Fastjson使用实例
相关文章地址链接：
Fastjson教程：
W3Cschool：FastJson 教程
FastJson使用范例(Java、Scala版)
在Scala中使用fastJson 解析json字符串
一、FastJson使用范例
1.1FastJson三个核心类
- JSON：fastjson的解析器，用于json字符串和javaBean、Json对象的转换
- JSONObject：fastJson提供的json对象
- JSONArray：fastJson提供json数组对象
1.2Maven依赖
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.47</version>
</dependency>
1.3Scala API
1.3.1反序列化
data.log
{"name":"张三","age":10}
{"name":"李四","age":11}
{"name":"李四"}
{"age":11}
data1.log
{"data":[{"label":"123","acc":1,"version":"4.3.1"}]}
{"data":[{"label":"789","acc":1,"version":"4.3.1"},{"label":"78","acc":100,"version":"4.3.1"}]}
{"data":[{"label":"5356","acc":1,"version":"4.3.1"}]}
反序列化简单json字符串
val spark = SparkSession.builder().master("local[2]").appName("FastJsonTest").getOrCreate()
val input1 = "data.log"
val jsonRDD1 = spark.sparkContext.textFile(input1)
val dataRDD1 = jsonRDD1.map(json => {
val jsonObject = JSON.parseObject(json)
val name = jsonObject.getOrDefault("name",null)
val age = jsonObject.getOrDefault("age",null)
(name,age)
})
dataRDD1.foreach(println)
// 输出结果
(李四,null)
(null,11)
(张三,10)
(李四,11)
反序列化简单json字符串组，实现一行变多行地解析json字符串。这个我也没找到很好的方法，欢迎读者指教一下
- 方法一：字符串处理
val input2 = "data1.log"
val jsonRDD2 = spark.sparkContext.textFile(input2)
val dataRDD2 = jsonRDD2.map(json => {
JSON.parseObject(json).getJSONArray("data").toString
}).map(x => x.substring(1,x.length-1).replace("},{","}---{")) // 去掉字符串中的[]，并替换},{成}---{，目的是用于区分
.flatMap(x => x.split("---")) // 字符串按----拆分
.map(x => JSON.parseObject(x))
val data2 = dataRDD2.map(jsonObject => {
val version = jsonObject.getOrDefault("version",null)
val label = jsonObject.getOrDefault("label",null)
val acc = jsonObject.getOrDefault("acc",null)
(version,label,acc)
})
data2.foreach(println)
// 输出结果
(4.3.1,5356,1)
(4.3.1,123,1)
(4.3.1,789,1)
(4.3.1,78,100)
- 方法二：List
val dataRDD3 = jsonRDD2.flatMap(json => {
val jsonArray = JSON.parseObject(json).getJSONArray("data")
var dataList : List[String] = List() // 创建一个List
for (i <- 0 to jsonArray.size()-1) {
dataList = jsonArray.get(i).toString :: dataList
}
dataList
}).map(x => JSON.parseObject(x))
val data3 = dataRDD3.map(jsonObject => {
val version = jsonObject.getOrDefault("version",null)
val label = jsonObject.getOrDefault("label",null)
val acc = jsonObject.getOrDefault("acc",null)
(version,label,acc)
})
data3.foreach(println)
// 输出结果
(4.3.1,5356,1)
(4.3.1,123,1)
(4.3.1,789,1)
(4.3.1,78,100)
1.3.2序列化
- 序列化一个简单java Bean对象
val arr = Seq("tom:10", "bob:14", "hurry:9")
val dataRdd = spark.sparkContext.parallelize(arr)
val dataString = dataRdd.map(x => {
val arr = x.split(":")
val name = arr(0)
val age = arr(1).toInt
val u = new User(name,age)
u
}).map(x => {
JSON.toJSONString(x,SerializerFeature.WriteMapNullValue) // 这里需要显示SerializerFeature中的某一个，否则会报同时匹配两个方法的错误
})
dataString.foreach(println)
// 输出结果
{"age":10,"name":"tom"}
{"age":14,"name":"bob"}
{"age":9,"name":"hurry"}
1.4Java API
1.4.1反序列化
- 反序列化一个简单Json字符串
String jsonString = "{"name":"张三","age":50}";
User user= JSON.parseObject(jsonString,User.class);
System.out.println("name:"+user.getName()+" age:"+user.getAge());
// 输出结果 name:张三 age:50
- 反序列化一个简单JSON字符串成Java对象组
String jsonArrayString = "[{"name":"张三","age":50},{"name":"李四","age":51}]";
List<User> userList = JSON.parseArray(jsonArrayString,User.class);
Iterator it = userList.iterator();
while (it.hasNext()) {
User u = (User)it.next();
System.out.println("name:"+u.getName()+" age:"+u.getAge());
}
// 输出结果 name:张三 age:50
name:李四 age:51
- 反序列化一个复杂的JSON字符串
String complexJsonString = "{"teacherName":"crystall","age":27,"course":{"courseName":"english","code":1270},"students":[{"id":1,"studentName":"lily","age":12},{"id":2,"studentName":"lucy","age":15}]}";
Teacher teacher = JSON.parseObject(complexJsonString,Teacher.class);
1.4.2序列化
- 序列化一个Java Bean对象
User u = new User();
u.setName("王五");
u.setAge(30);
System.out.println(JSON.toJSONString(u));
// 输出结果 {"age":30,"name":"王五"}
User u1 = new User();
u1.setAge(30);
System.out.println(JSON.toJSONString(u1,SerializerFeature.WriteMapNullValue)); // 输出null，输出结果 {"age":30,"name":null}
