A Java utility used to FLATTEN nested JSON objects and even more to UNFLATTEN it back.
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}
<dependency>
<groupId>com.github.wnameless.json</groupId>
<artifactId>json-flattener</artifactId>
<version>0.8.1</version>
</dependency>Since v0.5.0, Java 8 required.
Since v0.6.0, StringEscapePolicy.DEFAULT, which escapes all special characters but slash('/') and Unicode, becomes the default setting.
! Since v0.7.0, group ID is changed from [com.github.wnameless] to [com.github.wnameless.json].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}]JsonValueBase<?> jsonVal;
// JacksonJsonValue, which is provided by json-base lib, can wrap Jackson jsonNode to JsonValueBase
jsonVal = new JacksonJsonValue(jsonNode);
Map<String, Object> flattenJson = JsonFlattener.flattenAsMap(jsonVal);String json = "{\"ary\":[true,[1, 2, 3],false]}";
System.out.println(new JsonFlattener(json).withFlattenMode(FlattenMode.KEEP_PRIMITIVE_ARRAYS).flatten());
// {"ary[0]":true,"ary[1]":[1,2,3],"ary[2]":false}This mode only keeps arrays which contain only primitive types(strings, numbers, booleans, and null).
JsonValueBase<?> jsonVal;
// GsonJsonValue, which is provided by json-base lib, can wrap Gson jsonElement to JsonValueBase
jsonVal = new GsonJsonValue(jsonElement);
// JacksonJsonValue, which is provided by json-base lib, can wrap Jackson jsonNode to JsonValueBase
jsonVal = new JacksonJsonValue(jsonNode);
// MinimalJsonValue, which is provided by json-base lib, can wrap MinimalJson jsonValue to JsonValueBase
jsonVal = new MinimalJsonValue(jsonValue);
// You can also implement the JsonValueBase interface for any JSON lib you are using
jsonVal = new CostumeJsonValue(yourJsonVal);
new JsonFlattener(jsonVal);StringEscapePolicy.ALL // Escapes all JSON special characters and Unicode
StringEscapePolicy.ALL_BUT_SLASH // Escapes all JSON special characters and Unicode but slash('/')
StringEscapePolicy.ALL_BUT_UNICODE // Escapes all JSON special characters but Unicode
StringEscapePolicy.ALL_BUT_SLASH_AND_UNICODE // Escapes all JSON special characters but slash('/') and Unicode
StringEscapePolicy.DEFAULT // Escapes all JSON special characters but slash('/') and Unicodepublic class MyStringEscapePolicy implements CharSequenceTranslatorFactory { ... }StringEscapePolicy can be customized by implementing the CharSequenceTranslatorFactory interface.
For example, if you don't want the slash(/) and backslash(\) to be escaped:
new JsonFlattener(YOUR_JSON)
.withStringEscapePolicy(new CharSequenceTranslatorFactory() {
@Override
public CharSequenceTranslator getCharSequenceTranslator() {
return new AggregateTranslator(
new LookupTranslator(new HashMap<CharSequence, CharSequence>() {
private static final long serialVersionUID = 1L;
{
put("\"", "\\\"");
// put("\\", "\\\\");
// put("/", "\\/");
}
}), new LookupTranslator(EntityArrays.JAVA_CTRL_CHARS_ESCAPE));
}
});String json = "{\"abc\":{\"def\":[123]}}";
System.out.println(new JsonFlattener(json).withFlattenMode(FlattenMode.MONGODB).flatten());
// {"abc.def.0":123}
json = "{\"abc.def.0\":123}";
System.out.println(new JsonUnflattener(json).withFlattenMode(FlattenMode.MONGODB).unflatten());
// {"abc":{"def":[123]}}
// With FlattenMode.MONGODB, separator can still be changed
json = "{\"abc\":{\"def\":[123]}}";
System.out.println(new JsonFlattener(json).withFlattenMode(FlattenMode.MONGODB).withSeparator('*').flatten());
// {"abc*def*0":123}
json = "{\"abc*def*0\":123}";
System.out.println(new JsonUnflattener(json).withFlattenMode(FlattenMode.MONGODB).withSeparator('*').unflatten());
// {"abc":{"def":[123]}}String json = "{\"abc\":{\"de.f\":123}}";
JsonFlattener jf = new JsonFlattener(json).withFlattenMode(FlattenMode.MONGODB);
// This will throw an exception because FlattenMode.MONGODB won't support separator(.) in the key
jf.flatten();
// KeyTransformer can be used to manipulate keys before flattening
KeyTransformer kt = new KeyTransformer() {
@Override
public String transform(String key) {
return key.replace('.', '_');
}
};
jf.withKeyTransformer(kt);
System.out.println(jf.flatten());
// {"abc.de_f":123}
// KeyTransformer should be set in JsonUnflattener as well
json = "{\"abc.de_f\":123}";
kt = new KeyTransformer() {
@Override
public String transform(String key) {
return key.replace('_', '.');
}
};
JsonUnflattener ju = new JsonFlattener(json).withFlattenMode(FlattenMode.MONGODB).withKeyTransformer(kt);
System.out.println(ju.unflatten());
// {"abc":{"de.f":123}}// JsonFlattener - Brackets can be changed from square brackets([]) to any 2 arbitrary characters
String json = "{\"abc\":{\"def\":[123]}}";
System.out.println(new JsonFlattener(json).withLeftAndRightBrackets('(', ')').flatten());
// {"abc.def(0)":123}
// JsonUnflattener - if special brackets are using, it should be set into the unflattener as well
json = "{"abc.def(0)":123}";
System.out.println(new JsonUnflattener(json).withLeftAndRightBrackets('(', ')').unflatten());
// {"abc":{"def":[123]}}InputStream inputStream = new FileInputStream("simple.json");
Reader reader = new InputStreamReader(inputStream);
// Support Reader as input
JsonFlattener jf = new JsonFlattener(reader);
JsonUnflattener ju = new JsonUnflattener(reader);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]]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"}// 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}}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
// }
// }
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