9. GDA configuration

9.1. Spring configuration

9.1.1. The gda namespace Using the namespace in your XML files

To use elements from the gda namespace, you will need to declare the namespace by adding the following attribute to the <beans> element in your Spring configuration:


You will also need to add these entries to the xsi:schemaLocation attribute:

http://www.diamond.ac.uk/schema/gda/gda http://www.diamond.ac.uk/schema/gda/gda/gda-gda-1.0.xsd Adding the namespace to your XML Catalog in Eclipse

If you use elements from the gda namespace in your XML files, you should add the schema for the gda namespace to the Eclipse XML Catalog, so that Eclipse can validate XML files containing these custom elements. To do this:

  • Open the Eclipse preferences (Window → Preferences)
  • Go to XML → XML Catalog
  • Click “Add...”
  • Enter the following details:
    • Location: click “Workspace...” and select uk.ac.gda.core/src/gda/spring/namespaces/gda/gda-gda-1.0.xsd
    • Key Type: choose “Namespace Name”
    • Key: enter http://www.diamond.ac.uk/schema/gda/gda/gda-gda-1.0.xsd

9.1.2. FindableNameSetterPostProcessor

Putting this:

<bean class="gda.spring.FindableNameSetterPostProcessor" />

in your Spring XML file causes all Findable objects to have their name property set to be the same as the Spring id. Therefore you don’t (except in a couple of special cases) need:

<property name="name" value="..." />

9.1.3. Making properties from java.properties available

Use this:

<context:property-placeholder location="file:${gda.config}/properties/java.properties" />

It allows you to use properties in your Spring XML files. For example:

<property name="hostname" value="${gda.images.camerahost}" />

To make the tags in the context namespace are available to you, you will need to add the following attribute to the <beans> element in your Spring configuration:


You will also need to add these entries to the xsi:schemaLocation attribute:

http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd"

9.1.4. Instantiating EPICS devices directly

For example:

<bean id="S1_top_motor" class="gda.device.motor.EpicsMotor">
    <property name="pvName" value="BL04J-AL-SLITS-01:Y:PLUS" />

9.1.5. Instantiating using the EPICS interface “behind the scenes”

This is for those who don’t like having PVs in their XML files ;-)

To use Diamond’s GDA-EPICS interface file, generated during EPICS IOC build,

Put this somewhere in the Spring XML file (it doesn’t need an ID):

<bean class="gda.configuration.epics.EpicsConfiguration">
    <constructor-arg value="${gda.config}/xml/epics-interface.xml" />

Then do this:

<bean id="S1_top_motor" class="gda.spring.EpicsMotorFactoryBean">
    <property name="deviceName" value="S1.YP" />

EpicsMotorFactoryBean is a Spring factory bean - the S1_top_motor object will actually be an EpicsMotor.

In addition to EpicsMotorFactoryBean, there is also EpicsMonitorFactoryBean and EpicsPositionerFactoryBean (they all need a deviceName).

9.1.6. Importing one file into another

<import resource="S1.xml" />

Effectively, the <import> is replaced with the contents of the imported file. All the beans are in the same Spring context (i.e. no need to duplicate the PropertyPlaceholderConfigurer, the FindableNameSetterPostProcessor, etc.).

9.1.7. Please use the ref attribute!!!

Instead of this:

<bean id="s1_bottom" class="gda.device.scannable.ScannableMotor">
    <property name="motorName" value="S1_bottom_motor" />

you can do this:

<bean id="s1_bottom" class="gda.device.scannable.ScannableMotor">
    <property name="motor" ref="S1_bottom_motor" />

Note the property is motor, not motorName, and this uses the ref attribute - which plugs the S1_bottom_motor motor into the s1_bottom object (so the ScannableMotor doesn’t need to use the Finder to get the underlying motor - it’s already wired up using Spring).

Since Spring has this dependency injection capability, there’s no need to use the Finder in new classes - Spring can be used to do the wiring.

