json解析神器 jsonpath的使用

Levy_X 2017-12-19

展開全文

如果項目需求是從某些復(fù)雜的json里面取值進行計算,用jsonpath IK(ik-expression)來處理十分方便,jsonpath用來取json里面的值然后用IK自帶的函數(shù)進行計算,如果是特殊的計算那就自定義IK方法搞定,配置化很方便.

下面簡單介紹下jsonpath的使用方法,主要測試都在JsonPathDemo類里面:

下面是一個簡單的java項目demo:

這里寫圖片描述

注意: 其中他的max,min,avg,stddev函數(shù)只能類似于如下處理:

//正確寫法  但是感覺很雞肋
context.read('$.avg($.result.records[0].loan_type,$.result.records[1].loan_type,$.result.records[2].loan_type)');

不能傳入list 感覺比較雞肋,如果傳入list 他會報錯(如下錯誤寫法):

//這樣會報錯
Object maxV = context.read('$.max($.result.records[*].loan_type)');
//這樣也會報錯
Object maxV = context.read('$.result.records[*].loan_type.max()');
//如果json文件中是這樣:'loan_type':'2',也會報錯,'loan_type':2 這樣才被認(rèn)為是數(shù)字

報錯信息都一樣,如下:

Exception in thread 'main' com.jayway.jsonpath.JsonPathException: Aggregation function attempted to calculate value using empty array

JsonPathDemo是一個測試demo:

public class JsonPathDemo {
    public static void main(String[] args) {
        String json = FileUtils.readFileByLines('demo.json');
        ReadContext context = JsonPath.parse(json);

        //1 返回所有name
        List<String> names = context.read('$.result.records[*].name');
        //['張三','李四','王五']
        System.out.println(names);

        //2 返回所有數(shù)組的值
        List<Map<String, String>> objs = context.read('$.result.records[*]');
        //[{'name':'張三','pid':'500234199212121212','mobile':'18623456789','applied_at':'3','confirmed_at':'5','confirm_type':'overdue','loan_type':'1','test':'mytest','all':'2'},{'name':'李四','pid':'500234199299999999','mobile':'13098765432','applied_at':'1','confirmed_at':'','confirm_type':'overdue','loan_type':'3','all':'3'},{'name':'王五','pid':'50023415464654659','mobile':'1706454894','applied_at':'-1','confirmed_at':'','confirm_type':'overdue','loan_type':'3'}]
        System.out.println(objs);

        //3 返回第一個的name
        String name0 = context.read('$.result.records[0].name');
        //張三
        System.out.println(name0);

        //4 返回下標(biāo)為0 和 2 的數(shù)組值
        List<String> name0and2 = context.read('$.result.records[0,2].name');
        //['張三','王五']
        System.out.println(name0and2);

        //5 返回下標(biāo)為0 到 下標(biāo)為1的 的數(shù)組值  這里[0:2] 表示包含0 但是 不包含2
        List<String> name0to2 = context.read('$.result.records[0:2].name');
        //['張三','李四']
        System.out.println(name0to2);

        //6 返回數(shù)組的最后兩個值
        List<String> lastTwoName = context.read('$.result.records[-2:].name');
        //['李四','王五']
        System.out.println(lastTwoName);

        //7 返回下標(biāo)為1之后的所有數(shù)組值 包含下標(biāo)為1的
        List<String> nameFromOne = context.read('$.result.records[1:].name');
        //['李四','王五']
        System.out.println(nameFromOne);

        //8 返回下標(biāo)為3之前的所有數(shù)組值  不包含下標(biāo)為3的
        List<String> nameEndTwo = context.read('$.result.records[:3].name');
        //['張三','李四','王五']
        System.out.println(nameEndTwo);

        //9 返回applied_at大于等于2的值
        List<Map<String, String>> records = context.read('$.result.records[?(@.applied_at >= '2')]');
        //[{'name':'張三','pid':'500234199212121212','mobile':'18623456789','applied_at':'3','confirmed_at':'5','confirm_type':'overdue','loan_type':'1','test':'mytest','all':'2'}]
        System.out.println(records);

        //10 返回name等于李四的值
        List<Map<String, String>> records0 = context.read('$.result.records[?(@.name == '李四')]');
        //[{'name':'李四','pid':'500234199299999999','mobile':'13098765432','applied_at':'1','confirmed_at':'','confirm_type':'overdue','loan_type':'3'}]
        System.out.println(records0);

        //11 返回有test屬性的數(shù)組
        List<Map<String, String>> records1 = context.read('$.result.records[?(@.test)]');
        //[{'name':'張三','pid':'500234199212121212','mobile':'18623456789','applied_at':'3','confirmed_at':'5','confirm_type':'overdue','loan_type':'1','test':'mytest','all':'2'}]
        System.out.println(records1);

        //12 返回有test屬性的數(shù)組
        List<String> list = context.read('$..all');
        //['1','4','2','3']
        System.out.println(list);

