Jayway - Json-Path 使用（二）-阿里云开发者社区

JsonPath是一种简单的方法来提取给定JSON文档的部分内容。 JsonPath有许多编程语言，如Javascript，Python和PHP，Java。

JsonPath提供的json解析非常强大，它提供了类似正则表达式的语法，基本上可以满足所有你想要获得的json内容。下面我把官网介绍的每个表达式用代码实现，可以更直观的知道该怎么用它。

GitHub：https://github.com/json-path/JsonPath

以下是从GitHub中用我蹩脚的英格利希，翻译过来的，将就着看吧，推荐去管网上面阅读。

JsonPath可在Central Maven存储库中找到。 Maven用户将其添加到您的POM。

com.jayway.jsonpath

json-path

2.2.0

如果您需要帮助，请在Stack Overflow中提问。标记问题'jsonpath'和'java'。

JsonPath表达式总是以与XPath表达式结合使用XML文档相同的方式引用JSON结构。

JsonPath中的“根成员对象”始终称为$，无论是对象还是数组。

JsonPath表达式可以使用点表示法

$.store.book [0].title

或括号表示法

$['store']['book'][0]['title']

操作符

操作	说明
`$`	查询根元素。这将启动所有路径表达式。
`@`	当前节点由过滤谓词处理。
`*`	通配符，必要时可用任何地方的名称或数字。
`..`	深层扫描。必要时在任何地方可以使用名称。
`.<name>`	点，表示子节点
`['<name>' (, '<name>')]`	括号表示子项
`[<number> (, <number>)]`	数组索引或索引
`[start:end]`	数组切片操作
`[?(<expression>)]`	过滤表达式。表达式必须求值为一个布尔值。

函数

函数可以在路径的尾部调用，函数的输出是路径表达式的输出，该函数的输出是由函数本身所决定的。

函数	描述	输出
`min()`	提供数字数组的最小值	`Double`
`max()`	提供数字数组的最大值	`Double`
`avg()`	提供数字数组的平均值	`Double`
`stddev()`	提供数字数组的标准偏差值	`Double`
`length()`	提供数组的长度	Integer

过滤器运算符

过滤器是用于筛选数组的逻辑表达式。一个典型的过滤器将是[?(@.age > 18)]，其中@表示正在处理的当前项目。可以使用逻辑运算符&&和||创建更复杂的过滤器。字符串文字必须用单引号或双引号括起来([?(@.color == 'blue')] 或者 [?(@.color == "blue")]).

操作符	描述
`==`	left等于right（注意1不等于'1'）
`!=`	不等于
`<`	小于
`<=`	小于等于
`>`	大于
`>=`	大于等于
`=~`	匹配正则表达式[?(@.name =~ /foo.*?/i)]
`in`	左边存在于右边 [?(@.size in ['S', 'M'])]
`nin`	左边不存在于右边
`size`	（数组或字符串）长度
`empty`	（数组或字符串）为空

Java操作示例

JSON Demo

{
"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}

JsonPath (点击链接测试)	结果
$.store.book[*].author	获取json中store下book下的所有author值
$..author	获取所有json中所有author的值
$.store.*	所有的东西，书籍和自行车
$.store..price	获取json中store下所有price的值
$..book[2]	获取json中book数组的第3个值
$..book[-2]	倒数的第二本书
$..book[0,1]	前两本书
$..book[:2]	从索引0（包括）到索引2（排除）的所有图书
$..book[1:2]	从索引1（包括）到索引2（排除）的所有图书
$..book[-2:]	获取json中book数组的最后两个值
$..book[2:]	获取json中book数组的第3个到最后一个的区间值
$..book[?(@.isbn)]	获取json中book数组中包含isbn的所有值
$.store.book[?(@.price < 10)]	获取json中book数组中price<10的所有值
$..book[?(@.price <= $['expensive'])]	获取json中book数组中price<=expensive的所有值
$..book[?(@.author =~ /.*REES/i)]	获取json中book数组中的作者以REES结尾的所有值（REES不区分大小写）
$..*	逐层列出json中的所有值，层级由外到内
$..book.length()	获取json中book数组的长度

阅读文档

使用JsonPath的最简单的最直接的方法是通过静态读取API。

1.Stringjson="...";
2.List<String>authors=JsonPath.read(json, "$.store.book[*].author");

如果你只想读取一次，那么上面的代码就可以了。

如果你还想读取其他路径，现在上面不是很好的方法，因为他每次获取都需要再解析整个文档。所以，我们可以先解析整个文档，再选择调用路径。

Stringjson="...";
Objectdocument=Configuration.defaultConfiguration().jsonProvider().parse(json);
Stringauthor0=JsonPath.read(document, "$.store.book[0].author");
Stringauthor1=JsonPath.read(document, "$.store.book[1].author");

JsonPath还提供流畅的API。这也是最灵活的一个。

Stringjson="...";
ReadContextctx=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);

何时返回

当在java中使用JsonPath时，重要的是要知道你在结果中期望什么类型。 JsonPath将自动尝试将结果转换为调用者预期的类型。

// 抛出 java.lang.ClassCastException 异常List<String>list=JsonPath.parse(json).read("$.store.book[0].author")
// 正常Stringauthor=JsonPath.parse(json).read("$.store.book[0].author")

当评估路径时，你需要理解路径确定的概念。路径是不确定的，它包含

.. ：深层扫描操作
?() ：表达式
[, (, )] ：多个数组索引

不确定的路径总是返回一个列表（由当前的JsonProvider表示）。

默认情况下，MappingProvider SPI提供了一个简单的对象映射器。这允许您指定所需的返回类型，MappingProvider将尝试执行映射。在下面的示例中，演示了Long和Date之间的映射。

Stringjson="{\"date_as_long\" : 1411455611975}";
Datedate=JsonPath.parse(json).read("$['date_as_long']", Date.class);

如果您将JsonPath配置为使用JacksonMappingProvider或GsonMappingProvider，您甚至可以将JsonPath输出直接映射到POJO中。

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

要获取完整的泛型类型信息，请使用TypeRef。

1.TypeRef<List<String>>typeRef=newTypeRef<List<String>>(){};
2.List<String>titles=JsonPath.parse(JSON_DOCUMENT).read("$.store.book[*].titl

谓词

在JsonPath中创建过滤器谓词有三种不同的方法。

内联谓词

内联谓词是路径中定义的谓词。

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

你可以使用 && 和 || 结合多个谓词 [?(@.price < 10 && @.category == 'fiction')] , [?(@.category == 'reference' || @.price > 10)].

你也可以使用！否定一个谓词 [?(!(@.price < 10 && @.category == 'fiction'))].

过滤谓词

谓词可以使用Filter API构建，如下所示：

importstaticcom.jayway.jsonpath.JsonPath.parse;
importstaticcom.jayway.jsonpath.Criteria.where;
importstaticcom.jayway.jsonpath.Filter.filter;
...
...
FiltercheapFictionFilter=filter(
where("category").is("fiction").and("price").lte(10D)
);
List<Map<String, Object>>books=parse(json).read("$.store.book[?]", cheapFictionFilter);

注意占位符？为路径中的过滤器。当提供多个过滤器时，它们按照占位符数量与提供的过滤器数量相匹配的顺序应用。您可以在一个过滤器操作[？，？]中指定多个谓词占位符，这两个谓词都必须匹配。

过滤器也可以与“OR”和“AND”

FilterfooOrBar=filter(
where("foo").exists(true)).or(where("bar").exists(true)
);
FilterfooAndBar=filter(
where("foo").exists(true)).and(where("bar").exists(true)
);

自定义

第三个选择是实现你自己的谓词

PredicatebooksWithISBN=newPredicate() {
@Overridepublicbooleanapply(PredicateContextctx) {
returnctx.item(Map.class).containsKey("isbn");
    }
};
List<Map<String, Object>>books=reader.read("$.store.book[?].isbn", List.class, booksWithISBN);

Path vs Value

在Goessner实现中，JsonPath可以返回Path或Value。值是默认值，上面所有示例返回。如果你想让我们查询的元素的路径可以通过选项来实现。

Configurationconf=Configuration.builder().options(Option.AS_PATH_LIST).build();
List<String>pathList=using(conf).parse(json).read("$..author");
assertThat(pathList).containsExactly(
"$['store']['book'][0]['author']", "$['store']['book'][1]['author']",
"$['store']['book'][2]['author']", "$['store']['book'][3]['author']");

调整配置

选项创建配置时，有几个可以改变默认行为的选项标志。

DEFAULT_PATH_LEAF_TO_NULL

此选项使JsonPath对于缺少的叶子返回null。考虑下面的Json：

[
   {
"name" : "john",
"gender" : "male"   },
   {
"name" : "ben"   }
]

Configurationconf=Configuration.defaultConfiguration();
// 正常Stringgender0=JsonPath.using(conf).parse(json).read("$[0]['gender']");
// 异常 PathNotFoundException thrownStringgender1=JsonPath.using(conf).parse(json).read("$[1]['gender']");
Configurationconf2=conf.addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL);
// 正常Stringgender0=JsonPath.using(conf2).parse(json).read("$[0]['gender']");
// 正常 (返回 null)Stringgender1=JsonPath.using(conf2).parse(json).read("$[1]['gender']");

ALWAYS_RETURN_LIST

此选项配置JsonPath返回列表

Configurationconf=Configuration.defaultConfiguration();
// 正常List<String>genders0=JsonPath.using(conf).parse(json).read("$[0]['gender']");
// 异常 PathNotFoundException thrownList<String>genders1=JsonPath.using(conf).parse(json).read("$[1]['gender']");

SUPPRESS_EXCEPTIONS

该选项确保不会从路径评估传播异常。遵循这些简单的规则：

如果选项ALWAYS_RETURN_LIST存在，将返回一个空列表
如果选项ALWAYS_RETURN_LIST不存在返回null

JsonProvider SPI

JsonPath is shipped with three different JsonProviders:

更改配置默认值只能在应用程序初始化时完成。强烈不建议在运行时进行更改，尤其是在多线程应用程序中。

Configuration.setDefaults(newConfiguration.Defaults() {
privatefinalJsonProviderjsonProvider=newJacksonJsonProvider();
privatefinalMappingProvidermappingProvider=newJacksonMappingProvider();
@OverridepublicJsonProviderjsonProvider() {
returnjsonProvider;
    }
@OverridepublicMappingProvidermappingProvider() {
returnmappingProvider;
    }
@OverridepublicSet<Option>options() {
returnEnumSet.noneOf(Option.class);
    }
});

请注意，JacksonJsonProvider需要com.fasterxml.jackson.core：jackson-databind：2.4.5，GsonJsonProvider需要在您的类路径上使用com.google.code.gson：gson：2.3.1。

Cache SPI

在JsonPath 2.1.0中，引入了一种新的Cache SPI。这允许API消费者以适合其需求的方式配置路径缓存。缓存必须在首次访问之前配置，或者抛出JsonPathException。 JsonPath附带两个缓存实现

com.jayway.jsonpath.spi.cache.LRUCache（默认，线程安全）
com.jayway.jsonpath.spi.cache.NOOPCache（无缓存）

如果要实现自己的缓存，API很简单。

CacheProvider.setCache(newCache() {
//Not thread safe simple cacheprivateMap<String, JsonPath>map=newHashMap<String, JsonPath>();
@OverridepublicJsonPathget(Stringkey) {
returnmap.get(key);
    }
@Overridepublicvoidput(Stringkey, JsonPathjsonPath) {
map.put(key, jsonPath);
    }
});

Java操作示例源码

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": "JavaWeb",
"author": "X-rapido",
"title": "Top-link",
"isbn": "0-553-211231-3",
"price": 32.68            },
            {
"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}

Java1

importjava.io.BufferedReader;
importjava.io.FileReader;
importjava.util.Iterator;
importjava.util.List;
importcom.jayway.jsonpath.JsonPath;
publicclassTestJsonPath {
publicstaticvoidmain(String[] args) {
Stringsjson=readtxt();
print("--------------------------------------getJsonValue--------------------------------------");
getJsonValue(sjson);
    }
privatestaticStringreadtxt() {
StringBuildersb=newStringBuilder();
try {
FileReaderfr=newFileReader("D:/books.txt");
BufferedReaderbfd=newBufferedReader(fr);
Strings="";
while((s=bfd.readLine())!=null) {
sb.append(s);
            }
        } catch (Exceptione) {
e.printStackTrace();
        }
System.out.println(sb.toString());
returnsb.toString();
    }
privatestaticvoidgetJsonValue(Stringjson) {
//The authors of all books：获取json中store下book下的所有author值List<String>authors1=JsonPath.read(json, "$.store.book[*].author");
//All authors：获取所有json中所有author的值List<String>authors2=JsonPath.read(json, "$..author");
//All things, both books and bicycles //authors3返回的是net.minidev.json.JSONArray：获取json中store下的所有value值，不包含key，如key有两个，book和bicycleList<Object>authors3=JsonPath.read(json, "$.store.*");
//The price of everything：获取json中store下所有price的值List<Object>authors4=JsonPath.read(json, "$.store..price");
//The third book：获取json中book数组的第3个值List<Object>authors5=JsonPath.read(json, "$..book[2]");
//The first two books：获取json中book数组的第1和第2两个个值List<Object>authors6=JsonPath.read(json, "$..book[0,1]");
//All books from index 0 (inclusive) until index 2 (exclusive)：获取json中book数组的前两个区间值List<Object>authors7=JsonPath.read(json, "$..book[:2]");
//All books from index 1 (inclusive) until index 2 (exclusive)：获取json中book数组的第2个值List<Object>authors8=JsonPath.read(json, "$..book[1:2]");
//Last two books：获取json中book数组的最后两个值List<Object>authors9=JsonPath.read(json, "$..book[-2:]");
//Book number two from tail：获取json中book数组的第3个到最后一个的区间值List<Object>authors10=JsonPath.read(json, "$..book[2:]");
//All books with an ISBN number：获取json中book数组中包含isbn的所有值List<Object>authors11=JsonPath.read(json, "$..book[?(@.isbn)]");
//All books in store cheaper than 10：获取json中book数组中price<10的所有值List<Object>authors12=JsonPath.read(json, "$.store.book[?(@.price < 10)]");
//All books in store that are not "expensive"：获取json中book数组中price<=expensive的所有值List<Object>authors13=JsonPath.read(json, "$..book[?(@.price <= $['expensive'])]");
//All books matching regex (ignore case)：获取json中book数组中的作者以REES结尾的所有值（REES不区分大小写）List<Object>authors14=JsonPath.read(json, "$..book[?(@.author =~ /.*REES/i)]");
//Give me every thing：逐层列出json中的所有值，层级由外到内List<Object>authors15=JsonPath.read(json, "$..*");
//The number of books：获取json中book数组的长度List<Object>authors16=JsonPath.read(json, "$..book.length()");
print("**********authors1**********");
print(authors1);
print("**********authors2**********");
print(authors2);
print("**********authors3**********");
printOb(authors3);
print("**********authors4**********");
printOb(authors4);
print("**********authors5**********");
printOb(authors5);
print("**********authors6**********");
printOb(authors6);
print("**********authors7**********");
printOb(authors7);
print("**********authors8**********");
printOb(authors8);
print("**********authors9**********");
printOb(authors9);
print("**********authors10**********");
printOb(authors10);
print("**********authors11**********");
printOb(authors11);
print("**********authors12**********");
printOb(authors12);
print("**********authors13**********");
printOb(authors13);
print("**********authors14**********");
printOb(authors14);
print("**********authors15**********");
printOb(authors15);
print("**********authors16**********");
printOb(authors16);
    }
privatestaticvoidprint(List<String>list) {
for(Iterator<String>it=list.iterator();it.hasNext();) {
System.out.println(it.next());
        }
    }
privatestaticvoidprintOb(List<Object>list) {
for(Iterator<Object>it=list.iterator();it.hasNext();) {
System.out.println(it.next());
        }
    }
privatestaticvoidprint(Strings) {
System.out.println("\n"+s);
    }
}
输出{"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":"JavaWeb","author":"X-rapido","title":"Top-link","isbn":"0-553-211231-3","price":32.68},{"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}
--------------------------------------getJsonValue--------------------------------------SLF4J: ClasspathcontainsmultipleSLF4Jbindings.
SLF4J: Foundbindingin [jar:file:/D:/workSpaces/SupportPackge/MavenRepository/org/apache/logging/log4j/log4j-slf4j-impl/2.0.2/log4j-slf4j-impl-2.0.2.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Foundbindingin [jar:file:/D:/workSpaces/SupportPackge/MavenRepository/org/slf4j/slf4j-log4j12/1.7.10/slf4j-log4j12-1.7.10.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Seehttp://www.slf4j.org/codes.html#multiple_bindings for an explanation.SLF4J: Actualbindingisoftype [org.apache.logging.slf4j.Log4jLoggerFactory]
ERRORStatusLoggerNolog4j2configurationfilefound. Usingdefaultconfiguration: loggingonlyerrorstotheconsole.
**********authors1**********NigelReesEvelynWaughHermanMelvilleX-rapidoJ. R. R. Tolkien**********authors2**********NigelReesEvelynWaughHermanMelvilleX-rapidoJ. R. R. Tolkien**********authors3**********[{"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":"JavaWeb","author":"X-rapido","title":"Top-link","isbn":"0-553-211231-3","price":32.68},{"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}
**********authors4**********8.9512.998.9932.6822.9919.95**********authors5**********{category=fiction, author=HermanMelville, title=MobyDick, isbn=0-553-21311-3, price=8.99}
**********authors6**********{category=reference, author=NigelRees, title=SayingsoftheCentury, price=8.95}
{category=fiction, author=EvelynWaugh, title=SwordofHonour, price=12.99}
**********authors7**********{category=reference, author=NigelRees, title=SayingsoftheCentury, price=8.95}
{category=fiction, author=EvelynWaugh, title=SwordofHonour, price=12.99}
**********authors8**********{category=fiction, author=EvelynWaugh, title=SwordofHonour, price=12.99}
**********authors9**********{category=JavaWeb, author=X-rapido, title=Top-link, isbn=0-553-211231-3, price=32.68}
{category=fiction, author=J. R. R. Tolkien, title=TheLordoftheRings, isbn=0-395-19395-8, price=22.99}
**********authors10**********{category=fiction, author=HermanMelville, title=MobyDick, isbn=0-553-21311-3, price=8.99}
{category=JavaWeb, author=X-rapido, title=Top-link, isbn=0-553-211231-3, price=32.68}
{category=fiction, author=J. R. R. Tolkien, title=TheLordoftheRings, isbn=0-395-19395-8, price=22.99}
**********authors11**********{category=fiction, author=HermanMelville, title=MobyDick, isbn=0-553-21311-3, price=8.99}
{category=JavaWeb, author=X-rapido, title=Top-link, isbn=0-553-211231-3, price=32.68}
{category=fiction, author=J. R. R. Tolkien, title=TheLordoftheRings, isbn=0-395-19395-8, price=22.99}
**********authors12**********{category=reference, author=NigelRees, title=SayingsoftheCentury, price=8.95}
{category=fiction, author=HermanMelville, title=MobyDick, isbn=0-553-21311-3, price=8.99}
**********authors13**********{category=reference, author=NigelRees, title=SayingsoftheCentury, price=8.95}
{category=fiction, author=HermanMelville, title=MobyDick, isbn=0-553-21311-3, price=8.99}
**********authors14**********{category=reference, author=NigelRees, title=SayingsoftheCentury, price=8.95}
**********authors15**********{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":"JavaWeb","author":"X-rapido","title":"Top-link","isbn":"0-553-211231-3","price":32.68},{"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}}
10[{"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":"JavaWeb","author":"X-rapido","title":"Top-link","isbn":"0-553-211231-3","price":32.68},{"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}
{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=JavaWeb, author=X-rapido, title=Top-link, isbn=0-553-211231-3, price=32.68}
{category=fiction, author=J. R. R. Tolkien, title=TheLordoftheRings, isbn=0-395-19395-8, price=22.99}
referenceNigelReesSayingsoftheCentury8.95fictionEvelynWaughSwordofHonour12.99fictionHermanMelvilleMobyDick0-553-21311-38.99JavaWebX-rapidoTop-link0-553-211231-332.68fictionJ. R. R. TolkienTheLordoftheRings0-395-19395-822.99red19.95**********authors16**********5

Java2

importjava.io.BufferedReader;
importjava.io.FileReader;
importjava.util.Iterator;
importjava.util.List;
importjava.util.Map;
importcom.jayway.jsonpath.Configuration;
importcom.jayway.jsonpath.JsonPath;
importcom.jayway.jsonpath.ReadContext;
publicclassTestJsonPath3 {
publicstaticvoidmain(String[] args) {
Stringsjson=readtxt();
print("-----------------------getJsonValue0-----------------------");
getJsonValue0(sjson);
print("-----------------------getJsonValue1-----------------------");
getJsonValue1(sjson);
print("-----------------------getJsonValue2-----------------------");
getJsonValue2(sjson);
print("-----------------------getJsonValue3-----------------------");
getJsonValue3(sjson);
print("-----------------------getJsonValue4-----------------------");
getJsonValue4(sjson);
    }
privatestaticStringreadtxt() {
StringBuildersb=newStringBuilder();
try {
FileReaderfr=newFileReader("D:/books.txt");
BufferedReaderbfd=newBufferedReader(fr);
Strings="";
while((s=bfd.readLine())!=null) {
sb.append(s);
            }
        } catch (Exceptione) {
e.printStackTrace();
        }
System.out.println(sb.toString());
returnsb.toString();
    }
/*** 读取json的一种写法，得到匹配表达式的所有值* */privatestaticvoidgetJsonValue0(Stringjson) {
List<String>authors=JsonPath.read(json, "$.store.book[*].author");
print(authors);
    }
/*** 读取JSON得到某个具体值（推荐使用这种方法，一次解析多次调用）* */privatestaticvoidgetJsonValue1(Stringjson) {
Objectdocument=Configuration.defaultConfiguration().jsonProvider().parse(json);
Stringauthor0=JsonPath.read(document, "$.store.book[0].author");
Stringauthor1=JsonPath.read(document, "$.store.book[1].author");
print(author0);
print(author1);
    }
/*** 读取json的一种写法* */privatestaticvoidgetJsonValue2(Stringjson) {
ReadContextctx=JsonPath.parse(json);
// 获取json中book数组中包含isbn的作者List<String>authorsOfBooksWithISBN=ctx.read("$.store.book[?(@.isbn)].author");
// 获取json中book数组中价格大于10的对象List<Map<String, Object>>expensiveBooks=JsonPath                                    .using(Configuration.defaultConfiguration())
                                    .parse(json)
                                    .read("$.store.book[?(@.price > 10)]", List.class);
print(authorsOfBooksWithISBN);
print("********Map********");
printListMap(expensiveBooks);
    }
/*** 读取JSON得到的值是一个String，所以不能用List存储 * */privatestaticvoidgetJsonValue3(Stringjson) {
//Will throw an java.lang.ClassCastException    //List<String> list = JsonPath.parse(json).read("$.store.book[0].author");//由于会抛异常，暂时注释上面一行，要用的话，应使用下面的格式Stringauthor=JsonPath.parse(json).read("$.store.book[0].author");
print(author);
    }
/*** 读取json的一种写法，支持逻辑表达式，&&和||*/privatestaticvoidgetJsonValue4(Stringjson) {
List<Map<String, Object>>books1=JsonPath.parse(json).read("$.store.book[?(@.price < 10 && @.category == 'fiction')]");
List<Map<String, Object>>books2=JsonPath.parse(json).read("$.store.book[?(@.category == 'reference' || @.price > 10)]");
print("********books1********");
printListMap(books1);
print("********books2********");
printListMap(books2);
    }
privatestaticvoidprint(List<String>list) {
for(Iterator<String>it=list.iterator();it.hasNext();) {
System.out.println(it.next());
        }
    }
privatestaticvoidprintListMap(List<Map<String, Object>>list) {
for(Iterator<Map<String, Object>>it=list.iterator();it.hasNext();) {
Map<String, Object>map=it.next();
for(Iteratoriterator=map.entrySet().iterator();iterator.hasNext();) {
System.out.println(iterator.next());
            }
        }
    }
privatestaticvoidprint(Strings) {
System.out.println("\n"+s);
    }
}
输出{"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":"JavaWeb","author":"X-rapido","title":"Top-link","isbn":"0-553-211231-3","price":32.68},{"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}
-----------------------getJsonValue0-----------------------SLF4J: ClasspathcontainsmultipleSLF4Jbindings.
SLF4J: Foundbindingin [jar:file:/D:/workSpaces/SupportPackge/MavenRepository/org/apache/logging/log4j/log4j-slf4j-impl/2.0.2/log4j-slf4j-impl-2.0.2.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Foundbindingin [jar:file:/D:/workSpaces/SupportPackge/MavenRepository/org/slf4j/slf4j-log4j12/1.7.10/slf4j-log4j12-1.7.10.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Seehttp://www.slf4j.org/codes.html#multiple_bindings for an explanation.SLF4J: Actualbindingisoftype [org.apache.logging.slf4j.Log4jLoggerFactory]
ERRORStatusLoggerNolog4j2configurationfilefound. Usingdefaultconfiguration: loggingonlyerrorstotheconsole.
NigelReesEvelynWaughHermanMelvilleX-rapidoJ. R. R. Tolkien-----------------------getJsonValue1-----------------------NigelReesEvelynWaugh-----------------------getJsonValue2-----------------------HermanMelvilleX-rapidoJ. R. R. Tolkien********Map********category=fictionauthor=EvelynWaughtitle=SwordofHonourprice=12.99category=JavaWebauthor=X-rapidotitle=Top-linkisbn=0-553-211231-3price=32.68category=fictionauthor=J. R. R. Tolkientitle=TheLordoftheRingsisbn=0-395-19395-8price=22.99-----------------------getJsonValue3-----------------------NigelRees-----------------------getJsonValue4-----------------------********books1********category=fictionauthor=HermanMelvilletitle=MobyDickisbn=0-553-21311-3price=8.99********books2********category=referenceauthor=NigelReestitle=SayingsoftheCenturyprice=8.95category=fictionauthor=EvelynWaughtitle=SwordofHonourprice=12.99category=JavaWebauthor=X-rapidotitle=Top-linkisbn=0-553-211231-3price=32.68category=fictionauthor=J. R. R. Tolkientitle=TheLordoftheRingsisbn=0-395-19395-8price=22.99

过滤器示例

Java

publicstaticvoidmain(String[] args) {
Stringjson=readtxt();
Objectdocument=Configuration.defaultConfiguration().jsonProvider().parse(json);
// 过滤器链（查找包含isbn并category中有fiction或JavaWeb的值）Filterfilter=Filter.filter(Criteria.where("isbn").exists(true).and("category").in("fiction", "JavaWeb"));
List<Object>books=JsonPath.read(document, "$.store.book[?]", filter);
printOb(books);
System.out.println("\n----------------------------------------------\n");
// 自定义过滤器FiltermapFilter=newFilter() {
@Overridepublicbooleanapply(PredicateContextcontext) {
Map<String, Object>map=context.item(Map.class);    
if (map.containsKey("isbn")) {
returntrue;
            }
returnfalse;
        }
    };
List<Object>books2=JsonPath.read(document, "$.store.book[?]", mapFilter);
printOb(books2);
}
输出{category=fiction, author=HermanMelville, title=MobyDick, isbn=0-553-21311-3, price=8.99}
{category=JavaWeb, author=X-rapido, title=Top-link, isbn=0-553-211231-3, price=32.68}
{category=fiction, author=J. R. R. Tolkien, title=TheLordoftheRings, isbn=0-395-19395-8, price=22.99}
----------------------------------------------{category=fiction, author=HermanMelville, title=MobyDick, isbn=0-553-21311-3, price=8.99}
{category=JavaWeb, author=X-rapido, title=Top-link, isbn=0-553-211231-3, price=32.68}
{category=fiction, author=J. R. R. Tolkien, title=TheLordoftheRings, isbn=0-395-19395-8, price=22.99}

由此可见，使用过滤器，或者使用上述的表达式，都是可以达到理想的效果。

示例中的books2中，注意到context.item(Map.class)；这句话。

这句中的Map.class是根据预定的结果类型定义的，如果返回的是String类型值，那就改为String.class。

我的示例只简单判断了一下isbn属性，可以根据实际情况进行变更条件。

Jayway - Json-Path 使用（二）

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Jayway - Json-Path 使用（二）

操作符

函数

过滤器运算符

Java操作示例

阅读文档

何时返回

谓词

调整配置

Java操作示例源码

过滤器示例

热门文章

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