Added pagination support

components/device-mgt/org.wso2.carbon.device.mgt.common/src/main/java/org/wso2/carbon/device/mgt/common/Device.java

@@ -17,8 +17,6 @@
  */
 package org.wso2.carbon.device.mgt.common;
 
-import javax.xml.bind.annotation.XmlElement;
-import javax.xml.bind.annotation.XmlRootElement;
 import java.io.Serializable;
 import java.util.List;
 

components/device-mgt/org.wso2.carbon.device.mgt.common/src/main/java/org/wso2/carbon/device/mgt/common/DeviceManagementConstants.java

@@ -78,4 +78,16 @@ public final class DeviceManagementConstants {
         }
         public static final String NOTIFICATION_CONFIG_FILE = "notification-messages.xml";
     }
+
+    public static final class DataBaseTypes {
+        private DataBaseTypes() {
+            throw new AssertionError();
+        }
+        public static final String DB_TYPE_MYSQL = "MySQL";
+        public static final String DB_TYPE_ORACLE = "Oracle";
+        public static final String DB_TYPE_MSSQL = "MSSQL";
+        public static final String DB_TYPE_DB2 = "DB2";
+        public static final String DB_TYPE_H2 = "H2";
+        public static final String DB_TYPE_POSTGRESQL = "PostgreSQL";
+    }
 }

components/device-mgt/org.wso2.carbon.device.mgt.common/src/main/java/org/wso2/carbon/device/mgt/common/PaginationResult.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2015, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+ *
+ * WSO2 Inc. licenses this file to you under the Apache License,
+ * Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License.
+ * you may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.wso2.carbon.device.mgt.common;
+
+import java.io.Serializable;
+import java.util.List;
+
+/**
+ * This class holds necessary data to represent a paginated result.
+ */
+public class PaginationResult implements Serializable {
+
+    private static final long serialVersionUID = 1998101711L;
+    private int recordsTotal;
+    private int recordsFiltered;
+    private int draw;
+    private List<?> data;
+
+    public int getRecordsTotal() {
+        return recordsTotal;
+    }
+
+    public int getRecordsFiltered() {
+        return recordsFiltered;
+    }
+
+    public void setRecordsFiltered(int recordsFiltered) {
+        this.recordsFiltered = recordsFiltered;
+    }
+
+    public void setRecordsTotal(int recordsTotal) {
+        this.recordsTotal = recordsTotal;
+
+    }
+
+    public List<?> getData() {
+        return data;
+    }
+
+    public void setData(List<?> data) {
+        this.data = data;
+    }
+
+    public int getDraw() {
+        return draw;
+    }
+
+    public void setDraw(int draw) {
+        this.draw = draw;
+    }
+}

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/DeviceDAO.java

@@ -22,6 +22,7 @@ import org.wso2.carbon.device.mgt.common.Device;
 import org.wso2.carbon.device.mgt.common.DeviceIdentifier;
 import org.wso2.carbon.device.mgt.common.EnrolmentInfo;
 import org.wso2.carbon.device.mgt.common.EnrolmentInfo.Status;
+import org.wso2.carbon.device.mgt.common.PaginationResult;
 
 import java.util.HashMap;
 import java.util.List;
@@ -31,6 +32,16 @@ import java.util.List;
  */
 public interface DeviceDAO {
 
+    /**
+     * This method is used to add a device.
+     *
+     * @param type device type.
+     * @param tenantId tenant id.
+     * @return returns the device count of given type.
+     * @throws DeviceManagementDAOException
+     */
+    int getDeviceCount(String type, int tenantId) throws DeviceManagementDAOException;
+
     /**
      * This method is used to add a device.
      *
@@ -100,10 +111,33 @@ public interface DeviceDAO {
      */
     List<Device> getDevices(int tenantId) throws DeviceManagementDAOException;
 
