Jayway - Json-Path 使用（二）

JsonPath是一種簡單的方法來提取給定JSON文檔的部分內容。 JsonPath有許多編程語言，如Javascript，Python和PHP，Java。

JsonPath提供的json解析非常強大，它提供了類似正則表達式的語法，基本上可以滿足所有你想要獲得的json內容。下面我把官網介紹的每個表達式用代碼實現，可以更直觀的知道該怎麼用它。

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

以下是從GitHub中用我蹩腳的英格利希，翻譯過來的，將就着看吧，推薦去管網上面閱讀。

JsonPath可在Central Maven存儲庫中找到。 Maven用戶將其添加到您的POM。

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

如果您需要幫助，請在Stack Overflow中提問。標記問題'jsonpath'和'java'。

JsonPath表達式總是以與XPath表達式結合使用XML文檔相同的方式引用JSON結構。

JsonPath中的“根成員對象”始終稱爲$，無論是對象還是數組。

JsonPath表達式可以使用點表示法

$.store.book [0].title

或括號表示法

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

操作符

操作	說明
`$`	查詢根元素。這將啓動所有路徑表達式。
`@`	當前節點由過濾謂詞處理。
`*`	通配符，必要時可用任何地方的名稱或數字。
`..`	深層掃描。必要時在任何地方可以使用名稱。
`.<name>`	點，表示子節點
`['<name>' (, '<name>')]`	括號表示子項
`[<number> (, <number>)]`	數組索引或索引
`[start:end]`	數組切片操作
`[?(<expression>)]`	過濾表達式。表達式必須求值爲一個布爾值。

函數

函數可以在路徑的尾部調用，函數的輸出是路徑表達式的輸出，該函數的輸出是由函數本身所決定的。

函數	描述	輸出
`min()`	提供數字數組的最小值	`Double`
`max()`	提供數字數組的最大值	`Double`
`avg()`	提供數字數組的平均值	`Double`
`stddev()`	提供數字數組的標準偏差值	`Double`
`length()`	提供數組的長度	Integer

過濾器運算符

過濾器是用於篩選數組的邏輯表達式。一個典型的過濾器將是[?(@.age > 18)]，其中@表示正在處理的當前項目。可以使用邏輯運算符&&和||創建更復雜的過濾器。字符串文字必須用單引號或雙引號括起來([?(@.color == 'blue')] 或者 [?(@.color == "blue")]).

操作符	描述
`==`	left等於right（注意1不等於'1'）
`!=`	不等於
`<`	小於
`<=`	小於等於
`>`	大於
`>=`	大於等於
`=~`	匹配正則表達式[?(@.name =~ /foo.*?/i)]
`in`	左邊存在於右邊 [?(@.size in ['S', 'M'])]
`nin`	左邊不存在於右邊
`size`	（數組或字符串）長度
`empty`	（數組或字符串）爲空

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 (點擊鏈接測試)	結果
`$.store.book[*].author`	獲取json中store下book下的所有author值
`$..author`	獲取所有json中所有author的值
`$.store.*`	所有的東西，書籍和自行車
`$.store..price`	獲取json中store下所有price的值
`$..book[2]`	獲取json中book數組的第3個值
`$..book[-2]`	倒數的第二本書
`$..book[0,1]`	前兩本書
`$..book[:2]`	從索引0（包括）到索引2（排除）的所有圖書
`$..book[1:2]`	從索引1（包括）到索引2（排除）的所有圖書
`$..book[-2:]`	獲取json中book數組的最後兩個值
`$..book[2:]`	獲取json中book數組的第3個到最後一個的區間值
`$..book[?(@.isbn)]`	獲取json中book數組中包含isbn的所有值
`$.store.book[?(@.price < 10)]`	獲取json中book數組中price<10的所有值
`$..book[?(@.price <= $['expensive'])]`	獲取json中book數組中price<=expensive的所有值
`$..book[?(@.author =~ /.*REES/i)]`	獲取json中book數組中的作者以REES結尾的所有值（REES不區分大小寫）
`$..*`	逐層列出json中的所有值，層級由外到內
`$..book.length()`	獲取json中book數組的長度

