Using the JSON to Tuple Operator

Introduction

The JSON to Tuple Java operator converts JSON strings to StreamBase tuples. The operator's input port schema must contain a user defined string field that passes an JSON-encoded string to the operator. The operator parses the JSON string and populates tuple fields corresponding to the data found in the string. Each JSON string enqueued to the operator results in a single tuple emitted on its output port.

The operator's output schema determines the set of fields retrieved from the JSON string. The hierarchy of the fields in the schema must match that of the elements in the JSON string. Fields not present in the JSON string are set to null in the emitted tuple.

Properties View Settings

This section describes the properties you can set for a JSON to Tuple operator, using the various tabs of the Properties view in StreamBase Studio.

General Tab

Name: Use this required field to specify or change the name of this instance of this component, which must be unique in the current EventFlow module. The name must contain only alphabetic characters, numbers, and underscores, and no hyphens or other special characters. The first character must be alphabetic or an underscore.

Operator: A read-only field that shows the formal name of the operator.

Class: Shows the fully qualified class name that implements the functionality of this operator. If you need to reference this class name elsewhere in your application, you can right-click this field and select Copy from the context menu to place the full class name in the system clipboard.

Start with application: If this field is set to Yes (default) or to a module parameter that evaluates to true, this instance of this operator starts as part of the JVM engine that runs this EventFlow fragment. If this field is set to No or to a module parameter that evaluates to false, the operator instance is loaded with the engine, but does not start until you send an epadmin container resume command (or its sbadmin equivalent), or until you start the component with StreamBase Manager.

Enable Error Output Port: Select this check box to add an Error Port to this component. In the EventFlow canvas, the Error Port shows as a red output port, always the last port for the component. See Using Error Ports to learn about Error Ports.

Description: Optionally enter text to briefly describe the component's purpose and function. In the EventFlow canvas, you can see the description by pressing Ctrl while the component's tooltip is displayed.

Operator Properties Tab

Property Description
JSON Field Name The name of the field in the inbound tuple that contains the JSON string to convert to a tuple.
Enable Status Port If enabled (the default), status tuples are sent to port 2. If disabled, No status is reported. If disabled after previously being enabled, the arc connected to port 2 is deleted.
Enable Pass Through Fields If enabled, inbound tuples are copied to the outbound tuple.
Pass Through Fields Field Name The name of the field in the output tuple that is to contain a tuple of all the inbound data.
Log Level Controls the level of verbosity the adapter uses to send notifications to the console. This setting can be higher than the containing application's log level. If set lower, the system log level is used. Available values, in increasing order of verbosity, are: OFF, ERROR, WARN, INFO, DEBUG, TRACE.

JSON Tab

Property Description
Timestamp Format The format to use when converting time string values to timestamps.
Enable Loose Parsing If enabled, the parsing of the JSON string ignores fields that do not match the schema.

Edit Schema Tab

Use the Edit Schema tab to specify the schema of the output tuple for this adapter. For general instructions on using the Edit Schema tab, see the Properties: Edit Schema Tab section of the Defining Input Streams page.

Concurrency Tab

Use the Concurrency tab to specify parallel regions for this instance of this component, or multiplicity options, or both. The Concurrency tab settings are described in Concurrency Options, and dispatch styles are described in Dispatch Styles.

Caution

Concurrency settings are not suitable for every application, and using these settings requires a thorough analysis of your application. For details, see Execution Order and Concurrency, which includes important guidelines for using the concurrency options.

Operator Ports

The operator has one input port and two output ports to communicate with the surrounding application.

The JSON to Tuple operator's ports are used as follows:

  • DataIn: The JSON message to be converted to a tuple. The DataIn port can have any schema but must contain at least the field specified by the JSON Field Name property

  • TupleOut: This output port contains one or more top-level fields, each of which is used to receive the results of JSON string. If Enable Pass Through Fields is checked this port will also contain all the fields from the input port using the specified Pass Through Fields Field Name property as the name

  • Status: A tuple is emitted on this port when an attempt to convert an JSON string to a tuple fails. The Status port has the following schema:

    • type, string: Contains the following value describing the type of event that occurred:

      • Convert

    • action, string: Contains the following value indicating the conversion failed:

      • Failed

    • object, string: Contains a string representation of the input tuple.

    • message, string: Contains a human-readable description of the conversion failure.

    • time, timestamp: Contains the time of the conversion failure.

    • inputTuple, tuple: Contains a copy of the input tuple.