JsonPath学习.md

JsonPath学习

引用

最近项目中需要进行单元测试，主要是对Controller类的方法进行单元测试，测试的结果是返回json体，因此需要对返回的json进行解析（而非反序列化）。这时发现了JsonPath，能够满足单元测试对json进行检查的需求。

1.maven依赖

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.4.0</version>
</dependency>

2.基本知识

Operator	Description
$	The root element to query. This starts all path expressions.
@	The current node being processed by a filter predicate.
*	Wildcard. Available anywhere a name or numeric are required.
..	Deep scan. Available anywhere a name is required.
.<name>	Dot-notated child
['<name>' (, '<name>')]	Bracket-notated child or children
[<number> (, <number>)]	Array index or indexes
[start:end]	Array slice operator
[?(<expression>)]	Filter expression. Expression must evaluate to a boolean value.

Function	Description	Output
min()	Provides the min value of an array of numbers	Double
max()	Provides the max value of an array of numbers	Double
avg()	Provides the average value of an array of numbers	Double
stddev()	Provides the standard deviation value of an array of numbers	Double
length()	Provides the length of an array	Integer

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
subsetof	left is a subset of right [?(@.sizes subsetof ['S', 'M', 'L'])]
anyof	left has an intersection with right [?(@.sizes anyof ['M', 'L'])]
noneof	left has no intersection with right [?(@.sizes noneof ['M', 'L'])]
size	size of left (array or string) should match right
empty	left (array or string) should be empty

3.测试json串

{
    "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
}

controller方法：

    @GetMapping("json")
    public String jsonPathTest(@PathVariable("path") String path){
        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}";
        return  JsonPath.read(json, path);
    }

测试结果：

所有书的作者：$.store.book[*].author

[
   "Nigel Rees",
   "Evelyn Waugh",
   "Herman Melville",
   "J. R. R. Tolkien"
]

所有作者（不仅仅是书的）：$..author

[
   "Nigel Rees",
   "Evelyn Waugh",
   "Herman Melville",
   "J. R. R. Tolkien"
]

store下的所有东西：$.store.*

[
   [
      {
         "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
      }
   ],
   {
      "color" : "red",
      "price" : 19.95
   }
]

store节点下的所有价格：$.store..price

[
   8.95,
   12.99,
   8.99,
   22.99,
   19.95
]

第三本书：$..book[2]或者$..book[2:3]

[
   {
      "category" : "fiction",
      "author" : "Herman Melville",
      "title" : "Moby Dick",
      "isbn" : "0-553-21311-3",
      "price" : 8.99
   }
]

倒数第二本书：$..book[-2]

[
   {
      "category" : "fiction",
      "author" : "Herman Melville",
      "title" : "Moby Dick",
      "isbn" : "0-553-21311-3",
      "price" : 8.99
   }
]

前两本书：$..book[0,1]或者$..book[:2]

[
   {
      "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
   }
]

倒数二本书：$..book[-2:]

[
   {
      "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
   }
]

第三本书到最后：$..book[2:]

[
   {
      "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
   }
]

书中带isbn字段的：$..book[?(@.isbn)]

[
   {
      "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
   }
]

书的价格小于10的：$.store.book[?(@.price < 10)]或者$..book[?(@.price <= $['expensive'])]

[
   {
      "category" : "reference",
      "author" : "Nigel Rees",
      "title" : "Sayings of the Century",
      "price" : 8.95
   },
   {
      "category" : "fiction",
      "author" : "Herman Melville",
      "title" : "Moby Dick",
      "isbn" : "0-553-21311-3",
      "price" : 8.99
   }
]

作者匹配正则：$..book[?(@.author =~ /.*REES/i)]

[
   {
      "category" : "reference",
      "author" : "Nigel Rees",
      "title" : "Sayings of the Century",
      "price" : 8.95
   }
]

书本的数量：$..book.length()

[
   4
]

4.JsonPath高级特性：

(1)JasonPath解析方式：

通过静态读取API

String json =  “ ... ” ;
List < String > authors =  JsonPath 。read（json，“ $ .store.book [*]。author ”）;

多次调用：

String json = "...";
Object document = Configuration.defaultConfiguration().jsonProvider().parse(json);

String author0 = JsonPath.read(document, "$.store.book[0].author");
String author1 = JsonPath.read(document, "$.store.book[1].author");

链式获取：

String json = "...";

ReadContext ctx = JsonPath.parse(json);

List<String> authorsOfBooksWithISBN = ctx.read("$.store.book[?(@.isbn)].author");


List<Map<String, Object>> expensiveBooks = JsonPath
                            .using(configuration)
                            .parse(json)
                            .read("$.store.book[?(@.price > 10)]", List.class);

(2)返回数据类型转换

String author = JsonPath.parse(json).read("$.store.book[0].author")
    
    
String json = "{\"date_as_long\" : 1411455611975}";
Date date = JsonPath.parse(json).read("$['date_as_long']", Date.class);


Book book = JsonPath.parse(json).read("$.store.book[0]", Book.class);


TypeRef<List<String>> typeRef = new TypeRef<List<String>>() {};
List<String> titles = JsonPath.parse(JSON_DOCUMENT).read("$.store.book[*].title", typeRef);

(3).过滤器

import static com.jayway.jsonpath.JsonPath.parse;
import static com.jayway.jsonpath.Criteria.where;
import static com.jayway.jsonpath.Filter.filter;
...
...

Filter cheapFictionFilter = filter(
   where("category").is("fiction").and("price").lte(10D)
);

List<Map<String, Object>> books =  
   parse(json).read("$.store.book[?]", cheapFictionFilter);

[{
	"category": "fiction",
	"author": "Herman Melville",
	"title": "Moby Dick",
	"isbn": "0-553-21311-3",
	"price": 8.99
}]

其他：

Filter fooOrBar = filter(
   where("foo").exists(true)).or(where("bar").exists(true)
);
   
Filter fooAndBar = filter(
   where("foo").exists(true)).and(where("bar").exists(true)
);

自定义：

Predicate booksWithISBN = new Predicate() {
    @Override
    public boolean apply(PredicateContext ctx) {
        return ctx.item(Map.class).containsKey("isbn");
    }
};

List<Map<String, Object>> books = 
   reader.read("$.store.book[?].isbn", List.class, booksWithISBN);