В этом уроке мы покажем вам, как анализировать JSON с помощью JSON.simple
P.S Протестировано с помощью json-simple 3.1.0
1. Скачать JSON.simple
com.github.cliftonlabs json-simple 3.1.0
2. POJO + Js Приемлемый
2.1 Для преобразования объектов Java в/из JSON, JSON.simple требует, чтобы POJO реализовал Jsonable и переопределил toJSON()
package com.mkyong;
import com.github.cliftonlabs.json_simple.JsonObject;
import com.github.cliftonlabs.json_simple.Jsonable;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.math.BigDecimal;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
public class Staff implements Jsonable {
private String name;
private int age;
private String[] position;
private List skills;
private Map salary;
//..getters setters
@Override
public String toJson() {
final StringWriter writable = new StringWriter();
try {
this.toJson(writable);
} catch (final IOException e) {
}
return writable.toString();
}
@Override
public void toJson(Writer writer) throws IOException {
final JsonObject json = new JsonObject();
json.put("name", this.getName());
json.put("age", this.getAge());
json.put("position", this.getPosition());
json.put("skills", this.getSkills());
json.put("salary", this.getSalary());
json.toJson(writer);
}
}
3. Объекты Java для JSON
3.1 Преобразуйте объект Java в строку JSON и сохраните как .json файл.
package com.mkyong;
import com.github.cliftonlabs.json_simple.Jsoner;
import java.io.FileWriter;
import java.io.IOException;
import java.math.BigDecimal;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
public class JsonSimple1 {
public static void main(String[] args) throws IOException {
Staff staff = createStaff();
// Java objects to JSON String
String json = Jsoner.serialize(staff);
// pretty print
json = Jsoner.prettyPrint(json);
System.out.println(json);
// Java objects to JSON file
try (FileWriter fileWriter = new FileWriter("C:\\projects\\user3.json")) {
Jsoner.serialize(staff, fileWriter);
}
}
private static Staff createStaff() {
Staff staff = new Staff();
staff.setName("mkyong");
staff.setAge(38);
staff.setPosition(new String[]{"Founder", "CTO", "Writer"});
Map salary = new HashMap() {{
put("2010", new BigDecimal(10000));
put("2012", new BigDecimal(12000));
put("2018", new BigDecimal(14000));
}};
staff.setSalary(salary);
staff.setSkills(Arrays.asList("java", "python", "node", "kotlin"));
return staff;
}
}
Выход
{
"skills":[
"java",
"python",
"node",
"kotlin"
],
"name":"mkyong",
"position":[
"Founder",
"CTO",
"Writer"
],
"salary":{
"2018":14000,
"2012":12000,
"2010":10000
},
"age":38
}
{"skills":["java","python","node","kotlin"],"name":"mkyong","position":["Founder","CTO","Writer"],"salary":{"2018":14000,"2012":12000,"2010":10000},"age":38}
3.2 Преобразовать список объектов в массив JSON и сохранить как .json файл.
Staff staff = createStaff(); Listlist = Arrays.asList(createStaff(), createStaff()); // list of Java objects to JSON file try (FileWriter fileWriter = new FileWriter("C:\\projects\\user4.json")) { Jsoner.serialize(list, fileWriter); }
Выход
[
{"skills":["java","python","node","kotlin"],"name":"mkyong","position":["Founder","CTO","Writer"],"salary":{"2018":14000,"2012":12000,"2010":10000},"age":38},
{"skills":["java","python","node","kotlin"],"name":"mkyong","position":["Founder","CTO","Writer"],"salary":{"2018":14000,"2012":12000,"2010":10000},"age":38}
]
4. JSON для объектов Java
4.1 Чтобы преобразовать JSON обратно в объекты Java, нам нужна помощь из dozer сторонней библиотеки для копирования свойств объекта.
net.sf.dozer dozer 5.5.1
4.2 Строка JSON для объекта Java.
package com.mkyong;
import com.github.cliftonlabs.json_simple.JsonException;
import com.github.cliftonlabs.json_simple.JsonObject;
import com.github.cliftonlabs.json_simple.Jsoner;
import org.dozer.DozerBeanMapper;
import org.dozer.Mapper;
import java.io.FileReader;
import java.io.IOException;
public class JsonSimple2 {
public static void main(String[] args) throws IOException, JsonException {
// The file `user3.json` is generated from above example 3.1
try (FileReader fileReader = new FileReader(("C:\\projects\\user3.json"))) {
JsonObject deserialize = (JsonObject) Jsoner.deserialize(fileReader);
// need dozer to copy object to staff, json_simple no api for this?
Mapper mapper = new DozerBeanMapper();
// JSON to object
Staff staff = mapper.map(deserialize, Staff.class);
System.out.println(staff);
}
}
}
Выход
Staff{name='mkyong', age=38, position=[Founder, CTO, Writer],
skills=[java, python, node, kotlin], salary={2018=14000, 2012=12000, 2010=10000}}
4.3 Массив JSON в объект Java.
package com.mkyong;
import com.github.cliftonlabs.json_simple.JsonArray;
import com.github.cliftonlabs.json_simple.JsonException;
import com.github.cliftonlabs.json_simple.Jsoner;
import org.dozer.DozerBeanMapper;
import org.dozer.Mapper;
import java.io.FileReader;
import java.io.IOException;
import java.util.List;
import java.util.stream.Collectors;
public class JsonSimple3 {
public static void main(String[] args) throws IOException, JsonException {
// The file `user4.json` is generated from above example 3.2
try (FileReader fileReader = new FileReader(("C:\\projects\\user4.json"))) {
JsonArray objects = Jsoner.deserializeMany(fileReader);
Mapper mapper = new DozerBeanMapper();
JsonArray o = (JsonArray) objects.get(0);
List collect = o.stream()
.map(x -> mapper.map(x, Staff.class)).collect(Collectors.toList());
collect.forEach(x -> System.out.println(x));
}
}
}
Выход
Staff{name='mkyong', age=38, position=[Founder, CTO, Writer], skills=[java, python, node, kotlin], salary={2018=14000, 2012=12000, 2010=10000}}
Staff{name='mkyong', age=38, position=[Founder, CTO, Writer], skills=[java, python, node, kotlin], salary={2018=14000, 2012=12000, 2010=10000}}
Рекомендации
Оригинал: “https://mkyong.com/java/json-simple-how-to-parse-json/”