Fastjson使用实例

一、FastJson使用范例1.1FastJson三个核心类1.2Maven依赖1.3Scala API1.3.1反序列化1.3.2序列化 1.4Java API1.4.1反序列化1.4.2序列化1.4.3序列化和反序列日期1.4.4JsonObject的一些操作1.4.5 jsonArray的一些操作 二、Fastjson Obejct/Map/JSON/String互转三、Fastjson 对象或数组转JSON

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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

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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]]