+    /**
+     * This method is used to retrieve the devices of a given tenant as a paginated result.
+     *
+     * @param index start index of result set.
+     * @param limit number of records to be returned.
+     * @param tenantId tenant id.
+     * @return returns a PaginationResult including the requested data.
+     * @throws DeviceManagementDAOException
+     */
+    PaginationResult getDevices(int index, int limit, int tenantId) throws DeviceManagementDAOException;
+
+    /**
+     * This method is used to retrieve the devices of a given tenant and type as a paginated result.
+     *
+     * @param type device type.
+     * @param index start index of result set.
+     * @param limit number of records to be returned.
+     * @param tenantId tenant id.
+     * @return returns a PaginationResult including the requested data.
+     * @throws DeviceManagementDAOException
+     */
+    PaginationResult getDevices(String type, int index, int limit, int tenantId) throws DeviceManagementDAOException;
+
     /**
      * This method is used to retrieve all the devices of a given tenant and device type.
      *
-     * @param type     device type.
+     * @param type device type.
      * @param tenantId tenant id.
      * @return returns list of devices.
      * @throws DeviceManagementDAOException

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/DeviceManagementDAOFactory.java

@@ -20,6 +20,7 @@ package org.wso2.carbon.device.mgt.core.dao;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.wso2.carbon.device.mgt.common.DeviceManagementConstants;
 import org.wso2.carbon.device.mgt.common.IllegalTransactionStateException;
 import org.wso2.carbon.device.mgt.common.TransactionManagementException;
 import org.wso2.carbon.device.mgt.core.config.datasource.DataSourceConfig;
@@ -82,11 +83,27 @@ import java.util.List;
 public class DeviceManagementDAOFactory {
 
     private static DataSource dataSource;
+    private static String databaseEngine;
     private static final Log log = LogFactory.getLog(DeviceManagementDAOFactory.class);
     private static ThreadLocal<Connection> currentConnection = new ThreadLocal<Connection>();
 
+
     public static DeviceDAO getDeviceDAO() {
-        return new DeviceDAOImpl();
+        if(databaseEngine != null) {
+            switch (databaseEngine) {
+                case DeviceManagementConstants.DataBaseTypes.DB_TYPE_ORACLE:
+                    return new OracleDeviceDAOImpl();
+                case DeviceManagementConstants.DataBaseTypes.DB_TYPE_MSSQL:
+                    return new SQLServerDeviceDAOImpl();
+                case DeviceManagementConstants.DataBaseTypes.DB_TYPE_POSTGRESQL:
+                case DeviceManagementConstants.DataBaseTypes.DB_TYPE_H2:
+                case DeviceManagementConstants.DataBaseTypes.DB_TYPE_MYSQL:
+                default:
+                    return new GenericDeviceDAOImpl();
+            }
+        } else {
+            return new GenericDeviceDAOImpl();
+        }
     }
 
     public static DeviceTypeDAO getDeviceTypeDAO() {
@@ -107,10 +124,20 @@ public class DeviceManagementDAOFactory {
 
     public static void init(DataSourceConfig config) {
         dataSource = resolveDataSource(config);
+        try {
+            databaseEngine = dataSource.getConnection().getMetaData().getDatabaseProductName();
+        } catch (SQLException e) {
+            log.error("Error occurred while retrieving config.datasource connection", e);
+        }
     }
 
     public static void init(DataSource dtSource) {
         dataSource = dtSource;
+        try {
+            databaseEngine = dataSource.getConnection().getMetaData().getDatabaseProductName();
+        } catch (SQLException e) {
+            log.error("Error occurred while retrieving config.datasource connection", e);
+        }
     }
 
     public static void beginTransaction() throws TransactionManagementException {

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/impl/AbstractDeviceDAOImpl.java

@@ -34,7 +34,7 @@ import java.util.Iterator;
 import java.util.HashMap;
 import java.util.List;
 
-public class DeviceDAOImpl implements DeviceDAO {
+public abstract class AbstractDeviceDAOImpl implements DeviceDAO {
 