System.out.println(JSON.toJSONString(u1,SerializerFeature.WriteNullStringAsEmpty)); // 输出""，输出结果 {"age":30,"name":""}
1.4.3序列化和反序列日期
Date date = new Date();
String dateString = JSON.toJSONStringWithDateFormat(date, "yyyy-MM-dd HH:mm:ss");
System.out.println(dateString);
// 输出结果 "2018-08-03 09:44:21"
String dateString1 = "{"time":"2018-08-01 22:22:22"}";
System.out.println(JSON.parseObject(dateString1));
// 输出结果 {"time":"2018-08-01 22:22:22"}
1.4.4JsonObject的一些操作
String jsonString1 = "{"name":"张三","age":50}";
JSONObject jsonObject = JSON.parseObject(jsonString1);
System.out.println(jsonObject.keySet()); // 输出key集合，输出结果 [name, age]
if(jsonObject.containsKey("sex")) { // 判断key是否存在，输出结果 false
System.out.println(true);
} else {
System.out.println(false);
}
jsonObject.put("sex","man"); // 添加k/v键值对，输出结果 {"sex":"man","name":"张三","age":50}
System.out.println(jsonObject);
if (jsonObject.containsValue("man")) { // 判断value是否存在，输出结果 false
System.out.println(true);
} else {
System.out.println(false);
}
1.4.5 jsonArray的一些操作
String jsonArrayString1 = "[{"id":1,"studentName":"lily","age":12},{"id":2,"studentName":"lucy","age":15}]";
JSONArray jsonArray = JSON.parseArray(jsonArrayString1);
for (int i = 0; i < jsonArray.size(); i++) { // 遍历输出
JSONObject jsonObj= jsonArray.getJSONObject(i);
System.out.println(jsonObj.get("id"));
}
Student s3 = new Student(3,"学生乙",15);
jsonArray.add(s3); // 添加新jsonobject对象，输出结果 3
System.out.println(jsonArray.size());
if(jsonArray.contains(s3)) { // 判断是否存在，输出结果 true
System.out.println(true);
} else {
System.out.println(false);
}
二、Fastjson Obejct/Map/JSON/String互转
JSONObject json = new JSONObject();
json.put("aa", "11");
json.put("bb", "22");
json.put("cc", "33");
String jsonStr = json.toString();
System.out.println(jsonStr);
// {"aa":"11","bb":"22","cc":"33"}
System.out.println(JSONObject.parseObject(jsonStr).get("aa"));
// 11
String o = "{'area':{'area':'1','pagetype':'home'},'pagetype':'home'}";
System.out.println(((Map) JSONObject.parseObject(o).get("area")).get("area"));
// 1
String text = JSON.toJSONString(o);
Map<String, Object> userMap =
JSON.parseObject(o, new TypeReference<Map<String, Object>>() {});
System.out.println(((Map) userMap.get("area")).get("NotExsit"));
// null
System.out.println(JSON.toJSONString((Map) userMap.get("area")));
// {"area":"1","pagetype":"home"}
三、Fastjson 对象或数组转JSON
使用Fastjson 把对象或数组转JSON：
package test;
import java.util.ArrayList;
import java.util.List;
import com.alibaba.fastjson.JSON;
class User {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "User [name=" + name + ", age=" + age + "]";
}
};
class UserGroup {
private String name;
private List<User> users = new ArrayList<User>();
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;
}
@Override
public String toString() {
return "UserGroup [name=" + name + ", users=" + users + "]";
}
}
class FastJsonTest {
public static void main(String[] args) {
// 构建用户geust
User guestUser = new User();
guestUser.setName("guest");
guestUser.setAge(28);
// 构建用户root
User rootUser = new User();
rootUser.setName("root");
guestUser.setAge(35);
// 构建用户组对象
UserGroup group = new UserGroup();
group.setName("admin");
group.getUsers().add(guestUser);
group.getUsers().add(rootUser);
// 用户组对象转JSON串
String jsonString = JSON.toJSONString(group);
System.out.println("jsonString:" + jsonString);
// JSON串转用户组对象
UserGroup group2 = JSON.parseObject(jsonString, UserGroup.class);
System.out.println("group2:" + group2);
// 构建用户对象数组
User[] users = new User[2];
users[0] = guestUser;
users[1] = rootUser;
// 用户对象数组转JSON串
String jsonString2 = JSON.toJSONString(users);
System.out.println("jsonString2:" + jsonString2);
// JSON串转用户对象列表
List<User> users2 = JSON.parseArray(jsonString2, User.class);
System.out.println("users2:" + users2);
}
}
输出结果：
jsonString:{"name":"admin","users":[{"age":35,"name":"guest"},{"age":0,"name":"root"}]}
group2:UserGroup [name=admin, users=[User [name=guest, age=35], User [name=root, age=0]]]
jsonString2:[{"age":35,"name":"guest"},{"age":0,"name":"root"}]
users2:[User [name=guest, age=35], User [name=root, age=0]]