在 JsonPath 中，length() 函数用来返回 JsonPath 表达式返回的数组的长度。
Java 示例：
package com.hxstrive.json_path.function;
import com.jayway.jsonpath.JsonPath;
/**
* length() 函数
* @author hxstrive.com
*/
public class FunctionDemo05 {
public static void main(String[] args) {
String json = "{" +
" \"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" +
" }," +
" {" +
" \"category\": \"fiction\"," +
" \"author\": \"Herman Melville\"," +
" \"title\": \"Moby Dick\"," +
" \"isbn\": \"0-553-21311-3\"," +
" \"price\": 8.99" +
" }," +
" {" +
" \"category\": \"fiction\"," +
" \"author\": \"J. R. R. Tolkien\"," +
" \"title\": \"The Lord of the Rings\"," +
" \"isbn\": \"0-395-19395-8\"," +
" \"price\": 22.99" +
" }" +
" ]," +
" \"bicycle\": {" +
" \"color\": \"red\"," +
" \"price\": 19.95" +
" }" +
" }," +
" \"expensive\": 10" +
"}";
Object obj = JsonPath.read(json, "$..book");
System.out.println(obj);
obj = JsonPath.read(json, "$..book.length()");
System.out.println(obj);
}
}运行示例，输出如下：
[[{"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},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}]]
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