一、JSONPath使用需要的包
<dependency>
<groupId>com.jayway.jsonpath</groupId>
<artifactId>json-path</artifactId>
<version>2.4.0</version>
</dependency>二、使用说明
1、JSONPath是xpath在json的应用
2、JSONPath 是参照xpath表达式来解析xml文档的方式，json数据结构通常是匿名的并且不一定需要有根元素。
3、JSONPath 用一个抽象的名字$来表示最外层对象
4、JSONPath 允许使用通配符 * 表示所以的子元素名和数组索引
三、JSONPath表达式语法
JSONPath 表达式可以使用.符号解析Json：.store.book[0].title 或者使用[]符号 ['store']['book'][0]['title']
四、测试实例（1）
Json文件内容如下：
{ "store": {
"book": [
{ "category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{ "category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99,
"isbn": "0-553-21311-3"
}
],
"bicycle": {
"color": "red",
"price": 19.95
}
}
}首先，读取json文件，使用commons.io的 FileUtils的readFileToString方法：
String path =System.getProperty("user.dir")+File.separator+"testdata"+File.separator+"test.json";
String jsonString = FileUtils.readFileToString(new File(path),"utf-8");
ReadContext context = JsonPath.parse(json);其次，输出book[1]的author值。有两种方法：
方法一：
JsonPath.read(json,"$.store.book[1].author");
或
context.read("$.store.book[1].author");
输出：Evelyn Waugh方法二：
JsonPath.read(json,"$['store']['book'][1]['author']");
context.read("$['store']['book'][1]['author']");
输出：Evelyn Waugh// 输出book[*]中category == 'reference'的book
List<Object> categorys = context.read("$.store.book[?(@.category == 'reference')]");
for(Object st: categorys){
System.out.println(st.toString());
}
输出：{category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}// 输出book[*]中price>10的book
List<Object> prices = context.read("$.store.book[?(@.price>10)]");
for(Object p:prices){
System.out.println(p.toString());
}
输出：{category=fiction, author=Evelyn Waugh, title=Sword of Honour, price=12.99, isbn=0-553-21311-3}// bicycle[*]中含有color元素的bicycle
List<Object> color = context.read("$.store.bicycle[?(@.color)]");
for(Object is :color){
System.out.println(is.toString());
}
输出：//{color=red, price=19.95}// 输出该json中所有price的值
List<Object> pp = context.read("$..price");
for(Object p :pp){
System.out.println(p.toString());
}
输出：8.95 12.99 19.95
List<String> authors = context.read("$.store.book[*].author");
for (String str : authors) {
System.out.println(str);
}
输出：Nigel Rees Evelyn Waugh五、测试实例（2）
Demo.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
}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 [1,...]
List<String> nameFromOne = context.read("$.result.records[1:].name");
//["李四","王五"]
System.out.println(nameFromOne);
//8 返回下标为3之前的所有数组值 [0,3)
List<String> nameEndTwo = context.read("$.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);
}
}六、XPATH 和 JSONPath 获取元素的方法比较
[]在xpath表达式总是从前面的路径来操作数组，索引是从1开始。
使用JOSNPath的[]操作符操作一个对象或者数组，索引是从0开始。
