网站多久备案一次,有网站域名及空间 别人帮建网站,有专门做摄影画册的网站,云南房地产网站建设java类加载类的生命周期(类加载过程)LLIUUVPR加载(Loading)链接(Linking)验证(Verification)准备(Preparation)解析(Resolution)初始化(Initialization)使用(Using)卸载(Unloading) 类类加载器种类BootstrapClassLoader#xff1a;C编写#xff0c;负责加载java核心类库Launc…java类加载类的生命周期(类加载过程)LLIUUVPR加载(Loading)链接(Linking)验证(Verification)准备(Preparation)解析(Resolution)初始化(Initialization)使用(Using)卸载(Unloading) 类类加载器种类BootstrapClassLoaderC编写负责加载java核心类库Launcher.ExtClassLoaderLauncher中的内部类parent nullLauncher.AppClassLoaderLauncher中的内部类parent ExtClassLoader用户自定义ClassLoader继承自ClassLoaderparent AppClassLoader类加载机制java中默认的类加载机制是双亲委派模式。ClassLoader中关键的方法说明loadClass // 类加载入口包含下面这些步骤 findLoadedClass findLoadedClass0 // 先从缓存中查询一下看看目标类是否已加载过 findBootstrapClassOrNull findBootstrapClass // 用Bootstrap类加载器进行加载 findClass // 读取字节码文件然后加载字节码文件 defineClass // 加载字节码文件 preDefineClass // 加载前的检查 defineClassSourceLocation // 定义类加载的路径 defineClass1/defineClass2 // 调用native方法加载类 postDefineClass // resolveClass resolveClass0ClassLoader 部分源码package java.lang;import java.io.InputStream;...public abstract class ClassLoader {private final ClassLoader parent;// -- Class --protected Class loadClass(String name, boolean resolve)throws ClassNotFoundException{synchronized (getClassLoadingLock(name)) {// First, check if the class has already been loadedClass c findLoadedClass(name); // 缓存机制if (c null) {long t0 System.nanoTime();try {// 双亲委派机制if (parent ! null) {c parent.loadClass(name, false);} else {c findBootstrapClassOrNull(name);}} catch (ClassNotFoundException e) {// ClassNotFoundException thrown if class not found// from the non-null parent class loader}if (c null) {// If still not found, then invoke findClass in order// to find the class.long t1 System.nanoTime();c findClass(name);// this is the defining class loader; record the statssun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0);sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);sun.misc.PerfCounter.getFindClasses().increment();}}if (resolve) {resolveClass(c);}return c;}}// findClass由子类去实现protected Class findClass(String name) throws ClassNotFoundException {throw new ClassNotFoundException(name);}// defineClass 加载类protected final Class defineClass(String name, byte[] b, int off, int len,ProtectionDomain protectionDomain)throws ClassFormatError{protectionDomain preDefineClass(name, protectionDomain);String source defineClassSourceLocation(protectionDomain);Class c defineClass1(name, b, off, len, protectionDomain, source);postDefineClass(c, protectionDomain);return c;}private ProtectionDomain preDefineClass(String name,ProtectionDomain pd){if (!checkName(name))throw new NoClassDefFoundError(IllegalName: name);// Note: Checking logic in java.lang.invoke.MemberName.checkForTypeAlias// relies on the fact that spoofing is impossible if a class has a name// of the form java.*if ((name ! null) name.startsWith(java.)) {throw new SecurityException(Prohibited package name: name.substring(0, name.lastIndexOf(.)));}if (pd null) {pd defaultDomain;}if (name ! null) checkCerts(name, pd.getCodeSource());return pd;}private String defineClassSourceLocation(ProtectionDomain pd){CodeSource cs pd.getCodeSource();String source null;if (cs ! null cs.getLocation() ! null) {source cs.getLocation().toString();}return source;}private void postDefineClass(Class c, ProtectionDomain pd){if (pd.getCodeSource() ! null) {Certificate certs[] pd.getCodeSource().getCertificates();if (certs ! null)setSigners(c, certs);}}private native Class defineClass0(String name, byte[] b, int off, int len,ProtectionDomain pd);private native Class defineClass1(String name, byte[] b, int off, int len,ProtectionDomain pd, String source);private native Class defineClass2(String name, java.nio.ByteBuffer b,int off, int len, ProtectionDomain pd,String source);protected final void resolveClass(Class c) {resolveClass0(c);}private native void resolveClass0(Class c);private Class findBootstrapClassOrNull(String name) {if (!checkName(name)) return null;return findBootstrapClass(name);}// return null if not foundprivate native Class findBootstrapClass(String name);protected final Class findLoadedClass(String name) {if (!checkName(name))return null;return findLoadedClass0(name);}private native final Class findLoadedClass0(String name);// -- Resource --...// -- Hierarchy --...// -- Package --...// -- Native library access --...// -- Assertion management --...}双亲委派