閱讀文檔

使用JsonPath的最簡單的最直接的方法是通過靜態讀取API。

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

如果你只想讀取一次，那麼上面的代碼就可以了。

如果你還想讀取其他路徑，現在上面不是很好的方法，因爲他每次獲取都需要再解析整個文檔。所以，我們可以先解析整個文檔，再選擇調用路徑。

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");

JsonPath還提供流暢的API。這也是最靈活的一個。

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);

何時返回

當在java中使用JsonPath時，重要的是要知道你在結果中期望什麼類型。 JsonPath將自動嘗試將結果轉換爲調用者預期的類型。

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

// 正常
String author = JsonPath.parse(json).read("$.store.book[0].author")

當評估路徑時，你需要理解路徑確定的概念。路徑是不確定的，它包含

.. ：深層掃描操作
?(<expression>) ：表達式
[<number>, <number> (, <number>)] ：多個數組索引

不確定的路徑總是返回一個列表（由當前的JsonProvider表示）。

默認情況下，MappingProvider SPI提供了一個簡單的對象映射器。這允許您指定所需的返回類型，MappingProvider將嘗試執行映射。在下面的示例中，演示了Long和Date之間的映射。

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

如果您將JsonPath配置爲使用JacksonMappingProvider或GsonMappingProvider，您甚至可以將JsonPath輸出直接映射到POJO中。

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

要獲取完整的泛型類型信息，請使用TypeRef。

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

謂詞

在JsonPath中創建過濾器謂詞有三種不同的方法。

內聯謂詞

內聯謂詞是路徑中定義的謂詞。

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

你可以使用 && 和 || 結合多個謂詞 [?(@.price < 10 && @.category == 'fiction')] , [?(@.category == 'reference' || @.price > 10)].

你也可以使用！否定一個謂詞 [?(!(@.price < 10 && @.category == 'fiction'))].

過濾謂詞

謂詞可以使用Filter API構建，如下所示：

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);

注意佔位符？爲路徑中的過濾器。當提供多個過濾器時，它們按照佔位符數量與提供的過濾器數量相匹配的順序應用。您可以在一個過濾器操作[？，？]中指定多個謂詞佔位符，這兩個謂詞都必須匹配。

過濾器也可以與“OR”和“AND”

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

自定義

第三個選擇是實現你自己的謂詞

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);

Path vs Value

在Goessner實現中，JsonPath可以返回Path或Value。值是默認值，上面所有示例返回。如果你想讓我們查詢的元素的路徑可以通過選項來實現。

Configuration conf = 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']");

調整配置

選項創建配置時，有幾個可以改變默認行爲的選項標誌。

DEFAULT_PATH_LEAF_TO_NULL

此選項使JsonPath對於缺少的葉子返回null。考慮下面的Json：

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

Configuration conf = Configuration.defaultConfiguration();

// 正常
String gender0 = JsonPath.using(conf).parse(json).read("$[0]['gender']");
// 異常 PathNotFoundException thrown
String gender1 = JsonPath.using(conf).parse(json).read("$[1]['gender']");

Configuration conf2 = conf.addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL);

// 正常
String gender0 = JsonPath.using(conf2).parse(json).read("$[0]['gender']");
// 正常 (返回 null)
String gender1 = JsonPath.using(conf2).parse(json).read("$[1]['gender']");

ALWAYS_RETURN_LIST

此選項配置JsonPath返回列表

Configuration conf = Configuration.defaultConfiguration();

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

SUPPRESS_EXCEPTIONS

該選項確保不會從路徑評估傳播異常。遵循這些簡單的規則：

如果選項ALWAYS_RETURN_LIST存在，將返回一個空列表
如果選項ALWAYS_RETURN_LIST不存在返回null

JsonProvider SPI

JsonPath is shipped with three different JsonProviders:

