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Datei: This.java Sprache: JAVA

Original von: Isabelle^©

/*****************************************************************************
* *
* This file is part of the BeanShell Java Scripting distribution. *
* Documentation and updates may be found at http://www.beanshell.org/ *
* *
* Sun Public License Notice: *
* *
* The contents of this file are subject to the Sun Public License Version *
* 1.0 (the "License"); you may not use this file except in compliance with *
* the License. A copy of the License is available at http://www.sun.com *
* *
* The Original Code is BeanShell. The Initial Developer of the Original *
* Code is Pat Niemeyer. Portions created by Pat Niemeyer are Copyright *
* (C) 2000. All Rights Reserved. *
* *
* GNU Public License Notice: *
* *
* Alternatively, the contents of this file may be used under the terms of *
* the GNU Lesser General Public License (the "LGPL"), in which case the *
* provisions of LGPL are applicable instead of those above. If you wish to *
* allow use of your version of this file only under the terms of the LGPL *
* and not to allow others to use your version of this file under the SPL, *
* indicate your decision by deleting the provisions above and replace *
* them with the notice and other provisions required by the LGPL. If you *
* do not delete the provisions above, a recipient may use your version of *
* this file under either the SPL or the LGPL. *
* *
* Patrick Niemeyer ([email protected]) *
* Author of Learning Java, O'Reilly & Associates *
* http://www.pat.net/~pat/ *
* *
*****************************************************************************/

package org.gjt.sp.jedit.bsh;

/**
 'This' is the type of bsh scripted objects.
 A 'This' object is a bsh scripted object context. It holds a namespace
 reference and implements event listeners and various other interfaces.

 This holds a reference to the declaring interpreter for callbacks from
 outside of bsh.
*/
public class This implements java.io.Serializable, Runnable
{
 /**
 The namespace that this This reference wraps.
 */
 NameSpace namespace;

 /**
 This is the interpreter running when the This ref was created.
 It's used as a default interpreter for callback through the This
 where there is no current interpreter instance
 e.g. interface proxy or event call backs from outside of bsh.
 */
 transient Interpreter declaringInterpreter;

 /**
 getThis() is a factory for bsh.This type references. The capabilities
 of ".this" references in bsh are version dependent up until jdk1.3.
 The version dependence was to support different default interface
 implementations. i.e. different sets of listener interfaces which
 scripted objects were capable of implementing. In jdk1.3 the
 reflection proxy mechanism was introduced which allowed us to
 implement arbitrary interfaces. This is fantastic.

 A This object is a thin layer over a namespace, comprising a bsh object
 context. We create it here only if needed for the namespace.

 Note: this method could be considered slow because of the way it
 dynamically factories objects. However I've also done tests where
 I hard-code the factory to return JThis and see no change in the
 rough test suite time. This references are also cached in NameSpace.
 */
 static This getThis(
 NameSpace namespace, Interpreter declaringInterpreter )
 {
 try {
 Class c;
 if ( Capabilities.canGenerateInterfaces() )
 c = Class.forName( "org.gjt.sp.jedit.bsh.XThis" );
 else if ( Capabilities.haveSwing() )
 c = Class.forName( "org.gjt.sp.jedit.bsh.JThis" );
 else
 return new This( namespace, declaringInterpreter );

 return (This)Reflect.constructObject( c,
 new Object [] { namespace, declaringInterpreter } );

 } catch ( Exception e ) {
 throw new InterpreterError("internal error 1 in This: "+e);
 }
 }

 /**
 Get a version of this scripted object implementing the specified
 interface.
 */
 /*
 If this type of This implements it directly return this,
 else try complain that we don't have the proxy mechanism.
 */
 public Object getInterface( Class clas )
 throws UtilEvalError
 {
 if ( clas.isInstance( this ) )
 return this;
 else
 throw new UtilEvalError( "Dynamic proxy mechanism not available. "
 + "Cannot construct interface type: "+clas );
 }

 /**
 Get a version of this scripted object implementing the specified
 interfaces.
 */
 public Object getInterface( Class [] ca )
 throws UtilEvalError
 {
 for(int i=0; i<ca.length; i++)
 if ( !(ca[i].isInstance( this )) )
 throw new UtilEvalError(
 "Dynamic proxy mechanism not available. "
 + "Cannot construct interface type: "+ca[i] );

 return this;
 }

 /*
 I wish protected access were limited to children and not also
 package scope... I want this to be a singleton implemented by various
 children.
 */
 protected This( NameSpace namespace, Interpreter declaringInterpreter ) {
 this.namespace = namespace;
 this.declaringInterpreter = declaringInterpreter;
 //initCallStack( namespace );
 }

 public NameSpace getNameSpace() {
 return namespace;
 }

 public String toString() {
 return "'this' reference to Bsh object: " + namespace;
 }

 public void run() {
 try {
 invokeMethod( "run", new Object[0] );
 } catch( EvalError e ) {
 declaringInterpreter.error(
 "Exception in runnable:" + e );
 }
 }

 /**
 Invoke specified method as from outside java code, using the
 declaring interpreter and current namespace.
 The call stack will indicate that the method is being invoked from
 outside of bsh in native java code.
 Note: you must still wrap/unwrap args/return values using
 Primitive/Primitive.unwrap() for use outside of BeanShell.
 @see org.gjt.sp.jedit.bsh.Primitive
 */
 public Object invokeMethod( String name, Object [] args )
 throws EvalError
 {
 // null callstack, one will be created for us
 return invokeMethod(
 name, args, null/*declaringInterpreter*/, null, null,
 false/*declaredOnly*/ );
 }

 /**
 Invoke a method in this namespace with the specified args,
 interpreter reference, callstack, and caller info.
 

