Programming Stand-alone Clients

      

Reliably Sending Messages Using the JMS SAF Client

The following sections describe how to configure and use the JMS SAF Client feature to reliably send JMS messages from standalone JMS clients to server-side JMS destinations:

 

Overview of Using Store-and-Forward with JMS Clients

The JMS SAF Client feature extends the JMS store-and-forward service introduced in WebLogic Server 9.0 to standalone JMS clients. Now JMS clients can reliably send messages to server-side JMS destinations, even when the client cannot reach a destination (for example, due to a temporary network connection failure). While disconnected from the server, messages sent by a JMS SAF client are stored locally on the client file system and are forwarded to server-side JMS destinations when the client reconnects.

The JMS SAF client feature consists of two main parts: the JMS SAF client implementation that writes messages directly to a client-side persistent store on the local file system and a SAF forwarder that takes the messages written to the store and sends them to a WebLogic Server instance. There is also an optional SAFClient initialization API in weblogic.jms.extensions that allows JMS SAF clients to turn the SAF forwarder mechanism on and off whenever necessary. For more information, see The JMS SAF Client Initialization API.

For information on the server-side WebLogic JMS SAF for reliably sending JMS messages to potentially unavailable destinations, see Configuring SAF for JMS Messages in Configure WebLogic Store-and-Forward.

 

Configuring a JMS Client To Use Client-side SAF

No configuration is required on the server-side, but running client-side SAF does require some configuration on each client. These sections describe how to configure a JMS client to use client-side SAF.

 

Generating a JMS SAF Client Configuration File

Each client machine requires a JMS SAF client configuration file that specifies information about the server-side connection factories and destinations needed by the JMS SAF client environment to operate. You generate the JMS SAF client configuration file from a specified JMS module's configuration file by using the ClientSAFGenerate utility bundled with your WebLogic installation.

The ClientSAFGenerate utility creates entries for all connection factories, stand-alone destinations, and distributed destinations found in the source JMS configuration file, as described in Steps to Generate a JMS SAF Client Configuration File from a JMS Module. The generated file defines the connection factories and imported destinations that the JMS SAF client will interact with directly through the initial JNDI context described in Modify Your JMS Client Applications To Use the JMS SAF Client's Initial JNDI Provider. However, the generated file will not contain entries for any foreign JMS destinations or SAF destinations in server-side JMS modules. Furthermore, only JMS destinations with their SAF Export Policy set to All are added to the file (the default setting for destinations).

How the JMS SAF Client Configuration File Works

The JMS SAF client XML file conforms to the WebLogic Server weblogic-jms.xsd schema for JMS modules and contains the root element weblogic-client-jms. The weblogic-jms.xsd schema contains several top-level elements that correspond to server-side WebLogic JMS SAF features, as described in Valid SAF Elements for JMS SAF Client Configurations.

The top-level elements in the file describe the connection factory and imported destination elements that the JMS SAF client will interact with directly. The SAF sending agent, remote SAF context, and SAF error handling elements describe the function of the SAF forwarder. The persistent store element is used by both the JMS SAF client API and the SAF fowarder.

Steps to Generate a JMS SAF Client Configuration File from a JMS Module

Use the ClientSAFGenerate utility to generate a JMS SAF client configuration file from a JMS module configuration file in a WebLogic domain. You can also generate a configuration file from an existing JMS SAF client configuration file, as described in ClientSAFGenerate Utility Syntax.

Running the ClientSAFGenerate utility on a client machine to generate a configuration file from an existing JMS SAF client configuration file requires using the wlfullclient.jar in the CLASSPATH instead of the thin JMS and JMS SAF clients. See Installing the JMS SAF Client JAR Files on Client Machines.

These steps demonstrate how to use the ClientSAFGenerate utility to generate a JMS SAF client configuration file from the examples-jms.xml module file bundled in WebLogic Server installations.

  1. Navigate to the directory in the WebLogic domain containing the JMS module file that you want to use as the basis for the JMS SAF client configuration file: 
    c:\bea\wlserver_10.0\samples\domains\wl_server\config\jms

  2. From a Java command-line, run the ClientSAFGenerate utility: 
    > java weblogic.jms.extensions.ClientSAFGenerate -url http://10.61.6.138:7001 -username weblogic -moduleFile examples-jms.xml -outputFile d:\temp\ClientSAF-jms.xml

    Table 6-1 explains the valid ClientSAFGenerate arguments.