     @Override
     public int addDevice(int typeId, Device device, int tenantId) throws DeviceManagementDAOException {
@@ -122,7 +122,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             stmt.setInt(4, tenantId);
             rs = stmt.executeQuery();
             if (rs.next()) {
-                device = this.loadDevice(rs);
+                device = DeviceManagementDAOUtil.loadDevice(rs);
             }
         } catch (SQLException e) {
             throw new DeviceManagementDAOException("Error occurred while listing devices for type " +
@@ -152,7 +152,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             stmt.setString(2, deviceIdentifier.getId());
             rs = stmt.executeQuery();
             if (rs.next()) {
-                device = this.loadDevice(rs);
+                device = DeviceManagementDAOUtil.loadDevice(rs);
                 deviceHashMap.put(rs.getInt("TENANT_ID"), device);
             }
         } catch (SQLException e) {
@@ -184,7 +184,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             stmt.setInt(3, tenantId);
             rs = stmt.executeQuery();
             if (rs.next()) {
-                device = this.loadDevice(rs);
+                device = DeviceManagementDAOUtil.loadDevice(rs);
             }
         } catch (SQLException e) {
             throw new DeviceManagementDAOException("Error occurred while retrieving device for id " +
@@ -215,7 +215,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             rs = stmt.executeQuery();
             devices = new ArrayList<>();
             while (rs.next()) {
-                Device device = this.loadDevice(rs);
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
                 devices.add(device);
             }
         } catch (SQLException e) {
@@ -248,7 +248,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             rs = stmt.executeQuery();
             devices = new ArrayList<>();
             while (rs.next()) {
-                Device device = this.loadDevice(rs);
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
                 devices.add(device);
             }
         } catch (SQLException e) {
@@ -279,7 +279,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             ResultSet rs = stmt.executeQuery();
 
             while (rs.next()) {
-                Device device = this.loadDevice(rs);
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
                 devices.add(device);
             }
         } catch (SQLException e) {
@@ -324,6 +324,31 @@ public class DeviceDAOImpl implements DeviceDAO {
         return deviceCount;
     }
 
+    @Override
+    public int getDeviceCount(String type, int tenantId) throws DeviceManagementDAOException {
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        int deviceCount = 0;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT COUNT(d.ID) AS DEVICE_COUNT FROM DM_DEVICE d, (SELECT t.ID AS TYPE_ID FROM DM_DEVICE_TYPE t " +
+                         "WHERE t.NAME = ?) d1 WHERE TYPE_ID = d.DEVICE_TYPE_ID AND d.TENANT_ID = ?";
+            stmt = conn.prepareStatement(sql);
+            stmt.setString(1, type);
+            stmt.setInt(2, tenantId);
+            rs = stmt.executeQuery();
+            if (rs.next()) {
+                deviceCount = rs.getInt("DEVICE_COUNT");
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while getting the device count", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        return deviceCount;
+    }
+
     /**
      * Get the list of devices that matches with the given device name.
      *
@@ -352,7 +377,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             ResultSet rs = stmt.executeQuery();
 
             while (rs.next()) {
-                Device device = this.loadDevice(rs);
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
                 devices.add(device);
             }
         } catch (SQLException e) {
@@ -475,7 +500,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             stmt.setInt(5, tenantId);
             rs = stmt.executeQuery();
             if (rs.next()) {
-                enrolmentInfo = this.loadEnrolment(rs);
+                enrolmentInfo = DeviceManagementDAOUtil.loadEnrolment(rs);
             }
             return enrolmentInfo;
         } catch (SQLException e) {
@@ -551,7 +576,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             stmt.setInt(index, tenantId);
             rs = stmt.executeQuery();
             if (rs.next()) {
-                enrolments.add(this.loadEnrolment(rs));
+                enrolments.add(DeviceManagementDAOUtil.loadEnrolment(rs));
             }
             return enrolments;
         } catch (SQLException e) {
@@ -562,28 +587,6 @@ public class DeviceDAOImpl implements DeviceDAO {
         }
     }
 