9.1.8. Making remote objects available through CORBA

You’ll need this in your server-side configuration:

<corba:export namespace="stnBase" />

You need to declare the corba namespace by putting this at the top of the XML file:


and adding these entries to the xsi:schemaLocation attribute:

http://www.diamond.ac.uk/schema/gda/corba http://www.diamond.ac.uk/schema/gda/corba/gda-corba-1.0.xsd

Due to a limitation of Spring, property placeholders cannot be used in the namespace attribute when using <corba:export />. So this, for example:

<corba:export namespace="${gda.beamline.name}" />

will not work. (Property placeholders are typically resolved by a PropertyPlaceholderConfigurer, which is a BeanFactoryPostProcessor that operates on bean definitions in an application context. The <corba:export /> element itself is not transformed into a bean definition: it uses the namespace value to add bean definitions for remote objects. It is not possible for the PropertyPlaceholderConfigurer to resolve placeholders used in the namespace attribute before that value is used to find remote objects.)

9.1.9. Importing remote objects from another object server

You’ll need this in your client-side configuration:

<corba:import namespace="stnBase" />

As with <corba:export />, to use the corba namespace you need to declare it at the top of the XML file.

The good thing about using corba:import is that ‘hidden’ beans are added to the Spring context for all of the remote objects, so you can use them in any ref="..." attributes elsewhere in the file.

9.1.10. Enabling role-based access control using <gda:rbac />

To enable role-based access control (RBAC), add the following element to your Spring configuration:

<gda:rbac />

You must also set the gda.accesscontrol.useAccessControl property to true.

9.1.11. The corba namespace

As with the gda namespace, if you use the <corba:export> or <corba:import> elements described above, you should add the schema for the corba namespace to the Eclipse XML Catalog. To do this, follow the instructions for the gda namespace above, but use the following values:

  • Location: uk.ac.gda.core/src/gda/spring/namespaces/corba/gda-corba-1.0.xsd
  • Key: http://www.diamond.ac.uk/schema/gda/corba/gda-corba-1.0.xsd

Due to an issue with SpringSource Tool Suite, you may still get the following warning, which can be ignored:

Unable to locate Spring NamespaceHandler for element ‘corba:export’ of schema namespace ‘http://www.diamond.ac.uk/schema/gda/corba’

9.1.12. SingletonRegistrationPostProcessor

<bean class="gda.spring.SingletonRegistrationPostProcessor" />

This registers certain objects you create in the Spring context as the application-wide singleton instances (e.g. the metadata).

(Objects in Spring XML files are, by default, singletons. In a perfect world, the metadata and other singletons could be injected into other objects, rather than the other objects calling Whatever.getInstance(). In practice it’s difficult to do this because (1) there are too many objects that need the singletons; and (2) not all of those objects will be defined in the Spring XML file. It’s good to define the objects in the Spring XML file, as this gives us complete control over their configuration, and means we can swap the real objects for mock objects. But this means we need to register those objects with some kind of registry.)

9.1.13. Property editors

PropertyEditor (Javadoc) is a standard Java interface concerned with converting text representations of property values into their ‘real’ types (among other things).

In Spring they are used to convert the text values used in Spring configuration files into the type required by the bean being instantiated. Spring has built-in support for many types already, but by putting this in your Spring configuration:

<import resource="classpath:gda/spring/propertyeditors/registration.xml" />

you will also be able to set properties of these types:

and any other types supported by the PropertyEditors listed in the GdaPropertyEditorRegistrar class.

9.1.14. Example Spring configuration

The Diamond I04.1 beamline uses Spring exclusively for its configuation. If you have access to the GDA Subversion repository, you can view the I04.1 configuration. The Spring contexts for the two object servers are split into multiple XML files, which are all in the servers/main/live directory.

9.2. Logging

Logging messages can be generated not only by GDA classes, but also by third-party libraries such as Apache Commons Configuration. GDA classes typically use the SLF4J API for logging. Log entries from code that uses Commons Logging or Log4j are redirected into SLF4J using two SLF4J bindings: Commons Logging over SLF4J and Log4j over SLF4J.

