package org.jbpm.pvm.internal.script;
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import java.io.*;
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import java.util.Map;
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import javax.script.*;
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import bsh.*;
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import static javax.script.ScriptContext.*;
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/*
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Notes
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This engine supports open-ended pluggable scriptcontexts
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*/
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public class BshScriptEngine extends AbstractScriptEngine
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implements Compilable, Invocable
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{
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// The BeanShell global namespace for the interpreter is stored in the
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// engine scope map under this key.
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static final String engineNameSpaceKey = "org_beanshell_engine_namespace";
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private BshScriptEngineFactory factory;
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private bsh.Interpreter interpreter;
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public BshScriptEngine() {
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this( null );
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}
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public BshScriptEngine( BshScriptEngineFactory factory )
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{
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this.factory = factory;
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getInterpreter(); // go ahead and prime the interpreter now
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}
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protected Interpreter getInterpreter()
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{
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if ( interpreter == null ) {
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this.interpreter = new bsh.Interpreter();
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interpreter.setNameSpace(null); // should always be set by context
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}
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return interpreter;
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}
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public Object eval( String script, ScriptContext scriptContext )
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throws ScriptException
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{
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return evalSource( script, scriptContext );
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}
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public Object eval( Reader reader, ScriptContext scriptContext )
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throws ScriptException
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{
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return evalSource( reader, scriptContext );
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}
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/*
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This is the primary implementation method.
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We respect the String/Reader difference here in BeanShell because
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BeanShell will do a few extra things in the string case... e.g.
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tack on a trailing ";" semicolon if necessary.
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*/
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private Object evalSource( Object source, ScriptContext scriptContext )
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throws ScriptException
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{
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bsh.NameSpace contextNameSpace = getEngineNameSpace( scriptContext );
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Interpreter bsh = getInterpreter();
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bsh.setNameSpace( contextNameSpace );
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// This is a big hack, convert writer to PrintStream
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bsh.setOut( new PrintStream(
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new WriterOutputStream( scriptContext.getWriter() ) ) );
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bsh.setErr( new PrintStream(
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new WriterOutputStream( scriptContext.getErrorWriter() ) ) );
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try {
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if ( source instanceof Reader )
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return bsh.eval( (Reader) source );
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else
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return bsh.eval( (String) source );
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} catch ( ParseException e ) {
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// explicit parsing error
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throw new ScriptException(
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e.toString(), e.getErrorSourceFile(), e.getErrorLineNumber() );
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} catch ( TargetError e ) {
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// The script threw an application level exception
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// set it as the cause ?
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ScriptException se = new ScriptException(
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e.toString(), e.getErrorSourceFile(), e.getErrorLineNumber() );
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se.initCause( e.getTarget() );
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throw se;
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} catch ( EvalError e ) {
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// The script couldn't be evaluated properly
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throw new ScriptException(
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e.toString(), e.getErrorSourceFile(), e.getErrorLineNumber() );
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} catch ( InterpreterError e ) {
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// The interpreter had a fatal problem
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throw new ScriptException( e.toString() );
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}
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}
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/*
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Check the context for an existing global namespace embedded
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in the script context engine scope. If none exists, ininitialize the
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context with one.
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*/
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private static NameSpace getEngineNameSpace( ScriptContext scriptContext )
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{
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NameSpace ns = (NameSpace)scriptContext.getAttribute(
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engineNameSpaceKey, ENGINE_SCOPE );
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if ( ns == null )
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{
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// Create a global namespace for the interpreter
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Map engineView = new ScriptContextEngineView( scriptContext );
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ns = new ExternalNameSpace(
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null/*parent*/, "javax_script_context", engineView );
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scriptContext.setAttribute( engineNameSpaceKey, ns, ENGINE_SCOPE );
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}
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return ns;
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}
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public Bindings createBindings()
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{
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return new SimpleBindings();
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}
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public ScriptEngineFactory getFactory()
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{
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if ( factory == null )
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factory = new BshScriptEngineFactory();
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return factory;
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}
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/**
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* Compiles the script (source represented as a <code>String</code>) for later
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* execution.
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*
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* @param script The source of the script, represented as a
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* <code>String</code>.
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*
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* @return An subclass of <code>CompiledScript</code> to be executed later
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* using one of the <code>eval</code> methods of <code>CompiledScript</code>.
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*
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* @throws ScriptException if compilation fails.
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* @throws NullPointerException if the argument is null.
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*/
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public CompiledScript compile( String script ) throws
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ScriptException
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{
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return compile( new StringReader( script ) );
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}
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/**
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* Compiles the script (source read from <code>Reader</code>) for later
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* execution. Functionality is identical to <code>compile(String)</code> other
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* than the way in which the source is passed.
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*
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* @param script The reader from which the script source is obtained.
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*
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* @return An implementation of <code>CompiledScript</code> to be executed
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* later using one of its <code>eval</code> methods of
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* <code>CompiledScript</code>.
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*
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* @throws ScriptException if compilation fails.
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* @throws NullPointerException if argument is null.
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*/
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public CompiledScript compile( Reader script ) throws
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ScriptException
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{
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// todo
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throw new Error("unimplemented");
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}
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/**
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* Calls a procedure compiled during a previous script execution, which is
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* retained in the state of the <code>ScriptEngine<code>.
