JDK8/Java8源码在线阅读
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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*
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package java.beans;
import com.sun.beans.finder.ClassFinder;
import java.applet.Applet;
import java.applet.AppletContext;
import java.applet.AppletStub;
import java.applet.AudioClip;
import java.awt.Image;
import java.beans.beancontext.BeanContext;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import java.io.StreamCorruptedException;
import java.lang.reflect.Modifier;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Vector;
/**
* This class provides some general purpose beans control methods.
*/
public class Beans {
/**
* <p>
* Instantiate a JavaBean.
* </p>
* @return a JavaBean
* @param cls the class-loader from which we should create
* the bean. If this is null, then the system
* class-loader is used.
* @param beanName the name of the bean within the class-loader.
* For example "sun.beanbox.foobah"
*
* @exception ClassNotFoundException if the class of a serialized
* object could not be found.
* @exception IOException if an I/O error occurs.
*/
public static Object instantiate(ClassLoader cls, String beanName) throws IOException, ClassNotFoundException {
return Beans.instantiate(cls, beanName, null, null);
}
/**
* <p>
* Instantiate a JavaBean.
* </p>
* @return a JavaBean
*
* @param cls the class-loader from which we should create
* the bean. If this is null, then the system
* class-loader is used.
* @param beanName the name of the bean within the class-loader.
* For example "sun.beanbox.foobah"
* @param beanContext The BeanContext in which to nest the new bean
*
* @exception ClassNotFoundException if the class of a serialized
* object could not be found.
* @exception IOException if an I/O error occurs.
*/
public static Object instantiate(ClassLoader cls, String beanName, BeanContext beanContext) throws IOException, ClassNotFoundException {
return Beans.instantiate(cls, beanName, beanContext, null);
}
/**
* Instantiate a bean.
* <p>
* The bean is created based on a name relative to a class-loader.
* This name should be a dot-separated name such as "a.b.c".
* <p>
* In Beans 1.0 the given name can indicate either a serialized object
* or a class. Other mechanisms may be added in the future. In
* beans 1.0 we first try to treat the beanName as a serialized object
* name then as a class name.
* <p>
* When using the beanName as a serialized object name we convert the
* given beanName to a resource pathname and add a trailing ".ser" suffix.
* We then try to load a serialized object from that resource.
* <p>
* For example, given a beanName of "x.y", Beans.instantiate would first
* try to read a serialized object from the resource "x/y.ser" and if
* that failed it would try to load the class "x.y" and create an
* instance of that class.
* <p>
* If the bean is a subtype of java.applet.Applet, then it is given
* some special initialization. First, it is supplied with a default
* AppletStub and AppletContext. Second, if it was instantiated from
* a classname the applet's "init" method is called. (If the bean was
* deserialized this step is skipped.)
* <p>
* Note that for beans which are applets, it is the caller's responsiblity
* to call "start" on the applet. For correct behaviour, this should be done
* after the applet has been added into a visible AWT container.
* <p>
* Note that applets created via beans.instantiate run in a slightly
* different environment than applets running inside browsers. In
* particular, bean applets have no access to "parameters", so they may
* wish to provide property get/set methods to set parameter values. We
* advise bean-applet developers to test their bean-applets against both
* the JDK appletviewer (for a reference browser environment) and the
* BDK BeanBox (for a reference bean container).
*
* @return a JavaBean
* @param cls the class-loader from which we should create
* the bean. If this is null, then the system
* class-loader is used.
* @param beanName the name of the bean within the class-loader.
* For example "sun.beanbox.foobah"
* @param beanContext The BeanContext in which to nest the new bean
* @param initializer The AppletInitializer for the new bean
*
* @exception ClassNotFoundException if the class of a serialized
* object could not be found.
* @exception IOException if an I/O error occurs.
*/
public static Object instantiate(ClassLoader cls, String beanName, BeanContext beanContext, AppletInitializer initializer)
throws IOException, ClassNotFoundException {
InputStream ins;
ObjectInputStream oins = null;
Object result = null;
boolean serialized = false;
IOException serex = null;
// If the given classloader is null, we check if an
// system classloader is available and (if so)
// use that instead.
// Note that calls on the system class loader will
// look in the bootstrap class loader first.
if (cls == null) {
try {
cls = ClassLoader.getSystemClassLoader();
} catch (SecurityException ex) {
// We're not allowed to access the system class loader.
// Drop through.
