如何在不解析为 Java 对象的情况下通过键获取动态 JSON 值？

Question

I am trying to get a json(has unknown template) value with a dynamic key like;

"user.specs.id"

Problem is my json structure is not static and because of this I can't parse it to a java Object or get its properties with Gson methods.

{
    "user": {
        "specs": {
            "id": 12222,
            "name": "foo"
        } 
    }
}

Is there a way to extract some data from any json with some key?

EDIT: I have a service method like;

public Object getValueByKey(String json, String key);

possible values for "json" param;

{"name": "test"}    //possible key "name"

{"user": {"id": 1232}}   //possible key "user.id"

{"cars": ["car1", "car2"]}   //possible key "cars[0]"

Answer 1

As @Michał Ziober's comment, you can simply achieve this by using JsonPath as follows:

Maven dependency

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.4.0</version>
</dependency>

Code snippet

public static void main(String[] args) {
    getValueByKey("{\"name\": \"test\"}", "name");
    getValueByKey("{\"user\": {\"id\": 1232}}", "user.id");
    getValueByKey("{\"cars\": [\"car1\", \"car2\"]}", "cars[0]");
}

public static void getValueByKey(String json, String key) {
    DocumentContext jsonContext = JsonPath.parse(json);
    Object value = jsonContext.read(key);
    System.out.println(value.toString());
}

Console output

11:38:50.840 [main] DEBUG cjjinternal.path.CompiledPath - Evaluating path: $['name']
test
11:38:50.855 [main] DEBUG cjjinternal.path.CompiledPath - Evaluating path: $['user']['id']
1232
11:38:50.855 [main] DEBUG cjjinternal.path.CompiledPath - Evaluating path: $['cars'][0]
car1

---

Read more

• JsonPath
• Introduction to JsonPath

Answer 2

I hope Property to json may help you you can refer For reference

Java Properties to JSON From 5 version is not backward compatible! The way creation of own json type resolvers has been changed! But if you used only simple uses cases, migration (from 4.0) should pass without problems.

How to generate JSON from Java properties?

You can generate Json from:

from Java properties (java.util.Properties)
from Map<String,String> (import java.util.Map)
from Map<String,Object> (import java.util.Map)
from InputStream with properties (java.io.InputStream)
from File with properties (java.io.File)
from given localization of properties file

below variable "properties" as one of the above types:

Maven dependency

 <dependency>
        <groupId>pl.jalokim.propertiestojson</groupId>
        <artifactId>java-properties-to-json</artifactId>
        <version>5.1.1</version>
    </dependency>

Simple Example code snippet:

import pl.jalokim.propertiestojson.util.PropertiesToJsonConverter;

...
// properties as Map<String,String>, java.util.Properties, java.io.InputStream
String json = new PropertiesToJsonConverter().convertToJson(properties);

// convert from file
String jsonFromProperties = new PropertiesToJsonConverter().convertPropertiesFromFileToJson("/home/user/file.properties");
String jsonFromProperties2 = new PropertiesToJsonConverter().convertPropertiesFromFileToJson(new File("/home/user/file.properties"));

// for map with Object as value, String as key
Map<String,Object> valuesAsObjectMap = new HashMap<>();
String jsonFromProperties3 = new PropertiesToJsonConverter().convertFromValuesAsObjectMap(valuesAsObjectMap);

// converter Instance can be gathered through PropertiesToJsonConverterBuilder class, it has a few method for customization
PropertiesToJsonConverter propsToJsonConverter = PropertiesToJsonConverterBuilder.builder().build();

example properties:

object.man.name=John
object.man.surname=Doe
object.type=SOMETYPE
object.doubleNumber=1.2345
object.integerNumber=12
object.booleanValue1=true
object.booleanValue2=True
object.booleanValue3=false
object2.simpleArray[0]=value1
object2.simpleArray[1]=value2
object2.simpleArray[2]=value3
object2.simpleArray[3]=value4
object2.objectArray[0].field1=value1
object2.objectArray[0].field2=value2
object2.objectArray[0].field3=value3
object3.arrayWithDelimeter=value1,value2,value3
object3.simpleString=stringValue
object3.emptyValue=
object3.nullValue=null
multiDimArray[0][0]=00
multiDimArray[0][1]=01
multiDimArray[1][0]=10
multiDimArray[1][1]=11
objectFromText={"fieldName": "value"}
objectFromText.anotherField=anotherField_value

anotherMultiDimArray=[[12, true], [12, 123]]