 Note: If you use this method outside of the bsh package and wish to
 use variables with primitive values you will have to wrap them using
 bsh.Primitive. Consider using This getInterface() to make a true Java
 interface for invoking your scripted methods.
 

 This method also implements the default object protocol of toString(),
 hashCode() and equals() and the invoke() meta-method handling as a
 last resort.
 

 Note: The invoke() meta-method will not catch the Object protocol
 methods (toString(), hashCode()...). If you want to override them you
 have to script them directly.
 

 @see org.gjt.sp.jedit.bsh.This#invokeMethod(String methodName, Object [] args, Interpreter interpreter, CallStack callstack, SimpleNode callerInfo, boolean declaredOnly ) invokeMethod
 @param callstack if callStack is null a new CallStack will be created and
 initialized with this namespace.
 @param declaredOnly if true then only methods declared directly in the
 namespace will be visible - no inherited or imported methods will
 be visible.
 @see org.gjt.sp.jedit.bsh.Primitive Primitive
 */
 /*
 invokeMethod() here is generally used by outside code to callback
 into the bsh interpreter. e.g. when we are acting as an interface
 for a scripted listener, etc. In this case there is no real call stack
 so we make a default one starting with the special JAVACODE namespace
 and our namespace as the next.
 */
 public Object invokeMethod(
 String methodName, Object [] args,
 Interpreter interpreter, CallStack callstack, SimpleNode callerInfo,
 boolean declaredOnly )
 throws EvalError
 {
 /*
 Wrap nulls.
 This is a bit of a cludge to address a deficiency in the class
 generator whereby it does not wrap nulls on method delegate. See
 Class Generator.java. If we fix that then we can remove this.
 (just have to generate the code there.)
 */
 if ( args != null )
 {
 Object [] oa = new Object [args.length];
 for(int i=0; i<args.length; i++)
 oa[i] = ( args[i] == null ? Primitive.NULL : args[i] );
 args = oa;
 }

 if ( interpreter == null )
 interpreter = declaringInterpreter;
 if ( callstack == null )
 callstack = new CallStack( namespace );
 if ( callerInfo == null )
 callerInfo = SimpleNode.JAVACODE;

 // Find the bsh method
 Class [] types = Types.getTypes( args );
 BshMethod bshMethod = null;
 try {
 bshMethod = namespace.getMethod( methodName, types, declaredOnly );
 } catch ( UtilEvalError e ) {
 // leave null
 }

 if ( bshMethod != null )
 return bshMethod.invoke( args, interpreter, callstack, callerInfo );

 /*
 No scripted method of that name.
 Implement the required part of the Object protocol:
 public int hashCode();
 public boolean equals(java.lang.Object);
 public java.lang.String toString();
 if these were not handled by scripted methods we must provide
 a default impl.
 */
 // a default toString() that shows the interfaces we implement
 if ( methodName.equals("toString" ) )
 return toString();

 // a default hashCode()
 if ( methodName.equals("hashCode" ) )
 return Integer.valueOf(this.hashCode());

 // a default equals() testing for equality with the This reference
 if ( methodName.equals("equals" ) ) {
 Object obj = args[0];
 return Boolean.valueOf( this == obj );
 }

 // Look for a default invoke() handler method in the namespace
 // Note: this code duplicates that in NameSpace getCommand()
 // is that ok?
 try {
 bshMethod = namespace.getMethod(
 "invoke", new Class [] { null, null } );
 } catch ( UtilEvalError e ) { /*leave null*/ }

 // Call script "invoke( String methodName, Object [] args );
 if ( bshMethod != null )
 return bshMethod.invoke( new Object [] { methodName, args },
 interpreter, callstack, callerInfo );

 throw new EvalError("Method " +
 StringUtil.methodString( methodName, types ) +
 " not found in bsh scripted object: "+ namespace.getName(),
 callerInfo, callstack );
 }

 /**
 Bind a This reference to a parent's namespace with the specified
 declaring interpreter. Also re-init the callstack. It's necessary
 to bind a This reference before it can be used after deserialization.
 This is used by the bsh load() command.
 

 This is a static utility method because it's used by a bsh command
 bind() and the interpreter doesn't currently allow access to direct
 methods of This objects (small hack)
 */
 public static void bind(
 This ths, NameSpace namespace, Interpreter declaringInterpreter )
 {
 ths.namespace.setParent( namespace );
 ths.declaringInterpreter = declaringInterpreter;
 }

 /**
 Allow invocations of these method names on This type objects.
 Don't give bsh.This a chance to override their behavior.
 

 If the method is passed here the invocation will actually happen on
 the bsh.This object via the regular reflective method invocation
 mechanism. If not, then the method is evaluated by bsh.This itself
 as a scripted method call.
 */
 static boolean isExposedThisMethod( String name )
 {
 return
 name.equals("getClass")
 || name.equals("invokeMethod")
 || name.equals("getInterface")
 // These are necessary to let us test synchronization from scripts
 || name.equals("wait")
 || name.equals("notify")
 || name.equals("notifyAll");
 }

}

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