CoreDX DDS Java Reference Manual
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The DataReader entity allows the application to subscribe to and read data. More...
The DataReader entity allows the application to subscribe to and read data.
The DataReadre is an abstract class that is extended to support a particular data type required by the application. A DataReader is associated with a single TopicDescription (Topic, MultiTopic, or ContentFilteredTopic).
| QueryCondition create_querycondition | ( | long | sample_states, |
| long | view_states, | ||
| long | instance_states, | ||
| String | query_expression, | ||
| Vector | query_parameters | ||
| ) |
Creates a DDS_QueryCondition.
The returned QueryCondition can be used as an argument to read_w_condition() or take_w_condition().
Public Member Functions inherited from The \b query_expression is an SQL like condition expression, and \b query_parameters
provide optional parameters that are referenced by the \b query_expression.
The syntax of the query expression is similar to the WHERE clause in SQL. For example
"x<4" is a valid query expression. It would test that data member 'x' is less than value '4'.
If the query expression evaluates to TRUE, then the data sample will be available, otherwise
the data sample will be 'filtered' (excluded).
CoreDX %DDS supports the '<b>LIKE</b>' operator (and NOT LIKE) for regular expression string matching.
The pattern string in a LIKE clause can contain '%' to match zero or more characters, '_' to
match a single character, or '[<characters>]' to match a range of characters.
CoreDX %DDS also includes support for the '<b>IN</b>' operator. This provides a very powerful mechanism
for testing that a value appears in a set of values. For example "symbol IN ('ge', 'msft', 'ibm')"
will select all samples that have a symbol value of 'ge', 'msft', or 'ibm'. This could also be
written as a series of equality tests combined with the OR operator; however, the IN operator
is much more efficient. A query that matches on several hundred or even thousands of values
can be implemented very efficiently using the 'IN' operator.
The query_expression can refer to parameters. The syntax for paramters is the percent sign '%'
followed by a number. The number is the index of the paramter in the \b query_paramters sequence.
Parameters are counted starting at zero. So, "%0" refers to the first parameter, and "%4"
refers to the fifth paramter. Using this syntax, the expression "x<%0" would test the value
of 'x' against the first parameter in the sequence.
| ReadCondition create_readcondition | ( | long | sample_states, |
| long | view_states, | ||
| long | instance_states | ||
| ) |
Creates a ReadCondition that is associated with this DataReader. The returned condition can be added to a WaitSet or used in a call to the specialized read() or take() operations. For example see DataReaderFoo.read_w_condition();
| ReturnCode_t delete_contained_entities | ( | ) |
This operation deletes all the ReadCondition and QueryCondition objects previously created by means of the DataReader.create_readcondition() and DataReader.create_querycondition() operations.
After successful execution, the application may delete the Publisher by calling Subscriber.delete_datareader().
If any of the objects cannot be deleted, this routine will return ReturnCode_t.RETCODE_PRECONDITION_NOT_MET.
| ReturnCode_t delete_readcondition | ( | ReadCondition | rc | ) |
Destroys a ReadCondition (or QueryCondition). The provided a_condition must have been previously created via a call to DataReader.create_readcondition() or DataReader.create_querycondition().
The a_condition argument must belong to DataReader dr. Otherwise, the error ReturnCode_t.RETCODE_PRECONDITION_NOT_MET will be returned.
If the DataReader is actively processing the ReadCondition, this routine will return ReturnCode_t.RETCODE_ERROR; in this case, the delete_readcondition() call should be re-tried.
| ReturnCode_t enable | ( | ) |
Enables the DataReader. A DataReader is created either enabled or not based on the SubscriberQos setting entity_factory. When a DataReader is not enabled, only the following sub-set of all DataReader operations are legal:
Any other operation may return the ReturnCode_t.RETCODE_NOT_ENABLED error. DataReader_enable() may be called on an already enabled DataReader [it will have no effect].
| DataReaderListener get_listener | ( | ) |
This operation returns the currently installed DataReaderListener.
| ReturnCode_t get_liveliness_changed_status | ( | LivelinessChangedStatus | status | ) |
Provides access to the current LivelinessChangedStatus of the DataReader. As a side-effect, this routine will reset the total_count_change status field to zero.
| ReturnCode_t get_matched_publication_data | ( | PublicationBuiltinTopicData | publication_data, |
| InstanceHandle_t | publication_handle | ||
| ) |
This operation returns data that describes a particular matched DataWriter identified by publication_handle. An appropriate handle can be obtained through a call to DataReader.get_matched_publications().
If publication_handle does not identify a currently matched DataWriter, this routine will return ReturnCode_t.RETCODE_PRECONDITION_NOT_MET.
| ReturnCode_t get_matched_publications | ( | InstanceHandleSeq | publication_handles | ) |
This operation retrieves the list of DataWriters currently matched with this DataReader dr. This list will include the handles that identify DataWriters which have matching Topic and compatible QoS with DataReader.
If a DataWriter has been ignored by a call to DomainParticipant.ignore_publication(), then it will not appear in the list.
| publication_handles | A vector that will be populated with InstanceHandle_t(s). |
| ReturnCode_t get_qos | ( | DataReaderQos | qos | ) |
Returns the current DataReaderQos settings held in the DataReader dr. This routines copies data from the DataReader QoS properties into qos.
| ReturnCode_t get_requested_deadline_missed_status | ( | RequestedDeadlineMissedStatus | status | ) |
Provides access to the current RequestedDeadlineMissedStatus of the DataReader. As a side-effect, this routine will reset the total_count_change status field to zero.
| ReturnCode_t get_requested_incompatible_qos_status | ( | RequestedIncompatibleQosStatus | status | ) |
Provides access to the current RequestedIncompatibleQosStatus of the DataReader. As a side-effect, this routine will reset the total_count_change status field to zero.
| ReturnCode_t get_sample_lost_status | ( | SampleLostStatus | status | ) |
Provides access to the current SampleLostStatus of the DataReader. As a side-effect, this routine will reset the total_count_change status field to zero.
| ReturnCode_t get_sample_rejected_status | ( | SampleRejectedStatus | status | ) |
Provides access to the current SampleRejectedStatus of the DataReader. As a side-effect, this routine will reset the total_count_change status field to zero.
| Subscriber get_subscriber | ( | ) |
Returns the Subscribier that contains DataReader dr.
| ReturnCode_t get_subscription_matched_status | ( | SubscriptionMatchedStatus | status | ) |
Provides access to the current SubscriptionMatchedStatus of the DataReader. As a side-effect, this routine will reset the total_count_change status field to zero.
| TopicDescription get_topicdescription | ( | ) |
Returns the TopicDescription associated with DataReader dr.
| ReturnCode_t set_listener | ( | DataReaderListener | new_listener, |
| long | mask | ||
| ) |
Installs a DataReaderListener on DataReader dr. Only one listener may be attached to a DataReader at a time. A call to set_listener() will replace any current listener with a_listener.
a_listener can be NULL, which indicates a listener that does nothing.
| ReturnCode_t set_qos | ( | DataReaderQos | qos | ) |
Sets the DataReaderQos values. These QoS values affect the behavior of the DataReader. This routine may fail if the provided qos argument is not internally consistent. In this case, ReturnCode_t.RETCODE_INCONSISTENT_POLICY will be returned, and no changes will be made to the DataReader QoS.
| ReturnCode_t wait_for_historical_data | ( | Duration_t | max_wait | ) |
This routine blocks until all 'historical' data is received.
| max_wait | The maximum amount of time to block while waiting. Can be set to { INFINITE_SEC, INFINITE_NSEC } |