GDA uses Logback as the SLF4J implementation, so logging entries are passed from SLF4J to Logback.

The following diagram shows one of the logging configuration options - the centralised logging service - used on some of DLS beamlines


9.2.1. Log Server configuration

GDA provides an utility - gda.util.LogServer - for centrally logging messages from its objects running on both servers and clients as shown in the diagram above. You need to configure the log server using four properties:

Property Description
gda.logserver.port the port that the Log Server listening to
gda.logserver.xml the logging configuration file, for example, LogServer,xml, of the log Server
gda.logs.dir the directory in which GDA log file, for example gda.log, is to be stored
gda.logPanel.logging.port the port that the log viewer listening to, i.e. the port the Log Server forwarding message to

While the first two properties is required by the LogServer class and are essential, the last two are optional and only used in the LogServer.xml file to specify the log destinations.

LogServer.xml defines logging destinations (appenders), logger level filters, and file logging rules for the cental logging service at the Log Server.

9.2.2. GDA objects logging configuration

GDA objects are the sources of the logging messages in the system. Although it is possible to configure client objects logging differently from that of server objects, here we describe the situation that both client and server send their logging messages to the central Log Server as shown in the diagram above.

In this case, both clients and servers share the same logging configuration defined in, for example, LoggingConfiguration.xml or logBack.xml. Four properties (one is already defined above) need to be set:

Property Description
gda.logserver.port the remote port to which all messages are sent, i.e.the Log Server’s listening port
gda.logserver.host the remote host in which the Log Server is running.
gda.client.logging.xml the logging configuration file for GDA client objects
gda.server.logging.xml the logging configuration file for GDA server objects

LoggingConfiguration.xml defines the Log Server as log destination and sets the desired logger level filters for all/specific loggers used in GDA objects at the message sources.

The reason that there are two logging configuration file properties in the system is historical as we used to configure clients differently from servers. In the case we discussed here, the last two properties are pointed to the same LoggingConfiguration.xml file.

9.2.3. Log Viewer Configuration

GDA also provides a simple log viewer utility - gda.util.LogPanel for viewing the logging messages received from the central Log server. It connects to the Log server via a socket at port specified by property gda.logPanel.logging.port. This property are required to start the logPanel viewer.

Property Description
gda.logPanel.logging.port the port that the log viewer listening to, i.e. the port the Log Server forwarding message to
gda.logPanel.logging.xml the logging configuration file, for example, LogPanel.xml, for this log viewer.

LogPanel.xml provides you with opportunities to further configure your message display levels for all/specific loggers used in GDA objects at the display end.

9.2.4. Default server-side logging configuration

The server-side logging configuration is used for object servers, and for the event server.

GDA has a default server-side logging configuration file, located in the uk.ac.gda.core plugin in the file src/gda/util/logging/configurations/server-default.xml. It is currently used only to specify the log filters for some of the 3rd part libraries used in GDA.

A server-side logging configuration file for a particular GDA configuration can be specified using the gda.server.logging.xml property. The default server-side configuration will be applied first, followed by the custom configuration.

9.2.5. Default client-side logging configuration

GDA has a default client-side logging configuration file, located in the uk.ac.gda.core plugin in the file src/gda/util/logging/configurations/client-default.xml.It is currently used only to specify the log filters for some of the 3rd part libraries used in GDA.

A client-side logging configuration file for a particular GDA configuration can be specified using the gda.client.logging.xml property. The default client-side configuration will be applied first, followed by the custom configuration.

9.2.6. Using property placeholders in Logback configuration files

You can make properties defined in java.properties available for use in a Logback configuration file by adding the following element to the top of the file (inside the <configuration> element):

<property file="${gda.config}/properties/java.properties" />

(Use of ${gda.config} works here because gda.config is a system property.)