  3. A configuration file named SAFClient-jms.xml is created in the current directory. Here is a representative example of its contents: 
    <weblogic-client-jms xmlns="http://www.bea.com/ns/weblogic/100" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

      <connection-factory name="exampleTrader">

        <jndi-name>jms.connection.traderFactory</jndi-name>

        <transaction-params>

          <xa-connection-factory-enabled>false

          </xa-connection-factory-enabled>

        </transaction-params>

      </connection-factory>

      <saf-imported-destinations name="examples">

        <saf-queue name="exampleQueue">

          <remote-jndi-name>weblogic.examples.jms.exampleQueue

          </remote-jndi-name>

          <local-jndi-name>weblogic.examples.jms.exampleQueue

          </local-jndi-name>

        </saf-queue>

        <saf-topic name="quotes">

          <remote-jndi-name>quotes</remote-jndi-name>

          <local-jndi-name>quotes</local-jndi-name>

        </saf-topic>

      </saf-imported-destinations>

      <saf-remote-context name="RemoteContext0">

        <saf-login-context>

          <loginURL>t3://localhost:7001</loginURL>

          <username>weblogic</username>

        </saf-login-context>

      </saf-remote-context>

    </weblogic-client-jms>

    Tip: To include additional remote SAF connection factories and destinations from other JMS modules deployed in a cluster or domain, re-run the ClientSAFGenerate utility against these JMS module files and specify the same JMS SAF configuration file name in the -outputFile parameter. See ClientSAFGenerate Utility Syntax.

  4. The generated configuration file does not contain any encrypted passwords for the SAF remote contexts used to connect to remote servers. To create encrypted passwords for the remote SAF contexts and add them to the configuration file, follow the directions in Encrypting Passwords for Remote JMS SAF Contexts.

  5. Copy the generated configuration can file to the client machine(s) where you will run your JMS SAF client applications. See Installing the JMS SAF Client JAR Files on Client Machines.

    ClientSAF.xml is the default name expected in the current working directory of the JMS client, but you can also explicitly specify a file name by passing an argument in the JMS client, as described in Modify Your JMS Client Applications To Use the JMS SAF Client's Initial JNDI Provider.

ClientSAFGenerate Utility Syntax

The weblogic.jms.extensions.ClientSAFGenerate utility generates a JMS SAF client configuration file, using either a JMS module file or an existing JMS SAF client configuration file. 

java     [ weblogic.jms.extensions.ClientSAFGenerate ] 

    [ -url server-url ]

    [ -username name-of-user ]

    [ -existingClientFile file-path ]

    [ -moduleFile file-path ['@' plan-path ]]*

    [ -outputFile file-path  ]

Table 6-1 ClientSAFGenerate Arguments
Argument Definition
url The URL of the WebLogic Server instance where the JMS SAF client instance should connect.
username The name of a valid user that this JMS SAF client instance should use when forwarding messages.
existingClientFile The name of an existing JMS SAF client configuration file. If this parameter is specified, then the existing file will be read and new entries will be added. If any conflicts are detected between items being added and items already in the JMS SAF client configuration file, a warning will be given and the new item will not be added. If a JMS SAF client configuration file is specified but the file cannot be found, then an error is printed and the utility exits.
moduleFile The name of a JMS module configuration file and optional plan file.
outputFile The path to the generated output file. If a path is not specified, the utility sends its output to stdout. ClientSAF.xml is the default name expected in the current working directory of the JMS client, but you can also explicitly specify a file name by passing an argument in the JMS client.

Valid SAF Elements for JMS SAF Client Configurations

The weblogic-client-jms root element of the weblogic-jms.xsd schema contains several top-level elements that correspond to server-side WebLogic JMS SAF features. Table 6-2 makes clear what the relationship between the top-level element in the schema and the corresponding management MBean.

Table 6-2 weblogic-client-saf Elements
weblogic-client-jms Element WebLogic Server Management Bean
connection-factory JMSConnectionFactoryBean
saf-agent SAFAgentMBean
saf-imported-destinations SAFImportedDestinationsBean
saf-remote-context SAFRemoteContextBean
saf-error-handling SAFErrorHandlingBean
persistent-store For more information, see Default Store Options for JMS SAF Clients.

Caution: You can only specify one persistent-store and saf-agent element in a JMS SAF client configuration file.

All of the properties in these management MBeans work the same in the JMS SAF client implementation as they do in server-side SAF JMS configurations, except for those described in the following tables.

