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Developing Connectors DRAFT |
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This chapter describes Oracle GlassFish Server support for the Java EE
Connector Architecture, also known as
JSR 322
(http://jcp.org/en/jsr/detail?id=322).
The Java EE Connector Architecture provides a Java solution to the problem of connectivity between multiple application servers and existing enterprise information systems (EISs). By using the Java EE Connector architecture, EIS vendors no longer need to customize their product for each application server. Application server vendors who conform to the Java EE Connector architecture do not need to write custom code to add connectivity to a new EIS.
This chapter uses the terms connector and resource adapter interchangeably. Both terms refer to a resource adapter module that is developed in conformance with the Java EE Connector Architecture Specification.
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Note
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If you installed the Web Profile, connector modules that use only outbound communication features and work-management that does not involve inbound communication features are supported. Other connector features are supported only in the full GlassFish Server. |
For more information about connectors, see "https://javaee.github.io/tutorial/resources.html[Resource Adapters and Contracts]" in The Java EE 8 Tutorial.
For information about deploying a connector to the GlassFish Server, see the GlassFish Server Open Source Edition Application Deployment Guide.
The following topics are addressed here:
The GlassFish Server supports the development and deployment of resource adapters that are compatible with the Connector 1.6 specification (and, for backward compatibility, the Connector 1.0 and 1.5 specifications).
The Connector 1.0 specification defines the outbound connectivity system contracts between the resource adapter and the GlassFish Server. The Connector 1.5 specification introduces major additions in defining system level contracts between the GlassFish Server and the resource adapter with respect to inbound connectivity, life cycle management, and thread management. The Connector 1.6 specification introduces further additions in defining system level contracts between the GlassFish Server and the resource adapter with respect to the following:
Generic work context contract — A generic contract that enables a
resource adapter to control the execution context of a Work instance
that it has submitted to the GlassFish Server for execution. The
Generic work contract provides the mechanism for a resource adapter to
augment the runtime context of a Work instance with additional
contextual information flown-in from the EIS. This contract enables a
resource adapter to control, in a more flexible manner, the contexts in
which the Work instances submitted by it are executed by the
application server’s WorkManager.
Security work context — A standard contract that enables a resource
adapter to establish security information while submitting a Work
instance for execution to a WorkManager and while delivering
messages-to-message endpoints residing in the GlassFish Server. This
contract provides a mechanism to support the execution of a Work
instance in the context of an established identity. It also supports the
propagation of user information or Principal information from an EIS to
a MessageEndpoint during message inflow.
Transaction context — The transaction context contract between the
resource adapter and the application server leverages the Generic Work
Context mechanism by describing a standard WorkContext, the
TransactionContext. It represents the standard interface a resource
adapter can use to propagate transaction context information from the
EIS to the application server.
In the Administration Console, connector, JMS, and JDBC resources are handled differently, but they use the same underlying Connector architecture. In the GlassFish Server, all communication to an EIS, whether to a message provider or an RDBMS, happens through the Connector architecture. To provide JMS infrastructure to clients, the GlassFish Server uses the Open Message Queue software. To provide JDBC infrastructure to clients, the GlassFish Server uses its own JDBC system resource adapters. The GlassFish Server automatically makes these system resource adapters available to any client that requires them.
For more information about JMS in the GlassFish Server, see Using the Java Message Service. For more information about JDBC in the GlassFish Server, see Using the JDBC API for Database Access.
The GlassFish Server does not need to use sun-ra.xml, which previous
GlassFish Server versions used, to store server-specific deployment
information inside a Resource Adapter Archive (RAR) file. (However, the
sun-ra.xml file is still supported for backward compatibility.)
Instead, the information is stored in the server configuration. As a
result, you can create multiple connector connection pools for a
connection definition in a functional resource adapter instance, and you
can create multiple user-accessible connector resources (that is,
registering a resource with a JNDI name) for a connector connection
pool. In addition, dynamic changes can be made to connector connection
pools and the connector resource properties without restarting the
GlassFish Server.
