Functions min(), max() or sum() with jsonpath
问题
https://stackoverflow.com/questions/52817156/functions-min-max-or-sum-with-jsonpath
According toJsonPath on GitHubit shall be possible to access max(), min() or the sum() of an array but I dont know how. With this exampledata:
{
"store":{
"book":[
{
"category":"reference",
"author":"NigelRees",
"title":"SayingsoftheCentury",
"price":8.95
},
{
"category":"fiction",
"author":"EvelynWaugh",
"title":"SwordofHonour",
"price":12.99
},
{
"category":"fiction",
"author":"HermanMelville",
"title":"MobyDick",
"isbn":"0-553-21311-3",
"price":8.99
},
{
"category":"fiction",
"author":"J.R.R.Tolkien",
"title":"TheLordoftheRings",
"isbn":"0-395-19395-8",
"price":22.99
}
],
"bicycle":{
"color":"red",
"price":19.95
}
}
}
I would expect it to work like
$..book.length
so im trying
$..price.sum
but that didn't do the job.
Can someone help me?
解答
Json是记录集合，需要对各记录集合。示例代码以sum为例，min、max类似。jsonPath 只支持简单集合的聚合，以及枚举再聚合，不支持记录集合的聚合。
用Java 下的开源包 SPL 很容易写，只要 1 句：
A |
|
1 |
=json(file("data.json").read()).store.book.sum(price) |
SPL 提供了 JDBC 供 Java 调用，把上面的脚本存为 sum.splx，在 Java 中以存储过程的方式调用脚本文件：
…
Class.forName("com.esproc.jdbc.InternalDriver");
con= DriverManager.getConnection("jdbc:esproc:local://");
st = con.prepareCall("call sum()");
st.execute();
…
English version