Added MIMEParse class

Author: Miel Vander Sande

src/org/linkeddatafragments/util/MIMEParse.java

@@ -0,0 +1,262 @@
+package org.linkeddatafragments.util;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.lang.math.NumberUtils;
+
+/**
+ * MIME-Type Parser
+ * 
+ * This class provides basic functions for handling mime-types. It can handle
+ * matching mime-types against a list of media-ranges. See section 14.1 of the
+ * HTTP specification [RFC 2616] for a complete explanation.
+ * 
+ * http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
+ * 
+ * A port to Java of Joe Gregorio's MIME-Type Parser:
+ * 
+ * http://code.google.com/p/mimeparse/
+ * 
+ * Ported by Tom Zellman <[email protected]>.
+ * 
+ */
+public final class MIMEParse
+{
+
+    /**
+     * Parse results container
+     */
+    protected static class ParseResults
+    {
+        String type;
+
+        String subType;
+
+        // !a dictionary of all the parameters for the media range
+        Map<String, String> params;
+
+        @Override
+        public String toString()
+        {
+            StringBuffer s = new StringBuffer("('" + type + "', '" + subType
+                    + "', {");
+            for (String k : params.keySet())
+                s.append("'" + k + "':'" + params.get(k) + "',");
+            return s.append("})").toString();
+        }
+    }
+
+    /**
+     * Carves up a mime-type and returns a ParseResults object
+     * 
+     * For example, the media range 'application/xhtml;q=0.5' would get parsed
+     * into:
+     * 
+     * ('application', 'xhtml', {'q', '0.5'})
+     */
+    protected static ParseResults parseMimeType(String mimeType)
+    {
+        String[] parts = StringUtils.split(mimeType, ";");
+        ParseResults results = new ParseResults();
+        results.params = new HashMap<String, String>();
+
+        for (int i = 1; i < parts.length; ++i)
+        {
+            String p = parts[i];
+            String[] subParts = StringUtils.split(p, '=');
+            if (subParts.length == 2)
+                results.params.put(subParts[0].trim(), subParts[1].trim());
+        }
+        String fullType = parts[0].trim();
+
+        // Java URLConnection class sends an Accept header that includes a
+        // single "*" - Turn it into a legal wildcard.
+        if (fullType.equals("*"))
+            fullType = "*/*";
+        String[] types = StringUtils.split(fullType, "/");
+        results.type = types[0].trim();
+        results.subType = types[1].trim();
+        return results;
+    }
+
+    /**
+     * Carves up a media range and returns a ParseResults.
+     * 
+     * For example, the media range 'application/*;q=0.5' would get parsed into:
+     * 
+     * ('application', '*', {'q', '0.5'})
+     * 
+     * In addition this function also guarantees that there is a value for 'q'
+     * in the params dictionary, filling it in with a proper default if
+     * necessary.
+     * 
+     * @param range
+     */
+    protected static ParseResults parseMediaRange(String range)
+    {
+        ParseResults results = parseMimeType(range);
+        String q = results.params.get("q");
+        float f = NumberUtils.toFloat(q, 1);
+        if (StringUtils.isBlank(q) || f < 0 || f > 1)
+            results.params.put("q", "1");
+        return results;
+    }
+
+    /**
+     * Structure for holding a fitness/quality combo
+     */
+    protected static class FitnessAndQuality implements
+            Comparable<FitnessAndQuality>
+    {
+        int fitness;
+
+        float quality;
+
+        String mimeType; // optionally used
+
+        public FitnessAndQuality(int fitness, float quality)
+        {
+            this.fitness = fitness;
+            this.quality = quality;
+        }
+
+        public int compareTo(FitnessAndQuality o)
+        {
+            if (fitness == o.fitness)
+            {
+                if (quality == o.quality)
+                    return 0;
+                else
+                    return quality < o.quality ? -1 : 1;
+            }
+            else
+                return fitness < o.fitness ? -1 : 1;
+        }
+    }
+
+    /**
+     * Find the best match for a given mimeType against a list of media_ranges
+     * that have already been parsed by MimeParse.parseMediaRange(). Returns a
+     * tuple of the fitness value and the value of the 'q' quality parameter of
