Rework generic entity serialization using custom json serializers instead of json converter

Benjamin Rühl
1 parent 2c012f58
Showing 6 changed files with 199 additions and 2 deletions
services/Common/src/main/java/de/bht/beuthbot/persistence/GenericEntityAccessFacade.java
services/Common/src/main/java/de/bht/beuthbot/persistence/GenericEntityAttributeSerializer.java
services/Common/src/main/java/de/bht/beuthbot/persistence/GenericEntityAttributeValueSerializer.java
services/Common/src/main/java/de/bht/beuthbot/persistence/GenericEntityJsonConverter.java
services/Common/src/main/java/de/bht/beuthbot/persistence/GenericEntitySerializer.java
services/Common/src/main/java/de/bht/beuthbot/persistence/JsonMapUserType.java
@@ -8,6 +8,8 @@ import de.bht.beuthbot.model.entities.GenericEntityAttribute;
 import de.bht.beuthbot.model.entities.GenericEntityAttributeValue;
 import java.io.IOException;
+import java.io.StringWriter;
+import java.io.Writer;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -29,9 +31,9 @@ public class GenericEntityAccessFacade {
             String propertyAsJson;
             if (isPrimitiveOrWrapperAttributeType(attributeType)) {
-                propertyAsJson = GenericEntityJsonConverter.toJson(property.getFirstValueOrNull());
+                propertyAsJson = writeGenericHierarchyToJson(property.getFirstValueOrNull());
             } else {
-                propertyAsJson = GenericEntityJsonConverter.toJson(property);
+                propertyAsJson = writeGenericHierarchyToJson(property);
             }
             return (T) JsonHelper.fromJson(propertyAsJson, attributeType);
@@ -90,4 +92,17 @@ public class GenericEntityAccessFacade {
         return mapper.readValue(json, type);
     }
+
+    private static String writeGenericHierarchyToJson(Object value) throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+        SimpleModule module = new SimpleModule();
+        module.addSerializer(GenericEntity.class, new GenericEntitySerializer());
+        module.addSerializer(GenericEntityAttribute.class, new GenericEntityAttributeSerializer());
+        module.addSerializer(GenericEntityAttributeValue.class, new GenericEntityAttributeValueSerializer());
+        mapper.registerModule(module);
+
+        Writer stringWriter = new StringWriter();
+        mapper.writeValue(stringWriter, value);
+        return stringWriter.toString();
+    }
 }
+package de.bht.beuthbot.persistence;
+
+import com.fasterxml.jackson.core.JsonGenerationException;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.ser.std.StdSerializer;
+import de.bht.beuthbot.model.entities.GenericEntityAttribute;
+import de.bht.beuthbot.model.entities.GenericEntityAttributeValue;
+
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * Created by Benjamin Rühl on 14.01.2018.
+ */
+public class GenericEntityAttributeSerializer extends StdSerializer<GenericEntityAttribute> {
+
+    private GenericEntityAttributeValueSerializer attributeValueSerializer = new GenericEntityAttributeValueSerializer();
+
+    public GenericEntityAttributeSerializer() {
+        this(GenericEntityAttribute.class);
+    }
+
+    public GenericEntityAttributeSerializer(Class<GenericEntityAttribute> t) {
+        super(t);
+    }
+
+    @Override
+    public void serialize(GenericEntityAttribute value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {
+        List<GenericEntityAttributeValue> attributeValues = value.getValues();
+
+        jgen.writeStartObject();
+        jgen.writeFieldName(value.getName());
+
+        if (attributeValues == null || attributeValues.isEmpty()) {
+            jgen.writeNullField(value.getName());
+        } else if (attributeValues.size() == 1) {
+            attributeValueSerializer.serialize(value.getValues().get(0), jgen, provider);
+        } else {
+            jgen.writeArrayFieldStart(value.getName());
+
+            for (GenericEntityAttributeValue genericValue : value.getValues()) {
+                attributeValueSerializer.serialize(genericValue, jgen, provider);
+            }
+
+            jgen.writeEndArray();
+        }
+
+        jgen.writeEndObject();
+    }
+}
+package de.bht.beuthbot.persistence;
+
+import com.fasterxml.jackson.core.JsonGenerationException;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.ser.std.StdSerializer;
+import de.bht.beuthbot.model.entities.GenericEntityAttributeValue;
+
+import java.io.IOException;
+
+/**
+ * Created by Benjamin Rühl on 14.01.2018.
