Jmeter源码解析（1）

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查了很多网上的资料，对jmeter源码解释都很粗，对新接触的人没有什么帮助。好吧，那就自己干。一步一步学习。

持续更新，我下载的是jmeter3.1的源码。

先上启动类，jmeter/src/core/org.apache.jmeter/NewDriver.Java，是的，这就是jemter的总入口。

static {
final List<URL> jars = new LinkedList<>();
final String initial_classpath = System.getProperty(JAVA_CLASS_PATH);

// Find JMeter home dir from the initial classpath
String tmpDir=null;
StringTokenizer tok = new StringTokenizer(initial_classpath, File.pathSeparator);
if (tok.countTokens() == 1
|| (tok.countTokens() == 2 // Java on Mac OS can add a second entry to the initial classpath
&& OS_NAME_LC.startsWith("mac os x")// $NON-NLS-1$
)
) {
File jar = new File(tok.nextToken());
try {
tmpDir = jar.getCanonicalFile().getParentFile().getParent();
} catch (IOException e) {
}
} else {// e.g. started from IDE with full classpath
tmpDir = System.getProperty("jmeter.home","");// Allow override $NON-NLS-1$ $NON-NLS-2$
if (tmpDir.length() == 0) {
File userDir = new File(System.getProperty("user.dir"));// $NON-NLS-1$
tmpDir = userDir.getAbsoluteFile().getParent();
}
}
jmDir=tmpDir;

在定义各种静态变量后，开始找jemeter的本地安装路径，这里对mac的操作系统作了特别处理。基本所有的方法都很基础，全是I/O处理。

boolean usesUNC = OS_NAME_LC.startsWith("windows");// $NON-NLS-1$

// Add standard jar locations to initial classpathvbol+
StringBuilder classpath = new StringBuilder();
File[] libDirs = new File[] { new File(jmDir + File.separator + "lib"),// $NON-NLS-1$ $NON-NLS-2$
new File(jmDir + File.separator + "lib" + File.separator + "ext"),// $NON-NLS-1$ $NON-NLS-2$
new File(jmDir + File.separator + "lib" + File.separator + "junit")};// $NON-NLS-1$ $NON-NLS-2$
for (File libDir : libDirs) {
File[] libJars = libDir.listFiles(new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {// only accept jar files
return name.endsWith(".jar");// $NON-NLS-1$
}
});
if (libJars == null) {
new Throwable("Could not access " + libDir).printStackTrace();
continue;
}
Arrays.sort(libJars); // Bug 50708 Ensure predictable order of jars
for (File libJar : libJars) {
try {
String s = libJar.getPath();

// Fix path to allow the use of UNC URLs
if (usesUNC) {
if (s.startsWith("\\\\") && !s.startsWith("\\\\\\")) {// $NON-NLS-1$ $NON-NLS-2$
s = "\\\\" + s;// $NON-NLS-1$
} else if (s.startsWith("//") && !s.startsWith("///")) {// $NON-NLS-1$ $NON-NLS-2$
s = "//" + s;// $NON-NLS-1$
}
} // usesUNC

jars.add(new File(s).toURI().toURL());// See Java bug 4496398
classpath.append(CLASSPATH_SEPARATOR);
classpath.append(s);
} catch (MalformedURLException e) {
e.printStackTrace();
}
}
}

// ClassFinder needs the classpath
System.setProperty(JAVA_CLASS_PATH, initial_classpath + classpath.toString());
loader = AccessController.doPrivileged(
new java.security.PrivilegedAction<DynamicClassLoader>() {
@Override
public DynamicClassLoader run() {
return new DynamicClassLoader(jars.toArray(new URL[jars.size()]));
}
}
);
}

找到安装路径后，这里开始筛选bin里面的jar包，然后使用DynamicClassLoader加载。

剩下比较冗余就不贴代码了，分别是这个类的构造方法和一些静态方法。最后还有它：

public static void main(String[] args) {
Thread.currentThread().setContextClassLoader(loader);
if (System.getProperty("log4j.configuration") == null) {// $NON-NLS-1$ $NON-NLS-2$
File conf = new File(jmDir, "bin" + File.separator + "log4j.conf");// $NON-NLS-1$ $NON-NLS-2$
System.setProperty("log4j.configuration", "file:" + conf);
}

try {
Class<?> initialClass = loader.loadClass("org.apache.jmeter.JMeter");// $NON-NLS-1$
Object instance = initialClass.newInstance();
Method startup = initialClass.getMethod("start", new Class[] { new String[0].getClass() });// $NON-NLS-1$
startup.invoke(instance, new Object[] { args });
} catch(Throwable e){
e.printStackTrace();
System.err.println("JMeter home directory was detected as: "+jmDir);
}
}
}

设置新的系统属性，加载类org.apache.jmeter.JMeter，执行”start“方法。jmeter开始最初的启动。

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