Adding the DAO layer for vpp user management

fixes https://roadmap.entgra.net/issues/10169

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/dao/VppApplicationDAO.java

@@ -0,0 +1,14 @@
+package io.entgra.device.mgt.core.application.mgt.core.dao;
+
+import io.entgra.device.mgt.core.application.mgt.common.dto.VppUserDTO;
+import io.entgra.device.mgt.core.application.mgt.core.exception.ApplicationManagementDAOException;
+
+
+public interface VppApplicationDAO {
+
+    int addVppUser(VppUserDTO userDTO) throws ApplicationManagementDAOException;
+
+    VppUserDTO updateVppUser(VppUserDTO userDTO) throws ApplicationManagementDAOException;
+
+    VppUserDTO getUserByDMUsername(String emmUsername) throws ApplicationManagementDAOException;
+}

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/dao/common/ApplicationManagementDAOFactory.java

@@ -17,7 +17,7 @@
  */
 package io.entgra.device.mgt.core.application.mgt.core.dao.common;
 
-import io.entgra.device.mgt.core.application.mgt.core.dao.SPApplicationDAO;
+import io.entgra.device.mgt.core.application.mgt.core.dao.*;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.application.spapplication.GenericSPApplicationDAOImpl;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.application.spapplication.OracleSPApplicationDAOImpl;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.application.spapplication.PostgreSQLSPApplicationDAOImpl;
@@ -26,16 +26,14 @@ import io.entgra.device.mgt.core.application.mgt.core.dao.impl.visibility.Generi
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.visibility.OracleVisibilityDAOImpl;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.visibility.PostgreSQLVisibilityDAOImpl;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.visibility.SQLServerVisibilityDAOImpl;
+import io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp.GenericVppApplicationDAOImpl;
+import io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp.OracleVppApplicationDAOImpl;
+import io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp.PostgreSQLVppApplicationDAO;
+import io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp.SQLServerVppApplicationDAOImpl;
 import io.entgra.device.mgt.core.application.mgt.core.util.Constants;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import io.entgra.device.mgt.core.application.mgt.common.exception.UnsupportedDatabaseEngineException;
-import io.entgra.device.mgt.core.application.mgt.core.dao.ApplicationDAO;
-import io.entgra.device.mgt.core.application.mgt.core.dao.ApplicationReleaseDAO;
-import io.entgra.device.mgt.core.application.mgt.core.dao.LifecycleStateDAO;
-import io.entgra.device.mgt.core.application.mgt.core.dao.ReviewDAO;
-import io.entgra.device.mgt.core.application.mgt.core.dao.SubscriptionDAO;
-import io.entgra.device.mgt.core.application.mgt.core.dao.VisibilityDAO;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.application.PostgreSQLApplicationDAOImpl;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.application.SQLServerApplicationDAOImpl;
 import io.entgra.device.mgt.core.application.mgt.core.dao.impl.application.release.OracleApplicationReleaseDAOImpl;
@@ -232,4 +230,28 @@ public class ApplicationManagementDAOFactory {
         }
         throw new IllegalStateException("Database engine has not initialized properly.");
     }
+
+
+    /**
+     * To get the instance of VppApplicationImplementation of the particular database engine.
+     * @return specific VppApplicationImplementation
+     */
+    public static VppApplicationDAO getVppApplicationDAO() {
+        if (databaseEngine != null) {
+            switch (databaseEngine) {
+                case Constants.DataBaseTypes.DB_TYPE_H2:
+                case Constants.DataBaseTypes.DB_TYPE_MYSQL:
+                    return new GenericVppApplicationDAOImpl();
+                case Constants.DataBaseTypes.DB_TYPE_POSTGRESQL:
+                    return new PostgreSQLVppApplicationDAO();
+                case Constants.DataBaseTypes.DB_TYPE_ORACLE:
+                    return new OracleVppApplicationDAOImpl();
+                case Constants.DataBaseTypes.DB_TYPE_MSSQL:
+                    return new SQLServerVppApplicationDAOImpl();
+                default:
+                    throw new UnsupportedDatabaseEngineException("Unsupported database engine : " + databaseEngine);
+            }
+        }
+        throw new IllegalStateException("Database engine has not initialized properly.");
+    }
 }

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/dao/impl/vpp/GenericVppApplicationDAOImpl.java