-    private Device loadDevice(ResultSet rs) throws SQLException {
-        Device device = new Device();
-        device.setId(rs.getInt("DEVICE_ID"));
-        device.setName(rs.getString("DEVICE_NAME"));
-        device.setDescription(rs.getString("DESCRIPTION"));
-        device.setType(rs.getString("DEVICE_TYPE"));
-        device.setDeviceIdentifier(rs.getString("DEVICE_IDENTIFICATION"));
-        device.setEnrolmentInfo(this.loadEnrolment(rs));
-        return device;
-    }
-
-    private EnrolmentInfo loadEnrolment(ResultSet rs) throws SQLException {
-        EnrolmentInfo enrolmentInfo = new EnrolmentInfo();
-        enrolmentInfo.setId(rs.getInt("ENROLMENT_ID"));
-        enrolmentInfo.setOwner(rs.getString("OWNER"));
-        enrolmentInfo.setOwnership(EnrolmentInfo.OwnerShip.valueOf(rs.getString("OWNERSHIP")));
-        enrolmentInfo.setDateOfEnrolment(rs.getTimestamp("DATE_OF_ENROLMENT").getTime());
-        enrolmentInfo.setDateOfLastUpdate(rs.getTimestamp("DATE_OF_LAST_UPDATE").getTime());
-        enrolmentInfo.setStatus(EnrolmentInfo.Status.valueOf(rs.getString("STATUS")));
-        return enrolmentInfo;
-    }
-
     public List<Device> getDevicesByStatus(EnrolmentInfo.Status status, int tenantId)
             throws DeviceManagementDAOException {
         Connection conn;
@@ -604,7 +607,7 @@ public class DeviceDAOImpl implements DeviceDAO {
             ResultSet rs = stmt.executeQuery();
 
             while (rs.next()) {
-                Device device = this.loadDevice(rs);
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
                 devices.add(device);
             }
         } catch (SQLException e) {

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/impl/GenericDeviceDAOImpl.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2015, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+ *
+ * WSO2 Inc. licenses this file to you under the Apache License,
+ * Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License.
+ * you may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.wso2.carbon.device.mgt.core.dao.impl;
+
+import org.wso2.carbon.device.mgt.common.Device;
+import org.wso2.carbon.device.mgt.common.EnrolmentInfo;
+import org.wso2.carbon.device.mgt.common.PaginationResult;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOException;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOFactory;
+import org.wso2.carbon.device.mgt.core.dao.util.DeviceManagementDAOUtil;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This class holds the generic implementation of DeviceDAO which can be used to support ANSI db syntax.
+ */
+public class GenericDeviceDAOImpl extends AbstractDeviceDAOImpl {
+
+    @Override
+    public PaginationResult getDevices(int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID AS DEVICE_ID, " +
+                         "d.DESCRIPTION, d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE d.DEVICE_TYPE_ID = t.ID AND d.TENANT_ID = ?) d1 " +
+                         "WHERE d1.DEVICE_ID = e.DEVICE_ID AND TENANT_ID = ? LIMIT ?,?";
+           // String sql = "SELECT * FROM DM_DEVICE WHERE TENANT_ID = ? LIMIT ?,?";
+            stmt = conn.prepareStatement(sql);
+            stmt.setInt(1, tenantId);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, index);
+            stmt.setInt(4, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while retrieving information of all " +
+                                                   "registered devices", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    @Override
+    public PaginationResult getDevices(String type, int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.ID AS DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID, d.DESCRIPTION, " +
+                         "d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE DEVICE_TYPE_ID = t.ID AND t.NAME = ? " +
+                         "AND d.TENANT_ID = ?) d1 WHERE d1.ID = e.DEVICE_ID AND TENANT_ID = ? LIMIT ?,?";
+            //String sql = "SELECT * FROM DM_DEVICE d, (SELECT t.ID AS TYPE_ID FROM DM_DEVICE_TYPE t WHERE t.NAME = ?)" +
+            //             " d1 WHERE TYPE_ID = d.DEVICE_TYPE_ID AND d.TENANT_ID = ? LIMIT ?,?";
+            stmt = conn.prepareStatement(sql);
+            stmt.setString(1, type);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, tenantId);
+            stmt.setInt(4, index);
+            stmt.setInt(5, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while listing devices for type '" + type + "'", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(type, tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    private Connection getConnection() throws SQLException {
+        return DeviceManagementDAOFactory.getConnection();
+    }
+}

