postfixcommand.java

mysql集群

/*****************************************************************************
      SQLJEP - Java SQL Expression Parser 0.2
      November 1 2006
         (c) Copyright 2006, Alexey Gaidukov
      SQLJEP Author: Alexey Gaidukov

      SQLJEP is based on JEP 2.24 (http://www.singularsys.com/jep/)
           (c) Copyright 2002, Nathan Funk
 
      See LICENSE.txt for license information.
*****************************************************************************/

package com.meidusa.amoeba.sqljep.function;

import java.util.Stack;
import java.math.BigDecimal;

import com.meidusa.amoeba.sqljep.function.PostfixCommandI;
import com.meidusa.amoeba.sqljep.ASTFunNode;
import com.meidusa.amoeba.sqljep.JepRuntime;
import com.meidusa.amoeba.sqljep.ParseException;

/**
 * Function classes extend this class. It is an implementation of the 
 * PostfixMathCommandI interface.
 * <p>
 * It includes a numberOfParameters member, that is checked when parsing the
 * expression. This member should be initialized to an appropriate value for
 * all classes extending this class. If an arbitrary number of parameters
 * should be allowed, initialize this member to -1.
 */
public abstract class PostfixCommand implements PostfixCommandI {
	protected static final Integer ZERO = new Integer(0);
	public static final String PARAMS_NUMBER = "Wrong number of parameters";
	public static final String WRONG_TYPE = "Wrong type";
	public static final String INTERNAL_ERROR = "Internal error";
	public static final String NOT_IMPLIMENTED_EXCEPTION = "Not implimented";
	private String name;
	
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	/**
	 * Return the required number of parameters.
	 * Number of parameters a the function requires. Initialize this value to
	 * -1 if any number of parameters should be allowed.
	 */
	abstract public int getNumberOfParameters();
	
	/**
	 * Throws an exception because this method should never be called under
	 * normal circumstances. Each function should use it's own run() method
	 * for evaluating the function. This includes popping off the parameters
	 * from the stack, and pushing the result back on the stack.
	 */
	abstract public Comparable<?>[] evaluate(ASTFunNode node, JepRuntime runtime) throws ParseException;
	
	public boolean isAutoBox(){
		return true;
	}
	
	protected final void removeParams(Stack<Comparable> s, int num) {
		int i = 1;
		s.pop();
		while (i < num) {
			s.pop();
			i++;
		}
		s.push(null);
	}
	
	public static Comparable<?>  parse(String param) throws ParseException {
		try {
			return Integer.valueOf((String)param);
		} catch (NumberFormatException e) {
			try {
				BigDecimal d = new BigDecimal((String)param);
				if (d.scale() < 0) {
					d = d.setScale(0);
				}
				return d;
			} catch (NumberFormatException ex) {
				throw new ParseException("Not a number");
			}
		}
	}
	
	public static BigDecimal getBigDecimal(Number param) {
		// BigInteger is not supported
		if (param instanceof BigDecimal) {
			return (BigDecimal)param;
		}
		if (param instanceof Double || param instanceof Float) {
			return new BigDecimal(param.doubleValue());
		}
		return new BigDecimal(param.longValue());
	}
	
	public static int getInteger(Comparable<?>  param) throws ParseException {
		if (param instanceof Number) {
			return ((Number)param).intValue();
		}
		else if (param instanceof String) {
			try {
				BigDecimal d = new BigDecimal((String)param);
				return d.intValueExact();
			} catch (Exception e) {
				throw new ParseException("Cant parse integer: '"+(String)param+"'");
			}
		}
		throw new ParseException("Not Integer: "+(param != null ? param.getClass() : "null"));
	}
	
	public static double getDouble(Comparable<?>  param) throws ParseException {
		if (param instanceof Number) {
			Number n = (Number)param;
			return n.doubleValue();
		}
		else if (param instanceof String) {
			try {
				return Double.valueOf((String)param);
			} catch (NumberFormatException e) {
				throw new ParseException("Cant parse double: '"+(String)param+"'");
			}
		}
		throw new ParseException("Not Double: "+(param != null ? param.getClass() : "null"));
	}
}