Jmeter源码学习系列：启动Jmeter

深藏阁楼爱情的钟 2022-06-02 03:44 295阅读 0赞

网上有很多Jmeter学习资料，但是源码这块，貌似资料不是很多，经历一番痛苦之后，决定自己一点点来做，希望能坚持，也希望能给后来的同学做点借鉴。

今天先简单看看jmeter是如何启动的

**jmeter/src/core/org.apache.jmeter/NewDriver.Java是jmeter的总入口**

/**
     * Main class for JMeter - sets up initial classpath and the loader.
     *
     */
    public final class NewDriver {

**先定义一些静态变量**

private static final StringCLASSPATH_SEPARATOR= File.pathSeparator;
    
        private static final String OS_NAME=System.getProperty("os.name");// $NON-NLS-1$
    
        private static final StringOS_NAME_LC=OS_NAME.toLowerCase(java.util.Locale.ENGLISH);
    
        private static final String JAVA_CLASS_PATH= "java.class.path";//$NON-NLS-1$
    
        /** The classloader to use for loading JMeter classes. */
        privatestatic final DynamicClassLoaderloader;
    
        /** The directory JMeter isinstalled in. */
        privatestatic final StringJMETER_INSTALLATION_DIRECTORY;
    
        private static final List<Exception> EXCEPTIONS_IN_INIT=new ArrayList<>();
    
        static {
            finalList<URL> jars =new LinkedList<>();
            final String initial_classpath = System.getProperty(JAVA_CLASS_PATH);

**寻找Jmeter的安装目录，这边对Mac OS的Jmeter做了特殊处理**

// Find JMeter home dir from the initial classpath
            String tmpDir=null;
            StringTokenizer tok = newStringTokenizer(initial_classpath,File.pathSeparator);
            if (tok.countTokens() == 1
                    || (tok.countTokens() == 2 // Java on Mac OS can add a second entry to theinitial 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();
                }
            }
            JMETER_INSTALLATION_DIRECTORY=tmpDir;
    
            /*
             * Does the system support UNCpaths? If so, may need to fix them up
             * later
             */
            boolean usesUNC=OS_NAME_LC.startsWith("windows");// $NON-NLS-1$

**找到安装目录之后，对Jmeter lib目录下的jar包进行扫描，并使用DynamicClassLoader进行加载**

// Addstandard jar locations to initial classpath
            StringBuilderclasspath = newStringBuilder();
            File[]libDirs = newFile[] { newFile(JMETER_INSTALLATION_DIRECTORY+ File.separator+"lib"),// $NON-NLS-1$ $NON-NLS-2$
                    new File(JMETER_INSTALLATION_DIRECTORY+ File.separator+ "lib" + File.separator + "ext"),// $NON-NLS-1$ $NON-NLS-2$
                    new File(JMETER_INSTALLATION_DIRECTORY+ File.separator+ "lib" + File.separator + "junit")};// $NON-NLS-1$ $NON-NLS-2$
            for(File libDir : libDirs) {
                File[] libJars =libDir.listFiles((FilenameFilter) (dir,name) -> name.endsWith(".jar"));
                if (libJars == null) {
                    new Throwable("Could not access "+ libDir).printStackTrace();// NOSONAR No logging here
                    continue;
                }
                Arrays.sort(libJars); // Bug 50708 Ensurepredictable 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(newFile(s).toURI().toURL());// See Java bug 4496398
                        classpath.append(CLASSPATH_SEPARATOR);
                        classpath.append(s);
                    } catch(MalformedURLException e) { // NOSONAR
                        EXCEPTIONS_IN_INIT.add(newException("Error adding jar:"+libJar.getAbsolutePath(),e));
                    }
                }
            }
    
            //ClassFinder needs the classpath
            System.setProperty(JAVA_CLASS_PATH,initial_classpath + classpath.toString());
            loader= AccessController.doPrivileged(
                    new java.security.PrivilegedAction<DynamicClassLoader>(){
                        @Override
                        public DynamicClassLoaderrun() {
                            return new DynamicClassLoader(jars.toArray(newURL[jars.size()]));
                        }
                    }
            );
        }

**运行Jmeter的主方法**

/**
         * The main program which actuallyruns JMeter.
         *
         * @param args
         *            the command line arguments
         */
        publicstatic void main(String[] args) {
            if(!EXCEPTIONS_IN_INIT.isEmpty()) {
                System.err.println("Configuration error during init, see exceptions:"+exceptionsToString(EXCEPTIONS_IN_INIT));
            }else {
                Thread.currentThread().setContextClassLoader(loader);
    
                setLoggingProperties(args);
    
                try {
                    Class<?>initialClass = loader.loadClass("org.apache.jmeter.JMeter");// $NON-NLS-1$
                    Object instance = initialClass.newInstance();
                    Method startup = initialClass.getMethod("start", newClass[] { newString[0].getClass() });// $NON-NLS-1$
                    startup.invoke(instance,new Object[] { args });
                } catch(Throwable e){ // NOSONARWe want to log home directory in case of exception
                    e.printStackTrace(); // NOSONAR No logger at this step
                    System.err.println("JMeterhome directory was detected as: "+JMETER_INSTALLATION_DIRECTORY);
                }
            }
        }

还有一部分静态方法，就不贴了