diff --git a/src/main/java/cactusServer/models/Instances.java b/src/main/java/cactusServer/models/Instances.java
index 0180e76..04dbad1 100644
--- a/src/main/java/cactusServer/models/Instances.java
+++ b/src/main/java/cactusServer/models/Instances.java
@@ -1,6 +1,8 @@
 package cactusServer.models;
 
 import java.util.HashMap;
+import java.util.HashSet;
+
 import cactusServer.entities.Instance;
 
 /**
@@ -11,7 +13,8 @@
  */
 public class Instances {
 	private static Instances theInstance = null;
-	private HashMap<String, Instance> instanceMap = new HashMap<>();
+	private HashMap<String, Instance> instanceMap = new HashMap<>(); // instance��ID�Ǝ��̂��Ǘ�
+	private HashSet<String> instanceIdSet = new HashSet<>(); // �g�p�ς�ID�̏W��
 
 	private Instances() {
 
@@ -36,9 +39,13 @@
 	 *            Instance�����ʂ����ӂ�ID
 	 * @param name
 	 *            �C���X�^���X�� (��)
-	 * @return �V�����쐬���ꂽInstance
+	 * @return �V�����쐬���ꂽInstance<br>
+	 *         ������, instanceID���d�������ꍇ�͐V�KInstance���쐬������null��Ԃ�
 	 */
 	public Instance createInstance(String instanceId, String name) {
+		if (!instanceIdSet.add(instanceId)) {
+			return null;
+		}
 		Instance instance = new Instance(name);
 		instanceMap.put(instanceId, instance);
 		return instance;
@@ -55,4 +62,15 @@
 		return instanceMap.get(instanceId);
 	}
 
+	/**
+	 * ID�ɑΉ�����Instance��Map����폜���ĕԂ�
+	 * 
+	 * @param instanceId
+	 *            Instance�����ʂ����ӂ�ID
+	 * @return Map����폜���ꂽInstance
+	 */
+	public Instance destroyInstance(String instanceId) {
+		return instanceMap.remove(instanceId);
+	}
+
 }
diff --git a/src/main/java/cactusServer/utils/JSONConsumer.java b/src/main/java/cactusServer/utils/JSONConsumer.java
new file mode 100644
index 0000000..c3b4d23
--- /dev/null
+++ b/src/main/java/cactusServer/utils/JSONConsumer.java
@@ -0,0 +1,45 @@
+package cactusServer.utils;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Type;
+
+import javax.validation.constraints.Null;
+import javax.ws.rs.Consumes;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.ext.MessageBodyReader;
+import javax.ws.rs.ext.Provider;
+
+import net.arnx.jsonic.JSON;
+import net.arnx.jsonic.JSONException;
+
+@Provider
+@Consumes(MediaType.APPLICATION_JSON)
+public class JSONConsumer implements MessageBodyReader {
+
+	public boolean isReadable(java.lang.Class type, 
+		java.lang.reflect.Type genericType, java.lang.annotation.Annotation[] 
+		annotations, MediaType mediaType) {
+		return true;
+	}
+
+
+	@Override
+	public Object readFrom(Class type, Type genericType, Annotation[] annotations, MediaType mediaType,
+			MultivaluedMap httpHeaders, InputStream entityStream) throws IOException, WebApplicationException {
+		// TODO Auto-generated method stub
+		try {
+			return JSON.decode(entityStream,genericType);
+		} catch (JSONException e) {
+			// TODO Auto-generated catch block
+			return null;
+		} catch (IOException e) {
+			// TODO Auto-generated catch block
+			return null;
+		}
+	}
+	
+}
\ No newline at end of file
diff --git a/src/main/java/cactusServer/utils/JSONProvider.java b/src/main/java/cactusServer/utils/JSONProvider.java
new file mode 100644
index 0000000..09819fb
--- /dev/null
+++ b/src/main/java/cactusServer/utils/JSONProvider.java
@@ -0,0 +1,38 @@
+package cactusServer.utils;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Type;
+
+import javax.ws.rs.Produces;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.ext.MessageBodyWriter;
+import javax.ws.rs.ext.Provider;
+
+import net.arnx.jsonic.JSON;
+
+@Provider()
+@Produces(MediaType.APPLICATION_JSON)
+public class JSONProvider implements MessageBodyWriter {
+    @Override
+    public long getSize(Object arg0, Class arg1, Type arg2, Annotation[] arg3, MediaType arg4) {
+        try {
+            return JSON.encode(arg0).getBytes("UTF-8").length;
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    @Override
+    public boolean isWriteable(Class arg0, Type arg1, Annotation[] arg2, MediaType arg3) {
+        return true;
+    }
+
+    @Override
+    public void writeTo(Object arg0, Class arg1, Type arg2, Annotation[] arg3, MediaType arg4, MultivaluedMap arg5, OutputStream arg6) throws IOException, WebApplicationException {
+        JSON.encode(arg0, arg6);
+    }
+}
\ No newline at end of file