Synapse Expressions Sample¶

This sample contains a REST API that demonstrates the use of Synapse Expressions in WSO2 Micro Integrator.

The API have the following resources dedicated to explain different usages of Synapse Expressions.

Literal values
Accessing values from payloads, variables, properties etc.
Operators
Conditional expressions
Filter expressions
Functions
XPath expressions

Note

Above sections are explained in detail in the Synapse Expressions Syntax guide.

Deploying the sample¶

Open the sample by clicking on the Synapse Expressions card.
Give a folder location to save the sample.
Build and run the sample in your Micro Integrator.

Invoking the sample¶

You can download the Postman collection for this sample from here.

Literal values¶

If you are using the Postman collection, you can invoke the Literals resource.

If you are using cURL, you can invoke the API using the following command.

curl --location 'http://localhost:8290/test/literals'

You will get the following output in the server console.

Literal values in Synapse Expressions
Hello World
2025
true

Accessing values from payloads, variables, properties etc.¶

If you are using the Postman collection, you can invoke the Accessing values resource.

If you are using cURL, you can invoke the API using the following command.

curl --location 'http://localhost:8290/test/accessingValues/books?qParamKey=fiction' \
--header 'Content-Type: application/json' \
--data '{
    "books": [
        {
            "category": "fiction",
            "author": "Herman Melville",
            "title": "Moby Dick",
            "isbn": "0-553-21311-3",
            "price": 8.99
        },
        {
            "category": "fiction",
            "author": "J.R.R. Tolkien",
            "title": "The Lord of the Rings",
            "isbn": "0-395-19395-8",
            "price": 22.99
        },
        {
            "category": "fiction",
            "author": "Harper Lee",
            "title": "To Kill a Mockingbird",
            "price": 10.99
        },
        {
            "category": "fiction",
            "author": "George Orwell",
            "title": "Animal Farm",
            "price": 7.99
        }
    ]
}'

You will get a console output similar to follows

Accessing values in Synapse Expressions
Access paylod values : ["Moby Dick","The Lord of the Rings","To Kill a Mockingbird","Animal Farm"]
Access variable : [8.99,22.99,10.99,7.99]
Access headers : application/json
...

Operators¶

If you are using the Postman collection, you can invoke the Operators resource.

If you are using cURL, you can invoke the API using the following command.

curl --location 'http://localhost:8290/test/operators' \
--header 'Content-Type: application/json' \
--data '{
    "num1" : 10,
    "num2" : 5,
    "num3" : -2,
    "num4" : 6
}'

You will get a console output similar to the following:

Operations in Synapse Expressions

Arithmetic Operations
Addition : 15
Subtraction : 5
Multiplication : -20
...

Conditional expressions¶

If you are using the Postman collection, you can invoke the Conditional resource.

If you are using cURL, you can invoke the API using the following command:

curl --location 'http://localhost:8290/test/conditional' \
--header 'Content-Type: application/json' \
--data '{
    "age" : 17
}'

You will get the following output in the server console.

Conditional Expressions
Child

Filter expressions¶

If you are using the Postman collection, you can invoke the Filters resource.

If you are using cURL, you can invoke the API using the following command:

curl --location 'http://localhost:8290/test/filters' \
--header 'Content-Type: application/json' \
--data '{
    "store": {
      "books": [
        {
          "category": "reference",
          "author": "Nigel Rees",
          "title": "Sayings of the Century",
          "price": 8.95
        },
        {
          "category": "fiction",
          "author": "Herman Melville",
          "title": "Moby Dick",
          "isbn": "0-553-21311-3",
          "price": 8.99
        },
        {
          "category": "fiction",
          "author": "J.R.R. Tolkien",
          "title": "The Lord of the Rings",
          "isbn": "0-395-19395-8",
          "price": 22.99
        },
        {
          "category": "fiction",
          "author": "Harper Lee",
          "title": "To Kill a Mockingbird",
          "price": 10.99
        },
        {
          "category": "fiction",
          "author": "George Orwell",
          "title": "Animal Farm",
          "price": 7.99
        },
        {
          "category": "biography",
          "author": "Anne Frank",
          "title": "The Diary of a Young Girl",
          "price": 6.99
        }
      ]
    },
    "expensive": 20
  }
'

You will get the following output in the server console.

Filter Expressions
Filter books of category 'biography' : [{"category":"biography","author":"Anne Frank","title":"The Diary of a Young Girl","price":6.99}]
Filter expensive books : [{"category":"fiction","author":"J.R.R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}]

Functions¶

If you are using the Postman collection, you can invoke the Functions resource.

If you are using cURL, you can invoke the API using the following command:

curl --location 'http://localhost:8290/test/functions' \
--header 'Content-Type: application/json' \
--data '{
    "text" : "Hello World",
    "trimText" :"     Hello    ",
    "num1" : -2.6,
    "num2" : 1.2345,
    "num3" : 100,
    "encoded" : "SGVsbG8gV29ybGQ=",
    "url" : "search?query=hello world&category=books&sort=price&page=1",
    "encodedURL" : "https://example.com/search?query=hello%20world&category=books&sort=price&page=1",
    "array" : [1,2,3],
    "object" : "{\"a\":\"b\"}",
    "convert_int" : "123",
    "convert_float" : "3.14",
    "convert_boolean" : "true",
    "convert_array" : "[1,\"Hello\",true]"
}'

You will get a console output similar to the following:

Functions in Synapse Expressions

String functions
Length : 11
Upper case : HELLO WORLD
Lower case : hello world
Substring :  World , llo

XPath expressions¶

If you are using the Postman collection, you can invoke the XPath resource.

If you are using cURL, you can invoke the API using the following command:

curl --location 'http://localhost:8290/test/xpath' \
--header 'Content-Type: application/xml' \
--data '<?xml version="1.0" encoding="UTF-8"?>
<root xmlns:a="http://namespaceA.com" xmlns:b="http://namespaceB.com">
    <a:parent>
        <b:child>
            <a:value>Value1</a:value>
        </b:child>
    </a:parent>
</root>'

You will get the following output in the server console.

XPATH functions
Accessing XML elements with namespaces : Value1