java/src/main/com/google/apphosting/utils/config/IndexYamlReader.java

   1 // Copyright 2010 Google Inc. All Rights Reserved.
   2
   3 package com.google.apphosting.utils.config;
   4
   5 import net.sourceforge.yamlbeans.YamlException;
   6 import net.sourceforge.yamlbeans.YamlReader;
   7
   8 import java.io.Reader;
   9 import java.io.StringReader;
  10 import java.util.LinkedList;
  11 import java.util.List;
  12
  13 /**
  14  * Class to parse index.yaml into a IndexesXml object.
  15  *
  16  */
  17 public class IndexYamlReader {
  18
  19   public static final String INDEX_DEFINITIONS_TAG =
  20       "!!python/object:google.appengine.datastore.datastore_index.IndexDefinitions";
  21   public static final String INDEX_TAG =
  22       "!!python/object:google.appengine.datastore.datastore_index.Index";
  23   public static final String PROPERTY_TAG =
  24       "!!python/object:google.appengine.datastore.datastore_index.Property";
  25
  26   /**
  27    * Wrapper around IndexesXml to make the JavaBeans properties match the YAML
  28    * file syntax.
  29    */
  30   public static class IndexYaml {
  31
  32     /**
  33      * JavaBean wrapper for Index entries in IndexesXml.
  34      */
  35     public static class Index {
  36       public String kind;
  37       protected boolean ancestor;
  38       public List<Property> properties;
  39
  40       public void setAncestor(String ancestor) {
  41         this.ancestor = YamlUtils.parseBoolean(ancestor);
  42       }
  43
  44       public String getAncestor() {
  45         return "" + ancestor;
  46       }
  47     }
  48
  49     /**
  50      * JavaBean wrapper for IndexesXml properties.
  51      */
  52     public static class Property {
  53       public String name;
  54       private String direction = "asc";
  55
  56       public void setDirection(String direction) {
  57         if ("desc".equals(direction) || "asc".equals(direction)) {
  58           this.direction = direction;
  59         } else {
  60           throw new AppEngineConfigException(
  61               "Invalid direction '" + direction + "': expected 'asc' or 'desc'.");
  62         }
  63       }
  64
  65       public String getDirection() {
  66         return direction;
  67       }
  68
  69       public boolean isAscending() {
  70         return "asc".equals(direction);
  71       }
  72     }
  73
  74     private List<Index> indexes;
  75
  76     public List<Index> getIndexes() {
  77       return indexes;
  78     }
  79
  80     public void setIndexes(List<Index> indexes) {
  81       this.indexes = indexes;
  82     }
  83
  84     public IndexesXml toXml(IndexesXml xml) {
  85       if (indexes == null) {
  86         throw new AppEngineConfigException("Empty index configuration.");
  87       }
  88       if (xml == null) {
  89         xml = new IndexesXml();
  90       }
  91       for (Index yamlIndex : indexes) {
  92         if (yamlIndex.kind == null) {
  93           throw new AppEngineConfigException("Index missing required element 'kind'");
  94         }
  95         IndexesXml.Index xmlIndex = xml.addNewIndex(yamlIndex.kind, yamlIndex.ancestor);
  96         if (yamlIndex.properties != null) {
  97           for (Property property : yamlIndex.properties) {
  98             if (property.name == null) {
  99               throw new AppEngineConfigException("Property is missing required element 'name'.");
 100             }
 101             xmlIndex.addNewProperty(property.name, property.isAscending());
 102           }
 103         }
 104       }
 105       return xml;
 106     }
 107   }
 108
 109   public static IndexesXml parse(Reader yaml, IndexesXml xml) {
 110     List<IndexesXml> list;
 111     try {
 112       list = parseMultiple(yaml, xml);
 113     } catch (YamlException ex) {
 114       throw new AppEngineConfigException(ex.getMessage(), ex);
 115     }
 116     if (0 == list.size()) {
 117       throw new AppEngineConfigException("Empty index configuration.");
 118     }
 119     if (list.size() > 1) {
 120       throw new AppEngineConfigException(
 121           "yaml unexepectedly contains more than one document: " + list.size());
 122     }
 123     return list.get(0);
 124   }
 125
 126   /**
 127    * Parses the Yaml from {@code yaml} into a Yaml document and deserializes
 128    * the document into an instance of {@link IndexesXml}.
