Atitit json数据查询法 jsonpath
目录
XML的优点之一是处理的可用性-包括XPath-它被定义为W3C标准。对于JSON，出现了一个类似的名为JSONPath的工具。
本文将介绍Jayway JsonPath，它是JSONPath规范的Java实现。它描述了设置，语法，通用API以及用例的演示。
在JsonPath中，我们有几个有用的运算符：
根节点（$）：此符号表示JSON结构的根成员，无论它是对象还是数组。它的用法示例包含在前面的小节中。
当前节点（@）：表示正在处理的节点，通常用作谓词的输入表达式的一部分。假设我们在上面的JSON文档中处理book数组，表达式book [？（@。price == 49.99）]引用该数组中的第一本书。
通配符（*）：表示指定范围内的所有元素。例如，book [*]表示book数组内的所有节点
以$为root，.操作符或[]索引的方式获取指定 JsonPath 数据
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- # JSONPath expressions
JSONPath expressions always refer to a JSON structure in the same way as XPath expression are used in combination with an XML document. Since a JSON structure is usually anonymous and doesn't necessarily have a "root member object" JSONPath assumes the abstract name $ assigned to the outer level object.
JSONPath expressions can use the dot–notation
$.store.book[0].title
or the bracket–notation
$['store']['book'][0]['title']
for input pathes. Internal or output pathes will always be converted to the more general bracket–notation.
JSONPath allows the wildcard symbol * for member names and array indices. It borrows the descendant operator '..' from E4X and the array slice syntax proposal [start:end:step] from ECMASCRIPT 4.
Expressions of the underlying scripting language (<expr>) can be used as an alternative to explicit names or indices as in
$.store.book[(@.length-1)].title
using the symbol '@' for the current object. Filter expressions are supported via the syntax ?(<boolean expr>) as in
$.store.book[?(@.price < 10)].title
Here is a complete overview and a side by side comparison of the JSONPath syntax elements with its XPath counterparts.
| XPath | JSONPath | Description |
| / | $ | the root object/element |
| . | @ | the current object/element |
| / | . or [] | child operator |
| .. | n/a | parent operator |
| // | .. | recursive descent. JSONPath borrows this syntax from E4X. |
| * | * | wildcard. All objects/elements regardless their names. |
| @ | n/a | attribute access. JSON structures don't have attributes. |
| [] | [] | subscript operator. XPath uses it to iterate over element collections and for predicates. In Javascript and JSON it is the native array operator. |
| | | [,] | Union operator in XPath results in a combination of node sets. JSONPath allows alternate names or array indices as a set. |
| n/a | [start:end:step] | array slice operator borrowed from ES4. |
| [] | ?() | applies a filter (script) expression. |
| n/a | () | script expression, using the underlying script engine. |
| () | n/a | grouping in Xpath |
XPath has a lot more to offer (Location pathes in not abbreviated syntax, operators and functions) than listed here. Moreover there is a remarkable difference how the subscript operator works in Xpath and JSONPath.
- Square brackets in XPath expressions always operate on the node set resulting from the previous path fragment. Indices always start by 1.
- With JSONPath square brackets operate on the object or array addressed by the previous path fragment. Indices always start by 0.
Other syntax elements are described below.
| Expression | Description |
| $ | The root object or array. |
| .property | Selects the specified property in a parent object. |
| ['property'] | Selects the specified property in a parent object. Be sure to put single quotes around the property name. Tip: Use this notation if the property name contains special characters such as spaces, or begins with a character other than A..Za..z_. |
| [n] | Selects the n-th element from an array. Indexes are 0-based. |
| [index1,index2,…] | Selects array elements with the specified indexes. Returns a list. |
| ..property | Recursive descent: Searches for the specified property name recursively and returns an array of all values with this property name. Always returns a list, even if just one property is found. |
| * | Wildcard selects all elements in an object or an array, regardless of their names or indexes. For example, address.* means all properties of the address object, and book[*] means all items of the book array. |
| [start:end] | Selects array elements from the start index and up to, but not including, end index. If end is omitted, selects all elements from start until the end of the array. Returns a list. |
| [:n] | Selects the first n elements of the array. Returns a list. |
| [-n:] | Selects the last n elements of the array. Returns a list. |
| [?(expression)] | Filter expression. Selects all elements in an object or array that match the specified filter. Returns a list. |
| [(expression)] | Script expressions can be used instead of explicit property names or indexes. An example is [(@.length-1)] which selects the last item in an array. Here, length refers to the length of the current array rather than a JSON field named length. |
| @ | Used in filter expressions to refer to the current node being processed |
| XPath | JSONPath | Result |
| /store/book/author | $.store.book[*].author | the authors of all books in the store |
| //author | $..author | all authors |
| /store/* | $.store.* | all things in store, which are some books and a red bicycle. |
| /store//price | $.store..price | the price of everything in the store. |
| //book[3] | $..book[2] | the third book |
| //book[last()] | $..book[(@.length-1)] | the last book in order. |
| //book[position()<3] | $..book[0,1] | the first two books |
| //book[isbn] | $..book[?(@.isbn)] | filter all books with isbn number |
| //book[price<10] | $..book[?(@.price<10)] | filter all books cheapier than 10 |
| //* | $..* | all Elements in XML document. All members of JSON structure. |
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- |2007-08-22| e4# JSONPath implementation
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JSONPath is implemented in Javascript for clientside usage and ported over to PHP for use on the server.
