A Java utility used to FLATTEN nested JSON objects and even more to UNFLATTEN it back
##Purpose
Converts a nested JSON
{ "a": { "b": 1, "c": null, "d": [false, true] }, "e": "f", "g": 2.3 }
into a flattened JSON
{ "a.b": 1, "a.c": null, "a.d[0]": false, "a.d[1]": true, "e": f, "g": 2.3 }
or a Java Map
{a.b=1, a.c=null, a.d[0]=false, a.d[1]=true, e=f, g=2.3}
##Maven Repo
<dependency>
<groupId>com.github.wnameless</groupId>
<artifactId>json-flattener</artifactId>
<version>0.2.4</version>
</dependency>##Quick Start
String json = "{ \"a\" : { \"b\" : 1, \"c\": null, \"d\": [false, true] }, \"e\": \"f\", \"g\":2.3 }";
Map<String, Object> flattenJson = JsonFlattener.flattenAsMap(json);
System.out.println(flattenJson);
// Output: {a.b=1, a.c=null, a.d[0]=false, a.d[1]=true, e=f, g=2.3}
String jsonStr = JsonFlattener.flatten(json);
System.out.println(jsonStr);
// Output: {"a.b":1,"a.c":null,"a.d[0]":false,"a.d[1]":true,"e":"f","g":2.3}
String nestedJson = JsonUnflattener.unflatten(jsonStr);
System.out.println(nestedJson);
// {"a":{"b":1,"c":null,"d":[false,true]},"e":"f","g":2.3}
// Support JSON keys which contain dots or square brackets
String flattendJsonWithDotKey = JsonFlattener.flatten("[{\"a.a.[\":1},2,{\"c\":[3,4]}]");
System.out.println(flattendJsonWithDotKey);
// Output: {"[0][\"a.a.[\"]":12,"[1]":2,"[2].c[0]":3,"[2].c[1]":4}
String nestedJsonWithDotKey = JsonUnflattener.unflatten(
"{\"[1][0];\":2,\"[0]\":1,\"[1][1]\":3,\"[2]\":4,\"[3][\\\"ab.c.[\\\"]\":5}");
System.out.println(nestedJsonWithDotKey);
// Output: [1,[2,3],4,{"ab.c.[":5}]##New Features (since v0.2.0) ###FlattenMode
String json = "{\"abc\":{\"def\":[1,2,{\"g\":{\"h\":[3]}}]}}";
// FlattenMode.NORMAL(default) - flatten everything
System.out.println(new JsonFlattener(json).withFlattenMode(FlattenMode.NORMAL).flatten());
// {"abc.def[0]":1,"abc.def[1]":2,"abc.def[2].g.h[0]":3}
// FlattenMode.KEEP_ARRAYS - flatten all except arrays
System.out.println(new JsonFlattener(json).withFlattenMode(FlattenMode.KEEP_ARRAYS).flatten());
// {"abc.def":[1,2,{"g.h":[3]}]}
// When the flattened outcome can NOT suit in a Java Map, it will still be put in the Map with "root" as its key.
Map<String, Object> map = new JsonFlattener("[[123]]").withFlattenMode(FlattenMode.KEEP_ARRAYS).flattenAsMap();
System.out.println(map.get("root"));
// [[123]]###StringEscapePolicy
String json = "{\"abc\":{\"def\":\"太極\\t\"}}";
// StringEscapePolicy.NORMAL(default) - escape only speacial characters
System.out.println(new JsonFlattener(json).withStringEscapePolicy(StringEscapePolicy.NORMAL).flatten());
// {"abc.def":"太極\t"}
// StringEscapePolicy.ALL_UNICODES - escape speacial characters and unicodes
System.out.println(new JsonFlattener(json).withStringEscapePolicy(StringEscapePolicy.ALL_UNICODES).flatten());
// {"abc.def":"\u592A\u6975\t"}###Separator
// JsonFlattener - separator can be changed from dot(.) to an arbitrary character
String json = "{\"abc\":{\"def\":123}}";
System.out.println(new JsonFlattener(json).withSeparator('*').flatten());
// {"abc*def":123}
// JsonUnflattener - if a special separator is using, it should be set into the unflattener as well
json = "{\"abc*def\":123}";
System.out.println(new JsonUnflattener(json).withSeparator('*').unflatten());
// {"abc":{"def":123}}###PrintMode
String json = "{\"abc\":{\"def\":123}}";
// JsonFlattener
// PrintMode.MINIMAL(default)
System.out.println(new JsonFlattener(json).withPrintMode(PrintMode.MINIMAL).flatten());
// {"abc.def":123}
// PrintMode.REGULAR
System.out.println(new JsonFlattener(json).withPrintMode(PrintMode.REGULAR).flatten());
// { "abc.def": 123 }
// PrintMode.PRETTY
System.out.println(new JsonFlattener(json).withPrintMode(PrintMode.PRETTY).flatten());
// {
// "abc.def": 123
// }
// JsonUnflattener
// PrintMode.MINIMAL(default)
json = "{\"abc.def\":123}";
System.out.println(new JsonUnflattener(json).withPrintMode(PrintMode.MINIMAL).unflatten());
// {"abc":{"def":123}}
// PrintMode.REGULAR
System.out.println(new JsonUnflattener(json).withPrintMode(PrintMode.REGULAR).unflatten());
// {"abc": {"def": 123}}
// PrintMode.PRETTY
System.out.println(new JsonUnflattener(json).withPrintMode(PrintMode.PRETTY).unflatten());
// {
// "abc": {
// "def": 123
// }
// }