You can then use property placeholders elsewhere in the file. For example:

<appender name="SOCKET" class="ch.qos.logback.classic.net.SocketAppender">

Note that the include statement available in properties file is not read by the logging system. To handle multiple properties files add multiple <property .../> elements.

9.3. Java Properties and Customising the GDA

Properties to be shared throughout the code base are stored as name-value pairs in the java.properties file located in the config/properties folder. This is a common way to customise GDA behaviour.

Variable interpolation may be used when defining the java properties in the same manner as Spring or Logback xml files.

The following are the principal java properties which may need customising. However there are many more.

Java properties assumed to be set by -D flags when running the server processes:

Property Description
gda.root the plugins directory of the GDA installation. The features and third-party directories are assumed to be at the same level
gda.config location of the configuration directory. A standard sub-structure to this directory is assumed.
gda.data the top-level data directory. The sub-directories where data files are actually written is derived by the gda.data.scan.datawriter.datadir property which should use variable interpolation

Note that the RCP client will also rely on the gda.config and gda.data variables being set in its .ini file.

Properties which must be set by a -D flag when running the GDA Java processes (third-party software requirement). These flags are added automatically by the Python start script:

Property Description
jacorb.config.dir ${gda.config}/properties or ${gda.config}/jacorb/<mode> (new style configuration) - this is the directory containing the etc directory for JacORB
gov.aps.jca.JCALibrary.properties The JCA library properties file for connecting to EPICS PVs.

Properties most likely to be customised:

Property Description
gda.logs.dir global read-write directory for any logging processes. Note that the main logging system has its own configuration file as described above.
gda.data.scan.datawriter.datadir the directory where data files are to be written. This can be made to be dynamic using the $visit$ variable and configuring the ICAT system.
gda.data.scan.datawriter.dataFormat the data format which scans write
gda.rcp.workspace where workspaces are created for the RCP client. This will need to use variable interpolation if multiple RCP clients are to be allowed.

A properties file can include another properties file by using the include directive. For more information, see the Includes section in the Commons Configuration User’s Guide.

9.4. Metadata

9.4.1. ICAT

The ICAT subsystem talks to a database (an RDBMS or an xml file) which maps user id’s to beamlines and experiments. It is used to find which experiments the user who started each client belongs to and so where any data should be written to by scans collected under the command of that client.

If no ICAT is used then data is always written to the same folder as defined by the gda.data.scan.datawriter.datadir java property.

Some examples of different ICAT systems:

To always write to the same data dir:

gda.data                         = /scratch/data
gda.data.scan.datawriter.datadir = ${gda.data}

For no ICAT, but to change the data directory in every different experiment:

gda.data                         = /scratch/data
gda.data.metadata.icat.type      = gda.data.metadata.icat.NullIcat
gda.data.scan.datawriter.datadir = ${gda.data}/$visit$
# change this for every experiment:
gda.defVisit                     = myVisit

To use an ICAT to dynamically change the output directory depending on who is running the GDA client which has the baton (control of the beamline):

gda.data                               = /scratch/data
gda.data.scan.datawriter.datadir       = ${gda.data}/$year$/$visit$
gda.data.metadata.icat.type            = gda.data.metadata.icat.DLSIcat
gda.data.metadata.icat.url             = jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(HOST=${oracle.host})(PROTOCOL=tcp)(PORT=${oracle.port}))(CONNECT_DATA=(SID=xe)))
gda.data.metadata.icat.shift_tolerance = 1440
gda.data.metadata.dlsicat.user         = icatusername
gda.data.metadata.dlsicat.password     = icatpassword

The DLSIcat class provides connectivity to the ICAT database. There is an alternate class in the uk.ac.gda.core plugin called XMLIcat which uses an XML file as a database. This is primarily for use in unit testing or offsite demonstrations, but could also be used by other facilities if they do a database dump into that format.

At Diamond, the scripts in /dls_sw/dasc/bin/iKittenScripts can be used to diagnose problems with ICAT. For example:

  • getCurrentVisit will show the ID of the current visit, if there is one.
  • getFedIdsForCurrentVisit will show details of users on the current visit.
  • getDetailsOfVisit will show information about a particular visit.

