EL函数和自定义EL函数

package org.apache.taglibs.standard.functions;

import java.lang.reflect.Array;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.StringTokenizer;
import javax.servlet.jsp.JspTagException;
import org.apache.taglibs.standard.resources.Resources;
import org.apache.taglibs.standard.tag.common.core.Util;

public class Functions
{
  public static String toUpperCase(String input)
  {
    return input.toUpperCase();
  }

  public static String toLowerCase(String input)
  {
    return input.toLowerCase();
  }

  public static int indexOf(String input, String substring)
  {
    if (input == null) {
      input = "";
    }
    if (substring == null) {
      substring = "";
    }
    return input.indexOf(substring);
  }

  public static boolean contains(String input, String substring)
  {
    return indexOf(input, substring) != -1;
  }

  public static boolean containsIgnoreCase(String input, String substring)
  {
    if (input == null) {
      input = "";
    }
    if (substring == null) {
      substring = "";
    }
    String inputUC = input.toUpperCase();
    String substringUC = substring.toUpperCase();
    return indexOf(inputUC, substringUC) != -1;
  }

  public static boolean startsWith(String input, String substring)
  {
    if (input == null) {
      input = "";
    }
    if (substring == null) {
      substring = "";
    }
    return input.startsWith(substring);
  }

  public static boolean endsWith(String input, String substring)
  {
    if (input == null) {
      input = "";
    }
    if (substring == null) {
      substring = "";
    }
    int index = input.indexOf(substring);
    if (index == -1) {
      return false;
    }
    if ((index == 0) && (substring.length() == 0)) {
      return true;
    }
    return index == input.length() - substring.length();
  }

  public static String substring(String input, int beginIndex, int endIndex)
  {
    if (input == null) {
      input = "";
    }
    if (beginIndex >= input.length()) {
      return "";
    }
    if (beginIndex < 0) {
      beginIndex = 0;
    }
    if ((endIndex < 0) || (endIndex > input.length())) {
      endIndex = input.length();
    }
    if (endIndex < beginIndex) {
      return "";
    }
    return input.substring(beginIndex, endIndex);
  }

  public static String substringAfter(String input, String substring)
  {
    if (input == null) {
      input = "";
    }
    if (input.length() == 0) {
      return "";
    }
    if (substring == null) {
      substring = "";
    }
    if (substring.length() == 0) {
      return input;
    }
    int index = input.indexOf(substring);
    if (index == -1) {
      return "";
    }
    return input.substring(index + substring.length());
  }

  public static String substringBefore(String input, String substring)
  {
    if (input == null) {
      input = "";
    }
    if (input.length() == 0) {
      return "";
    }
    if (substring == null) {
      substring = "";
    }
    if (substring.length() == 0) {
      return "";
    }
    int index = input.indexOf(substring);
    if (index == -1) {
      return "";
    }
    return input.substring(0, index);
  }

  public static String escapeXml(String input)
  {
    if (input == null) {
      return "";
    }
    return Util.escapeXml(input);
  }

  public static String trim(String input)
  {
    if (input == null) {
      return "";
    }
    return input.trim();
  }

  public static String replace(String input, String substringBefore, String substringAfter)
  {
    if (input == null) {
      input = "";
    }
    if (input.length() == 0) {
      return "";
    }
    if (substringBefore == null) {
      substringBefore = "";
    }
    if (substringBefore.length() == 0) {
      return input;
    }
    StringBuffer buf = new StringBuffer(input.length());
    int startIndex = 0;
    int index;
    while ((index = input.indexOf(substringBefore, startIndex)) != -1)
    {
      buf.append(input.substring(startIndex, index)).append(substringAfter);
      startIndex = index + substringBefore.length();
    }
    return input.substring(startIndex);
  }

  public static String[] split(String input, String delimiters)
  {
    if (input == null) {
      input = "";
    }
    if (input.length() == 0)
    {
      String[] array = new String[1];
      array[0] = "";
      return array;
    }
    if (delimiters == null) {
      delimiters = "";
    }
    StringTokenizer tok = new StringTokenizer(input, delimiters);
    int count = tok.countTokens();
    String[] array = new String[count];
    int i = 0;
    while (tok.hasMoreTokens()) {
      array[(i++)] = tok.nextToken();
    }
    return array;
  }

  public static int length(Object obj)
    throws JspTagException
  {
    if (obj == null) {
      return 0;
    }
    if ((obj instanceof String)) {
      return ((String)obj).length();
    }
    if ((obj instanceof Collection)) {
      return ((Collection)obj).size();
    }
    if ((obj instanceof Map)) {
      return ((Map)obj).size();
    }
    int count = 0;
    if ((obj instanceof Iterator))
    {
      Iterator iter = (Iterator)obj;
      count = 0;
      while (iter.hasNext())
      {
        count++;
        iter.next();
      }
      return count;
    }
    if ((obj instanceof Enumeration))
    {
      Enumeration enum_ = (Enumeration)obj;
      count = 0;
      while (enum_.hasMoreElements())
      {
        count++;
        enum_.nextElement();
      }
      return count;
    }
    try
    {
      return Array.getLength(obj);
    }
    catch (IllegalArgumentException ex)
    {
      throw new JspTagException(Resources.getMessage("FOREACH_BAD_ITEMS"));
    }
  }

  public static String join(String[] array, String separator)
  {
    if (array == null) {
      return "";
    }
    if (separator == null) {
      separator = "";
    }
    StringBuffer buf = new StringBuffer();
    for (int i = 0; i < array.length; i++)
    {
      buf.append(array[i]);
      if (i < array.length - 1) {
        buf.append(separator);
      }
    }
    return buf.toString();
  }
}