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 3System.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"));// 11String o = "{'area':{'area':'1','pagetype':'home'},'pagetype':'home'}";System.out.println(((Map) JSONObject.parseObject(o).get("area")).get("area"));// 1String 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"));// nullSystem.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]]