coercions.java

jBpm是一个灵活可扩展的工作流管理系统。作为jBpm运行时server输入的业务流程使用简单强大的语言表达并打包在流程档案中

/*
 * The Apache Software License, Version 1.1
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 *    any, must include the following acknowlegement:  
 *       "This product includes software developed by the 
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
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package org.jbpm.jpdl.el.impl;

import java.beans.PropertyEditor;
import java.beans.PropertyEditorManager;
import java.math.BigInteger;
import java.math.BigDecimal;

import org.jbpm.jpdl.el.ELException;

/**
 *
 * <p>This class contains the logic for coercing data types before
 * operators are applied to them.
 *
 * <p>The following is the list of rules applied for various type
 * conversions.
 *
 * <ul><pre>
 * Applying arithmetic operator
 *   Binary operator - A {+,-,*} B
 *     if A and B are null
 *       return 0
 *     if A or B is BigDecimal, coerce both to BigDecimal and then:
 *       if operator is +, return <code>A.add(B)</code>
 *       if operator is -, return <code>A.subtract(B)</code>
 *       if operator is *, return <code>A.multiply(B)</code>
 *     if A or B is Float, Double, or String containing ".", "e", or "E"
 *       if A or B is BigInteger, coerce both A and B to BigDecimal and apply operator
 *       coerce both A and B to Double and apply operator
 *     if A or B is BigInteger, coerce both to BigInteger and then:
 *       if operator is +, return <code>A.add(B)</code>
 *       if operator is -, return <code>A.subtract(B)</code>
 *       if operator is *, return <code>A.multiply(B)</code>
 *     otherwise
 *       coerce both A and B to Long
 *       apply operator
 *     if operator results in exception (such as divide by 0), error
 * 
 *   Binary operator - A {/,div} B
 *     if A and B are null
 *       return 0
 *     if A or B is a BigDecimal or BigInteger, coerce both to BigDecimal and
 *      return <code>A.divide(B, BigDecimal.ROUND_HALF_UP)</code>
 *     otherwise
 *       coerce both A and B to Double
 *       apply operator
 *     if operator results in exception (such as divide by 0), error
 * 
 *   Binary operator - A {%,mod} B
 *     if A and B are null
 *       return 0
 *     if A or B is BigDecimal, Float, Double, or String containing ".", "e" or "E"
 *       coerce both to Double
 *       apply operator
 *     if A or B is BigInteger, coerce both to BigInteger and return
 *      <code>A.remainder(B)</code>
 *     otherwise
 *       coerce both A and B to Long
 *       apply operator
 *     if operator results in exception (such as divide by 0), error
 * 
 *   Unary minus operator - -A
 *     if A is null
 *       return 0
 *     if A is BigInteger or BigDecimal, return <code>A.negate()</code>
 *     if A is String
 *       if A contains ".", "e", or "E"
 *         coerce to Double, apply operator
 *       otherwise
 *         coerce to a Long and apply operator
 *     if A is Byte,Short,Integer,Long,Float,Double
 *       retain type, apply operator
 *     if operator results in exception, error
 *     otherwise
 *       error
 *
 * Applying "empty" operator - empty A
 *   if A is null
 *     return true
 *   if A is zero-length String
 *     return true
 *   if A is zero-length array
 *     return true
 *   if A is List and ((List) A).isEmpty()
 *     return true
 *   if A is Map and ((Map) A).isEmpty()
 *     return true
 *   if A is Collection an ((Collection) A).isEmpty()
 *     return true
 *   otherwise
 *     return false
 * 
 * Applying logical operators
 *   Binary operator - A {and,or} B
 *     coerce both A and B to Boolean, apply operator
 *   NOTE - operator stops as soon as expression can be determined, i.e.,
 *     A and B and C and D - if B is false, then only A and B is evaluated
 *   Unary not operator - not A
 *     coerce A to Boolean, apply operator
 * 
 * Applying relational operator
 *   A {<,>,<=,>=,lt,gt,lte,gte} B
 *     if A==B
 *       if operator is >= or <=
 *         return true
 *       otherwise
 *         return false
 *     if A or B is null
 *       return false
 *     if A or B is BigDecimal, coerce both A and B to BigDecimal and use the
 *      return value of <code>A.compareTo(B)</code>
 *     if A or B is Float or Double
 *       coerce both A and B to Double
 *       apply operator
 *     if A or B is BigInteger, coerce both A and B to BigInteger and use the
 *      return value of <code>A.compareTo(B)</code>
 *     if A or B is Byte,Short,Character,Integer,Long
 *       coerce both A and B to Long
 *       apply operator
 *     if A or B is String
 *       coerce both A and B to String, compare lexically
 *     if A is Comparable
 *       if A.compareTo (B) throws exception
 *         error
 *       otherwise
 *         use result of A.compareTo(B)
 *     if B is Comparable
 *       if B.compareTo (A) throws exception
 *         error
 *       otherwise
 *         use result of B.compareTo(A)
 *     otherwise
 *       error
 * 
 * Applying equality operator
 *   A {==,!=} B
 *     if A==B
 *       apply operator
 *     if A or B is null
 *       return false for ==, true for !=
 *     if A or B is BigDecimal, coerce both A and B to BigDecimal and then:
 *       if operator is == or eq, return <code>A.equals(B)</code>
 *       if operator is != or ne, return <code>!A.equals(B)</code>
 *     if A or B is Float or Double
 *       coerce both A and B to Double
 *       apply operator
 *     if A or B is BigInteger, coerce both A and B to BigInteger and then:
 *       if operator is == or eq, return <code>A.equals(B)</code>
 *       if operator is != or ne, return <code>!A.equals(B)</code>
 *     if A or B is Byte,Short,Character,Integer,Long
 *       coerce both A and B to Long
 *       apply operator
 *     if A or B is Boolean
 *       coerce both A and B to Boolean
 *       apply operator
 *     if A or B is String
 *       coerce both A and B to String, compare lexically
 *     otherwise
 *       if an error occurs while calling A.equals(B)
 *         error
 *       apply operator to result of A.equals(B)
 * 
 * coercions
 * 
 *   coerce A to String
 *     A is String
 *       return A
 *     A is null
 *       return ""
 *     A.toString throws exception
 *       error
 *     otherwise
 *       return A.toString
 * 
 *   coerce A to Number type N
 *     A is null or ""
 *       return 0
 *     A is Character
 *       convert to short, apply following rules
 *     A is Boolean
 *       error
 *     A is Number type N
 *       return A
 *     A is Number, coerce quietly to type N using the following algorithm
 *         If N is BigInteger
 *             If A is BigDecimal, return <code>A.toBigInteger()</code>
 *             Otherwise, return <code>BigInteger.valueOf(A.longValue())</code>
 *        if N is BigDecimal
 *             If A is a BigInteger, return <code>new BigDecimal(A)</code>
 *             Otherwise, return <code>new BigDecimal(A.doubleValue())</code>
 *        If N is Byte, return <code>new Byte(A.byteValue())</code>
 *        If N is Short, return <code>new Short(A.shortValue())</code>
 *        If N is Integer, return <code>new Integer(A.integerValue())</code>
 *        If N is Long, return <code>new Long(A.longValue())</code>
 *        If N is Float, return <code>new Float(A.floatValue())</code>
 *        If N is Double, return <code>new Double(A.doubleValue())</code>
 *        otherwise ERROR
 *     A is String
 *       If N is BigDecimal then:
 *            If <code>new BigDecimal(A)</code> throws an exception then ERROR
 *            Otherwise, return <code>new BigDecimal(A)</code>
 *       If N is BigInteger then:
 *            If <code>new BigInteger(A)</code> throws an exception, then ERROR
 *            Otherwise, return <code>new BigInteger(A)</code>
 *       new <code>N.valueOf(A)</code> throws exception
 *         error
 *       return <code>N.valueOf(A)</code>
 *     otherwise
 *       error
 * 
 *   coerce A to Character should be
 *     A is null or ""
 *       return (char) 0
 *     A is Character
 *       return A
 *     A is Boolean
 *       error
 *     A is Number with less precision than short
 *       coerce quietly - return (char) A
 *     A is Number with greater precision than short
 *       coerce quietly - return (char) A
 *     A is String
 *       return A.charAt (0)
 *     otherwise
 *       error
 * 
 *   coerce A to Boolean
 *     A is null or ""
 *       return false
 *     A is Boolean
 *       return A
 *     A is String
 *       Boolean.valueOf(A) throws exception
 *         error
 *       return Boolean.valueOf(A)
 *     otherwise
 *       error
 * 
 *   coerce A to any other type T
 *     A is null
 *       return null
 *     A is assignable to T
 *       coerce quietly
 *     A is String
 *       T has no PropertyEditor
 *         if A is "", return null
 *         otherwise error
 *       T's PropertyEditor throws exception
 *         if A is "", return null
 *         otherwise error
 *       otherwise
 *         apply T's PropertyEditor
 *     otherwise
 *       error
 * </pre></ul>
 *
 * @author Nathan Abramson - Art Technology Group
 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: tombaeyens $
 **/

