import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class EvalSample 
{
	public static void main(String[] args) 
	throws Exception
	{
    
    	String expression = "function f(param) { return (param > 10); } f(ext_param_1);";
        
        expression = expression.replace("ext_param_1","12");
        
		ScriptEngine e = new ScriptEngineManager().getEngineByName("js");
		
		Object res = e.eval(expression);

		System.out.println(res); //true
	}
}

// Dynamic Proxy나 AOP 대체로 가능할 듯.


(annotation 정의)
import java.lang.annotation.*;

@Inherited
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.METHOD })
public @interface MyAnnotation{
	String value() default "MyAnnotation";
}

(annotation 적용확인)

import java.lang.reflect.Method;
import MyAnnotation;

public class UseAnnotation{

	@MyAnnotation(value="Annotation Test")
	public void annotationTest(){
		System.out.println("Annotation Method");
	}

	public static void main(String[] args){
	
		Method[] ms = UseAnnotation.class.getMethods();

		for(Method m: methods){
			MyAnnotation an = m.getAnnotation(MyAnnotation.class);
			
			if(an != null){
				System.out.println("ANNOTATION : "+an.value());
				m.invoke(new UseAnnotation(), null);
			}
		}
	}

}

1. System.out -> 특정 Output Stream 전달.

   PrintStream ps = new PrintStream(new FileOutputStream("d:\\result.txt", true));
   System.setOut(ps);
   System.out.println("test string");  
   ps.close();
   
2. 파이프 이용

   PipedOutputStream pout = new PipedOutputStream();
   PipedInputStream pin = new PipedInputStream(pout);
   
   PrintStream ps1 = new PrintStream(pout);

   System.setOut(ps1);

   System.out.println("test string");

   byte[] data = new byte[pin.available()];
   
   pin.read(data, 0, data.length);
   
   //System.out 쓴 녀석이 pipe out으로 나가고 그 녀석을 pin에서 읽어와서 파일에 기록.
   PrintStream ps2 = new PrintStream(new FileOutputStream("d:\\log.txt", true));
   
   ps2.write(data, 0, data.length);