}
}
// Try to find a serialized object with this name
final String serName = beanName.replace('.','/').concat(".ser");
final ClassLoader loader = cls;
ins = AccessController.doPrivileged
(new PrivilegedAction<InputStream>() {
public InputStream run() {
if (loader == null)
return ClassLoader.getSystemResourceAsStream(serName);
else
return loader.getResourceAsStream(serName);
}
});
if (ins != null) {
try {
if (cls == null) {
oins = new ObjectInputStream(ins);
} else {
oins = new ObjectInputStreamWithLoader(ins, cls);
}
result = oins.readObject();
serialized = true;
oins.close();
} catch (IOException ex) {
ins.close();
// Drop through and try opening the class. But remember
// the exception in case we can't find the class either.
serex = ex;
} catch (ClassNotFoundException ex) {
ins.close();
throw ex;
}
}
if (result == null) {
// No serialized object, try just instantiating the class
Class<?> cl;
try {
cl = ClassFinder.findClass(beanName, cls);
} catch (ClassNotFoundException ex) {
// There is no appropriate class. If we earlier tried to
// deserialize an object and got an IO exception, throw that,
// otherwise rethrow the ClassNotFoundException.
if (serex != null) {
throw serex;
}
throw ex;
}
if (!Modifier.isPublic(cl.getModifiers())) {
throw new ClassNotFoundException("" + cl + " : no public access");
}
/*
* Try to instantiate the class.
*/
try {
result = cl.newInstance();
} catch (Exception ex) {
// We have to remap the exception to one in our signature.
// But we pass extra information in the detail message.
throw new ClassNotFoundException("" + cl + " : " + ex, ex);
}
}
if (result != null) {
// Ok, if the result is an applet initialize it.
AppletStub stub = null;
if (result instanceof Applet) {
Applet applet = (Applet) result;
boolean needDummies = initializer == null;
if (needDummies) {
// Figure our the codebase and docbase URLs. We do this
// by locating the URL for a known resource, and then
// massaging the URL.
// First find the "resource name" corresponding to the bean
// itself. So a serialzied bean "a.b.c" would imply a
// resource name of "a/b/c.ser" and a classname of "x.y"
// would imply a resource name of "x/y.class".
final String resourceName;
if (serialized) {
// Serialized bean
resourceName = beanName.replace('.','/').concat(".ser");
} else {
// Regular class
resourceName = beanName.replace('.','/').concat(".class");
}
URL objectUrl = null;
URL codeBase = null;
URL docBase = null;
// Now get the URL correponding to the resource name.
final ClassLoader cloader = cls;
objectUrl =
AccessController.doPrivileged
(new PrivilegedAction<URL>() {
public URL run() {
if (cloader == null)
return ClassLoader.getSystemResource
(resourceName);
else
return cloader.getResource(resourceName);
}
});
// If we found a URL, we try to locate the docbase by taking
// of the final path name component, and the code base by taking
// of the complete resourceName.
// So if we had a resourceName of "a/b/c.class" and we got an
// objectURL of "file://bert/classes/a/b/c.class" then we would
// want to set the codebase to "file://bert/classes/" and the
// docbase to "file://bert/classes/a/b/"
if (objectUrl != null) {
String s = objectUrl.toExternalForm();
if (s.endsWith(resourceName)) {
int ix = s.length() - resourceName.length();
codeBase = new URL(s.substring(0,ix));
docBase = codeBase;
ix = s.lastIndexOf('/');
if (ix >= 0) {
docBase = new URL(s.substring(0,ix+1));
}
}
}
// Setup a default context and stub.
BeansAppletContext context = new BeansAppletContext(applet);
stub = (AppletStub)new BeansAppletStub(applet, context, codeBase, docBase);
applet.setStub(stub);
} else {
initializer.initialize(applet, beanContext);
}
// now, if there is a BeanContext, add the bean, if applicable.
if (beanContext != null) {
unsafeBeanContextAdd(beanContext, result);
}
// If it was deserialized then it was already init-ed.
// Otherwise we need to initialize it.
if (!serialized) {
// We need to set a reasonable initial size, as many
// applets are unhappy if they are started without
// having been explicitly sized.
applet.setSize(100,100);
applet.init();
}
if (needDummies) {
((BeansAppletStub)stub).active = true;
} else initializer.activate(applet);
} else if (beanContext != null) unsafeBeanContextAdd(beanContext, result);
}
return result;
}
@SuppressWarnings("unchecked")
private static void unsafeBeanContextAdd(BeanContext beanContext, Object res) {
beanContext.add(res);
}
/**
* From a given bean, obtain an object representing a specified
* type view of that source object.
* <p>
* The result may be the same object or a different object. If
* the requested target view isn't available then the given
* bean is returned.