9.5. Role-Based Access Control

9.5.1. Concepts

The idea behind the RBAC system is not to provide cast-iron security to the system, but it to prevent users from accidentally operating hardware at the wrong time which could damage their experiment. E.g. preventing users from moving optical equipment which have been tuned or hardware shared between different branches Device protection

Every piece of equipment (class extending Device) can be assigned a protection level (default is 1), and every user assigned an authorisation level (default is 1, but this can be configured to a different value). When certain methods of an object representing a device are called then the user’s authorisation is compared to the protection level; if the authorisation is equal or greater than the protection level then the method is called, otherwise an gda.jython.accesscontrol.AccessDeniedException is thrown.

GDA developers do not have to write any special code in their device classes to implement this access logic. However if there is a method in a class or interface that needs protection (e.g. Motor.moveTo()) then in the Java source code you should annotate that method using the tag:


The RBAC system will search through the source code using reflection to find such annotations.

The idea is that certain methods will always check for protection whereas some will always be called no matter what the authorisation of the user (e.g. all users can ask the position of any motor, but may only be able to control certain motors). Client authorisation

When a GDA client is started the user id is either taken from the OS or a different user id and password maybe entered. If different details are entered they are authenticated against the whatever Authoriser has been configured (the single-sign-on LDAP system at Diamond).

The login in information is passed to the Command Server (Jython Server) from the client via the InterfaceProvider class. The client makes a unique registration with the Command Server so the source of each command may be identified. The Command Server then determines the authorisation level of that client by comparing the FedID that the Client uses against an xml database on that beamline. If the FedID is listed in the xml then the stored authorisation level is used, otherwise the client is given the default.

There is a tool (gda.jython.authoriser.EditPermissions) which developers or beamline scientists can use to set and change authorisation levels. It is recommended to only list users with elevated authorisation or beamline staff in the xml. The Baton

One beamlines implementing the RBAC system there is the option to use a baton to determine which client has control of the beamline if the beamline may have multiple clients running. Clients holding the baton have control of the beamline subject to their authorisation level, whereas other clients cannot operate the protected methods of any hardware no matter what their authorisation level.

A baton holder may release the baton, so any client can pick it up or it can give the baton to a specific client.

A client may also take the baton from the baton holder if the holder has a lower authorisation level.

There is a GUI panel which lists all the clients on the beamline and has controls for releasing/taking/passing the baton.

9.5.2. Configuration options java properties

To switch on rbac add the following element to your Spring configuration:

<gda:rbac />

and set the following java property:

gda.accesscontrol.useAccessControl = true

To switch on baton control (if this is set to true then you MUST use the BatonPanel in the Swing UI, it will be available by default in the SWT UI):

gda.accesscontrol.useBatonControl = true

To set the default authorisation level (default is 1):

gda.accesscontrol.defaultAuthorisationLevel = 1

To set the default authorisation level for staff (default is 2):

gda.accesscontrol.defaultStaffAuthorisationLevel = 2

For the first client after the server starts to automatically pick up the baton:

gda.accesscontrol.firstClientTakesBaton = true

To tell the server which class to use for authorisation (This class must implement gda.jython.authoriser.gda.jython.authoriser, this is mainly to distinguish between users and staff):

gda.gui.AcquisitionGUI.authorisationMethod = gda.jython.authoriser.LdapAuthoriser

A common implementation is the FileAuthoriser - in fact, the provided LDAPAuthoriser implementation uses a FileAuthoriser to provide a local override. FileAuthoriser uses an xml file, which it looks for in ${gda.user.permissions.dir} (or ${gda.config}/xml/ if the first property isn’t defined). Both have the same format, which is:


Where user_id identifies a particular user, and N is the numeric permission level. Entries in the file user_permissions.xml indicate what users exist and their device permissions.