        //12 以當(dāng)前json的某個值為條件查詢 這里ok為1 取出records數(shù)組中applied_at等于1的數(shù)組
        List<String> ok = context.read('$.result.records[?(@.applied_at == $['ok'])]');
        //['1','4','2','3']
        System.out.println(ok);

        //13 正則匹配
        List<String> regexName = context.read('$.result.records[?(@.pid =~ /.*999/i)]');
        //[{'name':'李四','pid':'500234199299999999','mobile':'13098765432','applied_at':'1','confirmed_at':'','confirm_type':'overdue','loan_type':'3','all':'3'}]
        System.out.println(regexName);

        //14 多條件
        List<String> mobile = context.read('$.result.records[?(@.all == '2' || @.name == '李四' )].mobile');
        //['18623456789','13098765432']
        System.out.println(mobile);

        //14 查詢數(shù)組長度
        Integer length01 = context.read('$.result.records.length()');
        //3
        System.out.println(length01);

        //15 查詢list里面每個對象長度
        List<Integer> length02 = context.read('$.result.records[?(@.all == '2' || @.name == '李四' )].length()');
        //[9,8]
        System.out.println(length02);

        //16 最大值
        Object maxV = context.read('$.max($.result.records[0].loan_type,$.result.records[1].loan_type,$.result.records[2].loan_type)');
        //3.0
        System.out.println(maxV);

        //17 最小值
        Object minV = context.read('$.min($.result.records[0].loan_type,$.result.records[1].loan_type,$.result.records[2].loan_type)');
        //1.0
        System.out.println(minV);

        //18 平均值
        double avgV = context.read('$.avg($.result.records[0].loan_type,$.result.records[1].loan_type,$.result.records[2].loan_type)');
        //2.3333333333333335
        System.out.println(avgV);

        //19 標(biāo)準(zhǔn)差
        double stddevV = context.read('$.stddev($.result.records[0].loan_type,$.result.records[1].loan_type,$.result.records[2].loan_type)');
        //0.9428090415820636
        System.out.println(stddevV);

        //20 讀取一個不存在的
        String haha = context.read('$.result.haha');
        //拋出異常
        //Exception in thread 'main' com.jayway.jsonpath.PathNotFoundException: No results for path: $['result']['haha']
        //at com.jayway.jsonpath.internal.path.EvaluationContextImpl.getValue(EvaluationContextImpl.java:133)
        //at com.jayway.jsonpath.JsonPath.read(JsonPath.java:187)
        //at com.jayway.jsonpath.internal.JsonContext.read(JsonContext.java:102)
        //at com.jayway.jsonpath.internal.JsonContext.read(JsonContext.java:89)
        //at cn.lijie.jsonpath.JsonPathDemo.main(JsonPathDemo.java:58)
        //at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        //at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        //at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        //at java.lang.reflect.Method.invoke(Method.java:498)
        //at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
        System.out.println(haha);
    }
}

pom文件引入:

        <dependency>
            <groupId>com.jayway.jsonpath</groupId>
            <artifactId>json-path</artifactId>
            <version>2.3.0</version>
        </dependency>

其中demo.json是一個測試json:

{
  'action': '/interface.service/xxx/queryBlackUserData',
  'all': '1',
  'result': {
    'count': 2,
    'tenant_count': 2,
    'records': [
      {
        'name': '張三',
        'pid': '500234199212121212',
        'mobile': '18623456789',
        'applied_at': '3',
        'confirmed_at': '5',
        'confirm_type': 'overdue',
        'loan_type': 1,
        'test': 'mytest',
        'all': '2'
      },
      {
        'name': '李四',
        'pid': '500234199299999999',
        'mobile': '13098765432',
        'applied_at': '1',
        'confirmed_at': '',
        'confirm_type': 'overdue',
        'loan_type': 3,
        'all': '3'
      },
      {
        'name': '王五',
        'pid': '50023415464654659',
        'mobile': '1706454894',
        'applied_at': '-1',
        'confirmed_at': '',
        'confirm_type': 'overdue',
        'loan_type': 3
      }
    ],
    'all': '4'
  },
  'code': 200,
  'subtime': '1480495123550',
  'status': 'success',
  'ok': 3
}

FileUtils類是用于讀取xx.json文件為字符串的json:

public class FileUtils {
    /**
     * 以行為單位讀取文件，常用于讀面向行的格式化文件
     */
    public static String readFileByLines(String fileName) {
        File file = new File(fileName);
        BufferedReader reader = null;
        String str = '';
        try {
            InputStream is = FileUtils.class.getClassLoader().getResourceAsStream(fileName);
            reader = new BufferedReader(new InputStreamReader(is));
            String tempString = null;
            int line = 1;
            // 一次讀入一行，直到讀入null為文件結(jié)束
            while ((tempString = reader.readLine()) != null) {
                // 顯示行號
                str  = tempString;
            }
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e1) {
                }
            }
        }
        return str;
    }
}