使用 json-path 解析 json 数据

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JsonPath 表达式可以用 类似 XPath 解析 XML 文档 的方式来解析 JSON 结构。

JsonPath expressions always refer to a JSON structure in the same way as XPath expression are used in combination with an XML document

依赖

JsonPath 已加入 Maven 中央仓库，添加依赖

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<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.2.0</version>
</dependency>

表达式

Operator 描述 Description
$ 根节点 The root element to query. This starts all path expressions.
@ 当前节点 The current node being processed by a filter predicate.
* 匹配任何一个数字和name Wildcard. Available anywhere a name or numeric are required.
.. 深度扫描 Deep scan. Available anywhere a name is required.
.<name> 选择name Dot-notated child
[] 迭代器标示，如数组下标
['<name>' (, '<name>')] 一个或者多个name Bracket-notated child or children
[<number> (, <number>)] 一个或者多个name Array index or indexes
[start:end] 数组切片运算符 Array slice operator
[?(<expression>)] 支持过滤操作 Filter expression. Expression must evaluate to a boolean value.

测试数据

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{
    "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
}

测试

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import com.jayway.jsonpath.Criteria;
import com.jayway.jsonpath.DocumentContext;
import com.jayway.jsonpath.Filter;
import com.jayway.jsonpath.JsonPath;

import java.io.IOException;
import java.net.URISyntaxException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.Map;

import static com.jayway.jsonpath.Criteria.*;
import static com.jayway.jsonpath.Filter.*;

/**
 * Created by Kail on 2017/3/17.
 * Copyright(c) ttpai All Rights Reserved.
 */
public class JsonPathMain {

    static String readFile(String fileName) throws URISyntaxException, IOException {
        List<String> lines = Files.readAllLines(Paths.get(JsonPathMain.class.getResource(fileName).toURI()), Charset.forName("UTF-8"));
        StringBuilder jsonBuilder = new StringBuilder();
        for (String line : lines) {
            jsonBuilder.append(line);
        }
        return jsonBuilder.toString();
    }

    static void print(Object obj) {
        System.out.println();
        System.out.println(obj);
    }

    public static void main(String[] args) throws Exception {

        String json = readFile("store.json");

        // 获取所有书的作者:
        List<String> allAuthors = JsonPath.read(json, "$.store.book[*].author");
        print(allAuthors);

        // 获得第一本书的个作者
        String firstAuthor = JsonPath.read(json, "$.store.book[1].author");
        print(firstAuthor);

        // 过滤出来 category 为 reference 的书
        List<Object> bookCategoryFilter1 = JsonPath.read(json, "$.store.book[?(@.category == 'reference')]");
        List<Object> bookCategoryFilter2 = JsonPath.read(json, "$.store.book[?]", filter(where("category").is("reference")));
        print(bookCategoryFilter1);
        print(bookCategoryFilter2);

        // 过滤出来 price > 10 的书
        List<Object> bookPriceFilter1 = JsonPath.read(json, "$.store.book[?(@.price > 10)]");
        List<Object> bookPriceFilter2 = JsonPath.read(json, "$.store.book[?]", filter(where("price").gt(10)));
        print(bookPriceFilter1);
        print(bookPriceFilter2);

        // 查找 有isbn属性 的书
        List<Object> bookExistIsbn1 = JsonPath.read(json, "$.store.book[?(@.isbn)]");
        List<Object> bookExistIsbn2 = JsonPath.read(json, "$.store.book[?]", filter(where("isbn").exists(true)));
        print(bookExistIsbn1);
        print(bookExistIsbn2);

        // 过滤链
        Filter filter = filter(where("isbn").exists(true).and("category").in("fiction", "reference"));
        List<Object> chainedFilters = JsonPath.read(json, "$.store.book[?]", filter);
        print(chainedFilters);

        // 所有的Price字段
        List<Double> allPrices = JsonPath.read(json, "$..price");
        print(allPrices);

        // 编译Json
        DocumentContext documentContext = JsonPath.parse(json);
        // 编译 path
        JsonPath allBooksPath = JsonPath.compile("$.store.book[*]");
        List<Object> allBooks = documentContext.read(allBooksPath);
        print(allBooks);
    }

}

函数

Functions can be invoked at the tail end of a path - the input to a function is the output of the path expression. The function output is dictated by the function itself.

函数 描述 Description
min() 最小值 Provides the min value of an array of numbers
max() 最大值 Provides the max value of an array of numbers
avg() 平均值 Provides the average value of an array of numbers
stddev() 标准差=方差的算术平方根 Provides the standard deviation value of an array of numbers
length() 长度 Provides the length of an array

示例

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{"numbers": [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] }
函数 描述
$..book.length() 书的个数
$.numbers.max() 数组的最大值
$.numbers.avg() 数组的平均值

https://github.com/jayway/JsonPath/pull/167

过滤器操作

Operator Description
== left is equal to right (note that 1 is not equal to ‘1’)
!= left is not equal to right
< left is less than right
<= left is less or equal to right
> left is greater than right
>= left is greater than or equal to right
=~ left matches regular expression [?(@.name =~ /foo.*?/i)]
in left exists in right [?(@.size in ['S', 'M'])]
nin left does not exists in right
size size of left (array or string) should match right
empty left (array or string) should be empty

示例

  • [?(@.price < 10 && @.category == 'fiction')]
  • [?(@.category == 'reference' || @.price > 10)]

拓展阅读

JsonPath Github
在线测试工具
json-path解析json方便可靠