json-transform-plugin

This project contains few examples of json-transform plugins. json-transform can be extended by writing Java plugins for the following transform directives:

• $constraints ([code] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/main/java/com/pros/jsontransform/plugin/constraint) [examples] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/test/java/com/pros/jsontransform/plugin/constraint))
• $expression ([code] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/main/java/com/pros/jsontransform/plugin/expression) [examples] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/test/java/com/pros/jsontransform/plugin/expression))
• $include / $exclude ([code] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/main/java/com/pros/jsontransform/plugin/filter) [examples] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/test/java/com/pros/jsontransform/plugin/filter))
• $sort ([code] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/main/java/com/pros/jsontransform/plugin/sort) [examples] (https://github.com/PROSPricing/json-transform-plugin/tree/master/src/test/java/com/pros/jsontransform/plugin/sort))

How Plugins Work

As an example, the [FunctionAvgChildrenAge] (https://github.com/PROSPricing/json-transform-plugin/blob/master/src/main/java/com/pros/jsontransform/plugin/expression/FunctionAvgChildrenAge.java) plugin to the $expression directive works on a children array object with age information and calculates the average children age.

The source JSON

{
    "person":
    {
        "firstName":"Peter",
        "lastName":"Smith",
        "age":33,
        "children":
        [
            {"name":"Chris", "age":10},
            {"name":"Helen", "age":13}
        ],
        "carCount": 2,
        "boatCount": 0
    }
}

The transform map

See how the plugin is activated as part of the $expression directive. The plugin works in the context of the ObjectTransformer, which in this case is the root source object. The typical format for specifying plugins in the JSON transform map is as follows:

{"$plugin.class.name":{"$arg1":"...", "$arg2":123, ... }}

{
    "fullName":
    {
        "$value":"person|firstName",
        "$expression":
        [
            {"$append":{"$what":" "}},
            {"$append":{"$what":{"$value":"person|lastName"}}}
        ]
    },
    "avgChildrenAge":
    {
        "$expression":
        [
            {
                "$com.transform.plugin.expression.FunctionAvgChildrenAge":
                {
                    "$value":"person|children"
                }
            }
        ]
    }
}

The target JSON

The result of the transformation process is the target JSON.

{
  "fullName" : "Peter Smith",
  "avgChildrenAge" : 11.5
}

How To Use

After plugins are deployed to a suitable plugin folder, the ObjectTransformer is configured to load the plugin Java classes and perform the corresponding plugin functions.

ObjectMapper mapper = new ObjectMapper();
Properties properties = new Properties();
properties.setProperty("plugin.folder", "true");
ObjectTransformer transformer = new ObjectTransformer(properties, mapper);
JsonNode result = transformer.transform(jsonSource, jsonTransform);

How To Build

Before importing the project in your favourite IDE, building the source with gradle is recommended to retrieve the necessary dependencies as well as verify integrity of the code (unit tests). A prerequisite is that json-transform has been built with gradle and the corresponding jar file is available to the json-transform-plugin build. It may be necessary to modify the gradle/build.gradle to indicate the correct location of the json-transform.jar artifact. From the project root folder at the command line:

• cd gradle
• gradlew build

The gradle build follows the standard gradle java plugin setup:

• gradle/build/classes contains the compiled source
• gradle/build/libs contains the json-transform-plugin.jar
• <user home>/.gradle/caches/modules-2/files-2.1 contains the jar files json-transform-plugin depends on