The following topics are addressed here:
Connectors can submit work instances to the GlassFish Server for execution. By default, the GlassFish Server services work requests for all connectors from its default thread pool. However, you can associate a specific user-created thread pool to service work requests from a connector. A thread pool can service work requests from multiple resource adapters. To create a thread pool:
In the Administration Console, select Thread Pools under the relevant configuration. For details, click the Help button in the Administration Console.
Use the asadmin create-threadpool command. For details, see the
GlassFish Server Open Source Edition Reference Manual.
To associate a connector with a thread pool:
In the Administration Console, open the Applications component and select Resource Adapter Configs. Specify the name of the thread pool in the Thread Pool ID field. For details, click the Help button in the Administration Console.
Use the --threadpoolid option of the
asadmin create-resource-adapter-config command. For details, see the
GlassFish Server Open Source Edition Reference Manual.
If you create a resource adapter configuration for a connector module that is already deployed, the connector module deployment is restarted with the new configuration properties.
Create a security map for a connector connection pool to map an application principal or a user group to a back end EIS principal. The security map is usually used in situations where one or more EIS back end principals are used to execute operations (on the EIS) initiated by various principals or user groups in the application.
To create or update security maps for a connector connection pool:
In the Administration Console, open the Resources component, select Connectors, select Connector Connection Pools, and select the Security Maps tab. For details, click the Help button in the Administration Console.
Use the asadmin create-connector-security-map command. For details,
see the GlassFish Server Open Source Edition Reference
Manual.
If a security map already exists for a connector connection pool, the
new security map is appended to the previous one. The connector security
map configuration supports the use of the wildcard asterisk (*) to
indicate all users or all user groups.
When an application principal initiates a request to an EIS, the GlassFish Server first checks for an exact match to a mapped back end EIS principal using the security map defined for the connector connection pool. If there is no exact match, the GlassFish Server uses the wild card character specification, if any, to determined the mapped back end EIS principal.
A work security map for a resource adapter maps an EIS principal or group to a application principal or group. A work security map is useful in situations where one or more application principals execute operations initiated by principals or user groups in the EIS. A resource adapter can have multiple work security maps. A work security map can map either principals or groups, but not both.
To create a work security map, use the
asadmin create-connector-work-security-map command. For details, see
the GlassFish Server Open Source Edition Reference Manual.
The work security map configuration supports the wildcard asterisk (*)
character to indicate all users or all user groups. When an EIS
principal sends a request to the GlassFish Server, the GlassFish Server
first checks for an exact match to a mapped application principal using
the work security map defined for the resource adapter. If there is no
exact match, the GlassFish Server uses the wild card character
specification, if any, to determine the application principal.
You can override the properties (config-property elements) specified
in the ra.xml file of a resource adapter:
In the Administration Console, open the Resources component and select Resource Adapter Configs. Create a new resource adapter configuration or select an existing one to edit. Then enter property names and values in the Additional Properties table. For details, click the Help button in the Administration Console.
Use the asadmin create-resource-adapter-config command to create a
configuration for a resource adapter. Use this command’s --property
option to specify a name-value pair for a resource adapter property. For
details, see the GlassFish Server Open Source Edition
Reference Manual.
You can specify configuration properties either before or after resource adapter deployment. If you specify properties after deploying the resource adapter, the existing resource adapter is restarted with the new properties.
You can also use token replacement for overriding resource adapter
configuration properties in individual server instances when the
resource adapter is deployed to a cluster. For example, for a property
called inboundPort, you can assign the value ${inboundPort}. You can
then assign a different value to this property for each server instance.
Changes to system properties take effect upon server restart.
You can test a connector connection pool for usability in one of these ways:
In the Administration Console, open the Resources component, open the Connector component, select Connection Pools, and select the connection pool you want to test. Then select the Ping button in the top right corner of the page. For details, click the Help button in the Administration Console.