Table 6-3 describes the differences between the standard SAFAgentMBean fields and the fields in the JMS SAF client configuration file.

Table 6-3 Modified SAFAgentMBean Fields
Server-side SAF Fields Difference in JMS SAF Client Configuration File
PersistentStore Not available. There is only one persistent store defined.
ServiceType Not available. This can only be a sending agent.
BytesThresholdHigh Threshold properties are not available.
BytesThresholdLow Threshold properties are not available.
MessagesThresholdHigh Threshold properties are not available.
MessagesThresholdLow Threshold properties are not available.
ConversationIdleTimeMaximum Not available. This field is only valid for receiving messages.
AcknowledgeInterval Not available. Only valid for receiving messages.
IncomingPausedAtStartup Not available. No way to unpause; same effect achieved by not setting the JMS SAF client property.
ForwardingPausedAtStartup Not available. No way to unpause; same effect achieved by not setting the JMS SAF client property.
ReceivingPausedAtStartup Not available. No way to unpause; same effect achieved by not setting the JMS SAF client property.

Caution: You can only specify one saf-agent element in a JMS SAF client configuration file.

Table 6-4 describes the differences between the standard JMSConnectionFactoryBean fields and the fields in the JMS SAF client configuration file.

Table 6-4 Modified JMSConnectionFactoryBean Fields
Server-side SAF Fields Difference in JMS SAF Client Configuration File
SubDeploymentName Ignored. These connection factories are not targeted.
ClientParamsBean: MulticastOverrunPolicy Ignored. This client cannot do multicast receives.
TransactionParamsBean: XAConnectionFactoryEnabled Ignored. JMS SAF client cannot do XA transactions.
FlowControlParamsBean All fields are ignored. JMS SAF client cannot receive messages.
LoadBalancingParamsBean All fields are ignored. JMS SAF client cannot load balance since it is not connected to a server.

Table 6-5 describes the differences between the standard SAFImportedDestinationsBean fields and the fields in the JMS SAF client configuration file.

Table 6-5 Modified SAFImportedDestinationsBean Fields
Server-side SAF Fields Difference in JMS SAF Client Configuration File
SubDeploymentName Ignored. These are targeted to the single SAF agent defined in this file.
UnitOfOrderRouting Ignored. Message unit-of-order is not supported.

Default Store Options for JMS SAF Clients

Each JMS SAF client has a default store that requires no configuration, and which can be shared by multiple JMS SAF clients. The default store is a file-based store that maintains its data in a group of files directly under the JMS SAF client configuration directory.

Using the persistent-store element, you can specify another location for the default store and also change its default write policy by specifying the following elements in the JMS SAF client configuration file:

Table 6-6 persistent-store Elements
Element Name What it does
directory-path Specifies the path to the directory on the file system where the file store is kept.
synchronous-write-policy Defines how hard a file store will try to flush records to the disk. Values are: Direct-Write (default), Cache-Flush, and Disabled.

Caution: You can only specify one persistent-store element in a JMS SAF client configuration file.

Here's an example of a customized JMS SAF client default store in a JMS SAF client configuration file: 

  <persistent-store>

    <directory-path>config/jms/storesdom</directory-path>

    <synchronous-write-policy>Disabled</synchronous-write-policy>

  </persistent-store>

For more information on using the Synchronous Write Policy for a file store, see Using the WebLogic Persistent Store in Configuring WebLogic Server Environments.

 

Encrypting Passwords for Remote JMS SAF Contexts

The generated SAF configuration file does not contain any encrypted passwords for its generated SAF remote contexts, regardless of whether any were configured in the source JMS module file. If security credentials are configured for the remote cluster or server contexts defined in the JMS SAF client configuration file, then encrypted passwords are required to connect to the remote servers or cluster.

To create encrypted passwords for your remote SAF contexts, use the ClientSAFEncrypt utility bundled with your WebLogic installation, which encrypts cleartext strings for use with the JMS SAF client feature.

The existing weblogic.security.Encrypt command-line utility cannot be used because it expects access to the domain security files, which are not available on the client.

Steps to Generate Encrypted Passwords

The following steps demonstrate how to use the ClientSAFEncrypt to generate encrypted passwords:

  1. From a Java command-line, run the ClientSAFEncrypt utility: 
    > java -Dweblogic.management.allowPasswordEcho=true weblogic.jms.extensions.ClientSAFEncrypt [ key-password ] [ remote-password ]*

  2. If the key-password or the remote-password fields are not specified, then you will be prompted for the key-password and the remote-password interactively.

