Progress on JSON

[lgpl/argeo-commons.git] / server / runtime / org.argeo.server.json / src / main / java / org / argeo / server / json / GenericJsonDeserializer.java

diff --git a/server/runtime/org.argeo.server.json/src/main/java/org/argeo/server/json/GenericJsonDeserializer.java b/server/runtime/org.argeo.server.json/src/main/java/org/argeo/server/json/GenericJsonDeserializer.java
new file mode 100644 (file)
index 0000000..c91f76d
--- /dev/null
+++ b/server/runtime/org.argeo.server.json/src/main/java/org/argeo/server/json/GenericJsonDeserializer.java
@@ -0,0 +1,73 @@
+package org.argeo.server.json;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.argeo.server.ArgeoServerException;
+import org.codehaus.jackson.JsonFactory;
+import org.codehaus.jackson.JsonGenerator;
+import org.codehaus.jackson.JsonNode;
+import org.codehaus.jackson.JsonParser;
+import org.codehaus.jackson.JsonProcessingException;
+import org.codehaus.jackson.ObjectCodec;
+import org.codehaus.jackson.map.DeserializationContext;
+import org.codehaus.jackson.map.JsonDeserializer;
+import org.codehaus.jackson.map.ObjectMapper;
+
+public class GenericJsonDeserializer<T> extends JsonDeserializer<T> {
+       private final static Log log = LogFactory
+                       .getLog(GenericJsonDeserializer.class);
+
+       private JsonFactory jsonFactory = new JsonFactory();
+       private ObjectCodec objectCodec = new ObjectMapper();
+
+       private String typeField = "type";
+
+       private List<JsonObjectFactory> objectFactories = new ArrayList<JsonObjectFactory>();
+
+       @Override
+       public T deserialize(JsonParser parser, DeserializationContext ctxt)
+                       throws IOException, JsonProcessingException {
+               // first read as Json DOM in order to extract the type
+               // TODO: optimize with streaming API
+               JsonNode root = parser.readValueAsTree();
+               String type = root.get(typeField).getTextValue();
+
+               // Write it back as a string
+               StringWriter writer = new StringWriter();
+               JsonGenerator generator = jsonFactory.createJsonGenerator(writer);
+               generator.setCodec(objectCodec);
+               generator.writeTree(root);
+               String str = writer.toString();
+
+               if (log.isDebugEnabled())
+                       log.debug("Deserialize object of type=" + type + ", str=" + str);
+
+               JsonObjectFactory objectFactory = null;
+               jofs: for (JsonObjectFactory jof : objectFactories) {
+                       if (jof.supports(type)) {
+                               objectFactory = jof;
+                               break jofs;
+                       }
+               }
+
+               if (objectFactory == null)
+                       throw new ArgeoServerException(
+                                       "Cannot find JSON object factory for type " + type);
+
+               return (T) objectFactory.readValue(type, str);
+       }
+
+       public void setTypeField(String typeField) {
+               this.typeField = typeField;
+       }
+
+       public void setObjectFactories(List<JsonObjectFactory> objectFactories) {
+               this.objectFactories = objectFactories;
+       }
+
+}