@@ -0,0 +1,152 @@
+package io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp;
+
+import io.entgra.device.mgt.core.application.mgt.common.dto.VppUserDTO;
+import io.entgra.device.mgt.core.application.mgt.common.exception.DBConnectionException;
+import io.entgra.device.mgt.core.application.mgt.core.dao.VppApplicationDAO;
+import io.entgra.device.mgt.core.application.mgt.core.dao.impl.AbstractDAOImpl;
+import io.entgra.device.mgt.core.application.mgt.core.exception.ApplicationManagementDAOException;
+import io.entgra.device.mgt.core.application.mgt.core.exception.UnexpectedServerErrorException;
+import io.entgra.device.mgt.core.application.mgt.core.util.DAOUtil;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import java.sql.*;
+
+public class GenericVppApplicationDAOImpl  extends AbstractDAOImpl implements VppApplicationDAO {
+    private static final Log log = LogFactory.getLog(GenericVppApplicationDAOImpl.class);
+
+    @Override
+    public int addVppUser(VppUserDTO userDTO)
+            throws ApplicationManagementDAOException {
+        int vppUserId = -1;
+        String sql = "INSERT INTO "
+                + "AP_VPP_USER("
+                + "CLIENT_USER_ID, "
+                + "DM_USERNAME, "
+                + "TENANT_ID, "
+                + "EMAIL, "
+                + "INVITE_CODE, "
+                + "STATUS,"
+                + "CREATED_TIME,"
+                + "LAST_UPDATED_TIME,"
+                + "MANAGED_ID,"
+                + "TEMP_PASSWORD) "
+                + "VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
+        try {
+            Connection conn = this.getDBConnection();
+            try (PreparedStatement stmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS)) {
+                long currentTime = System.currentTimeMillis();
+                stmt.setString(1, userDTO.getClientUserId());
+                stmt.setString(2, userDTO.getDmUsername());
+                stmt.setInt(3, userDTO.getTenantId());
+                stmt.setString(4, userDTO.getEmail());
+                stmt.setString(5, userDTO.getInviteCode());
+                stmt.setString(6, userDTO.getStatus());
+                stmt.setLong(7, currentTime);
+                stmt.setLong(8, currentTime);
+                stmt.setString(9, userDTO.getManagedId());
+                stmt.setString(10, userDTO.getTmpPassword());
+                stmt.executeUpdate();
+                try (ResultSet rs = stmt.getGeneratedKeys()) {
+                    if (rs.next()) {
+                        vppUserId = rs.getInt(1);
+                    }
+                }
+                return vppUserId;
+            }
+        } catch (DBConnectionException e) {
+            String msg = "Error occurred while obtaining database connection when adding the vpp user";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        } catch (SQLException e) {
+            String msg = "Error occurred when processing SQL to add  the vpp user.";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        }
+    }
+
+    public VppUserDTO updateVppUser(VppUserDTO userDTO)
+            throws ApplicationManagementDAOException {
+
+        String sql = "UPDATE "
+                + "AP_VPP_USER "
+                + "SET "
+                + "CLIENT_USER_ID = ?,"
+                + "DM_USERNAME = ?, "
+                + "TENANT_ID = ?, "
+                + "EMAIL = ?, "
+                + "INVITE_CODE = ?, "
+                + "STATUS = ?, "
+                + "LAST_UPDATED_TIME = ?, "
+                + "MANAGED_ID = ?, "
+                + "TEMP_PASSWORD = ? "
+                + "WHERE ID = ?";
+        try {
+            Connection conn = this.getDBConnection();
+            long updatedTime = System.currentTimeMillis();
+            try (PreparedStatement stmt = conn.prepareStatement(sql)) {
+                stmt.setString(1, userDTO.getClientUserId());
+                stmt.setString(2, userDTO.getDmUsername());
+                stmt.setInt(3, userDTO.getTenantId());
+                stmt.setString(4, userDTO.getEmail());
+                stmt.setString(5, userDTO.getInviteCode());
+                stmt.setString(6, userDTO.getStatus());
+                stmt.setLong(7, updatedTime);
+                stmt.setString(8, userDTO.getManagedId());
+                stmt.setString(9, userDTO.getTmpPassword());
+                stmt.setInt(10, userDTO.getId());
+                stmt.executeUpdate();
+                if (stmt.executeUpdate() == 1) {
+                    return userDTO;
+                }
+                return null;
+            }
+        } catch (DBConnectionException e) {
+            String msg = "Error occurred while obtaining database connection when updating the vpp user";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        } catch (SQLException e) {
+            String msg = "Error occurred when processing SQL to updating the vpp user.";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        }
+    }
+
+    public VppUserDTO getUserByDMUsername(String emmUsername)
+            throws ApplicationManagementDAOException {
+        String sql = "SELECT "
+                + "ID, "
+                + "CLIENT_USER_ID, "
+                + "TENANT_ID, "
+                + "EMAIL, "
+                + "INVITE_CODE, "
+                + "STATUS, "
+                + "CREATED_TIME, "
+                + "LAST_UPDATED_TIME, "
+                + "MANAGED_ID, "
+                + "TEMP_PASSWORD "
+                + "FROM AP_VPP_USER "
+                + "WHERE DM_USERNAME = ?";
+        try {
+            Connection conn = this.getDBConnection();
+            try (PreparedStatement stmt = conn.prepareStatement(sql)) {
+                stmt.setString(1, emmUsername);
+                try (ResultSet rs = stmt.executeQuery()) {
+                    return DAOUtil.loadVppUser(rs);
+                }
+            }
+        } catch (DBConnectionException e) {
+            String msg = "Error occurred while obtaining database connection when retrieving vpp user by EMM Username.";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        } catch (SQLException e) {
+            String msg = "Error occurred when processing SQL to retrieve vpp user by EMM Username.";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        } catch (UnexpectedServerErrorException e) {
+            String msg = "Found more than one user for: " + emmUsername;
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        }
+    }
+}

