bsh
Class Interpreter

java.lang.Object
  |
  +--bsh.Interpreter

All Implemented Interfaces:

ConsoleInterface, java.lang.Runnable, java.io.Serializable

public class Interpreter

extends java.lang.Object

implements java.lang.Runnable, ConsoleInterface, java.io.Serializable

The BeanShell script interpreter. An instance of Interpreter can be used to source scripts and evaluate statements or expressions.

Here are some examples:

                Interpeter bsh = new Interpreter();

                // Evaluate statements and expressions
                bsh.eval("foo=Math.sin(0.5)");
                bsh.eval("bar=foo*5; bar=Math.cos(bar);");
                bsh.eval("for(i=0; i<10; i++) { print(\"hello\"); }");
                // same as above using java syntax and apis only
                bsh.eval("for(int i=0; i<10; i++) { System.out.println(\"hello\"); }");

                // Source from files or streams
                bsh.source("myscript.bsh");  // or bsh.eval("source(\"myscript.bsh\")");

                // Use set() and get() to pass objects in and out of variables
                bsh.set( "date", new Date() );
                Date date = (Date)bsh.get( "date" );
                // This would also work:
                Date date = (Date)bsh.eval( "date" );

                bsh.eval("year = date.getYear()");
                Integer year = (Integer)bsh.get("year");  // primitives use wrappers

                // With Java1.3+ scripts can implement arbitrary interfaces...
                // Script an awt event handler (or source it from a file, more likely)
                bsh.eval( "actionPerformed( e ) { print( e ); }");
                // Get a reference to the script object (implementing the interface)
                ActionListener scriptedHandler = 
                        (ActionListener)bsh.eval("return (ActionListener)this");
                // Use the scripted event handler normally...
                new JButton.addActionListener( script );
        

In the above examples we showed a single interpreter instance, however you may wish to use many instances, depending on the application and how you structure your scripts. Interpreter instances are very light weight to create, however if you are going to execute the same script repeatedly and require maximum performance you should consider scripting the code as a method and invoking the scripted method each time on the same interpreter instance (using eval()).

See the BeanShell User's Manual for more information.

See Also:

Serialized Form

Field Summary

static boolean	DEBUG
protected boolean	evalOnly
protected boolean	interactive
static boolean	LOCALSCOPING
static boolean	TRACE
static java.lang.String	VERSION

Constructor Summary

Interpreter()
Create an interpreter for evaluation only.

Interpreter(ConsoleInterface console)
Construct a new interactive interpreter attached to the specified console.

Interpreter(ConsoleInterface console, NameSpace globalNameSpace)
Construct a new interactive interpreter attached to the specified console using the specified parent namespace.

Interpreter(java.io.Reader in, java.io.PrintStream out, java.io.PrintStream err, boolean interactive)

Interpreter(java.io.Reader in, java.io.PrintStream out, java.io.PrintStream err, boolean interactive, NameSpace namespace)

Interpreter(java.io.Reader in, java.io.PrintStream out, java.io.PrintStream err, boolean interactive, NameSpace namespace, Interpreter parent, java.lang.String sourceFileInfo)
The main constructor.