 129    * @param yaml  A {@link String} from which to read the Yaml. This String is allowed to
 130    * be in the style generated by the admin server, including the Python-specific tags.
 131    * This method will safely ignore those tags.
 132    * @return An instance of {@link IndexesXml}.
 133    */
 134   public static IndexesXml parse(String yaml) {
 135     return parse(new StringReader(clean(yaml)), null);
 136   }
 137
 138   /**
 139    * Parses the Yaml from {@code yaml} into one or more documents, and
 140    * deserializes the documents into one or more instances of {@link IndexesXml}
 141    * which are returned in a {@link List}.
 142    *
 143    * @param yaml A {@link String} from which to read the Yyaml. This String is
 144    *        allowed to be in the style generated by the admin server, including
 145    *        the Python-specific tags. This method will safely ignore those tags.
 146    * @return A {@link List} of {@link IndexesXml} instances representing one or
 147    *         more parsed Yaml documents.
 148    */
 149   public static List<IndexesXml> parseMultiple(String yaml) {
 150     try {
 151       return parseMultiple(new StringReader(clean(yaml)), null);
 152     } catch (YamlException ex) {
 153       throw new AppEngineConfigException(ex.getMessage(), ex);
 154     }
 155   }
 156
 157   /**
 158    * Cleans a Yaml String by removing Pyton-specific tags.
 159    * These tags are written by the admin server when it generates
 160    * Yaml representing indexes.
 161    * @param yaml A {@link String} containing Yaml
 162    * @return The cleaned {@link String}
 163    */
 164   private static String clean(String yaml) {
 165     return yaml
 166         .replaceAll(INDEX_DEFINITIONS_TAG, "")
 167         .replaceAll(INDEX_TAG, "")
 168         .replaceAll(PROPERTY_TAG, "")
 169         .trim();
 170   }
 171
 172   /**
 173    * Parses the Yaml from {@code yaml} into one or more documents, and
 174    * deserializes the documents into one or more instances of {@link IndexesXml}
 175    * which are returned in a {@link List}.
 176    *
 177    * @param yaml A {@link Reader} from which to read the yaml
 178    * @param xml A possibly {@code null} {@link IndexesXml} instance. If this
 179    *        parameter is not {@code null} then each of the yaml documents will
 180    *        be deserialized into it. This parameter is intended to be
 181    *        used in cases where there is only one Yaml document expected and so
 182    *        there will only be one instance of {@link IndexesXml} in the
 183    *        returned {@link List}. If this parameter is not {@code null} and the
 184    *        returned list has length greater than 1, then the list will contain
 185    *        multiple copies of this parameter.
 186    * @return A {@link List} of {@link IndexesXml} instances representing one or
 187    *         more parsed Yaml documents.
 188    * @throws YamlException If the Yaml parser has trobule parsing.
 189    */
 190   private static List<IndexesXml> parseMultiple(Reader yaml, IndexesXml xml) throws YamlException {
 191     YamlReader reader = new YamlReader(yaml);
 192     reader.getConfig().setPropertyElementType(IndexYaml.class, "indexes", IndexYaml.Index.class);
 193     reader.getConfig().setPropertyElementType(
 194         IndexYaml.Index.class, "properties", IndexYaml.Property.class);
 195     List<IndexesXml> list = new LinkedList<IndexesXml>();
 196     while (true) {
 197       IndexYaml indexYaml = reader.read(IndexYaml.class);
 198       if (null == indexYaml) {
 199         break;
 200       } else {
 201         list.add(indexYaml.toXml(xml));
 202       }
 203     }
 204     return list;
 205   }
 206
 207 }