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/dao/impl/vpp/OracleVppApplicationDAOImpl.java

@@ -0,0 +1,64 @@
+package io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp;
+
+import io.entgra.device.mgt.core.application.mgt.common.dto.VppUserDTO;
+import io.entgra.device.mgt.core.application.mgt.common.exception.DBConnectionException;
+import io.entgra.device.mgt.core.application.mgt.core.exception.ApplicationManagementDAOException;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import java.sql.*;
+
+public class OracleVppApplicationDAOImpl extends GenericVppApplicationDAOImpl  {
+
+    private static final Log log = LogFactory.getLog(GenericVppApplicationDAOImpl.class);
+
+    @Override
+    public int addVppUser(VppUserDTO userDTO)
+            throws ApplicationManagementDAOException {
+        int vppUserId = -1;
+        String sql = "INSERT INTO "
+                + "AP_VPP_USER("
+                + "CLIENT_USER_ID, "
+                + "DM_USERNAME, "
+                + "TENANT_ID, "
+                + "EMAIL, "
+                + "INVITE_CODE, "
+                + "STATUS,"
+                + "CREATED_TIME,"
+                + "LAST_UPDATED_TIME,"
+                + "MANAGED_ID,"
+                + "TEMP_PASSWORD) "
+                + "VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
+        try {
+            Connection conn = this.getDBConnection();
+            try (PreparedStatement stmt = conn.prepareStatement(sql, new String[] {"ID"})) {
+                long currentTime = System.currentTimeMillis();
+                stmt.setString(1, userDTO.getClientUserId());
+                stmt.setString(2, userDTO.getDmUsername());
+                stmt.setInt(3, userDTO.getTenantId());
+                stmt.setString(4, userDTO.getEmail());
+                stmt.setString(5, userDTO.getInviteCode());
+                stmt.setString(6, userDTO.getStatus());
+                stmt.setLong(7, currentTime);
+                stmt.setLong(8, currentTime);
+                stmt.setString(9, userDTO.getManagedId());
+                stmt.setString(10, userDTO.getTmpPassword());
+                stmt.executeUpdate();
+                try (ResultSet rs = stmt.getGeneratedKeys()) {
+                    if (rs.next()) {
+                        vppUserId = rs.getInt(1);
+                    }
+                }
+                return vppUserId;
+            }
+        } catch (DBConnectionException e) {
+            String msg = "Error occurred while obtaining database connection when adding the vpp user";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        } catch (SQLException e) {
+            String msg = "Error occurred when processing SQL to add  the vpp user.";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        }
+    }
+}

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/dao/impl/vpp/PostgreSQLVppApplicationDAO.java