+     * the best match, or (-1, 0) if no match was found. Just as for
+     * quality_parsed(), 'parsed_ranges' must be a list of parsed media ranges.
+     * 
+     * @param mimeType
+     * @param parsedRanges
+     */
+    protected static FitnessAndQuality fitnessAndQualityParsed(String mimeType,
+            Collection<ParseResults> parsedRanges)
+    {
+        int bestFitness = -1;
+        float bestFitQ = 0;
+        ParseResults target = parseMediaRange(mimeType);
+
+        for (ParseResults range : parsedRanges)
+        {
+            if ((target.type.equals(range.type) || range.type.equals("*") || target.type
+                    .equals("*"))
+                    && (target.subType.equals(range.subType)
+                            || range.subType.equals("*") || target.subType
+                            .equals("*")))
+            {
+                for (String k : target.params.keySet())
+                {
+                    int paramMatches = 0;
+                    if (!k.equals("q") && range.params.containsKey(k)
+                            && target.params.get(k).equals(range.params.get(k)))
+                    {
+                        paramMatches++;
+                    }
+                    int fitness = (range.type.equals(target.type)) ? 100 : 0;
+                    fitness += (range.subType.equals(target.subType)) ? 10 : 0;
+                    fitness += paramMatches;
+                    if (fitness > bestFitness)
+                    {
+                        bestFitness = fitness;
+                        bestFitQ = NumberUtils
+                                .toFloat(range.params.get("q"), 0);
+                    }
+                }
+            }
+        }
+        return new FitnessAndQuality(bestFitness, bestFitQ);
+    }
+
+    /**
+     * Find the best match for a given mime-type against a list of ranges that
+     * have already been parsed by parseMediaRange(). Returns the 'q' quality
+     * parameter of the best match, 0 if no match was found. This function
+     * bahaves the same as quality() except that 'parsed_ranges' must be a list
+     * of parsed media ranges.
+     * 
+     * @param mimeType
+     * @param parsedRanges
+     * @return
+     */
+    protected static float qualityParsed(String mimeType,
+            Collection<ParseResults> parsedRanges)
+    {
+        return fitnessAndQualityParsed(mimeType, parsedRanges).quality;
+    }
+
+    /**
+     * Returns the quality 'q' of a mime-type when compared against the
+     * mediaRanges in ranges. For example:
+     * 
+     * @param mimeType
+     * @param parsedRanges
+     */
+    public static float quality(String mimeType, String ranges)
+    {
+        List<ParseResults> results = new LinkedList<ParseResults>();
+        for (String r : StringUtils.split(ranges, ','))
+            results.add(parseMediaRange(r));
+        return qualityParsed(mimeType, results);
+    }
+
+    /**
+     * Takes a list of supported mime-types and finds the best match for all the
+     * media-ranges listed in header. The value of header must be a string that
+     * conforms to the format of the HTTP Accept: header. The value of
+     * 'supported' is a list of mime-types.
+     * 
+     * MimeParse.bestMatch(Arrays.asList(new String[]{"application/xbel+xml",
+     * "text/xml"}), "text/*;q=0.5,*; q=0.1") 'text/xml'
+     * 
+     * @param supported
+     * @param header
+     * @return
+     */
+    public static String bestMatch(Collection<String> supported, String header)
+    {
+        List<ParseResults> parseResults = new LinkedList<ParseResults>();
+        List<FitnessAndQuality> weightedMatches = new LinkedList<FitnessAndQuality>();
+        for (String r : StringUtils.split(header, ','))
+            parseResults.add(parseMediaRange(r));
+
+        for (String s : supported)
+        {
+            FitnessAndQuality fitnessAndQuality = fitnessAndQualityParsed(s,
+                    parseResults);
+            fitnessAndQuality.mimeType = s;
+            weightedMatches.add(fitnessAndQuality);
+        }
+        Collections.sort(weightedMatches);
+
+        FitnessAndQuality lastOne = weightedMatches
+                .get(weightedMatches.size() - 1);
+        return NumberUtils.compare(lastOne.quality, 0) != 0 ? lastOne.mimeType
+                : "";
+    }
+
+    // hidden
+    private MIMEParse()
+    {
+    }
+}