXIT) {
        log.warn("About to run System.exit(0) on " + host);
        Thread t = new Thread() {
            @Override
            public void run() {
                pause(1000); 
                log.info("Bye from " + host);
                System.out.println("Bye from " + host); 
                System.exit(0); 
            }
        };
        t.start();
    }
}

boolean isActive()

引擎是否有效的标识，在测试结束时设为false

public boolean isActive() {
    return active;
}

在confgiure()的时候设该值为true，在执行完测试(指的是该JMeterEngine所有ThreadGroup)之后设置为false。如果active==true，则说明该JMeterEngine已经配置完测试并且还没执行完，我们不能再进行configure或者runTest了；若active == false, 则该JMeterEngine是空闲的，我们可以重新配置HashTree，执行新的测试.

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原文连接 http://blog.youkuaiyun.com/yue530tomtom/article/details/78016823