@@ -0,0 +1,63 @@
+package io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp;
+
+import io.entgra.device.mgt.core.application.mgt.common.dto.VppUserDTO;
+import io.entgra.device.mgt.core.application.mgt.common.exception.DBConnectionException;
+import io.entgra.device.mgt.core.application.mgt.core.exception.ApplicationManagementDAOException;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import java.sql.*;
+
+public class PostgreSQLVppApplicationDAO extends GenericVppApplicationDAOImpl {
+
+    private static final Log log = LogFactory.getLog(GenericVppApplicationDAOImpl.class);
+
+    public int addVppUser(VppUserDTO userDTO)
+            throws ApplicationManagementDAOException {
+        int vppUserId = -1;
+        String sql = "INSERT INTO "
+                + "AP_VPP_USER("
+                + "CLIENT_USER_ID, "
+                + "DM_USERNAME, "
+                + "TENANT_ID, "
+                + "EMAIL, "
+                + "INVITE_CODE, "
+                + "STATUS,"
+                + "CREATED_TIME,"
+                + "LAST_UPDATED_TIME,"
+                + "MANAGED_ID,"
+                + "TEMP_PASSWORD) "
+                + "VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
+        try {
+            Connection conn = this.getDBConnection();
+            try (PreparedStatement stmt = conn.prepareStatement(sql, new String[]{"ID"})) {
+                long currentTime = System.currentTimeMillis();
+                stmt.setString(1, userDTO.getClientUserId());
+                stmt.setString(2, userDTO.getDmUsername());
+                stmt.setInt(3, userDTO.getTenantId());
+                stmt.setString(4, userDTO.getEmail());
+                stmt.setString(5, userDTO.getInviteCode());
+                stmt.setString(6, userDTO.getStatus());
+                stmt.setLong(7, currentTime);
+                stmt.setLong(8, currentTime);
+                stmt.setString(9, userDTO.getManagedId());
+                stmt.setString(10, userDTO.getTmpPassword());
+                stmt.executeUpdate();
+                try (ResultSet rs = stmt.getGeneratedKeys()) {
+                    if (rs.next()) {
+                        vppUserId = rs.getInt(1);
+                    }
+                }
+                return vppUserId;
+            }
+        } catch (DBConnectionException e) {
+            String msg = "Error occurred while obtaining database connection when adding the vpp user";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        } catch (SQLException e) {
+            String msg = "Error occurred when processing SQL to add  the vpp user.";
+            log.error(msg, e);
+            throw new ApplicationManagementDAOException(msg, e);
+        }
+    }
+}

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/dao/impl/vpp/SQLServerVppApplicationDAOImpl.java

@@ -0,0 +1,4 @@
+package io.entgra.device.mgt.core.application.mgt.core.dao.impl.vpp;
+
+public class SQLServerVppApplicationDAOImpl extends GenericVppApplicationDAOImpl {
+}

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/impl/VppApplicationManagerImpl.java

@@ -24,6 +24,8 @@ import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import io.entgra.device.mgt.core.application.mgt.common.dto.ProxyResponse;
 import io.entgra.device.mgt.core.application.mgt.common.dto.VppItuneUserDTO;
+import io.entgra.device.mgt.core.application.mgt.common.exception.DBConnectionException;
+import io.entgra.device.mgt.core.application.mgt.common.exception.TransactionManagementException;
 import io.entgra.device.mgt.core.application.mgt.common.wrapper.VppItuneUserRequestWrapper;
 import io.entgra.device.mgt.core.application.mgt.common.dto.VppUserDTO;
 import io.entgra.device.mgt.core.application.mgt.common.exception.ApplicationManagementException;
@@ -32,9 +34,12 @@ import io.entgra.device.mgt.core.application.mgt.common.wrapper.VppItuneUserResp
 import io.entgra.device.mgt.core.application.mgt.core.dao.ApplicationDAO;
 import io.entgra.device.mgt.core.application.mgt.core.dao.SPApplicationDAO;
 import io.entgra.device.mgt.core.application.mgt.core.dao.VisibilityDAO;
+import io.entgra.device.mgt.core.application.mgt.core.dao.VppApplicationDAO;
 import io.entgra.device.mgt.core.application.mgt.core.dao.common.ApplicationManagementDAOFactory;
+import io.entgra.device.mgt.core.application.mgt.core.exception.ApplicationManagementDAOException;
 import io.entgra.device.mgt.core.application.mgt.core.internal.DataHolder;
 import io.entgra.device.mgt.core.application.mgt.core.lifecycle.LifecycleStateManager;
+import io.entgra.device.mgt.core.application.mgt.core.util.ConnectionManagerUtil;
 import io.entgra.device.mgt.core.application.mgt.core.util.Constants;
 import io.entgra.device.mgt.core.application.mgt.core.util.VppHttpUtil;
 import org.apache.commons.logging.Log;
@@ -56,6 +61,7 @@ public class VppApplicationManagerImpl implements VPPApplicationManager {
     private SPApplicationDAO spApplicationDAO;
     private VisibilityDAO visibilityDAO;
     private final LifecycleStateManager lifecycleStateManager;
+    private VppApplicationDAO vppApplicationDAO;
 
