How to redirect output from Groovy script?

I wonder if there is any way I could change the default output (System.out) for the groovy script that I'm executing from my Java code.

Here is the Java code:

public void exec(File file, OutputStream output) throws Exception {
    GroovyShell shell = new GroovyShell();
    shell.evaluate(file);
}

And the sample groovy script:

def name='World'
println "Hello $name!"

Currently the execution of the method, evaluates scripts that writes "开发者_StackOverflow社区Hello World!" to the console (System.out). How can I redirect output to the OutputStream passed as a parameter?

---

Try this using Binding

public void exec(File file, OutputStream output) throws Exception {
    Binding binding = new Binding()
    binding.setProperty("out", output) 
    GroovyShell shell = new GroovyShell(binding);
    shell.evaluate(file);
}

After comments

public void exec(File file, OutputStream output) throws Exception {
    Binding binding = new Binding()
    binding.setProperty("out", new PrintStream(output)) 
    GroovyShell shell = new GroovyShell(binding);
    shell.evaluate(file);
}

Groovy Script

def name='World'
out << "Hello $name!"

---

How about using javax.script.ScriptEngine? You can specify its writer.

ScriptEngine engine = new ScriptEngineManager().getEngineByName("Groovy");
PrintWriter writer = new PrintWriter(new StringWriter());
engine.getContext().setWriter(writer);
engine.getContext().setErrorWriter(writer);
engine.eval("println 'HELLO'")

---

Use SystemOutputInterceptor class. You can start intercepting output before script evaluation and stop after.

def output = "";
def interceptor = new SystemOutputInterceptor({ output += it; false});
interceptor.start()
println("Hello")
interceptor.stop()

---

I suspect you could do this quite nicely by overwriting the println method in your GroovyShell's metaClass. The following works in Groovy Console:

StringBuilder b = new StringBuilder()

this.metaClass.println = {
    b.append(it)
    System.out.println it
}

println "Hello, world!"
System.out.println b.toString()

output:

Hello, world!
Hello, world!

---

System.setOut() is just what you need.