更改配置默認值只能在應用程序初始化時完成。強烈不建議在運行時進行更改，尤其是在多線程應用程序中。

Configuration.setDefaults(new Configuration.Defaults() {

    private final JsonProvider jsonProvider = new JacksonJsonProvider();
    private final MappingProvider mappingProvider = new JacksonMappingProvider();
      
    @Override
    public JsonProvider jsonProvider() {
        return jsonProvider;
    }

    @Override
    public MappingProvider mappingProvider() {
        return mappingProvider;
    }
    
    @Override
    public Set<Option> options() {
        return EnumSet.noneOf(Option.class);
    }
});

請注意，JacksonJsonProvider需要com.fasterxml.jackson.core：jackson-databind：2.4.5，GsonJsonProvider需要在您的類路徑上使用com.google.code.gson：gson：2.3.1。

Cache SPI

在JsonPath 2.1.0中，引入了一種新的Cache SPI。這允許API消費者以適合其需求的方式配置路徑緩存。緩存必須在首次訪問之前配置，或者拋出JsonPathException。 JsonPath附帶兩個緩存實現

com.jayway.jsonpath.spi.cache.LRUCache（默認，線程安全）
com.jayway.jsonpath.spi.cache.NOOPCache（無緩存）

如果要實現自己的緩存，API很簡單。

CacheProvider.setCache(new Cache() {
    //Not thread safe simple cache
    private Map<String, JsonPath> map = new HashMap<String, JsonPath>();

    @Override
    public JsonPath get(String key) {
        return map.get(key);
    }

    @Override
    public void put(String key, JsonPath jsonPath) {
        map.put(key, jsonPath);
    }
});

Java操作示例源碼

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

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Iterator;
import java.util.List;
import com.jayway.jsonpath.JsonPath;

public class TestJsonPath {
    public static void main(String[] args) {
        String sjson = readtxt();
        print("--------------------------------------getJsonValue--------------------------------------");
        getJsonValue(sjson);
    }

    private static String readtxt() {
        StringBuilder sb = new StringBuilder();
        try {
            FileReader fr = new FileReader("D:/books.txt");
            BufferedReader bfd = new BufferedReader(fr);
            String s = "";
            while((s=bfd.readLine())!=null) {
                sb.append(s);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(sb.toString());
        return sb.toString();
    }
    
    private static void getJsonValue(String json) {
        //The authors of all books：獲取json中store下book下的所有author值
        List<String> authors1 = JsonPath.read(json, "$.store.book[*].author");
        
        //All authors：獲取所有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：獲取json中store下的所有value值，不包含key，如key有兩個，book和bicycle
        List<Object> authors3 = JsonPath.read(json, "$.store.*");
        
        //The price of everything：獲取json中store下所有price的值
        List<Object> authors4 = JsonPath.read(json, "$.store..price");
        
        //The third book：獲取json中book數組的第3個值
        List<Object> authors5 = JsonPath.read(json, "$..book[2]");
        
        //The first two books：獲取json中book數組的第1和第2兩個個值
        List<Object> authors6 = JsonPath.read(json, "$..book[0,1]");
        
        //All books from index 0 (inclusive) until index 2 (exclusive)：獲取json中book數組的前兩個區間值
        List<Object> authors7 = JsonPath.read(json, "$..book[:2]");
        
        //All books from index 1 (inclusive) until index 2 (exclusive)：獲取json中book數組的第2個值
        List<Object> authors8 = JsonPath.read(json, "$..book[1:2]");
        
        //Last two books：獲取json中book數組的最後兩個值
        List<Object> authors9 = JsonPath.read(json, "$..book[-2:]");
        
        //Book number two from tail：獲取json中book數組的第3個到最後一個的區間值
        List<Object> authors10 = JsonPath.read(json, "$..book[2:]");
        
