Python工程师Java之路（r）把字符串转成JSON

概述

• JSON(JavaScript Object Notation, JS 对象简谱)
  是一种轻量级的数据交换格式
  采用完全独立于编程语言的文本格式来存储和表示数据

使用fastjson，把字符串转成JSON

MAVEN依赖

<dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>fastjson</artifactId>
  <version>1.2.47</version>
</dependency>

Java版

import com.alibaba.fastjson.JSONObject;

public class JsonDemo {
    public static void main(String[] args) {
        // 字符串->JSON
        String s = "{\"b\": \"BB\",\"c\":{\"cc\":43 }}";
        JSONObject j = JSONObject.parseObject(s);

        System.out.println(s);
        // {"b": "BB","c":{"cc":43 }}

        System.out.println(j);
        // {"b":"BB","c":{"cc":43}}

        System.out.println(j.getClass());
        // class com.alibaba.fastjson.JSONObject

        System.out.println(j.getString("b"));
        // BB

        System.out.println(j.getJSONObject("c").getInteger("cc"));
        // 43
    }
}

Scala版

import com.alibaba.fastjson.{JSON, JSONObject}

object JsDemo {
  def main(args: Array[String]): Unit = {
    // 字符串->JSON
    val s: String = "{\"b\": \"BB\",\"c\":{\"cc\":43 }}"
    val b: JSONObject = JSON.parseObject(s)
    // 打印
    println(s)
    // {"b": "BB","c":{"cc":43 }}
    println(b.getClass)
    // class com.alibaba.fastjson.JSONObject
    println(b)
    // {"b":"BB","c":{"cc":43}}
    println(b.getString("b"))
    // BB
    println(b.getJSONObject("c").getInteger("cc"))
    // 43
  }
}

Spark版

pom.xml

<dependencies>
    <dependency>
        <groupId>org.apache.spark</groupId>
        <artifactId>spark-core_2.12</artifactId>
        <version>3.0.0</version>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.47</version>
    </dependency>
</dependencies>

SparkDemo.scala

import com.alibaba.fastjson.{JSON, JSONObject}
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.rdd.RDD

case class UP(user_id: String, page_id: String, timestamp: BigInt, hms: String)

object SparkDemo {
  def main(args: Array[String]): Unit = {
    // 创建SparkContext
    val c0: SparkConf = new SparkConf().setAppName("a0").setMaster("local[2]")
    val sc: SparkContext = new SparkContext(c0)
    // 读数据
    val r: RDD[String] = sc.textFile("src/main/resources/a.txt")
    // JSON解析
    val js: RDD[UP] = r.map {
      line =>
        val j: JSONObject = JSON.parseObject(line)
        UP(
          j.getString("user_id"),
          j.getString("page_id"),
          j.getBigInteger("timestamp"),
          j.getString("hms"),
        )
    }
    js.foreach(println)
  }
}

a.txt

{"user_id": "u102", "page_id": "p7", "timestamp": 1649997187106, "hms": "2022-04-15 12:33:07"}
{"user_id": "u0", "page_id": "p7", "timestamp": 1649997307206, "hms": "2022-04-15 12:35:07"}
{"user_id": "u216", "page_id": "p6", "timestamp": 1649997427304, "hms": "2022-04-15 12:37:07"}
{"user_id": "u51", "page_id": "p7", "timestamp": 1649997547403, "hms": "2022-04-15 12:39:07"}
{"user_id": "u75", "page_id": "p6", "timestamp": 1649997667504, "hms": "2022-04-15 12:41:07"}
{"user_id": "u53", "page_id": "p3", "timestamp": 1649997787603, "hms": "2022-04-15 12:43:07"}
{"user_id": "u93", "page_id": "p8", "timestamp": 1649997907704, "hms": "2022-04-15 12:45:07"}
{"user_id": "u119", "page_id": "p5", "timestamp": 1649998027803, "hms": "2022-04-15 12:47:07"}
{"user_id": "u177", "page_id": "p7", "timestamp": 1649998147902, "hms": "2022-04-15 12:49:07"}

使用fastjson，把JSON转成JavaBean

<properties>
    <fastjson.version>2.0.19</fastjson.version>
    <lombok.version>1.18.24</lombok.version>
</properties>

<dependencies>
    <!-- JSON解析 -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>${fastjson.version}</version>
    </dependency>
    <!-- 简化JavaBean书写 -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>${lombok.version}</version>
    </dependency>
</dependencies>

import com.alibaba.fastjson.JSONObject;
import lombok.AllArgsConstructor;
import lombok.Data;

public class Hi {
    public static void main(String[] args) {
        //字符串
        String s = "{\"device_id\": \"d2\", \"timestamp\": 1666540800}";
        System.out.println(s); //{"device_id": "d2", "timestamp": 1666540800}

        //字符串转JSON对象
        JSONObject j = JSONObject.parseObject(s);
        System.out.println(j); //{"device_id":"d2","timestamp":1666540800}

        //JSON对象转JavaBean
        DataU b = j.toJavaObject(DataU.class);
        System.out.println(b); //Hi.DataU(deviceId=d2, timestamp=1666540800)

        //JSON对象转字符串
        String js = j.toJSONString();
        System.out.println(js); //{"device_id":"d2","timestamp":1666540800}
    }

    @Data
    @AllArgsConstructor
    public static class DataU {
        String deviceId;
        Long timestamp;
    }
}

封装成工具类

import com.alibaba.fastjson.JSONException;
import com.alibaba.fastjson.JSONObject;

public class JsTool {
    public static void main(String[] args) {
        String s1 = "{\"device_id\": \"d2\", \"timestamp\": 1666540800}";
        System.out.println(strToJSON(s1));
        System.out.println(isValidJSON(s1));
        String s2 = "1666540800";
        System.out.println(strToJSON(s2));
        System.out.println(isValidJSON(s2));
    }

    /**
     * 字符串转JSON对象，转换失败时返回null
     */
    public static JSONObject strToJSON(String s) {
        try {
            return JSONObject.parseObject(s);
        } catch (JSONException e) {
            return null;
        }
    }

    /**
     * 判断字符串是否能转换成合法的JSON
     */
    public static boolean isValidJSON(String string) {
        try {
            JSONObject.parseObject(string);
            return true;
        } catch (JSONException e) {
            return false;
        }
    }
}