Use the asadmin ping-connection-pool command. For details, see the
GlassFish Server Open Source Edition Reference Manual.
Both these commands fail and display an error message unless they successfully connect to the connection pool.
You can also specify that a connection pool is automatically tested when
created or reconfigured by setting the Ping attribute to true (the
default is false) in one of the following ways:
Enter a Ping value in the Connector Connection Pools page in the Administration Console. For more information, click the Help button in the Administration Console.
Specify the --ping option in the
asadmin create-connector-connection-pool command. For more
information, see the GlassFish Server Open Source Edition
Reference Manual.
Flushing a connector connection pool recreates all the connections in the pool and brings the pool to the steady pool size without the need for reconfiguring the pool. Connection pool reconfiguration can result in application redeployment, which is a time-consuming operation. Flushing destroys existing connections, and any existing transactions are lost and must be retired.
You can flush a connector connection pool in one of these ways:
In the Administration Console, open the Resources component, open the Connector component, select Connection Pools, and select the connection pool you want to flush. Then select the Flush button in the top right corner of the page. For details, click the Help button in the Administration Console.
Use the asadmin flush-connection-pool command. For details, see the
GlassFish Server Open Source Edition Reference Manual.
If a resource adapter generates a ConnectionErrorOccured event, the
GlassFish Server considers the connection invalid and removes the
connection from the connection pool. Typically, a resource adapter
generates a ConnectionErrorOccured event when it finds a
ManagedConnection object unusable. Reasons can be network failure with
the EIS, EIS failure, fatal problems with the resource adapter, and so
on.
If the fail-all-connections setting in the connection pool
configuration is set to true, and a single connection fails, all
connections are closed and recreated. If this setting is false,
individual connections are recreated only when they are used. The
default is false.
The is-connection-validation-required setting specifies whether
connections have to be validated before being given to the application.
If a resource’s validation fails, it is destroyed, and a new resource is
created and returned. The default is false.
The prefer-validate-over-recreate property specifies that validating
idle connections is preferable to closing them. This property has no
effect on non-idle connections. If set to true, idle connections are
validated during pool resizing, and only those found to be invalid are
destroyed and recreated. If false, all idle connections are destroyed
and recreated during pool resizing. The default is false.
You can set the fail-all-connections,
is-connection-validation-required, and prefer-validate-over-recreate
configuration settings during creation of a connector connection pool.
Or, you can use the asadmin set command to dynamically reconfigure a
setting. For example:
asadmin set server.resources.connector-connection-pool.CCP1.fail-all-connections="true"
asadmin set server.resources.connector-connection-pool.CCP1.is-connection-validation-required="true"
asadmin set server.resources.connector-connection-pool.CCP1.property.prefer-validate-over-recreate="true"For details, see the GlassFish Server Open Source Edition Reference Manual.
The interface ValidatingManagedConnectionFactory exposes the method
getInvalidConnections to allow retrieval of the invalid connections.
The GlassFish Server checks if the resource adapter implements this
interface, and if it does, invalid connections are removed when the
connection pool is resized.
According to the Connector specification, while an application server shuts down, all resource adapters should be stopped. A resource adapter might hang during shutdown, since shutdown is typically a resource intensive operation. To avoid such a situation, you can set a timeout that aborts resource adapter shutdown if exceeded. The default timeout is 30 seconds per resource adapter module. To configure this timeout:
In the Administration Console, select Connector Service under the relevant configuration and edit the shutdown Timeout field. For details, click the Help button in the Administration Console.
Use the following asadmin set command:
asadmin set server.connector-service.shutdown-timeout-in-seconds="num-secs"
For details, see the GlassFish Server Open Source Edition Reference Manual.
The GlassFish Server deactivates all message-driven bean deployments before stopping a resource adapter.
