fastjson 简单使用 及其JSONObject使用
阿里巴巴FastJson是一个Json处理工具包，包括“序列化”和“反序列化”两部分，它具备如下特征：
速度最快，测试表明，fastjson具有极快的性能，超越任其他的Java Json parser。包括自称最快的JackJson；
功能强大，完全支持Java Bean、集合、Map、日期、Enum，支持范型，支持自省；无依赖，能够直接运行在Java SE 5.0以上版本；支持Android；开源 (Apache 2.0)
源码地址：https://github.com/alibaba/fastjson
Fastjson API入口类是com.alibaba.fastjson.JSON，常用的序列化操作都可以在JSON类上的静态方法直接完成。
public static final Object parse(String text); // 把JSON文本parse为JSONObject或者JSONArray
*public static final JSONObject parseObject(String text)； // 把JSON文本parse成JSONObject
*public static final T parseObject(String text, Class clazz); // 把JSON文本parse为JavaBean
*public static final JSONArray parseArray(String text); // 把JSON文本parse成JSONArray
*public static final List parseArray(String text, Class clazz); //把JSON文本parse成JavaBean集合
*public static final String toJSONString(Object object); // 将JavaBean序列化为JSON文本
public static final String toJSONString(Object object, boolean prettyFormat); // 将JavaBean序列化为带格式的JSON文本
public static final Object toJSON(Object javaObject); 将JavaBean转换为JSONObject或者JSONArray。
maven:
<!-- https://mvnrepository.com/artifact/net.sf.json-lib/json-lib --> <dependency> <groupId>net.sf.json-lib</groupId> <artifactId>json-lib</artifactId> <version>2.4</version> <classifier>jdk15</classifier> </dependency> <!-- https://mvnrepository.com/artifact/com.alibaba/fastjson --> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.31</version> </dependency>
一般只用第二个fastjson就可以
demo:
import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.TypeReference; import java.util.ArrayList; import java.util.List; import lombok.ToString; public class fastjson { public static void main(String[] args) { Group group = new Group(); group.setId(0L); group.setName("admin"); User guestUser = new User(); guestUser.setId(2L); guestUser.setName("guest"); User rootUser = new User(); rootUser.setId(3L); rootUser.setName("root"); group.getUsers().add(guestUser); group.getUsers().add(rootUser); String jsonString = JSON.toJSONString(group); System.out.println(jsonString); Group group2 = JSON.parseObject(jsonString, Group.class); System.out.println("===============List=============="); String strList=JSON.toJSONString(group.getUsers()); System.out.println(strList); List<User> list=JSON.parseArray(strList,User.class); System.out.println(JSON.toJSONString(list)); List<User> list2=JSON.parseObject(strList,new TypeReference<List<User>>(){}); System.out.println(JSON.toJSONString(list2)); } } @ToString class User { private Long id; private String name; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } class Group { private Long id; private String name; private List<User> users = new ArrayList<User>(); public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<User> getUsers() { return users; } public void setUsers(List<User> users) { this.users = users; } }
output:
{"id":0,"name":"admin","users":[{"id":2,"name":"guest"},{"id":3,"name":"root"}]}
Disconnected from the target VM, address: '127.0.0.1:1655', transport: 'socket'
===============List==============
[{"id":2,"name":"guest"},{"id":3,"name":"root"}]
[{"id":2,"name":"guest"},{"id":3,"name":"root"}]
[{"id":2,"name":"guest"},{"id":3,"name":"root"}]
特别注意上面的反序列化数组，有两种不同的方式。
2.查看JSONObject的使用
这个JSONObject在很多包里面都存在这个类，这里说的是fastjson包里面的使用
package com.qhong.fastjson; //import com.alibaba.fastjson.JSONObject; //import net.sf.json.JSONObject; import com.alibaba.fastjson.JSONObject; import java.util.HashMap; import java.util.Map; public class OperatorJSON { public static void main(String[] args) { createJson(); createJsonByMap(); createJsonByJavaBean(); } private static void createJson() { JSONObject obj = new JSONObject(); obj.put("name", "John"); obj.put("sex", "male"); obj.put("age", 22); obj.put("is_student", true); obj.put("hobbies", new String[] {"hiking", "swimming"}); //调用toString()方法可直接将其内容打印出来 System.out.println(obj.toString()); } private static void createJsonByMap() { Map<String, Object> data = new HashMap<String, Object>(); data.put("name", "John"); data.put("sex", "male"); data.put("age", 22); data.put("is_student", true); data.put("hobbies", new String[] {"hiking", "swimming"}); JSONObject obj = new JSONObject(data); System.out.println(obj.toString()); } private static void createJsonByJavaBean() { PersonInfo info = new PersonInfo(); info.setName("John"); info.setSex("male"); info.setAge(22); info.setStudent(true); info.setHobbies(new String[] {"hiking", "swimming"}); String text= JSONObject.toJSONString(info); System.out.println(text); // JSONObject obj = JSONObject.toJSON(info); // System.out.println(obj); } } class PersonInfo { private String name; private String sex; private int age; private boolean isStudent; private String[] hobbies; public void setName(String name) { this.name = name; } public void setSex(String sex) { this.sex = sex; } public void setAge(int age) { this.age = age; } public void setStudent(boolean isStudent) { this.isStudent = isStudent; } public void setHobbies(String[] hobbies) { this.hobbies = hobbies; } //getter不能少 public String getName() { return name; } public String getSex() { return sex; } public int getAge() { return age; } public boolean isStudent() { return isStudent; } public String[] getHobbies() { return hobbies; } }
output:
{"hobbies":["hiking","swimming"],"sex":"male","name":"John","is_student":true,"age":22}
{"hobbies":["hiking","swimming"],"sex":"male","name":"John","is_student":true,"age":22}
{"age":22,"hobbies":["hiking","swimming"],"name":"John","sex":"male","student":true}
Process finished with exit code 0
可以从注释的区域看出，这个是fastjson包里面的，如果切换到net.sf.json包里面，那么就会报错！