Method Summary

static void	debug(java.lang.String s) Print a debug message on debug stream associated with this interpreter only if debugging is turned on.
void	error(java.lang.String s) Print an error message in a standard format on the output stream associated with this interpreter.
java.lang.Object	eval(java.io.Reader in) Evaluate the inputstream in this interpreter's global namespace.
java.lang.Object	eval(java.io.Reader in, NameSpace nameSpace, java.lang.String sourceFileInfo) Spawn a non-interactive local interpreter to evaluate text in the specified namespace.
java.lang.Object	eval(java.lang.String statements) Evaluate the string in this interpreter's global namespace.
java.lang.Object	eval(java.lang.String statements, NameSpace nameSpace) Evaluate the string in the specified namespace.
java.lang.Object	get(java.lang.String name) Get the value of the name.
BshClassManager	getClassManager() Get the class manager associated with this interpreter (the BshClassManager of this interpreter's global namespace).
java.io.PrintStream	getErr() Get the error output stream associated with this interpreter.
java.io.Reader	getIn() Get the input stream associated with this interpreter.
java.lang.Object	getInterface(java.lang.Class interf) Get a reference to the interpreter (global namespace), cast to the specified interface type.
NameSpace	getNameSpace() Get the global namespace of this interpreter.
java.io.PrintStream	getOut() Get the outptut stream associated with this interpreter.
Interpreter	getParent() Get the parent Interpreter of this interpreter, if any.
java.lang.String	getSourceFileInfo() Specify the source of the text from which this interpreter is reading.
boolean	getStrictJava()
static void	main(java.lang.String[] args) Run the text only interpreter on the command line or specify a file.
java.io.File	pathToFile(java.lang.String fileName) Localize a path to the file name based on the bsh.cwd interpreter working directory.
void	print(java.lang.String s)
void	println(java.lang.String s)
static void	redirectOutputToFile(java.lang.String filename)
void	run() Run interactively.
void	set(java.lang.String name, boolean value)
void	set(java.lang.String name, double value)
void	set(java.lang.String name, float value)
void	set(java.lang.String name, int value)
void	set(java.lang.String name, long value)
void	set(java.lang.String name, java.lang.Object value) Assign the value to the name.
void	setClassLoader(java.lang.ClassLoader externalCL) Set an external class loader to be used for all basic class loading in BeanShell.
void	setConsole(ConsoleInterface console) Attach a console Note: this method is incomplete.
void	setErr(java.io.PrintStream err)
void	setExitOnEOF(boolean value) Specify whether, in interactive mode, the interpreter exits Java upon end of input.
void	setNameSpace(NameSpace globalNameSpace) Set the global namespace for this interpreter.
void	setOut(java.io.PrintStream out)
void	setStrictJava(boolean b) Set strict Java mode on or off.
java.lang.Object	source(java.lang.String filename) Read text from fileName and eval it.
java.lang.Object	source(java.lang.String filename, NameSpace nameSpace) Read text from fileName and eval it.
void	unset(java.lang.String name) Unassign the variable name.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

VERSION

public static final java.lang.String VERSION

See Also:

Constant Field Values

DEBUG

public static boolean DEBUG

TRACE

public static boolean TRACE

LOCALSCOPING

public static boolean LOCALSCOPING

evalOnly

protected boolean evalOnly

interactive

protected boolean interactive

Constructor Detail

Interpreter

public Interpreter(java.io.Reader in,
                   java.io.PrintStream out,
                   java.io.PrintStream err,
                   boolean interactive,
                   NameSpace namespace,
                   Interpreter parent,
                   java.lang.String sourceFileInfo)

The main constructor. All constructors should now pass through here.

Parameters:

namespace - If namespace is non-null then this interpreter's root namespace will be set to the one provided. If it is null a new one will be created for it.

parent - The parent interpreter if this interpreter is a child of another. May be null. Children share a BshClassManager with their parent instance.

sourceFileInfo - An informative string holding the filename or other description of the source from which this interpreter is reading... used for debugging. May be null.

Interpreter

public Interpreter(java.io.Reader in,
                   java.io.PrintStream out,
                   java.io.PrintStream err,
                   boolean interactive,
                   NameSpace namespace)

Interpreter

public Interpreter(java.io.Reader in,
                   java.io.PrintStream out,
                   java.io.PrintStream err,
                   boolean interactive)

Interpreter

public Interpreter(ConsoleInterface console,
                   NameSpace globalNameSpace)

Construct a new interactive interpreter attached to the specified console using the specified parent namespace.

Interpreter

public Interpreter(ConsoleInterface console)

Construct a new interactive interpreter attached to the specified console.

Interpreter

public Interpreter()

Create an interpreter for evaluation only.

Method Detail

setConsole

public void setConsole(ConsoleInterface console)

Attach a console Note: this method is incomplete.

setNameSpace

public void setNameSpace(NameSpace globalNameSpace)

Set the global namespace for this interpreter.

Note: This is here for completeness. If you're using this a lot it may be an indication that you are doing more work than you have to. For example, caching the interpreter instance rather than the namespace should not add a significant overhead. No state other than the debug status is stored in the interpreter.