+ */
+public class GenericEntityAttributeValueSerializer extends StdSerializer<GenericEntityAttributeValue> {
+
+    public GenericEntityAttributeValueSerializer() {
+        this(GenericEntityAttributeValue.class);
+    }
+
+    public GenericEntityAttributeValueSerializer(Class<GenericEntityAttributeValue> t) {
+        super(t);
+    }
+
+    @Override
+    public void serialize(GenericEntityAttributeValue value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {
+        if (value.getValueAsBool() != null) {
+            jgen.writeBoolean(value.getValueAsBool());
+        } else if (value.getValueAsLong() != null) {
+            jgen.writeNumber(value.getValueAsLong());
+        } else if (value.getValueAsDouble() != null) {
+            jgen.writeNumber(value.getValueAsDouble());
+        } else if (value.getValueAsString() != null) {
+            jgen.writeString(value.getValueAsString());
+        } else if (value.getValueAsEntity() != null) {
+            new GenericEntitySerializer().serialize(value.getValueAsEntity(), jgen, provider);
+        }
+    }
+}
@@ -18,6 +18,7 @@ import java.util.List;
 /**
  * Created by Benjamin Rühl on 22.12.2017.
  * Helper class to serialize GenericEntity as if its generic attributes were normal fields
+ * @deprecated replaced by generic entity serializers
  */
 public class GenericEntityJsonConverter {
+package de.bht.beuthbot.persistence;
+
+import com.fasterxml.jackson.core.JsonGenerationException;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.ser.std.StdSerializer;
+import de.bht.beuthbot.model.entities.GenericEntity;
+import de.bht.beuthbot.model.entities.GenericEntityAttribute;
+import de.bht.beuthbot.model.entities.GenericEntityAttributeValue;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Created by Benjamin Rühl on 14.01.2018.
+ */
+public class GenericEntitySerializer extends StdSerializer<GenericEntity> {
+
+    private GenericEntityAttributeSerializer attributeSerializer = new GenericEntityAttributeSerializer();
+
+    public GenericEntitySerializer() {
+        this(GenericEntity.class);
+    }
+
+    public GenericEntitySerializer(Class<GenericEntity> t) {
+        super(t);
+    }
+
+    /**
+     * Uses a JsonGenerator to append a GenericEntity and its content to json.
+     * Does not open the json object because this part depends on whether the object stands for itself or is the value of a field.
+     * However it does close the object.
+     * @throws IOException
+     */
+    @Override
+    public void serialize(GenericEntity value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {
+        jgen.writeStartObject();
+
+        writeClassFieldsWithoutGenericEntityHierarchy(jgen, value);
+
+        for (GenericEntityAttribute genericAttribute : value.getAttributes()) {
+            attributeSerializer.serialize(genericAttribute, jgen, provider);
+        }
+
+        jgen.writeEndObject();
+    }
+
+    /**
+     * Uses a JsonGenerator to append all fields and their values of the targetObject to json.
+     * Ignores fields that have GenericEntity, GenericEntityAttribute or GenericEntityAttributeValue as type or generic list parameter.
+     * @throws IOException
+     */
+    private void writeClassFieldsWithoutGenericEntityHierarchy(JsonGenerator jsonGenerator, Object targetObject) throws IOException {
+        for (Field field : targetObject.getClass().getFields()) {
+            if (isGenericEntityHierarchyType(field))
+                continue;
+
+            try {
+                jsonGenerator.writeObjectField(field.getName(), field.get(targetObject));
+            } catch (Exception e) {
+                jsonGenerator.writeStringField(field.getName(), e.getClass().getName());
+                e.printStackTrace();
+            }
+        }
+    }
+
+    /**
+     * Determines whether the field's type is GenericEntity, GenericEntityAttribute or GenericEntityAttributeValue
+     * or a list type with one of those types as generic type parameter.
+     */
+    private boolean isGenericEntityHierarchyType(Field field) {
+        List<Class> typesOfGenericEntityHierarchy = Arrays.asList(GenericEntity.class, GenericEntityAttribute.class, GenericEntityAttributeValue.class);
+
+        // check for list types
+        try {
+            if (Iterable.class.isAssignableFrom(field.getType())) {
+                Type fieldFirstGenericType = ((ParameterizedType)field.getGenericType()).getActualTypeArguments()[0];
+                if (typesOfGenericEntityHierarchy.contains(fieldFirstGenericType.getClass()))
+                    return true;
+            }
+        } catch (Exception e) {
+            // not a list or not generic
+        }
+
+        return typesOfGenericEntityHierarchy.contains(field.getType());
+    }
+}
@@ -18,6 +18,7 @@ import java.util.Map;
 /**
  * Created by Benjamin Rühl on 03.12.2017.
  * Custom Hibernate UserType for mapping json typed columns in postgres to java maps
+ * @deprecated Currently not in use
  * @see <a href="http://vojtechruzicka.com/postgresqls-jsonb-type-mapping-using-hibernate/">vojtechruzicka.com</a>
  */
 public class JsonMapUserType implements UserType {