Example index

Setting Attributes Programatically

There is one program source file:


The example source code is organized as a Java class.

Configuring Context Attributes

In order to configure a UM context, an attributes object must first be created:

00024              LBMContextAttributes ctxAttr = new LBMContextAttributes();
00025              ctxAttr.setObjectRecycler(objRec, null);
00027              /* Modify resolver address by setting attributes */
00028              ctxAttr.setValue("resolver_multicast_address", "");

When an attributes object is created, a snapshot of the current configuration is loaded. In this example, the attributes contained in ctxAttr will be default. This is not always the case. If a configuration file has been loaded via the API, or set via environmental variables, these values may not be default.

These attributes will be used to configure a new context:

00030              ctx = new LBMContext(ctxAttr);

The constructor is passed a reference to the attributes object, letting the UM library know that it should configure the new context with these specific attributes.

Configuring Source Attributes

Sources are configured slightly differently. To create a source, a topic ojbect is required. So instead of passing the attributes object directly into the sources constructor, it is used to initialized a topic object:

00032              srcAttr = new LBMSourceAttributes();
00033              srcAttr.setObjectRecycler(objRec, null);
00035              /* Set configuration value using strings */
00036              srcAttr.setValue("transport", "lbtrm");
00038              /* The Java API only accepts string values. ints, for example */
00039              /* must be converted to strings */
00040              desPort = 14001;
00041              srcAttr.setValue("transport_lbtrm_destination_port", Integer.toString(desPort));
00043              /* Create topic for the first source with configured attributes */
00044              topic1 = new LBMTopic(ctx, "test.topic1", srcAttr);
This topic object is then used to initialize a source with the given set of attributes.
00045              src1 = new LBMSource(ctx, topic1);

In this example a second source is configured to use a different transport_lbtrm_destination_port. It is common for topics to be programatically configured to use different settings, and this example demonstrates how the same source attributes object can be used to configure 2 different sources with their own unique set of attributes:

00047              desPort = 14002;
00048              srcAttr.setValue("transport_lbtrm_destination_port", Integer.toString(desPort));
00050              /* Create second topic and source using modified configuration values */ 
00051              topic2 = new LBMTopic(ctx, "test.topic2", srcAttr);
00052              src2 = new LBMSource(ctx, topic2);

Cleaning Up Attributes

In object oriented languages, UM uses slightly different aproach to cleaning up attributes. Due to shared resources with the unerdlying native C library, the .close method is used to clean up native memory allocation. *Attributes objects are different from other UM objects in that they do not have .close() methods. In order to clean them up, they can be assigned an LBMObjectRecycler which can be .close()d. This is done via the setObjectRecycler method as shown below:

00062              objRec.close();
00063              src2.close();
00064              src1.close();
00065              ctx.close();