Use the class-loading-policy setting to determine which resource
adapters accessible to applications. Allowed values are:
derived — Applications access resource adapters based on references
in their deployment descriptors. These references can be resource-ref,
resource-env-ref, resource-adapter-mid, or equivalent annotations.
global — All stand-alone resource adapters are available to all
applications.
To configure this setting, use the asadmin set command. For example:
asadmin set server.connector-service.class-loading-policy="global"For details, see the GlassFish Server Open Source Edition Reference Manual.
Transactions that involve multiple resources or multiple participant processes are distributed or global transactions. A global transaction can involve one non-XA resource if last agent optimization is enabled. Otherwise, all resources must be XA. For more information about transactions in the GlassFish Server, see Using the Transaction Service.
The Connector specification requires that if a resource adapter supports
XATransaction, the ManagedConnection created from that resource
adapter must support both distributed and local transactions. Therefore,
even if a resource adapter supports XATransaction, you can configure
its connector connection pools as non-XA or without transaction support
for better performance. A non-XA resource adapter becomes the last agent
in the transactions in which it participates.
The value of the connection pool configuration property
transaction-support defaults to the value of the transaction-support
property in the ra.xml file. The connection pool configuration
property can override the ra.xml file property if the transaction
level in the connection pool configuration property is lower. If the
value in the connection pool configuration property is higher, it is
ignored.
To disable connection pooling, set the Pooling attribute to false. The default is true. You can enable or disable connection pooling in one of the following ways:
Enter a Pooling value in the Connector Connection Pools page in the Administration Console. For more information, click the Help button in the Administration Console.
Specify the --pooling option in the
asadmin create-connector-connection-pool command. For more
information, see the GlassFish Server Open Source Edition
Reference Manual.
You can define an application-scoped connector or other resource for an
enterprise application, web module, EJB module, connector module, or
application client module by supplying a glassfish-resources.xml
deployment descriptor file. For details, see
"Application-Scoped Resources" in GlassFish Server
Open Source Edition Application Deployment Guide.
The Connector specification defines the transaction and message inflow system contracts for achieving inbound connectivity from an EIS. The message inflow contract also serves as a standard message provider pluggability contract, thereby allowing various message providers to seamlessly plug in their products with any application server that supports the message inflow contract. In the inbound communication model, the EIS initiates all communication to an application. An application can be composed of enterprise beans (session, entity, or message-driven beans), which reside in an EJB container.
Incoming messages are received through a message endpoint, which is a message-driven bean. This message-driven bean asynchronously consumes messages from a message provider. An application can also synchronously send and receive messages directly using messaging style APIs.
A resource adapter supporting inbound communication provides an instance
of an ActivationSpec JavaBean class for each supported message
listener type. Each class contains a set of configurable properties that
specify endpoint activation configuration information during
message-driven bean deployment. The required config-property element
in the ra.xml file provides a list of configuration property names
required for each activation specification. An endpoint activation fails
if the required property values are not specified. Values for the
properties that are overridden in the message-driven bean’s deployment
descriptor are applied to the ActivationSpec JavaBean when the
message-driven bean is deployed.
Administered objects can also be specified for a resource adapter, and these JavaBeans are specific to a messaging style or message provider. For example, some messaging styles may need applications to use special administered objects (such as Queue and Topic objects in JMS). Applications use these objects to send and synchronously receive messages using connection objects using messaging style APIs. For more information about administered objects, see Using the Java Message Service.
The Connector specification defines the system contracts for achieving
outbound connectivity from an EIS. A resource adapter supporting
outbound communication provides an instance of a
ManagedConnectionFactory JavaBean class. A ManagedConnectionFactory
JavaBean represents outbound connectivity information to an EIS instance
from an application.