public class Coercions
{
   private static final Number ZERO = new Integer(0);
  //-------------------------------------
  /**
   *
   * Coerces the given value to the specified class.
   **/
  public static Object coerce (Object pValue,
			       Class pClass,
			       Logger pLogger)
    throws ELException
  {
    if (pClass == String.class) {
      return coerceToString (pValue, pLogger);
    }
    else if (isNumberClass (pClass)) {
      return coerceToPrimitiveNumber (pValue, pClass, pLogger);
    }
    else if (pClass == Character.class ||
	     pClass == Character.TYPE) {
      return coerceToCharacter (pValue, pLogger);
    }
    else if (pClass == Boolean.class ||
	     pClass == Boolean.TYPE) {
      return coerceToBoolean (pValue, pLogger);
    }
    else {
      return coerceToObject (pValue, pClass, pLogger);
    }
  }

  //-------------------------------------
  /**
   *
   * Returns true if the given class is Byte, Short, Integer, Long,
   * Float, Double, BigInteger, or BigDecimal
   **/
  static boolean isNumberClass (Class pClass)
  {
    return
      pClass == Byte.class ||
      pClass == Byte.TYPE ||
      pClass == Short.class ||
      pClass == Short.TYPE ||
      pClass == Integer.class ||
      pClass == Integer.TYPE ||
      pClass == Long.class ||
      pClass == Long.TYPE ||
      pClass == Float.class ||
      pClass == Float.TYPE ||
      pClass == Double.class ||
      pClass == Double.TYPE ||
      pClass == BigInteger.class ||
      pClass == BigDecimal.class;
  }

  //-------------------------------------
  /**
   *
   * Coerces the specified value to a String
   **/
  public static String coerceToString (Object pValue,
				       Logger pLogger)
    throws ELException
  {
    if (pValue == null) {
      return "";
    }
    else if (pValue instanceof String) {
      return (String) pValue;
    }
    else {
      try {
	return pValue.toString ();
      }
      catch (Exception exc) {
	if (pLogger.isLoggingError ()) {
	  pLogger.logError (Constants.TOSTRING_EXCEPTION,
			    exc,
			    pValue.getClass ().getName ());
	}
	return "";
      }
    }
  }