     public VppApplicationManagerImpl() {
         initDataAccessObjects();
@@ -66,6 +72,7 @@ public class VppApplicationManagerImpl implements VPPApplicationManager {
         this.applicationDAO = ApplicationManagementDAOFactory.getApplicationDAO();
         this.visibilityDAO = ApplicationManagementDAOFactory.getVisibilityDAO();
         this.spApplicationDAO = ApplicationManagementDAOFactory.getSPApplicationDAO();
+        this.vppApplicationDAO = ApplicationManagementDAOFactory.getVppApplicationDAO();
     }
 
     @Override
@@ -96,10 +103,30 @@ public class VppApplicationManagerImpl implements VPPApplicationManager {
                             .getInviteCode());
                     userDTO.setStatus(vppItuneUserResponseWrapper.getUser().get(0).getStatus());
                     log.error("userDTO " + userDTO.toString());
-                    // TODO: Save the userDTO in the DAO
+                    try {
-
+                        ConnectionManagerUtil.beginDBTransaction();
-
+                        if (vppApplicationDAO.addVppUser(userDTO) != -1) {
-                    return userDTO;
+                            ConnectionManagerUtil.commitDBTransaction();
+                            return userDTO;
+                        }
+                        ConnectionManagerUtil.rollbackDBTransaction();
+                        return null;
+                    } catch (ApplicationManagementDAOException e) {
+                        ConnectionManagerUtil.rollbackDBTransaction();
+                        String msg = "Error occurred while adding the Vpp User.";
+                        log.error(msg, e);
+                        throw new ApplicationManagementException(msg, e);
+                    } catch (TransactionManagementException e) {
+                        String msg = "Error occurred while executing database transaction for adding Vpp User.";
+                        log.error(msg, e);
+                        throw new ApplicationManagementException(msg, e);
+                    } catch (DBConnectionException e) {
+                        String msg = "Error occurred while retrieving the database connection for adding Vpp User.";
+                        log.error(msg, e);
+                        throw new ApplicationManagementException(msg, e);
+                    } finally {
+                        ConnectionManagerUtil.closeDBConnection();
+                    }
                 }
 
             }
@@ -113,8 +140,20 @@ public class VppApplicationManagerImpl implements VPPApplicationManager {
 
     @Override
     public VppUserDTO getUserByDMUsername(String emmUsername) throws ApplicationManagementException {
-        // TODO: Return from DAO in a tenanted manner
+        try {
-        return null;
+            ConnectionManagerUtil.openDBConnection();
+            return vppApplicationDAO.getUserByDMUsername(emmUsername);
+        } catch (DBConnectionException e) {
+            String msg = "DB Connection error occurs while getting vpp User data related to EMM user  " + emmUsername + ".";
+            log.error(msg, e);
+            throw new ApplicationManagementException(msg, e);
+        }  catch (ApplicationManagementDAOException e) {
+            String msg = "Error occurred while getting vpp User data related to EMM user  " + emmUsername + ".";
+            log.error(msg, e);
+            throw new ApplicationManagementException(msg, e);
+        } finally {
+            ConnectionManagerUtil.closeDBConnection();
+        }
     }
 
     @Override
@@ -131,12 +170,35 @@ public class VppApplicationManagerImpl implements VPPApplicationManager {
                     HttpStatus.SC_CREATED) && proxyResponse.getData().contains(Constants.VPP.EVENT_ID)) {
 
                 log.error("userDTO " + userDTO.toString());
-                // TODO: Save the userDTO in the DAO
-
 
