json解析神器 jsonpath的使用

如果项目需求是从某些复杂的json里面取值进行计算,用jsonpath IK(ik-expression)来处理十分方便,jsonpath用来取json里面的值然后用IK自带的函数进行计算,如果是特殊的计算那就自定义IK方法搞定,配置化很方便.

下面简单介绍下jsonpath的使用方法,主要测试都在JsonPathDemo类里面:

下面是一个简单的java项目demo:

注意: 其中他的max,min,avg,stddev函数只能类似于如下处理:

//正确写法 但是感觉很鸡肋context.read('$.avg($.result.records[0].loan_type,$.result.records[1].loan_type,$.result.records[2].loan_type)');

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不能传入list 感觉比较鸡肋,如果传入list 他会报错(如下错误写法):

//这样会报错Object maxV = context.read('$.max($.result.records[*].loan_type)');//这样也会报错Object maxV = context.read('$.result.records[*].loan_type.max()');//如果json文件中是这样:'loan_type':'2',也会报错,'loan_type':2 这样才被认为是数字

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报错信息都一样,如下:

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

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JsonPathDemo是一个测试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('$.result.records[*].name'); //['张三','李四','王五'] System.out.println(names); //2 返回所有数组的值 List<Map<String, String>> objs = context.read('$.result.records[*]'); //[{'name':'张三','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 返回第一个的name String name0 = context.read('$.result.records[0].name'); //张三 System.out.println(name0); //4 返回下标为0 和 2 的数组值 List<String> name0and2 = context.read('$.result.records[0,2].name'); //['张三','王五'] System.out.println(name0and2); //5 返回下标为0 到 下标为1的 的数组值 这里[0:2] 表示包含0 但是 不包含2 List<String> name0to2 = context.read('$.result.records[0:2].name'); //['张三','李四'] System.out.println(name0to2); //6 返回数组的最后两个值 List<String> lastTwoName = context.read('$.result.records[-2:].name'); //['李四','王五'] System.out.println(lastTwoName); //7 返回下标为1之后的所有数组值 包含下标为1的 List<String> nameFromOne = context.read('$.result.records[1:].name'); //['李四','王五'] System.out.println(nameFromOne); //8 返回下标为3之前的所有数组值 不包含下标为3的 List<String> nameEndTwo = context.read('$.result.records[:3].name'); //['张三','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('$.result.records[?(@.applied_at >= '2')]'); //[{'name':'张三','pid':'500234199212121212','mobile':'18623456789','applied_at':'3','confirmed_at':'5','confirm_type':'overdue','loan_type':'1','test':'mytest','all':'2'}] System.out.println(records); //10 返回name等于李四的值 List<Map<String, String>> records0 = context.read('$.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属性的数组 List<Map<String, String>> records1 = context.read('$.result.records[?(@.test)]'); //[{'name':'张三','pid':'500234199212121212','mobile':'18623456789','applied_at':'3','confirmed_at':'5','confirm_type':'overdue','loan_type':'1','test':'mytest','all':'2'}] System.out.println(records1); //12 返回有test属性的数组 List<String> list = context.read('$..all'); //['1','4','2','3'] System.out.println(list); //12 以当前json的某个值为条件查询 这里ok为1 取出records数组中applied_at等于1的数组 List<String> ok = context.read('$.result.records[?(@.applied_at == $['ok'])]'); //['1','4','2','3'] System.out.println(ok); //13 正则匹配 List<String> regexName = context.read('$.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 多条件 List<String> mobile = context.read('$.result.records[?(@.all == '2' || @.name == '李四' )].mobile'); //['18623456789','13098765432'] System.out.println(mobile); //14 查询数组长度 Integer length01 = context.read('$.result.records.length()'); //3 System.out.println(length01); //15 查询list里面每个对象长度 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,$.result.records[2].loan_type)'); //2.3333333333333335 System.out.println(avgV); //19 标准差 double stddevV = context.read('$.stddev($.result.records[0].loan_type,$.result.records[1].loan_type,$.result.records[2].loan_type)'); //0.9428090415820636 System.out.println(stddevV); //20 读取一个不存在的 String haha = context.read('$.result.haha'); //抛出异常 //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); }}

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---

pom文件引入:

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

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其中demo.json是一个测试json:

{ 'action': '/interface.service/xxx/queryBlackUserData', 'all': '1', 'result': { 'count': 2, 'tenant_count': 2, 'records': [ { 'name': '张三', '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}

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FileUtils类是用于读取xx.json文件为字符串的json:

public class FileUtils { /** * 以行为单位读取文件，常用于读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; // 一次读入一行，直到读入null为文件结束 while ((tempString = reader.readLine()) != null) { // 显示行号 str = tempString; } reader.close(); } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e1) { } } } return str; }}

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