        //All books with an ISBN number：獲取json中book數組中包含isbn的所有值
        List<Object> authors11 = JsonPath.read(json, "$..book[?(@.isbn)]");
        
        //All books in store cheaper than 10：獲取json中book數組中price<10的所有值
        List<Object> authors12 = JsonPath.read(json, "$.store.book[?(@.price < 10)]");
        
        //All books in store that are not "expensive"：獲取json中book數組中price<=expensive的所有值
        List<Object> authors13 = JsonPath.read(json, "$..book[?(@.price <= $['expensive'])]");
        
        //All books matching regex (ignore case)：獲取json中book數組中的作者以REES結尾的所有值（REES不區分大小寫）
        List<Object> authors14 = JsonPath.read(json, "$..book[?(@.author =~ /.*REES/i)]");
        
        //Give me every thing：逐層列出json中的所有值，層級由外到內
        List<Object> authors15 = JsonPath.read(json, "$..*");
        
        //The number of books：獲取json中book數組的長度
        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);
        
    }
    
    private static void print(List<String> list) {
        for(Iterator<String> it = list.iterator();it.hasNext();) {
            System.out.println(it.next());
        }
    }
    
    private static void printOb(List<Object> list) {
        for(Iterator<Object> it = list.iterator();it.hasNext();) {
            System.out.println(it.next());
        }
    }
    
    private static void print(String s) {
        System.out.println("\n"+s);
    }

}

輸出
{"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: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [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: Found binding in [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: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.

**********authors1**********
Nigel Rees
Evelyn Waugh
Herman Melville
X-rapido
J. R. R. Tolkien

**********authors2**********
Nigel Rees
Evelyn Waugh
Herman Melville
X-rapido
J. 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**********
8.95
12.99
8.99
32.68
22.99
19.95

**********authors5**********
{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}

**********authors6**********
{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}

**********authors7**********
{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}

**********authors8**********
{category=fiction, author=Evelyn Waugh, title=Sword of Honour, 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=The Lord of the Rings, isbn=0-395-19395-8, price=22.99}

**********authors10**********
{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}

**********authors11**********
{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}

**********authors12**********
{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}

**********authors13**********
{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}

**********authors14**********
{category=reference, author=Nigel Rees, title=Sayings of the Century, 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=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}
reference
Nigel Rees
Sayings of the Century
8.95
fiction
Evelyn Waugh
Sword of Honour
12.99
fiction
Herman Melville
Moby Dick
0-553-21311-3
8.99
JavaWeb
X-rapido
Top-link
0-553-211231-3
32.68
fiction
J. R. R. Tolkien
The Lord of the Rings
0-395-19395-8
22.99
red
19.95

**********authors16**********
5

Java2

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import com.jayway.jsonpath.Configuration;
import com.jayway.jsonpath.JsonPath;
import com.jayway.jsonpath.ReadContext;

public class TestJsonPath3 {
    public static void main(String[] args) {
        String sjson = readtxt();
        print("-----------------------getJsonValue0-----------------------");
        getJsonValue0(sjson);
        print("-----------------------getJsonValue1-----------------------");
        getJsonValue1(sjson);
        print("-----------------------getJsonValue2-----------------------");
        getJsonValue2(sjson);
        print("-----------------------getJsonValue3-----------------------");
        getJsonValue3(sjson);
        print("-----------------------getJsonValue4-----------------------");
        getJsonValue4(sjson);
    }

    private static String readtxt() {
        StringBuilder sb = new StringBuilder();
        try {
            FileReader fr = new FileReader("D:/books.txt");
            BufferedReader bfd = new BufferedReader(fr);
            String s = "";
            while((s=bfd.readLine())!=null) {
                sb.append(s);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(sb.toString());
        return sb.toString();
    }
    

    /**
     * 讀取json的一種寫法，得到匹配表達式的所有值
     * */
    private static void getJsonValue0(String json) {
        List<String> authors = JsonPath.read(json, "$.store.book[*].author");
        print(authors);
        
