tim/prune/save/xml/XmlUtils.java

   1 package tim.prune.save.xml;
   2
   3 import java.io.File;
   4 import java.io.FileOutputStream;
   5 import java.io.IOException;
   6 import java.io.OutputStreamWriter;
   7 import java.nio.charset.Charset;
   8
   9 /**
  10  * Collection of utility functions for handling XML
  11  */
  12 public abstract class XmlUtils
  13 {
  14         /** Start of Cdata sequence */
  15         private static final String CDATA_START = "<![CDATA[";
  16         /** End of Cdata sequence */
  17         private static final String CDATA_END = "]]>";
  18         /** Cached copy of system encoding string */
  19         private static String _systemEncoding = null;
  20
  21         /**
  22          * Fix the CDATA blocks in the given String to give valid xml
  23          * @param inString String to modify
  24          * @return fixed String
  25          */
  26         public static String fixCdata(String inString)
  27         {
  28                 if (inString == null || inString.isEmpty()) return "";
  29                 if (!hasIllegalCharacter(inString)) {
  30                         return inString;
  31                 }
  32                 String result = inString;
  33                 // Remove cdata block at start if present
  34                 if (result.startsWith(CDATA_START)) {
  35                         result = result.substring(CDATA_START.length());
  36                 }
  37                 // Remove all instances of end block
  38                 result = result.replaceAll(CDATA_END, "");
  39                 // Now check whether cdata block is required
  40                 if (!XmlUtils.hasIllegalCharacter(result)) {
  41                         return result;
  42                 }
  43                 return CDATA_START + result + CDATA_END;
  44         }
  45
  46         /**
  47          * Checks the input string for the three illegal characters,
  48          * but only looping through the string once instead of three times
  49          * @param inValue string to check
  50          * @return true if at least one of the illegal characters is found
  51          */
  52         public static boolean hasIllegalCharacter(String inValue)
  53         {
  54                 if (inValue == null) return false;
  55                 final int numChars = inValue.length();
  56                 for (int i=0; i<numChars; i++)
  57                 {
  58                         final char c = inValue.charAt(i);
  59                         if (c == '<' || c == '>' || c == '&')
  60                         {
  61                                 return true;
  62                         }
  63                 }
  64                 return false;
  65         }
  66
  67         /**
  68          * @return true if system uses UTF-8 by default
  69          */
  70         public static boolean isSystemUtf8()
  71         {
  72                 String systemEncoding = getSystemEncoding();
  73                 return (systemEncoding != null && systemEncoding.toUpperCase().equals("UTF-8"));
  74         }
  75
  76         /**
  77          * @return name of the system's character encoding
  78          */
  79         public static String getSystemEncoding()
  80         {
  81                 if (_systemEncoding == null) {
  82                         _systemEncoding = determineSystemEncoding();
  83                 }
  84                 return _systemEncoding;
  85         }
  86
  87         /**
  88          * Use a temporary file to obtain the name of the default system encoding
  89          * @return name of default system encoding, or null if write failed
  90          */
  91         private static String determineSystemEncoding()
  92         {
  93                 File tempFile = null;
  94                 String encoding = null;
  95                 try
  96                 {
  97                         tempFile = File.createTempFile("gpsprune", null);
  98                         OutputStreamWriter writer = new OutputStreamWriter(new FileOutputStream(tempFile));
  99                         encoding = getEncoding(writer);
 100                         writer.close();
 101                 }
 102                 catch (IOException e) {} // value stays null
 103                 // Delete temp file
 104                 if (tempFile != null && tempFile.exists()) {
 105                         if (!tempFile.delete()) {
 106                                 System.err.println("Cannot delete temp file: " + tempFile.getAbsolutePath());
 107                         }
 108                 }
 109                 // If writing failed (eg permissions) then just ask system for default
 110                 if (encoding == null) encoding = Charset.defaultCharset().name();
 111                 return encoding;
 112         }
 113
 114
 115         /**
 116          * Get the default system encoding using a writer
 117          * @param inWriter writer object
 118          * @return string defining encoding
 119          */
 120         public static String getEncoding(OutputStreamWriter inWriter)
 121         {
 122                 String encoding = inWriter.getEncoding();
 123                 try {
 124                         encoding =  Charset.forName(encoding).name();
 125                 }
 126                 catch (Exception e) {} // ignore failure to find encoding
 127                 return encoding;
 128         }
 129 }