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/impl/OracleDeviceDAOImpl.java

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2015, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+ *
+ * WSO2 Inc. licenses this file to you under the Apache License,
+ * Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License.
+ * you may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.wso2.carbon.device.mgt.core.dao.impl;
+
+import org.wso2.carbon.device.mgt.common.Device;
+import org.wso2.carbon.device.mgt.common.PaginationResult;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOException;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOFactory;
+import org.wso2.carbon.device.mgt.core.dao.util.DeviceManagementDAOUtil;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This class holds the generic implementation of DeviceDAO which can be used to support ANSI db syntax.
+ */
+public class OracleDeviceDAOImpl extends AbstractDeviceDAOImpl {
+
+    @Override
+    public PaginationResult getDevices(int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID AS DEVICE_ID, " +
+                         "d.DESCRIPTION, d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE d.DEVICE_TYPE_ID = t.ID AND d.TENANT_ID = ?) d1 " +
+                         "WHERE d1.DEVICE_ID = e.DEVICE_ID AND TENANT_ID = ? LIMIT ?,? ROW_NUMBER <= ?";
+            stmt = conn.prepareStatement(sql);
+            stmt.setInt(1, tenantId);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, index);
+            stmt.setInt(4, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while retrieving information of all " +
+                                                   "registered devices", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    @Override
+    public PaginationResult getDevices(String type, int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.ID AS DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID, d.DESCRIPTION, " +
+                         "d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE DEVICE_TYPE_ID = t.ID AND t.NAME = ? " +
+                         "AND d.TENANT_ID = ?) d1 WHERE d1.ID = e.DEVICE_ID AND TENANT_ID = ? LIMIT ?,?";
+            stmt = conn.prepareStatement(sql);
+            stmt.setString(1, type);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, tenantId);
+            stmt.setInt(4, index);
+            stmt.setInt(5, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while listing devices for type '" + type + "'", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(type, tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    private Connection getConnection() throws SQLException {
+        return DeviceManagementDAOFactory.getConnection();
+    }
+}

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/impl/PostgreSQLDeviceDAOImpl.java

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2015, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+ *
+ * WSO2 Inc. licenses this file to you under the Apache License,
+ * Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License.
+ * you may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.wso2.carbon.device.mgt.core.dao.impl;
+
+import org.wso2.carbon.device.mgt.common.Device;
+import org.wso2.carbon.device.mgt.common.PaginationResult;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOException;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOFactory;
+import org.wso2.carbon.device.mgt.core.dao.util.DeviceManagementDAOUtil;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This class holds the generic implementation of DeviceDAO which can be used to support ANSI db syntax.
+ */
+public class PostgreSQLDeviceDAOImpl extends AbstractDeviceDAOImpl {
+
+    @Override
+    public PaginationResult getDevices(int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID AS DEVICE_ID, " +
+                         "d.DESCRIPTION, d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE d.DEVICE_TYPE_ID = t.ID AND d.TENANT_ID = ?) d1 " +
+                         "WHERE d1.DEVICE_ID = e.DEVICE_ID AND TENANT_ID = ? OFFSET ? LIMIT ?";
+            stmt = conn.prepareStatement(sql);
+            stmt.setInt(1, tenantId);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, index);
+            stmt.setInt(4, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while retrieving information of all " +
+                                                   "registered devices", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    @Override
+    public PaginationResult getDevices(String type, int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.ID AS DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID, d.DESCRIPTION, " +
+                         "d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE DEVICE_TYPE_ID = t.ID AND t.NAME = ? " +
+                         "AND d.TENANT_ID = ?) d1 WHERE d1.ID = e.DEVICE_ID AND TENANT_ID = ? OFFSET ? LIMIT ?";
+            stmt = conn.prepareStatement(sql);
+            stmt.setString(1, type);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, tenantId);
+            stmt.setInt(4, index);
+            stmt.setInt(5, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while listing devices for type '" + type + "'", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(type, tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    private Connection getConnection() throws SQLException {
+        return DeviceManagementDAOFactory.getConnection();
+    }
+}