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*
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* @param name The name of the script method to be called.
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* @param thiz thiz is an instance of the script class returned by a previous execution or
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* invocation, the named method is called through that instance.
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* @param args Arguments to pass to the procedure. The rules for converting
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* the arguments to scripting variables are implementation-specific.
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*
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* @return The value returned by the method. The rules for converting the
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* scripting variable returned by the procedure to a Java Object are
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* implementation-specific.
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*
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* @throws javax.script.ScriptException if an error occurrs during invocation
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* of the method.
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* @throws NoSuchMethodException if method with given name or matching argument
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* types cannot be found.
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* @throws NullPointerException if method name is null.
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*/
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public Object invokeMethod( Object thiz, String name, Object... args ) throws ScriptException, NoSuchMethodException
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{
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if ( ! (thiz instanceof bsh.This) )
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throw new ScriptException( "Illegal objec type: " +thiz.getClass() );
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bsh.This bshObject = (bsh.This)thiz;
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try {
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return bshObject.invokeMethod( name, args );
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} catch ( ParseException e ) {
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// explicit parsing error
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throw new ScriptException(
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e.toString(), e.getErrorSourceFile(), e.getErrorLineNumber() );
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} catch ( TargetError e ) {
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// The script threw an application level exception
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// set it as the cause ?
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ScriptException se = new ScriptException(
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e.toString(), e.getErrorSourceFile(), e.getErrorLineNumber() );
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se.initCause( e.getTarget() );
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throw se;
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} catch ( EvalError e ) {
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// The script couldn't be evaluated properly
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throw new ScriptException(
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e.toString(), e.getErrorSourceFile(), e.getErrorLineNumber() );
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} catch ( InterpreterError e ) {
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// The interpreter had a fatal problem
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throw new ScriptException( e.toString() );
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}
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}
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/**
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* Used to call top-level procedures defined in scripts.
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*
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* @param name Name of the procedure
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* @param args Arguments to pass to the procedure
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*
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* @return The value returned by the procedure
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*
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* @throws javax.script.ScriptException if an error occurrs during invocation
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* of the method.
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* @throws NoSuchMethodException if procedure with given name or matching
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* argument types cannot be found.
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* @throws NullPointerException if procedure name is null.
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*/
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public Object invokeFunction( String name, Object... args )
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throws ScriptException, NoSuchMethodException
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{
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return invokeMethod( getGlobal(), name, args );
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}
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/**
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* Returns an implementation of an interface using procedures compiled in the
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* interpreter. The methods of the interface may be implemented using the
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* <code>invokeFunction</code> method.
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*
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* @param clasz The <code>Class</code> object of the interface to return.
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*
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* @return An instance of requested interface - null if the requested interface
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* is unavailable, i. e. if compiled methods in the
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* <code>ScriptEngine</code> cannot be found matching the ones in the
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* requested interface.
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*
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* @throws IllegalArgumentException if the specified <code>Class</code> object
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* does not exist or is not an interface.
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*/
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public <T> T getInterface( Class<T> clasz )
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{
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try {
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return (T) getGlobal().getInterface( clasz );
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} catch ( UtilEvalError utilEvalError ) {
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utilEvalError.printStackTrace();
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return null;
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}
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}
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/**
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* Returns an implementation of an interface using member functions of a
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* scripting object compiled in the interpreter. The methods of the interface
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* may be implemented using invokeMethod(Object, String, Object...) method.
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*
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* @param thiz The scripting object whose member functions are used to
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* implement the methods of the interface.
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* @param clasz The <code>Class</code> object of the interface to return.
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*
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* @return An instance of requested interface - null if the requested
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* interface is unavailable, i. e. if compiled methods in the
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* <code>ScriptEngine</code> cannot be found matching the ones in the
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* requested interface.
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*
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* @throws IllegalArgumentException if the specified <code>Class</code> object
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* does not exist or is not an interface, or if the specified Object is null
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* or does not represent a scripting object.
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*/
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public <T> T getInterface( Object thiz, Class<T> clasz )
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{
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if ( !(thiz instanceof bsh.This) )
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throw new IllegalArgumentException(
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"invalid object type: "+thiz.getClass() );
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try {
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bsh.This bshThis = (bsh.This)thiz;
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return (T) bshThis.getInterface( clasz );
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} catch ( UtilEvalError utilEvalError ) {
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utilEvalError.printStackTrace( System.err );
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return null;
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}
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}
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private bsh.This getGlobal()
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{
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// requires 2.0b5 to make getThis() public
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return getEngineNameSpace( getContext() ).getThis( getInterpreter() );
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}
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/*
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This is a total hack. We need to introduce a writer to the
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Interpreter.
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*/
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class WriterOutputStream extends OutputStream
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{
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Writer writer;
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WriterOutputStream( Writer writer )
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{
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this.writer = writer;
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}
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public void write( int b ) throws IOException
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{
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writer.write(b);
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}
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public void flush() throws IOException
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{
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writer.flush();
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}
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public void close() throws IOException
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{
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writer.close();
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}
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}
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}
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