All features of the namespace can also be accessed using the interpreter via eval() and the script variable 'this.namespace' (or global.namespace as necessary).

getNameSpace

public NameSpace getNameSpace()

Get the global namespace of this interpreter.

Note: This is here for completeness. If you're using this a lot it may be an indication that you are doing more work than you have to. For example, caching the interpreter instance rather than the namespace should not add a significant overhead. No state other than the debug status is stored in the interpreter.

All features of the namespace can also be accessed using the interpreter via eval() and the script variable 'this.namespace' (or global.namespace as necessary).

main

public static void main(java.lang.String[] args)

Run the text only interpreter on the command line or specify a file.

run

public void run()

Run interactively. (printing prompts, etc.)

Specified by:

run in interface java.lang.Runnable

source

public java.lang.Object source(java.lang.String filename,
                               NameSpace nameSpace)
                        throws java.io.FileNotFoundException,
                               java.io.IOException,
                               EvalError

Read text from fileName and eval it.

java.io.FileNotFoundException

java.io.IOException

EvalError

source

public java.lang.Object source(java.lang.String filename)
                        throws java.io.FileNotFoundException,
                               java.io.IOException,
                               EvalError

Read text from fileName and eval it. Convenience method. Use the global namespace.

java.io.FileNotFoundException

java.io.IOException

EvalError

eval

public java.lang.Object eval(java.io.Reader in,
                             NameSpace nameSpace,
                             java.lang.String sourceFileInfo)
                      throws EvalError

Spawn a non-interactive local interpreter to evaluate text in the specified namespace. Return value is the evaluated object (or corresponding primitive wrapper).

Parameters:

sourceFileInfo - is for information purposes only. It is used to display error messages (and in the future may be made available to the script).

Throws:

EvalError - on script problems

TargetError - on unhandled exceptions from the script

eval

public java.lang.Object eval(java.io.Reader in)
                      throws EvalError

Evaluate the inputstream in this interpreter's global namespace.

EvalError

eval

public java.lang.Object eval(java.lang.String statements)
                      throws EvalError

Evaluate the string in this interpreter's global namespace.

EvalError

eval

public java.lang.Object eval(java.lang.String statements,
                             NameSpace nameSpace)
                      throws EvalError

Evaluate the string in the specified namespace.

EvalError

error

public final void error(java.lang.String s)

Print an error message in a standard format on the output stream associated with this interpreter. On the GUI console this will appear in red, etc.

Specified by:

error in interface ConsoleInterface

getIn

public java.io.Reader getIn()

Get the input stream associated with this interpreter. This may be be stdin or the GUI console.

Specified by:

getIn in interface ConsoleInterface

getOut

public java.io.PrintStream getOut()

Get the outptut stream associated with this interpreter. This may be be stdout or the GUI console.

Specified by:

getOut in interface ConsoleInterface

getErr

public java.io.PrintStream getErr()

Get the error output stream associated with this interpreter. This may be be stderr or the GUI console.

Specified by:

getErr in interface ConsoleInterface

println

public final void println(java.lang.String s)

Specified by:

println in interface ConsoleInterface

print

public final void print(java.lang.String s)

Specified by:

print in interface ConsoleInterface

debug

public static final void debug(java.lang.String s)

Print a debug message on debug stream associated with this interpreter only if debugging is turned on.

get

public java.lang.Object get(java.lang.String name)
                     throws EvalError

Get the value of the name. name may be any value. e.g. a variable or field

EvalError

set

public void set(java.lang.String name,
                java.lang.Object value)
         throws EvalError

Assign the value to the name. name may evaluate to anything assignable. e.g. a variable or field.

EvalError

set

public void set(java.lang.String name,
                long value)
         throws EvalError

EvalError

set

public void set(java.lang.String name,
                int value)
         throws EvalError

EvalError

set

public void set(java.lang.String name,
                double value)
         throws EvalError

EvalError

set

public void set(java.lang.String name,
                float value)
         throws EvalError

EvalError

set

public void set(java.lang.String name,
                boolean value)
         throws EvalError

EvalError

unset

public void unset(java.lang.String name)
           throws EvalError

Unassign the variable name. Name should evaluate to a variable.

