1 | package org.greenstone.gatherer.util;
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2 |
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3 | import java.io.Reader;
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4 | import java.io.IOException;
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5 |
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6 | import java.io.File;
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7 | import java.io.FileReader;
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8 |
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9 | import java.util.regex.Pattern;
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10 |
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11 | public class RemoveContentBeforeRootElementXMLReader extends Reader {
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12 |
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13 | static final Pattern[] xmlIndicators;
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14 | static Pattern commentStart;
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15 | static Pattern commentStop;
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16 |
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17 | static {
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18 | // generate the xml starting sequences we will try to match against
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19 | xmlIndicators = new Pattern[3];
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20 | try{
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21 | xmlIndicators[0] = Pattern.compile("<\\?xml"); //usual xml declaration
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22 | xmlIndicators[1] = Pattern.compile("<!DOCTYPE"); //doctype declaration
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23 | xmlIndicators[2] = Pattern.compile("<[a-zA-Z-]+[ >/]"); // the beginning of a root node
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24 |
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25 | commentStart = Pattern.compile("<!--");
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26 | commentStop = Pattern.compile("-->");
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27 |
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28 | } catch ( java.util.regex.PatternSyntaxException pse ) {
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29 | System.err.println( "Pattern no good. " + pse );
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30 | xmlIndicators[0] = xmlIndicators[1] = xmlIndicators[2] = null;
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31 | commentStart = commentStop = null;
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32 | }
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33 | }
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34 |
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35 | Reader ur;
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36 |
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37 | String finalBuffer = null;
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38 | int finalBufferIndex = 0;
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39 |
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40 | public RemoveContentBeforeRootElementXMLReader( Reader ur ) {
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41 |
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42 | this.ur = ur;
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43 |
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44 | int found = -1;
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45 | boolean inComment = false;
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46 | StringBuffer buffer = null;
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47 |
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48 | for ( int c = 0; c != -1 && found == -1; ) {
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49 |
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50 | //read a character
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51 | try {
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52 | c = ur.read();
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53 | } catch( Exception e ) {
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54 | System.err.println( "Exception while reading underlying Reader in RemoveContentBeforeRootElementXMLReader" );
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55 | }
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56 |
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57 | //break out if we have reached the end of the input
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58 | if ( c == -1 ) {
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59 | break;
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60 | }
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61 |
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62 | //we start buffering when we come across the first <
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63 | //regardless of whether it turns out to be a relevant < or not
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64 | if ( buffer == null && (char)c == '<' ) {
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65 | buffer = new StringBuffer();
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66 | }
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67 |
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68 | //if not buffering, just display the character and move onto next character
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69 | if ( buffer == null ) {
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70 | System.err.print( (char)c );
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71 | continue;
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72 | }
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73 |
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74 | buffer.append( (char)c );
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75 |
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76 | //check for comment open or close
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77 | if ( !inComment ) {
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78 | if ( commentStart.matcher(buffer.toString()).find() ) {
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79 | inComment = true;
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80 | System.err.print( buffer.toString() );
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81 | buffer = new StringBuffer();
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82 | }
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83 | } else {
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84 | if ( commentStop.matcher(buffer.toString()).find() ) {
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85 | inComment = false;
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86 | System.err.print( buffer.toString() );
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87 | buffer = new StringBuffer();
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88 |
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89 | //skip to reading next character
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90 | continue;
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91 | }
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92 | }
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93 |
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94 | if ( !inComment ) {
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95 |
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96 | //check each indicator to see if found
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97 | for ( int i = 0; i < xmlIndicators.length && found == -1; i++ ) {
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98 | if ( xmlIndicators[i].matcher(buffer.toString()).find() ) {
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99 | found = i;
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100 | String line = buffer.toString();
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101 | int lastIndex = line.lastIndexOf('<');
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102 | //flush the previous characters in the buffer to the console
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103 | System.err.print(line.substring(0, lastIndex));
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104 | buffer.delete(0, lastIndex);
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105 | finalBuffer = buffer.toString();
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106 | }
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107 | }
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108 |
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109 | }
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110 | }
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111 |
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112 | if ( found == -1 ) {
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113 | System.err.println( "RemoveContentBeforeRootElementXMLReader:\n" +
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114 | "The XML being loaded was not valid: couldn't find start of XML input" );
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115 | }
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116 |
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117 | }
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118 |
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119 | public int read( char[] cbuf, int off, int len ) throws IOException {
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120 |
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121 | for ( int i=off; i<off+len && i<cbuf.length; i++ ) {
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122 |
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123 | //read from underlying reader
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124 | int c = read();
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125 |
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126 | //catch end of stream
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127 | if ( c == -1 ) {
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128 | if ( i == off ) {
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129 | return -1;
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130 | }
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131 | return i - off;
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132 | }
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133 |
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134 | //insert character into the array
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135 | cbuf[i] = (char)c;
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136 | }
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137 | return len;
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138 |
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139 | }
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140 |
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141 | public int read() throws IOException {
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142 |
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143 | //flush the buffer containing the opening XML sequence
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144 | if ( finalBuffer != null && finalBuffer.length() > finalBufferIndex ) {
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145 | char c = finalBuffer.charAt(finalBufferIndex++);
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146 | if ( finalBufferIndex == finalBuffer.length() ) {
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147 | finalBuffer = null;
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148 | }
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149 | return c;
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150 | }
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151 |
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152 | return ur.read();
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153 | }
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154 |
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155 | public void close() throws IOException {
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156 | ur.close();
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157 | }
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158 |
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159 | public static void main ( String[] args ) {
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160 |
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161 | //init
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162 | System.out.println( "------------\nWill now initialise the test reader\n------------" );
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163 | RemoveContentBeforeRootElementXMLReader parser = null;
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164 | try {
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165 | parser = new RemoveContentBeforeRootElementXMLReader(
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166 | new FileReader( new File("text.xml") ) );
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167 | } catch ( java.io.FileNotFoundException fnfe ) {
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168 | System.err.println( "Please create text.xml to test this class" );
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169 | System.exit(-1);
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170 | }
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171 |
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172 | //read the rest of the input
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173 | System.out.println( "------------\nWill now read the rest of the input\n------------" );
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174 | try {
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175 | int c = 0;
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176 | while ( ( c = parser.read() ) != -1 ) {
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177 | System.out.print( (char)c );
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178 | }
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179 | } catch ( Exception e ) {
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180 | System.err.println("Exception: " + e);
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181 | }
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182 |
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183 | }
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184 |
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185 |
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186 | }
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