* <p>
* This method is provided in Beans 1.0 as a hook to allow the
* addition of more flexible bean behaviour in the future.
*
* @return an object representing a specified type view of the
* source object
* @param bean Object from which we want to obtain a view.
* @param targetType The type of view we'd like to get.
*
*/
public static Object getInstanceOf(Object bean, Class<?> targetType) {
return bean;
}
/**
* Check if a bean can be viewed as a given target type.
* The result will be true if the Beans.getInstanceof method
* can be used on the given bean to obtain an object that
* represents the specified targetType type view.
*
* @param bean Bean from which we want to obtain a view.
* @param targetType The type of view we'd like to get.
* @return "true" if the given bean supports the given targetType.
*
*/
public static boolean isInstanceOf(Object bean, Class<?> targetType) {
return Introspector.isSubclass(bean.getClass(), targetType);
}
/**
* Test if we are in design-mode.
*
* @return True if we are running in an application construction
* environment.
*
* @see DesignMode
*/
public static boolean isDesignTime() {
return ThreadGroupContext.getContext().isDesignTime();
}
/**
* Determines whether beans can assume a GUI is available.
*
* @return True if we are running in an environment where beans
* can assume that an interactive GUI is available, so they
* can pop up dialog boxes, etc. This will normally return
* true in a windowing environment, and will normally return
* false in a server environment or if an application is
* running as part of a batch job.
*
* @see Visibility
*
*/
public static boolean isGuiAvailable() {
return ThreadGroupContext.getContext().isGuiAvailable();
}
/**
* Used to indicate whether of not we are running in an application
* builder environment.
*
* <p>Note that this method is security checked
* and is not available to (for example) untrusted applets.
* More specifically, if there is a security manager,
* its <code>checkPropertiesAccess</code>
* method is called. This could result in a SecurityException.
*
* @param isDesignTime True if we're in an application builder tool.
* @exception SecurityException if a security manager exists and its
* <code>checkPropertiesAccess</code> method doesn't allow setting
* of system properties.
* @see SecurityManager#checkPropertiesAccess
*/
public static void setDesignTime(boolean isDesignTime)
throws SecurityException {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPropertiesAccess();
}
ThreadGroupContext.getContext().setDesignTime(isDesignTime);
}
/**
* Used to indicate whether of not we are running in an environment
* where GUI interaction is available.
*
* <p>Note that this method is security checked
* and is not available to (for example) untrusted applets.
* More specifically, if there is a security manager,
* its <code>checkPropertiesAccess</code>
* method is called. This could result in a SecurityException.
*
* @param isGuiAvailable True if GUI interaction is available.
* @exception SecurityException if a security manager exists and its
* <code>checkPropertiesAccess</code> method doesn't allow setting
* of system properties.
* @see SecurityManager#checkPropertiesAccess
*/
public static void setGuiAvailable(boolean isGuiAvailable)
throws SecurityException {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPropertiesAccess();
}
ThreadGroupContext.getContext().setGuiAvailable(isGuiAvailable);
}
}
/**
* This subclass of ObjectInputStream delegates loading of classes to
* an existing ClassLoader.
*/
class ObjectInputStreamWithLoader extends ObjectInputStream
{
private ClassLoader loader;
/**
* Loader must be non-null;
*/
public ObjectInputStreamWithLoader(InputStream in, ClassLoader loader)
throws IOException, StreamCorruptedException {
super(in);
if (loader == null) {
throw new IllegalArgumentException("Illegal null argument to ObjectInputStreamWithLoader");
}
this.loader = loader;
}
/**
* Use the given ClassLoader rather than using the system class
*/
@SuppressWarnings("rawtypes")
protected Class resolveClass(ObjectStreamClass classDesc)
throws IOException, ClassNotFoundException {
String cname = classDesc.getName();
return ClassFinder.resolveClass(cname, this.loader);
}
}
/**
* Package private support class. This provides a default AppletContext
* for beans which are applets.
*/
class BeansAppletContext implements AppletContext {
Applet target;
Hashtable<URL,Object> imageCache = new Hashtable<>();
BeansAppletContext(Applet target) {
this.target = target;
}
public AudioClip getAudioClip(URL url) {
// We don't currently support audio clips in the Beans.instantiate
// applet context, unless by some luck there exists a URL content
// class that can generate an AudioClip from the audio URL.
try {
return (AudioClip) url.getContent();
} catch (Exception ex) {
return null;
}
}
public synchronized Image getImage(URL url) {
Object o = imageCache.get(url);
if (o != null) {
return (Image)o;
}
try {
o = url.getContent();
if (o == null) {
return null;
}
if (o instanceof Image) {
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