Executing code read from a JTextArea

[Jesper Sahner]

Hi!

I use a JTextArea as an area for inputting Java-code, and the text can
be read with the getText()-method.

But how do I execute the code?

Regards,
Jesper

 

[Rhino]

Hi!

I use a JTextArea as an area for inputting Java-code, and the text can
be read with the getText()-method.

But how do I execute the code?

You can't just execute it directly; you have to compile it into bytecode
first via 'javac'. If the compile works, you hand the bytecode to 'java' to
execute.

You could do both "under the covers" if you just invoke Ant programatically
and hand it the source code from the JTextArea.

By the way, there is another way of doing what you want to do: if you have
Eclipse, you can use Scrapbook pages to execute code fragments.

Rhino

 

[Rogan Dawes]

Hi!

I use a JTextArea as an area for inputting Java-code, and the text can
be read with the getText()-method.

But how do I execute the code?

Regards,
Jesper

Take a look at BeanShell

Rogan

 

[Bill Tschumy]

Hi!

I use a JTextArea as an area for inputting Java-code, and the text can
be read with the getText()-method.

But how do I execute the code?

Regards,
Jesper

Check out:

<http://java.sun.com/developer/JDCTechTips/2003/tt0722.html#2>

Tells you exactly what you need to know.

 

[jespersahner]

Hi Bill!

Thanx for the link!

The technique used is either calling 'javac' using Runtime.exec() or
com.sun.tools.javac.Main.compile().

However this only solves the problem of compiling and running a "full"
class
as far as I can see.

In general I would like to make all kinds of Java-statements, like:

Integer i = new Integer(5);
int j=7;

and compile and execute it as part of the running session.
Regards,
Jesper

 

[jespersahner]

Hi Rogan!

Looks very interesting. I wonder how BeanShell does the "trick".
Any comments on this?

Regards,
Jesper

 

[Anton Spaans]

Hi Bill!

Thanx for the link!

The technique used is either calling 'javac' using Runtime.exec() or
com.sun.tools.javac.Main.compile().

However this only solves the problem of compiling and running a "full"
class
as far as I can see.

In general I would like to make all kinds of Java-statements, like:

Integer i = new Integer(5);
int j=7;

and compile and execute it as part of the running session.
Regards,
Jesper

Then wrap a dummy class around that code, so that the final compiling code
would be:
public class Dummy1
{
public static void exec()
{
/* Contents of Text-Area here: */
Integer i = new Integer(5);
int j=7;
/* End */
}
}

and call, after compilation the exec() of Dummy1.

Also, take a look at BCEL, in which you can engineer your own bytecode on
the fly:
http://jakarta.apache.org/bcel/

-- Anton.

 

[jespersahner]

Hi Anton!

You could do that, agreed. However then the statements
Integer i=new Integer(5);
int j=7;
only exists within the "scope" of a Dummy1-object as I see it.

Let's say that you want to refer to 'i' and 'j' like e.g.:
Vector v=new Vector();
v.add(i);
int k;
k=j+3;

How would you do that?

Jesper

 

[Thufir Hawat]

anonymous inner classes?

 

[Anton Spaans]

Hi Anton!

You could do that, agreed. However then the statements
Integer i=new Integer(5);
int j=7;
only exists within the "scope" of a Dummy1-object as I see it.

Let's say that you want to refer to 'i' and 'j' like e.g.:
Vector v=new Vector();
v.add(i);
int k;
k=j+3;

How would you do that?

Jesper

Aha... after the user types in some code (and hits Enter, for example), the
code is executed immediately and all the variables, etc., remain in scope
for the next set of instructions that the user want executed. Am i correct?

If so, then you are writing a scripting language. "Scripted Java" in this
case (not to be confused with the already existing "Javascript"... hehehe).
I don't know if Java (with BCEL or other libraries/tools) is capable of
being scripted that way. Is it possible to have your users use good-old
Javascript instead? If this is possible, there are already ways of doing
that. More info here:
http://jakarta.apache.org/bsf/
-- Anton.

 

[Anton Spaans]

Aha... after the user types in some code (and hits Enter, for example), the
code is executed immediately and all the variables, etc., remain in scope
for the next set of instructions that the user want executed. Am i correct?

If so, then you are writing a scripting language. "Scripted Java" in this
case (not to be confused with the already existing "Javascript"... hehehe).
I don't know if Java (with BCEL or other libraries/tools) is capable of
being scripted that way. Is it possible to have your users use good-old
Javascript instead? If this is possible, there are already ways of doing
that. More info here:
http://jakarta.apache.org/bsf/
-- Anton.

And using BSF to use Java as a scripting language is called BeanShell: See
also Rogan Dawes post.
-- Anton.