EvalError

getInterface

public java.lang.Object getInterface(java.lang.Class interf)
                              throws EvalError

Get a reference to the interpreter (global namespace), cast to the specified interface type. Assuming the appropriate methods of the interface are defined in the interpreter, then you may use this interface from Java, just like any other Java object.

For example:

                        Interpreter interpreter = new Interpreter();
                        // define a method called run()
                        interpreter.eval("run() { ... }");
                
                        // Fetch a reference to the interpreter as a Runnable
                        Runnable runnable = 
                                (Runnable)interpreter.getInterface( Runnable.class );
                

Note that the interpreter does *not* require that any or all of the methods of the interface be defined at the time the interface is generated. However if you attempt to invoke one that is not defined you will get a runtime exception.

Note also that this convenience method has exactly the same effect as evaluating the script:

                        (Type)this;
                

For example, the following is identical to the previous example:

                        // Fetch a reference to the interpreter as a Runnable
                        Runnable runnable = 
                                (Runnable)interpreter.eval( "(Runnable)this" );
                

Version requirement Although standard Java interface types are always available, to be used with arbitrary interfaces this feature requires that you are using Java 1.3 or greater.

Throws:

EvalError - if the interface cannot be generated because the version of Java does not support the proxy mechanism.

pathToFile

public java.io.File pathToFile(java.lang.String fileName)
                        throws java.io.IOException

Localize a path to the file name based on the bsh.cwd interpreter working directory.

java.io.IOException

redirectOutputToFile

public static void redirectOutputToFile(java.lang.String filename)

setClassLoader

public void setClassLoader(java.lang.ClassLoader externalCL)

Set an external class loader to be used for all basic class loading in BeanShell.

BeanShell will use this at the same point it would otherwise use the plain Class.forName(). i.e. if no explicit classpath management is done from the script (addClassPath(), setClassPath(), reloadClasses()) then BeanShell will only use the supplied classloader. If additional classpath management is done then BeanShell will perform that in addition to the supplied external classloader. However BeanShell is not currently able to reload classes supplied through the external classloader.

See Also:

BshClassManager.setClassLoader( ClassLoader )

getClassManager

public BshClassManager getClassManager()

Get the class manager associated with this interpreter (the BshClassManager of this interpreter's global namespace). This is primarily a convenience method.

setStrictJava

public void setStrictJava(boolean b)

Set strict Java mode on or off. This mode attempts to make BeanShell syntax behave as Java syntax, eliminating conveniences like loose variables, etc. When enabled, variables are required to be declared or initialized before use and method arguments are reqired to have types.

This mode will become more strict in a future release when classes are interpreted and there is an alternative to scripting objects as method closures.

getStrictJava

public boolean getStrictJava()

See Also:

setStrictJava( boolean )

getSourceFileInfo

public java.lang.String getSourceFileInfo()

Specify the source of the text from which this interpreter is reading. Note: there is a difference between what file the interrpeter is sourcing and from what file a method was originally parsed. One file may call a method sourced from another file. See SimpleNode for origination file info.

See Also:

SimpleNode.getSourceFile()

getParent

public Interpreter getParent()

Get the parent Interpreter of this interpreter, if any. Currently this relationship implies the following: 1) Parent and child share a BshClassManager 2) Children indicate the parent's source file information in error reporting. When created as part of a source() / eval() the child also shares the parent's namespace. But that is not necessary in general.

setOut

public void setOut(java.io.PrintStream out)

setErr

public void setErr(java.io.PrintStream err)

setExitOnEOF

public void setExitOnEOF(boolean value)

Specify whether, in interactive mode, the interpreter exits Java upon end of input. If true, when in interactive mode the interpreter will issue a System.exit(0) upon eof. If false the interpreter no System.exit() will be done.

Note: if you wish to cause an EOF externally you can try closing the input stream. This is not guaranteed to work in older versions of Java due to Java limitations, but should work in newer JDK/JREs. (That was the motivation for the Java NIO package).