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/impl/SQLServerDeviceDAOImpl.java

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2015, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+ *
+ * WSO2 Inc. licenses this file to you under the Apache License,
+ * Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License.
+ * you may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.wso2.carbon.device.mgt.core.dao.impl;
+
+import org.wso2.carbon.device.mgt.common.Device;
+import org.wso2.carbon.device.mgt.common.PaginationResult;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOException;
+import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOFactory;
+import org.wso2.carbon.device.mgt.core.dao.util.DeviceManagementDAOUtil;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This class holds the generic implementation of DeviceDAO which can be used to support ANSI db syntax.
+ */
+public class SQLServerDeviceDAOImpl extends AbstractDeviceDAOImpl {
+
+    @Override
+    public PaginationResult getDevices(int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID AS DEVICE_ID, " +
+                         "d.DESCRIPTION, d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE d.DEVICE_TYPE_ID = t.ID AND d.TENANT_ID = ?) d1 " +
+                         "WHERE d1.DEVICE_ID = e.DEVICE_ID AND TENANT_ID = ? OFFSET ? ROWS FETCH NEXT ? ROWS ONLY";
+            stmt = conn.prepareStatement(sql);
+            stmt.setInt(1, tenantId);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, index);
+            stmt.setInt(4, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while retrieving information of all " +
+                                                   "registered devices", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    @Override
+    public PaginationResult getDevices(String type, int index, int limit, int tenantId)
+            throws DeviceManagementDAOException {
+        PaginationResult result = new PaginationResult();
+        Connection conn;
+        PreparedStatement stmt = null;
+        ResultSet rs = null;
+        List<Device> devices = null;
+        try {
+            conn = this.getConnection();
+            String sql = "SELECT d1.ID AS DEVICE_ID, d1.DESCRIPTION, d1.NAME AS DEVICE_NAME, d1.DEVICE_TYPE, " +
+                         "d1.DEVICE_IDENTIFICATION, e.OWNER, e.OWNERSHIP, e.STATUS, e.DATE_OF_LAST_UPDATE, " +
+                         "e.DATE_OF_ENROLMENT, e.ID AS ENROLMENT_ID FROM DM_ENROLMENT e, (SELECT d.ID, d.DESCRIPTION, " +
+                         "d.NAME, d.DEVICE_IDENTIFICATION, t.NAME AS DEVICE_TYPE FROM DM_DEVICE d, " +
+                         "DM_DEVICE_TYPE t WHERE DEVICE_TYPE_ID = t.ID AND t.NAME = ? " +
+                         "AND d.TENANT_ID = ?) d1 WHERE d1.ID = e.DEVICE_ID AND TENANT_ID = ? OFFSET ? ROWS FETCH NEXT ? ROWS ONLY";
+            stmt = conn.prepareStatement(sql);
+            stmt.setString(1, type);
+            stmt.setInt(2, tenantId);
+            stmt.setInt(3, tenantId);
+            stmt.setInt(4, index);
+            stmt.setInt(5, limit);
+            rs = stmt.executeQuery();
+            devices = new ArrayList<>();
+            while (rs.next()) {
+                Device device = DeviceManagementDAOUtil.loadDevice(rs);
+                devices.add(device);
+            }
+        } catch (SQLException e) {
+            throw new DeviceManagementDAOException("Error occurred while listing devices for type '" + type + "'", e);
+        } finally {
+            DeviceManagementDAOUtil.cleanupResources(stmt, rs);
+        }
+        int count = this.getDeviceCount(type, tenantId);
+        result.setData(devices);
+        result.setRecordsFiltered(count);
+        result.setRecordsTotal(count);
+        return result;
+    }
+
+    private Connection getConnection() throws SQLException {
+        return DeviceManagementDAOFactory.getConnection();
+    }
+}