All you need to do is downloading either of the files
include it in your program and use the simple API consisting of one single function.
jsonPath(obj, expr [, args])
.. ：深层扫描操作
?(<expression>) ：表达式
Filters are logical expressions used to filter arrays. An example of a JSONPath expression with a filter is
$.store.book[?(@.price < 10)]
where @ represents the current array item or object being processed. Filters can also use $ to refer to the properties outside of the current object:
$.store.book[?(@.price < $.expensive)]
An expression that specifies just a property name, such as [?(@.isbn)], matches all items that have this property, regardless of the value.
Additionally, filters support the following operators:
| Operator | Description |
| == | Equals to. 1 and '1' are considered equal. String values must be enclosed in single quotes (not double quotes): [?(@.color=='red')]. |
| != | Not equal to. String values must be enclosed in single quotes. |
| > | Greater than. |
| >= | Greater than or equal to. |
| < | Less than. |
| <= | Less than or equal to. |
| =~ | Match a JavaScript regular expression. For example, [?(@.description =~ /cat.*/i)] matches items whose description starts with cat (case-insensitive). Note: Not supported at locations that use Ready! API 1.1. |
| ! | Use to negate a filter: [?(!@.isbn)] matches items that do not have the isbn property. Note: Not supported at locations that use Ready! API 1.1. |
| && | Logical AND, used to combine multiple filter expressions: [?(@.category=='fiction' && @.price < 10)] |
| || | Logical OR, used to combine multiple filter expressions: [?(@.category=='fiction' || @.price < 10)] Note: Not supported at locations that use Ready! API 1.1. |
JsonPath还具有可用于路径末尾以综合该路径的输出表达式的函数：min（），max（），avg（），stddev（），length（）。
最后–我们有过滤器；这些是布尔表达式，用于将返回的节点列表限制为仅调用方法所需的节点列表。
一些示例包括等式（==），正则表达式匹配（=〜），包含（in），检查是否为空（empty）。过滤器主要用于谓词。
有关不同运算符，函数和过滤器的完整列表和详细说明，请参阅JsonPath GitHub项目
| 名称 | 描述 | 输出 |
| min() | 获取数值类型数组的最小值 | Double |
| max() | 获取数值类型数组的最大值 | Double |
| avg() | 获取数值类型数组的平均值 | Double |
| stddev() | 获取数值类型数组的标准差 | Double |
| length() | 获取数值类型数组的长度 | Integer |
| 操作符 | 描述 |
| == | 等于符号，但数字1不等于字符1(note that 1 is not equal to ‘1’) |
| != | 不等于符号 |
| < | 小于符号 |
| <= | 小于等于符号 |
| > | 大于符号 |
| >= | 大于等于符号 |
| =~ | 判断是否符合正则表达式，例如[?(@.name =~ /foo.*?/i)] |
| in | 所属符号，例如[?(@.size in [‘S’, ‘M’])] |
| nin | 排除符号 |
| size | size of left (array or string) should match right |
| empty | 判空符号 |
| XPath | JSONPath | Description |
| / | $ | 根结点 |
| . | @ | 当前结点 |
| / | . or [] | 取子结点 |
| .. | n/a | 取父节点 |
| // | .. | 选择所有符合条件的 |
| * | * | 匹配所有元素 |
| @ | n/a | 根据属性访问 |
| [] | [] | 迭代器标示. XPath 用来选择集合元素. js或json中用作数组下标. |
| | | [,] | 迭代器中多选 |
| n/a | [start:end:step] | 数组分隔 |
| [] | ?() | 过滤操作 |
| n/a | () | 表达式计算 |
| () | n/a | xpath中分组 |
<script src="jquery/3.4.1/jquery.js"></script>
<script src="jsonpath.jquery.js"></script>
<Script>
var accList = [{
'accnum': '83457834758947598', 'holdername': '李一', 'bank': '中国银行', 'branch': '上海分行xxx支行'
},
{
'accnum': '22222222222',
'holdername': '王er',
'bank': '农业银行',
'branch': '上海分行农业银行第一支行'
},
{
'accnum': '287488347958940',
'holdername': '李三',
'bank': '招商银行',
'branch': '上海分行招商银行第2支行'
},
From root where accnum=’5555’
var path = $.JSONPath({ data: accList, keepHistory: false });
var rs = path.query('$[?(@.accnum=="5555555555555555555555")]'); // filter all books cheapier
alert(rs);
$("#txt_bank").val(rs[0].bank);
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- # Issues
- Currently only single quotes allowed inside of JSONPath expressions.
- Script expressions inside of JSONPath locations are currently not recursively evaluated by jsonPath. Only the global $ and local @ symbols are expanded by a simple regular expression.
- An alternative for jsonPath to return false in case of no match may be to return an empty array in future.
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