Package org.czeal.jsonfilter

Class InclusionFilter

  • All Implemented Interfaces:
    Filter
    public class InclusionFilter
extends Object
implements Filter
    A filter implementation that includes only specified JSON elements from a given JSON element. The inclusion rules are defined using a comma-separated string where nested fields can be specified using parentheses.

    Example of node specification:

    • "a,b(c,d)" - Includes only the top-level elements a and sub-elements c and d inside b.
    • "x(y)" - Includes only x.y but keeps other elements in x.

    If the input JSON is a primitive value or null, it is returned as is.

    Author:
    Hideki Ikeda

    • Constructor Detail

      • InclusionFilter

        public InclusionFilter()

    • Method Detail

      • apply

        public com.google.gson.JsonElement apply​(com.google.gson.JsonElement source,
                                         String nodes)
        Creates a JSON element by extracting JSON elements from the given JSON element based on the nodes string. The nodes are provided as a comma-separated string, where each node defines a portion of the JSON structure to include in the result. Nested fields can be specified using parentheses. For example, a nodes string might be "a,b(c,d)", indicating that the output should include the top-level element a and the element b with only the c and d sub-nodes.

        Examples:

        Example 1: For a flat JSON object

        
 JsonElement jsonElement = JsonParser.parseString("{\"a\":1,\"b\":2,\"c\":3}");

 JsonElement filtered = new InclusionFilter().apply(jsonElement, "a,b");

 System.out.println(filtered); // {"a":1,"b":2}

        Example 2: For a nested JSON object

        
 JsonElement jsonElement = JsonParser.parseString("{\"x\":{\"y\":{\"z\":5},\"w\":10},\"v\":20}");

 JsonElement filtered = new InclusionFilter().apply(jsonElement, "x(y)");

 System.out.println(filtered); // {"x":{"y":{"z":5}}}

        Example 3: For nested arrays

        
 JsonElement jsonElement = JsonParser.parseString("[[[{\"name\":\"john\",\"type\":0}]]]");

 JsonElement filtered = new InclusionFilter().apply(jsonElement, "name");

 System.out.println(filtered); // [[[{"name":"john"}]]]

        If the source JSON is a primitive or null, filtering is not applicable and the deep copy of the source is returned unmodified.

        Specified by:
        apply in interface Filter
        Parameters:
        source - The source JSON element to filter, which should be either a JSON object or an array.
        nodes - A comma-separated string defining allowed JSON nodes to include. Each node can specify nested fields using parentheses.
        Returns:
        A new JsonElement instance built by filtering the source based on the given nodes.
        Throws:
        IllegalArgumentException - If the source JSON element is an invalid JSON element.