    }
    
    /**
     * 讀取JSON得到某個具體值（推薦使用這種方法，一次解析多次調用）
     * */
    private static void getJsonValue1(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");
        print(author0);
        print(author1);
        
    }
    
    /**
     * 讀取json的一種寫法
     * */
    private static void getJsonValue2(String json) {
        ReadContext ctx = JsonPath.parse(json);
        // 獲取json中book數組中包含isbn的作者
        List<String> authorsOfBooksWithISBN = ctx.read("$.store.book[?(@.isbn)].author");
        
        // 獲取json中book數組中價格大於10的對象
        List<Map<String, Object>> expensiveBooks = JsonPath
                                    .using(Configuration.defaultConfiguration())
                                    .parse(json)
                                    .read("$.store.book[?(@.price > 10)]", List.class);
        print(authorsOfBooksWithISBN);
        print("********Map********");
        printListMap(expensiveBooks);
    }
    
    /**
     * 讀取JSON得到的值是一個String，所以不能用List存儲 
     * */
    private static void getJsonValue3(String json) {
        //Will throw an java.lang.ClassCastException    
        //List<String> list = JsonPath.parse(json).read("$.store.book[0].author");
        //由於會拋異常，暫時註釋上面一行，要用的話，應使用下面的格式
        
        String author = JsonPath.parse(json).read("$.store.book[0].author");
        print(author);
    }
    
    /**
     * 讀取json的一種寫法，支持邏輯表達式，&&和||
     */
    private static void getJsonValue4(String json) {
        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);
    }
    
    private static void print(List<String> list) {
        for(Iterator<String> it = list.iterator();it.hasNext();) {
            System.out.println(it.next());
        }
    }
    
    private static void printListMap(List<Map<String, Object>> list) {
        for(Iterator<Map<String, Object>> it = list.iterator();it.hasNext();) {
            Map<String, Object> map = it.next();
            for(Iterator iterator =map.entrySet().iterator();iterator.hasNext();) {
                System.out.println(iterator.next());
            }
        }
    }
    
    private static void print(String s) {
        System.out.println("\n"+s);
    }

}

輸出
{"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: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [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: Found binding in [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: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.
Nigel Rees
Evelyn Waugh
Herman Melville
X-rapido
J. R. R. Tolkien

-----------------------getJsonValue1-----------------------

Nigel Rees

Evelyn Waugh

-----------------------getJsonValue2-----------------------
Herman Melville
X-rapido
J. R. R. Tolkien

********Map********
category=fiction
author=Evelyn Waugh
title=Sword of Honour
price=12.99
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

-----------------------getJsonValue3-----------------------

Nigel Rees

-----------------------getJsonValue4-----------------------

********books1********
category=fiction
author=Herman Melville
title=Moby Dick
isbn=0-553-21311-3
price=8.99

********books2********
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=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

過濾器示例

Java

public static void main(String[] args) {
    String json = readtxt();
    Object document = Configuration.defaultConfiguration().jsonProvider().parse(json);
    
    // 過濾器鏈（查找包含isbn並category中有fiction或JavaWeb的值）
    Filter filter = 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");
    
    // 自定義過濾器
    Filter mapFilter = new Filter() {
        @Override
        public boolean apply(PredicateContext context) {
            Map<String, Object> map = context.item(Map.class);    
            if (map.containsKey("isbn")) {
                return true;
            }
            return false;
        }
    };
    List<Object> books2 = JsonPath.read(document, "$.store.book[?]", mapFilter);
    
    printOb(books2);
    
}

輸出
{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}

----------------------------------------------

{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}

由此可見，使用過濾器，或者使用上述的表達式，都是可以達到理想的效果。

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

這句中的Map.class是根據預定的結果類型定義的，如果返回的是String類型值，那就改爲String.class。

我的示例只簡單判斷了一下isbn屬性，可以根據實際情況進行變更條件。

Jayway - Json-Path 使用（二）

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Java操作示例

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過濾器示例

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