The 1.6 Connector specification introduces a mechanism through which the
transaction level of a ManagedConnectionFactory can be detected at
runtime. During the configuration of a ManagedConnectionFactory in the
Connector Connection Pools page in the Administration Console, the
Administration Console can instantiate the ManagedConnectionFactory
and show the level of transaction support. The three levels are no-tx,
local-tx, xa-tx. If a ManagedConnectionFactory returns local-tx
as the level it can support, it is assumed that xa-tx is not
supported, and the Administration Console shows only no-tx and
local-tx as the available support levels.
For more information, click the Help button in the Administration Console.
The Connectors specification’s message inflow contract provides a generic mechanism to plug in a wide-range of message providers, including JMS, into a Java-EE-compatible application server. Message providers use a resource adapter and dispatch messages to message endpoints, which are implemented as message-driven beans.
The message-driven bean developer provides activation configuration
information in the message-driven bean’s ejb-jar.xml file.
Configuration information includes messaging-style-specific
configuration details, and possibly message-provider-specific details as
well. The message-driven bean deployer uses this configuration
information to set up the activation specification JavaBean. The
activation configuration properties specified in ejb-jar.xml override
configuration properties in the activation specification definition in
the ra.xml file.
According to the EJB specification, the messaging-style-specific
descriptor elements contained within the activation configuration
element are not specified because they are specific to a messaging
provider. In the following sample message-driven bean ejb-jar.xml, a
message-driven bean has the following activation configuration property
names: destinationType, SubscriptionDurability, and
MessageSelector.
<!-- A sample MDB that listens to a JMS Topic -->
<!-- message-driven bean deployment descriptor -->
...
<activation-config>
<activation-config-property>
<activation-config-property-name>
destinationType
</activation-config-property-name>
<activation-config-property-value>
javax.jms.Topic
</activation-config-property-value>
</activation-config-property>
<activation-config-property>
<activation-config-property-name>
SubscriptionDurability
</activation-config-property-name>
<activation-config-property-value>
Durable
</activation-config-property-value>
</activation-config-property>
<activation-config-property>
<activation-config-property-name>
MessageSelector
</activation-config-property-name>
<activation-config-property-value>
JMSType = 'car' AND color = 'blue'
</activation-config-property-value>
</activation-config-property>
...
</activation-config>
...When the message-driven bean is deployed, the value for the
resource-adapter-mid element in the glassfish-ejb-jar.xml file is
set to the resource adapter module name that delivers messages to the
message endpoint (to the message-driven bean). In the following example,
the jmsra JMS resource adapter, which is the bundled resource adapter
for the Message Queue message provider, is specified as the resource
adapter module identifier for the SampleMDB bean.
<glassfish-ejb-jar>
<enterprise-beans>
<unique-id>1</unique-id>
<ejb>
<ejb-name>SampleMDB</ejb-name>
<jndi-name>SampleQueue</jndi-name>
<!-- JNDI name of the destination from which messages would be
delivered from MDB needs to listen to -->
...
<mdb-resource-adapter>
<resource-adapter-mid>jmsra</resource-adapter-mid>
<!-- Resource Adapter Module Id that would deliver messages to
this message endpoint -->
</mdb-resource-adapter>
...
</ejb>
...
</enterprise-beans>
...
</glassfish-ejb-jar>When the message-driven bean is deployed, the GlassFish Server uses the
resourceadapter-mid setting to associate the resource adapter with a
message endpoint through the message inflow contract. This message
inflow contract with the GlassFish Server gives the resource adapter a
handle to the MessageEndpointFactory and the ActivationSpec
JavaBean, and the adapter uses this handle to deliver messages to the
message endpoint instances (which are created by the
MessageEndpointFactory).
When a message-driven bean first created for use on the GlassFish Server
7 is deployed, the Connector runtime transparently transforms the
previous deployment style to the current connector-based deployment
style. If the deployer specifies neither a resource-adapter-mid
element nor the Message Queue resource adapter’s activation
configuration properties, the Connector runtime maps the message-driven
bean to the jmsra system resource adapter and converts the
JMS-specific configuration to the Message Queue resource adapter’s
activation configuration properties.
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