  3. Here's an example of obtaining an encrypted password: 
    Password Key ("quit" to end):

    Password ("quit" to end):

    <password-encrypted>{Algorithm}PBEWithMD5AndDES{Salt}9IsTPAuZdcQ={Data}d6SSPp3GwPAfEXn8izyZA0IRCV/izT8H</password-encrypted>

    Password ("quit" to end):

  4. Continue generating as many remote passwords as necessary for the remote contexts defined in the JMS SAF client configuration file.

  5. Copy the encrypted remote password before the closing </saf-login-context> stanza in the JMS SAF client configuration file. For example: 
    <saf-remote-context name="RemoteContext0">

    <saf-login-context>

    <loginURL>http://10.61.6.138:7001</loginURL>

    <username>weblogic</username>

    <password-encrypted>{Algorithm}PBEWithMD5AndDES{Salt}dWENfrgXh8U={Data}u8xZ968dElHckso/ZYm2LQ6xVNBPpBGQ</password-encrypted>

    </saf-login-context>

    </saf-remote-context>

    Use the ClientSAFEncrypt utility for all passwords (with the same key-password) required by the remote contexts defined in the JMS SAF client configuration file. When a client starts using the JMS SAF client, it must supply the same key-password that was provided to the ClientSAFEncrypt utility.

  6. Type quit to exit the ClientSAFEncrypt utility.

ClientSAFEncrypt Utility Syntax

The weblogic.jms.extensions.ClientSAFEncrypt utility encrypts cleartext strings for use with JMS SAF clients in order to access remote SAF contexts. 

java     [ -Dweblogic.management.allowPasswordEcho=true ] 

    weblogic.jms.extensions.ClientSAFEncrypt [ key-password ]

    weblogic.jms.extensions.ClientSAFEncrypt [ remote-password ]

Table 6-7 ClientSAFEncrypt Arguments
Argument Definition
weblogic.management.allowPasswordEcho Optional. Allows echoing characters entered on the command line. weblogic.jms.extensions.ClientSAFEncrypt expects that no-echo is available; if no-echo is not available, set this property to true.
key-password The key to use when encrypting all remote passwords needed for the remote contexts defined in the JMS SAF client configuration file. If omitted from the command line, you will be prompted to enter a key-password.
remote-password Cleartext string to be encrypted. Multiple passwords for each remote context can be generated in one session. If omitted from the command line, you are prompted to enter a remote-password.

 

Installing the JMS SAF Client JAR Files on Client Machines

How you install the JMS SAF client depends on whether your client machines require smaller JAR files (thin clients) or whether they can accommodate using the single, higher-performing wlfullclient.jar file, which contains all the necessary functionality and is also the recommended best practice.

The required WebLogic JAR files are located in the WL_HOME\server\lib subdirectory of the WebLogic Server installation directory, where WL_HOME is the top-level installation directory for the entire WebLogic product installation (for example, c:\bea\weblogic92\server\lib).

When smaller JAR sizes are required for thin clients, the JMS SAF client requires installing the following JAR files to a directory on the client machine's file system and added to its CLASSPATH:

The wljmsclient.jar has a reference to the wlclient.jar so it is only necessary to put one or the other JAR in the client machine's CLASSPATH.

Again, the recommended best practice is to use the larger, higher-performing wlfullclient.jar, which must be installed to a directory on the client machine's file system and added to its CLASSPATH. Using the wlfullclient.jar file also allows you to run the ClientSAFGenerate utility on a client machine to generate a configuration file from an existing JMS SAF client configuration file, as described in Steps to Generate a JMS SAF Client Configuration File from a JMS Module.

For more information on deploying thin clients, see Developing a Java EE Application Client (Thin Client).

 

Modify Your JMS Client Applications To Use the JMS SAF Client's Initial JNDI Provider

The JMS SAF client requires a special initial JNDI provider to look up the server-side JMS connection factories and destinations specified in the JMS SAF client configuration file that was generated during Steps to Generate a JMS SAF Client Configuration File from a JMS Module.

Required JNDI Context Factory for JMS SAF Clients

Modify your JMS client applications to use the JMS SAF client JNDI context factory in place of the standard server initial context. The name used for the JMS SAF client JNDI property java.naming.factory.initial is weblogic.jms.safclient.jndi.InitialContextFactoryImpl.