+                try {
+                    ConnectionManagerUtil.beginDBTransaction();
+                    if (vppApplicationDAO.updateVppUser(userDTO) == null) {
+                        ConnectionManagerUtil.rollbackDBTransaction();
+                        String msg = "Unable to update the Vpp user " +userDTO.getId();
+                        log.error(msg);
+                        throw new ApplicationManagementException(msg);
+                    }
+                    ConnectionManagerUtil.commitDBTransaction();
+                } catch (ApplicationManagementDAOException e) {
+                    ConnectionManagerUtil.rollbackDBTransaction();
+                    String msg = "Error occurred while updating the Vpp User.";
+                    log.error(msg, e);
+                    throw new ApplicationManagementException(msg, e);
+                } catch (TransactionManagementException e) {
+                    String msg = "Error occurred while executing database transaction for Vpp User update.";
+                    log.error(msg, e);
+                    throw new ApplicationManagementException(msg, e);
+                } catch (DBConnectionException e) {
+                    String msg = "Error occurred while retrieving the database connection for Vpp User update.";
+                    log.error(msg, e);
+                    throw new ApplicationManagementException(msg, e);
+                } finally {
+                    ConnectionManagerUtil.closeDBConnection();
+                }
             }
         } catch (IOException e) {
-            String msg = "Error while callng VPP backend to update";
+            String msg = "Error while calling VPP backend to update";
             log.error(msg, e);
             throw new ApplicationManagementException(msg, e);
         }

components/application-mgt/io.entgra.device.mgt.core.application.mgt.core/src/main/java/io/entgra/device/mgt/core/application/mgt/core/util/DAOUtil.java

@@ -32,6 +32,7 @@ import io.entgra.device.mgt.core.application.mgt.common.dto.ApplicationReleaseDT
 import io.entgra.device.mgt.core.application.mgt.common.dto.DeviceSubscriptionDTO;
 import io.entgra.device.mgt.core.application.mgt.common.dto.ReviewDTO;
 import io.entgra.device.mgt.core.application.mgt.common.dto.ScheduledSubscriptionDTO;
+import io.entgra.device.mgt.core.application.mgt.common.dto.VppUserDTO;
 import io.entgra.device.mgt.core.device.mgt.common.DeviceIdentifier;
 
 import java.sql.PreparedStatement;
@@ -43,6 +44,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Date;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
@@ -344,6 +346,42 @@ public class DAOUtil {
         return subscriptionDTOS;
     }
 
+    public static VppUserDTO loadVppUser(ResultSet rs) throws SQLException, UnexpectedServerErrorException {
+        List<VppUserDTO> vppUserDTOS = loadVppUsers(rs);
+        if (vppUserDTOS.isEmpty()) {
+            return null;
+        }
+        if (vppUserDTOS.size() > 1) {
+            String msg = "Internal server error. Found more than one vpp user for requested emmUsername";
+            log.error(msg);
+            throw new UnexpectedServerErrorException(msg);
+        }
+        return vppUserDTOS.get(0);
+    }
+
+    public static List<VppUserDTO> loadVppUsers (ResultSet rs) throws SQLException {
+        List<VppUserDTO> vppUserDTOS = new ArrayList<>();
+        while (rs.next()) {
+            VppUserDTO vppUserDTO = new VppUserDTO();
+            vppUserDTO.setId(rs.getInt("ID"));
+            vppUserDTO.setClientUserId(rs.getString("CLIENT_USER_ID"));
+            vppUserDTO.setTenantId(rs.getInt("TENANT_ID"));
+            vppUserDTO.setEmail(rs.getString("EMAIL"));
+            vppUserDTO.setInviteCode(rs.getString("INVITE_CODE"));
+            vppUserDTO.setStatus(rs.getString("STATUS"));
+            vppUserDTO.setManagedId(rs.getString("MANAGED_ID"));
+            vppUserDTO.setTmpPassword(rs.getString("TEMP_PASSWORD"));
+            if (rs.getLong("CREATED_TIME") != 0) {
+                vppUserDTO.setCreatedTime(new Date(rs.getLong(("CREATED_TIME")) * 1000).toString());
+            }
+            if (rs.getLong("LAST_UPDATED_TIME") != 0) {
+                vppUserDTO.setLastUpdatedTime(new Date(rs.getLong(("LAST_UPDATED_TIME")) * 1000).toString());
+            }
+            vppUserDTOS.add(vppUserDTO);
+        }
+        return vppUserDTOS;
+    }
+
     /**
      * Cleans up the statement and resultset after executing the query
      *