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/dao/util/DeviceManagementDAOUtil.java

@@ -20,6 +20,8 @@ package org.wso2.carbon.device.mgt.core.dao.util;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.wso2.carbon.context.CarbonContext;
+import org.wso2.carbon.device.mgt.common.Device;
+import org.wso2.carbon.device.mgt.common.EnrolmentInfo;
 import org.wso2.carbon.device.mgt.core.dao.DeviceManagementDAOException;
 import org.wso2.carbon.device.mgt.core.internal.DeviceManagementDataHolder;
 import org.wso2.carbon.user.api.UserStoreException;
@@ -120,4 +122,26 @@ public final class DeviceManagementDAOUtil {
 		}
 	}
 
+    public static Device loadDevice(ResultSet rs) throws SQLException {
+        Device device = new Device();
+        device.setId(rs.getInt("DEVICE_ID"));
+        device.setName(rs.getString("DEVICE_NAME"));
+        device.setDescription(rs.getString("DESCRIPTION"));
+        device.setType(rs.getString("DEVICE_TYPE"));
+        device.setDeviceIdentifier(rs.getString("DEVICE_IDENTIFICATION"));
+        device.setEnrolmentInfo(loadEnrolment(rs));
+        return device;
+    }
+
+    public static EnrolmentInfo loadEnrolment(ResultSet rs) throws SQLException {
+        EnrolmentInfo enrolmentInfo = new EnrolmentInfo();
+        enrolmentInfo.setId(rs.getInt("ENROLMENT_ID"));
+        enrolmentInfo.setOwner(rs.getString("OWNER"));
+        enrolmentInfo.setOwnership(EnrolmentInfo.OwnerShip.valueOf(rs.getString("OWNERSHIP")));
+        enrolmentInfo.setDateOfEnrolment(rs.getTimestamp("DATE_OF_ENROLMENT").getTime());
+        enrolmentInfo.setDateOfLastUpdate(rs.getTimestamp("DATE_OF_LAST_UPDATE").getTime());
+        enrolmentInfo.setStatus(EnrolmentInfo.Status.valueOf(rs.getString("STATUS")));
+        return enrolmentInfo;
+    }
+
 }

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/internal/SCEPManagerServiceComponent.java

@@ -4,11 +4,18 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.osgi.framework.BundleContext;
 import org.osgi.service.component.ComponentContext;
+import org.wso2.carbon.device.mgt.core.app.mgt.ApplicationManagementProviderService;
 import org.wso2.carbon.device.mgt.core.scep.SCEPManager;
 import org.wso2.carbon.device.mgt.core.scep.SCEPManagerImpl;
 
 /**
  * @scr.component name="org.wso2.carbon.device.mgt.core.scep" immediate="true"
+ * @scr.reference name="app.mgt.service"
+ * interface="org.wso2.carbon.device.mgt.core.app.mgt.ApplicationManagementProviderService"
+ * cardinality="1..1"
+ * policy="dynamic"
+ * bind="setApplicationManagementProviderService"
+ * unbind="unsetApplicationManagementProviderService"
  */
 public class SCEPManagerServiceComponent {
 
@@ -40,4 +47,14 @@ public class SCEPManagerServiceComponent {
         }
     }
 
+    protected void unsetApplicationManagementProviderService(ApplicationManagementProviderService
+                                                                     applicationManagementProviderService) {
+        //do nothing
+    }
+
+    protected void setApplicationManagementProviderService(ApplicationManagementProviderService
+                                                                   applicationManagementProviderService) {
+        //do nothing
+    }
+
 }

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/service/DeviceManagementProviderService.java

@@ -36,6 +36,10 @@ public interface DeviceManagementProviderService extends OperationManager {
 
     List<Device> getAllDevices() throws DeviceManagementException;
 