An example JNDI initial context factory could look like this in a JMS SAF client application: 

   public final static String JNDI_FACTORY="weblogic.jms.safclient.jndi.InitialContextFactoryImpl";

With the standard JNDI lookup, the JMS SAF client is started automatically and looks up the server-side JMS connection factories and destinations specified in the configuration file. For the configuration file, ClientSAF.xml is the default name expected in the current working directory of the JMS client, but you can also explicitly specify a configuration file name by passing an argument in the JMS client.

Items returned from the initial context created with the JMS SAF client do not work in JMS calls from third-party JMS providers. Also, there can be no mixing of JMS SAF client initial contexts with server initial contexts, as described in No Mixing of JMS SAF Client Contexts and Server Contexts.

You can also update your JMS client applications to use the weblogic.jms.extensions.ClientSAF extension class, which allows the JMS client to control when the JMS SAF client system is in use. See The JMS SAF Client Initialization API.

Optional JNDI Properties for JMS SAF Clients

There are also two optional JMS SAF client JNDI properties:

The local JNDI provider only supports the lookup(String) and close() APIs. All other APIs throw an exception stating that the functionality is not supported.

 

JMS SAF Client Management Tools

The following management features are available for use with the JMS SAF client implementation.

 

The JMS SAF Client Initialization API

The weblogic.jms.extensions.ClientSAF extension class allows the JMS client to control when the JMS SAF client system is in use. JMS clients do not need to use this extension mechanism, but can do so in order to get finer control of the JMS SAF client system. For example, the close() method can be used to stop a JMS client from forwarding messages.

 

Client-Side Store Administration Utility

The JMS SAF client provides a utility to administer the default file store used by JMS SAF clients. Similar to the server-side WebLogic Store utility, it enables you to troubleshoot a JMS SAF client store or extract its data. Run the utility from a Java command line or from the WebLogic Scripting Tool (WLST). The store utility operates only on a store that is not currently opened by a running JMS SAF client.

The most common uses-cases for store administration are for compacting a file store to reduce its size and for dumping the contents of a file store to an XML file for troubleshooting purposes. For more information, see Administering a Persistent Store in Configuring WebLogic Server Environments.

 

JMS Programming Considerations with JMS SAF Clients

The following JMS programming considerations apply when you use the JMS SAF client.

 

How the JMSReplyTo Field Is Handled In JMS SAF Client Messages

Generally, JMS applications can use the JMSReplyTo header field to advertise its temporary destination name to other applications. However, as with server-side JMS SAF imported destinations, the use of temporary destinations with a JMSReplyTo field is not supported for JMS SAF clients.

For more information on using JMS temporary destinations, see Using Temporary Destinations in Programming WebLogic JMS.

 

No Mixing of JMS SAF Client Contexts and Server Contexts

When items returned from the JMS SAF client naming context are used in conjunction with items returned from a server initial context, the JMS API fails with a reasonable exception message. Likewise, when items returned from a server initial context is used in conjunction with items returned from the JMS SAF client naming context, the JMS API fails with a reasonable exception message.

 

Using Transacted Sessions With JMS SAF Clients

Transacted sessions are supported with JMS SAF clients, but Client SAF operations do not participate in any global (XA) transactions. If there is an XA transaction, the message send operation is done outside the XA transaction and no exception is thrown.

 

JMS SAF Client Interoperability Guidelines

The interoperability guidelines apply when using the JMS SAF client to forward messages to server-side WebLogic JMS destinations.

 

Java Runtime

Each client machine must have J2SE 1.4 runtime or higher installed.

 

WebLogic Server Versions

The WebLogic JMS SAF client system only works with WebLogic Server 9.2 and later.

On the client-side, the WebLogic JMS SAF client code must be running with WebLogic Server JAR files that are release 9.2 or later. For more information on installing WebLogic Server JAR files, see Installing the JMS SAF Client JAR Files on Client Machines.

 

Tuning JMS SAF Clients

JMS SAF clients can take advantage of the tuning parameters available with the server-side SAF service. For more information, see Tuning WebLogic JMS Store-and-Forward in the WebLogic Performance and Tuning Guide.

 

Limitations of Using the JMS SAF Client

In addition to the field-level limitations discussed in Valid SAF Elements for JMS SAF Client Configurations, the following limitations apply to the JMS SAF client: