JsonCBR (Json Content Based Routing) is used to route the incoming messages onto different destinations based on the content of the messages. The component creates a port for each of the JsonPath expressions specified and the messages satisfying the particular JsonPath expression is sent onto the respective port. In addition to these ports, an output port OUT_FALSE is created and messages whose content does not satisfy any of the JsonPath expressions will be sent out of this port. If more than one JsonPath expression is true, the message is sent on all the ports for which the JsonPath expression evaluates to true.
Configuration and Testing
The JsonCBR component can be configured using its Custom Property Sheet (CPS) wizard.
Figure 1: JsonPath(s) to be evaluated on the input messages
JsonPath
JsonPaths, based on which the routing is done, can be configured in JsonCBR Configuration Page. A valid JsonPath expression can be typed directly into the table.
For each configured JsonPath expression, an output port is created with the name provided in Port Name column, messages satisfying the given Json Objects condition are routed onto this port. Port names ON_EXCEPTION and OUT_FALSE are reserved and cannot be set in Port Name column.
- Json values which are passed in input Json object should only be any of these types: Long, Integer, Double, String, Boolean, BigInteger, BigDecimal, or another JsonPath.
| Comparison of the JSONPath syntax elements with its XPath counterparts | ||
| XPath | JSONPath | Description |
|---|---|---|
| / | $ | the root object/element |
| .. | n/a | parent operator |
| // | .. | recursive descent. JSONPath borrows this syntax from E4X. |
| * | * | wildcard. All objects/elements regardless their names. |
| @ | n/a | attribute access. JSON structures don't have attributes. |
| [] | [] | subscript operator. XPath uses it to iterate over element collections and for predicates. In Javascript and JSON, it is the native array operator. |
| | | [,] | Union operator in XPath results in a combination of node sets. JSONPath allows alternate names or array indices as a set. |
| n/a | [start:end:step] | array slice operator borrowed from ES4. |
| [] | ?() | applies a filter (script) expression. |
| n/a | () | script expression, using the underlying script engine. |
| () | n/a | grouping in XPath |
Operators
This field includes boolean operators like ==, !=, <, >, <=, >=, EXISTS, NONEXISTENT.
- The EXISTS operator returns true if the given JsonPath element exists in the input Json.
- While NONEXISTENT operator returns true when the given JsonPath element is nonexistent in the input Json.
Value
This field can be any of these types: Long, Integer, Double, String, Boolean, BigInteger, BigDecimal, and JsonPath. If a "$" precedes any value, then it is treated as a JsonPath. In this case, values of the two JsonPaths are compared for evaluating the expression.
Functional Demonstration
Scenario
JsonCBR is configured to filter the messages on the basis of book price in the input message. It is sent to one of the output ports depending on the JsonPath specified in the JsonCBR CPS.
Configure the JsonCBR as described in Configuration and Testing section and use feeder and display component to send sample input and check the response respectively.
Figure2: Demonstrating the Scenario with sample input and output
Sample Input
Sample Output
JsonOutput5: As $.store.book[0].price is 8.95 which is less than 18.4, the following output is displayed.
JsonOutput4: As $.store.book[1].title is "Sword of Honour", which is not equal to "abc", the following output is displayed.
JsonOutput3: As $.store.book[2].category is "fiction", which is equal to $.store.book[1].category, the following output is displayed.
JsonOutput2: As $.store.book[0].isbn does not exist, no output is displayed.
JsonOutput1: As some Json expressions were evaluated as 'true', the OUT_FALSE gets no output, hence no output is displayed.