trunk/server/runtime/org.argeo.server.json/src/main/java/org/argeo/server/json/GenericJsonDeserializer.java

   1 /*
   2  * Copyright (C) 2007-2012 Argeo GmbH
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *         http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package org.argeo.server.json;
  17
  18 import java.io.IOException;
  19 import java.io.StringWriter;
  20 import java.util.ArrayList;
  21 import java.util.List;
  22
  23 import org.apache.commons.logging.Log;
  24 import org.apache.commons.logging.LogFactory;
  25 import org.argeo.ArgeoException;
  26 import org.codehaus.jackson.JsonFactory;
  27 import org.codehaus.jackson.JsonGenerator;
  28 import org.codehaus.jackson.JsonNode;
  29 import org.codehaus.jackson.JsonParser;
  30 import org.codehaus.jackson.JsonProcessingException;
  31 import org.codehaus.jackson.ObjectCodec;
  32 import org.codehaus.jackson.map.DeserializationContext;
  33 import org.codehaus.jackson.map.JsonDeserializer;
  34 import org.codehaus.jackson.map.ObjectMapper;
  35
  36 public class GenericJsonDeserializer<T> extends JsonDeserializer<T> {
  37         private final static Log log = LogFactory
  38                         .getLog(GenericJsonDeserializer.class);
  39
  40         private JsonFactory jsonFactory = new JsonFactory();
  41         private ObjectCodec objectCodec = new ObjectMapper();
  42         private JsonObjectFactory defaultObjectFactory = new JsonObjectFactoryImpl();
  43
  44         private String typeField = "type";
  45
  46         private List<JsonObjectFactory> objectFactories = new ArrayList<JsonObjectFactory>();
  47
  48         @SuppressWarnings("unchecked")
  49         @Override
  50         public T deserialize(JsonParser parser, DeserializationContext ctxt)
  51                         throws IOException, JsonProcessingException {
  52                 // first read as Json DOM in order to extract the type
  53                 // TODO: optimize with streaming API
  54                 JsonNode root = parser.readValueAsTree();
  55                 String type = root.get(typeField).getTextValue();
  56
  57                 // Write it back as a string
  58                 StringWriter writer = new StringWriter();
  59                 JsonGenerator generator = jsonFactory.createJsonGenerator(writer);
  60                 generator.setCodec(objectCodec);
  61                 generator.writeTree(root);
  62                 String str = writer.toString();
  63
  64                 if (log.isTraceEnabled())
  65                         log.debug("Deserialize object of type=" + type + ", str=" + str);
  66
  67                 JsonObjectFactory objectFactory = null;
  68                 jofs: for (JsonObjectFactory jof : objectFactories) {
  69                         if (jof.supports(type)) {
  70                                 objectFactory = jof;
  71                                 break jofs;
  72                         }
  73                 }
  74
  75                 if (objectFactory == null)
  76                         objectFactory = defaultObjectFactory;
  77
  78                 if (objectFactory == null || !objectFactory.supports(type))
  79                         throw new ArgeoException(
  80                                         "Cannot find JSON object factory for type " + type);
  81
  82                 return (T) objectFactory.readValue(type, str);
  83         }
  84
  85         public void setTypeField(String typeField) {
  86                 this.typeField = typeField;
  87         }
  88
  89         public void setObjectFactories(List<JsonObjectFactory> objectFactories) {
  90                 this.objectFactories = objectFactories;
  91         }
  92
  93         public List<JsonObjectFactory> getObjectFactories() {
  94                 return objectFactories;
  95         }
  96
  97 }