JarCastingjson
json is small library for manipulating json data structures.It is useful, when you need to create small json data directly (without java binding).
It is possible to parse json string info java tree like data structure and build java tree like data structure and convert them into json string.
Data structures
All provided data structures are defined by set of interfaces. Library provides implementation for all of those interfaces. Most of them can be instantiated using factory class JsonFactory.
JsonValue
Generic json value. It is abstract representation of one of JsonObject, JsonArray or one onf JsonLiteral instance. It is not possible to instantiate this type of object.
JsonObject
json object representation with set of named attrinutes. (JsonFactory.object())
JsonArray
json array representation with set of json values. (JsonFactory.array()) .
JsonLiteral
Generic json literal value. There are set of subclasses of this class.
- JsonBoolLiteral - boolean json literal (true, false) (JsonFactory.boolLiteral())
- JsonExpLiteral - exponential json literal (12E-1, -2E12, ...) (JsonFactory.expLiteral())
- JsonFracLiteral - fraction json literal (12.3, -33.23, ...) (JsonFactory.fracLiteral())
- JsonIntLiteral - int json literal (1, 2212342, ...) (JsonFactory.intLiteral())
- JsonNullLiteral - null json literal (null) (JsonFactory.nullLiteral())
- JsonStringLiteral - string json literal ("foo", "bar", ...) (JsonFactory.stringLiteral())
Json parsing to tree
You can parse json strings easily by calling
String jsonvalue = .....
JsonValue value = JsonParser.parse(jsonvalue);
or
Reader jsonvalue = .....
JsonValue value = JsonParser.parse(jsonvalue);
Json to string conversion
To obtain string representation of json data structure you can call
JsonValue jsonvalue = .....
String onelinestring = jsonvalue.toCompactString();
String indendedstirng = jsonvalue.toPrettyString("\t");
Building json structure
To create simple instances of json data structures you can use JsonFactory class. Than it is possible to use appropriate API from JsonObject or JsonArray to build whole json data structure tree.
This is simple example of such construction of following data structure
{
"name" : "John",
"surname" : "Smith",
"titles" : [
"Mudr.",
"Phd."
]
}
JsonObject person = JsonFactory.object()
.add("name", JsonFactory.stringLiteral("John"))
.add("surname", JsonFactory.stringLiteral("Smith"))
.add("titles", JsonFactory.array()
.add(JsonFactory.stringLiteral("Mudr."))
.add(JsonFactory.stringLiteral("Phd."))
);
Searching json structure
If you have json structure and you can identify some substructure by path, you can find them by calling
JsonObject o = ...
JsonValue v = o.findFirst(SimplePathMatcher.instance("menu", "popup", "menuitem", "*", "value"));
List<JsonValue> list = o.findAll(SimplePathMatcher.instance("menu", "popup", "menuitem", "*", "value"));
Character '*' stands for any path item.
If you search for literal values you can call
JsonObject o = ...
Stirng v = o.findFirstLiteral(SimplePathMatcher.instance("menu", "popup", "menuitem", "*", "value"));
List<String> list = o.findAllLiterals(SimplePathMatcher.instance("menu", "popup", "menuitem", "*", "value"));
If you search for literal from big structure and you don;t want to parse if first. values you can call following code. But it is faster only for special cases
String value = LiteralParser.firstAsString(
StringSource.instance(json)
, SimplePathMatcher.instance("*", "cars", "*"));
Wild Searching json structure
It is possible to use WildPathMatcher for searching. In this case there are two types of path elements.
- single wild path element - it is direct name or you van use * and ? to represent more/single characters in single path element. (like "car-*" or "car-??")
- multiple wild path element "**" - it represents any sequence of path elements. JsonObject Example:
List<String> list = o.findAllLiterals(WPM.fromPath("**/person-*/surname"));
Templating
JsonValue can be used as parameter for some template frameworks like freemarker. Method JsonValue.asTemplateParam() converts JsonValue to
- JsonObject to read only Map
- JsonArray to read only List
- JsonLiteral to its internal value (String, Long, BigDecimal, Boolean) So it is possible to use it directly as parameter for template framework.
Example of data
{
"title": "Ing.",
"name": "Jano",
"surname": "Novotny",
"contractid": "1212321",
"raw" : {
"simple": "12321",
"complex" : {"sub1": "2222"},
"list" : ["4444", "5555"],
"persons" : [
{"name":"Jano"},
{"name":"Peter"},
{"name":"Juraj"}
]
}
}
Example of freemarker template
Hello ${name!} ${surname!"Dear client"} ${title}
Your contract ${contractid} is registered.
Example of data ${raw.complex.sub1}
Simple list
<#list raw.list as string>
${string}
</#list>
Complex list
<#list raw.persons as person>
person: ${person.name}
</#list>
Result
Hello Jano Novotny Ing.
Your contract 1212321 is registered.
Example of data 2222
Simple list
4444
5555
Complex list
person: Jano
person: Peter
person: Juraj
Formatting without complete parsing
If you have a json structure and you want to transform it to noindent form or to indent form and you don't want to parse it You can use simplified formatting. It works for well formated json structures only.
The class don't make full parsing of input. Implementation just tries to recognize blank characters and string literals and transform them somehow.
String json = ...
String formatedJson = JsonFormat.from(json).indent(2, ' ').toText();
String formatedJson = JsonFormat.from(json).noindent().toText();
Or you can use Reader/Writer version
Reader jsonReader = ...
Writer jsonWriter = ...
String formatedJson = JsonFormat.from(jsonReader).indent(2, ' ').toWriter(jsonWriter);
String formatedJson = JsonFormat.from(jsonReader).noindent().toWriter(jsonWriter);
There is also possible to cut string literals to defined length. This can be useful for logging json which contains very long data (like binaries), which are not necessary to log fully.
String json = ...
String formatedJson = JsonFormat.from(json).indent(2, ' ').cutStringLiterals(50).toText();
The result can looks like
{
"name" : "image.jpg",
"bytes" : "VGhlcmUgaXMgYWxzbyBwb3NzaWJsZSB0byBjdXQgc3RyaW5nIGxpdG ..."
}
Maven usage
<dependency>
<groupId>com.github.antonsjava</groupId>
<artifactId>json</artifactId>
<version>1.9</version>
</dependency>