在本教程中，我们将向您展示如何使用JSON.simple解析JSON。
JSON.simple短历史
该项目以前是Yidong的Google代码项目中的 JSON.simple 1.x，现在由Clifton Labs维护，请阅读此JSON.simple历史记录
PS经过json-simple 3.1.0测试
1.下载JSON.simple
pom.xml
<dependency>
<groupId>com.github.cliftonlabs</groupId>
<artifactId>json-simple</artifactId>
<version>3.1.0</version>
</dependency>2. POJO + Jsonable
2.1要将Java对象与JSON相互转换，JSON.simple要求POJO实现Jsonable ，并重写toJson()
Staff.java
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<String> skills;
private Map<String, BigDecimal> 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. Java对象转换为JSON
3.1将Java对象转换为JSON字符串并另存为.json文件。
JsonSimple1.java
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<String, BigDecimal> 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;
}
}输出量
Terminal
{
"skills":[
"java",
"python",
"node",
"kotlin"
],
"name":"mkyong",
"position":[
"Founder",
"CTO",
"Writer"
],
"salary":{
"2018":14000,
"2012":12000,
"2010":10000
},
"age":38
}
C:\\projects\\user3.json
{"skills":["java","python","node","kotlin"],"name":"mkyong","position":["Founder","CTO","Writer"],"salary":{"2018":14000,"2012":12000,"2010":10000},"age":38} 3.2将对象列表转换为JSON数组并另存为.json文件。
Staff staff = createStaff();
List<Staff> list = Arrays.asList(createStaff(), createStaff());
// list of Java objects to JSON file
try (FileWriter fileWriter = new FileWriter("C:\\projects\\user4.json")) {
Jsoner.serialize(list, fileWriter);
}输出量
C:\\projects\\user4.json
[
{"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到Java对象
4.1要将JSON转换回Java对象，我们需要dozer第三方库的帮助来复制对象属性。
pom.xml
<dependency>
<groupId>net.sf.dozer</groupId>
<artifactId>dozer</artifactId>
<version>5.5.1</version>
</dependency>4.2 JSON字符串转换为Java对象。
JsonSimple2.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);
}
}
}输出量
Staff{name='mkyong', age=38, position=[Founder, CTO, Writer],
skills=[java, python, node, kotlin], salary={2018=14000, 2012=12000, 2010=10000}}4.3 JSON数组转换为Java对象。
JsonSimple3.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<Staff> collect = o.stream()
.map(x -> mapper.map(x, Staff.class)).collect(Collectors.toList());
collect.forEach(x -> System.out.println(x));
}
}
}输出量
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}}