+    PaginationResult getAllDevices(String deviceType, int index, int limit) throws DeviceManagementException;
+
+    PaginationResult getAllDevices(int index, int limit) throws DeviceManagementException;
+
     void sendEnrolmentInvitation(EmailMessageProperties config) throws DeviceManagementException;
 
     void sendRegistrationEmail(EmailMessageProperties config) throws DeviceManagementException;

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/service/DeviceManagementProviderServiceImpl.java

@@ -348,6 +348,84 @@ public class DeviceManagementProviderServiceImpl implements DeviceManagementProv
         return devices;
     }
 
+    @Override
+    public PaginationResult getAllDevices(String deviceType, int index, int limit) throws DeviceManagementException {
+        PaginationResult paginationResult;
+        List<Device> devices = new ArrayList<>();
+        List<Device> allDevices;
+        try {
+            DeviceManagementDAOFactory.openConnection();
+            paginationResult = deviceDAO.getDevices(deviceType, index, limit, this.getTenantId());
+        } catch (DeviceManagementDAOException e) {
+            throw new DeviceManagementException("Error occurred while retrieving device list pertaining to " +
+                                                "the current tenant", e);
+        } catch (SQLException e) {
+            throw new DeviceManagementException("Error occurred while opening a connection to the data source", e);
+        } finally {
+            DeviceManagementDAOFactory.closeConnection();
+        }
+        allDevices = (List<Device>) paginationResult.getData();
+        for (Device device : allDevices) {
+            DeviceManager deviceManager = this.getDeviceManager(device.getType());
+            if (deviceManager == null) {
+                if (log.isDebugEnabled()) {
+                    log.debug("Device Manager associated with the device type '" + device.getType() + "' is null. " +
+                              "Therefore, not attempting method 'isEnrolled'");
+                }
+                devices.add(device);
+                continue;
+            }
+            Device dmsDevice =
+                    deviceManager.getDevice(new DeviceIdentifier(device.getDeviceIdentifier(), device.getType()));
+            if (dmsDevice != null) {
+                device.setFeatures(dmsDevice.getFeatures());
+                device.setProperties(dmsDevice.getProperties());
+            }
+            devices.add(device);
+        }
+        paginationResult.setData(devices);
+        return paginationResult;
+    }
+
+    @Override
+    public PaginationResult getAllDevices(int index, int limit) throws DeviceManagementException {
+        PaginationResult paginationResult;
+        List<Device> devices = new ArrayList<>();
+        List<Device> allDevices;
+        try {
+            DeviceManagementDAOFactory.openConnection();
+            paginationResult = deviceDAO.getDevices(index, limit, this.getTenantId());
+        } catch (DeviceManagementDAOException e) {
+            throw new DeviceManagementException("Error occurred while retrieving device list pertaining to " +
+                                                "the current tenant", e);
+        } catch (SQLException e) {
+            throw new DeviceManagementException("Error occurred while opening a connection to the data source", e);
+        } finally {
+            DeviceManagementDAOFactory.closeConnection();
+        }
+        allDevices = (List<Device>) paginationResult.getData();
+        for (Device device : allDevices) {
+            DeviceManager deviceManager = this.getDeviceManager(device.getType());
+            if (deviceManager == null) {
+                if (log.isDebugEnabled()) {
+                    log.debug("Device Manager associated with the device type '" + device.getType() + "' is null. " +
+                              "Therefore, not attempting method 'isEnrolled'");
+                }
+                devices.add(device);
+                continue;
+            }
+            Device dmsDevice =
+                    deviceManager.getDevice(new DeviceIdentifier(device.getDeviceIdentifier(), device.getType()));
+            if (dmsDevice != null) {
+                device.setFeatures(dmsDevice.getFeatures());
+                device.setProperties(dmsDevice.getProperties());
+            }
+            devices.add(device);
+        }
+        paginationResult.setData(devices);
+        return paginationResult;
+    }
+
     @Override
     public List<Device> getAllDevices(String deviceType) throws DeviceManagementException {
         List<Device> devices = new ArrayList<>();