To tell the server which class to use for authentication (implements gda.jython.authenticator.Authenticator interface. If this is not defined then no login screen will appear and OS authentication will be used - this is recommended):

gda.gui.AcquisitionGUI.authenticationMethod = gda.jython.authenticator.LdapAuthenticator

(for Diamond we now use ldap as the cclrc ldap server can also be used to distinguish staff and user accounts) xml files

To identify specific accounts as staff there should be an xml file placed in the configuration which lists all staff (non-user) accounts which are outside of the ldap server.

This is xml/beamlinestaff.xml and a copy of this is in the example configuration.

The difference between staff and users in the RBAC system is that staff get a different default permission level and if no visit can be found in the ICAT system for that user ID then the default visit is used (defined by a java.property). If a non-staff account has no associated visit in the ICAT system then the UI will not start. xml tags

On devices and DOFs in the Object server xml file:


The protection level MUST be greater than 0!

In the client xml file (Swing UI only):

    <name>Baton Control</name>

9.5.3. How to setup RBAC on a beamline on Diamond

1. set the java properties as listed above.
2. add the appropriate tags to the server and client xml configuration files for each piece of hardware to control access to.
3. add the beamlinestaff.xml file to your configuration to list which accounts should be treated as staff
4. run the tool to build the authorisation database for that beamline if you wish to give certain users elevated permissions above the user default level: java -Dgda.root=/dls/ixx/software/gda -Dgda.config=/dls/ixx/software/gda/config -Dgda.propertiesFiles=/dls/ixx/software/gda/config/properties/java.properties gda.jython.authoriser.EditPermissions
5. restart the GDA !

9.6. New configuration layout

Starting with GDA 8.10, a simplified startup mechanism is supported that allows two additional parameters to be specified when using the gda launcher.

Parameter Default setting Purpose
--profile main Used to distinguish between different types of GDA object server or client
--mode live Allows different variants of the configuration; for example, a ‘live’ mode that connects to real hardware, or a ‘dummy’ mode where dummy devices are used

To allow these parameters to be used, a new directory layout must be used for the configuration. All of the following directories must exist in the top level of the configuration directory:

Directory Purpose
clients Contains client-related XML configuration files
jacorb Contains jacorb.properties files required by JacORB
jca Contains JCALibrary.properties files required by JCA
servers Contains server-related XML configuration files

The following settings will then be automatically determined, and do not need to be specified when running the gda launcher:

Setting Value
Properties file $CONFIG/properties/<mode>/java.properties
JacORB configuration directory $CONFIG/jacorb/<mode>
JCA configuration file $CONFIG/jca/<mode>/JCALibrary.properties
Server XML file $CONFIG/servers/<profile>/<mode>/server.xml
Client XML file $CONFIG/clients/<profile>/<mode>/client.xml

Notes on the new layout:

  • The properties directory must contain a subdirectory for each mode (e.g. dummy and live); each subdirectory must contain a java.properties file.
  • The jacorb directory must contain a subdirectory for each mode; each subdirectory must contain the etc directory required by JacORB (which in turn contains jacorb.properties).
  • The jca directory must contain a subdirectory for each mode; each subdirectory must contain a JCALibrary.properties file.
  • The only files that must be present in the servers and clients subdirectories are <profile>/<mode>/server.xml and <profile>/<mode>/client.xml respectively. Other files can be placed at any level under servers and clients as required.

9.6.1. Object server startup file

Any client or server that starts up an object server or creates an objectServerImpl will create a startup file. The name of this file is different if the new configuration layout with profile name is used.

  • <xmlfile> is the base name (without paths or suffix) of the XML file used to start the client or server
  • <initialisationCompleteFolder> is defined in the Java property gda.objectserver.initialisationCompleteFolder that specifies where this file is to be created
Layout format Startup file name
Old <initialisationCompleteFolder>/object_server_startup_<xmlfile>
New with profile <initialisationCompleteFolder>/object_server_startup_<xmlfile>_<profilename>

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