fastJson 之 JSONPath使用

淡淡的烟草味﹌ 2022-06-04 09:22 138阅读 0赞

# 1. JSONPath介绍 #

官网地址: [https://github.com/alibaba/fastjson/wiki/JSONPath][https_github.com_alibaba_fastjson_wiki_JSONPath]

fastjson 1.2.0之后的版本支持JSONPath。这是一个很强大的功能，可以在java框架中当作对象查询语言（OQL）来使用。

# 2. API #

package com.alibaba.fastjson;
    
    public class JSONPath {           
         // 求值，静态方法
         public static Object eval(Object rootObject, String path);
    
         // 计算Size，Map非空元素个数，对象非空元素个数，Collection的Size，数组的长度。其他无法求值返回-1
         public static int size(Object rootObject, String path);
    
         // 是否包含，path中是否存在对象
         public static boolean contains(Object rootObject, String path) { }
    
         // 是否包含，path中是否存在指定值，如果是集合或者数组，在集合中查找value是否存在
         public static boolean containsValue(Object rootObject, String path, Object value) { }
    
         // 修改制定路径的值，如果修改成功，返回true，否则返回false
         public static boolean set(Object rootObject, String path, Object value) {}
    
         // 在数组或者集合中添加元素
         public static boolean array_add(Object rootObject, String path, Object... values);
    }

建议缓存JSONPath对象，这样能够提高求值的性能。

# 3. 支持语法 #

<table> 
 <tbody> 
 <tr> 
 <td>JSONPATH</td> 
 <td>描述</td> 
 </tr> 
 <tr> 
 <td> &lt;/td&gt;&lt;td&gt;根对象，例如 &lt;script type="math/tex" id="MathJax-Element-1"&gt;</td> 
 <td>根对象，例如&lt;/script&gt;.name</td> 
 </tr> 
 <tr> 
 <td>[num]</td> 
 <td>数组访问，其中num是数字，可以是负数。例如$[0].leader.departments[-1].name</td> 
 </tr> 
 <tr> 
 <td>[num0,num1,num2…]</td> 
 <td>数组多个元素访问，其中num是数字，可以是负数，返回数组中的多个元素。例如$[0,3,-2,5]</td> 
 </tr> 
 <tr> 
 <td>[start:end]</td> 
 <td>数组范围访问，其中start和end是开始小表和结束下标，可以是负数，返回数组中的多个元素。例如$[0:5]</td> 
 </tr> 
 <tr> 
 <td>[start:end :step]</td> 
 <td>数组范围访问，其中start和end是开始小表和结束下标，可以是负数；step是步长，返回数组中的多个元素。例如$[0:5:2]</td> 
 </tr> 
 <tr> 
 <td>[?(key)]</td> 
 <td>对象属性非空过滤，例如$.departs[?(name)]</td> 
 </tr> 
 <tr> 
 <td>[key &gt; 123]</td> 
 <td>数值类型对象属性比较过滤，例如$.departs[id &gt;= 123]，比较操作符支持=,!=,&gt;,&gt;=,&lt;,&lt;= </td> 
 </tr> 
 <tr> 
 <td>[key = ‘123’]</td> 
 <td>字符串类型对象属性比较过滤，例如$.departs[name = ‘123’]，比较操作符支持=,!=,&gt;,&gt;=,&lt;,&lt;= </td> 
 </tr> 
 <tr> 
 <td>[key like ‘aa%’]</td> 
 <td>字符串类型like过滤， 例如$.departs[name like ‘sz*’]，通配符只支持% 支持not like</td> 
 </tr> 
 <tr> 
 <td>[key rlike ‘regexpr’]</td> 
 <td>字符串类型正则匹配过滤， 例如departs[name like ‘aa(.)*’]， 正则语法为jdk的正则语法，支持not rlike </td> 
 </tr> 
 <tr> 
 <td>[key in (‘v0’, ‘v1’)]</td> 
 <td>IN过滤, 支持字符串和数值类型 例如: .departs[namein(′wenshao′,′Yako′)]&lt;br/&gt; .departs[id not in (101,102)]</td> 
 </tr> 
 <tr> 
 <td>[key between 234 and 456]</td> 
 <td>BETWEEN过滤, 支持数值类型，支持not between 例如: .departs[idbetween101and201]&lt;br/&gt; .departs[id not between 101 and 201]</td> 
 </tr> 
 <tr> 
 <td>length() 或者 size()</td> 
 <td>数组长度。例如$.values.size() 支持类型java.util.Map和java.util.Collection和数组</td> 
 </tr> 
 <tr> 
 <td>.</td> 
 <td>属性访问，例如$.name</td> 
 </tr> 
 <tr> 
 <td>..</td> 
 <td>deepScan属性访问，例如$..name</td> 
 </tr> 
 <tr> 
 <td>*</td> 
 <td>对象的所有属性，例如$.leader.*</td> 
 </tr> 
 <tr> 
 <td>[‘key’]</td> 
 <td>属性访问。例如$[‘name’]</td> 
 </tr> 
 <tr> 
 <td>[‘key0’,’key1’]</td> 
 <td>多个属性访问。例如$[‘id’,’name’]</td> 
 </tr> 
 </tbody> 
</table>

以下两种写法的语义是相同的：

$.store.book[0].title

和

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

# 4. 语法示例 #

<table> 
 <tbody> 
 <tr> 
 <td>JSONPath</td> 
 <td>语义</td> 
 </tr> 
 <tr> 
 <td>$</td> 
 <td>根对象</td> 
 </tr> 
 <tr> 
 <td>$[-1]</td> 
 <td>最后元素</td> 
 </tr> 
 <tr> 
 <td>$[:-2]</td> 
 <td>第1个至倒数第2个</td> 
 </tr> 
 <tr> 
 <td>$[1:]</td> 
 <td>第2个之后所有元素</td> 
 </tr> 
 <tr> 
 <td>$[1,2,3]</td> 
 <td>集合中1,2,3个元素</td> 
 </tr> 
 </tbody> 
</table>

# 5. API 示例 #

### 5.1 例1 ###

public void test_entity() throws Exception {
       Entity entity = new Entity(123, new Object());
    
      Assert.assertSame(entity.getValue(), JSONPath.eval(entity, "$.value")); 
      Assert.assertTrue(JSONPath.contains(entity, "$.value"));
      Assert.assertTrue(JSONPath.containsValue(entity, "$.id", 123));
      Assert.assertTrue(JSONPath.containsValue(entity, "$.value", entity.getValue())); 
      Assert.assertEquals(2, JSONPath.size(entity, "$"));
      Assert.assertEquals(0, JSONPath.size(new Object[], "$")); 
    }
    
    public static class Entity { 
       private Integer id;
       private String name;
       private Object value;
    
       public Entity() {}
       public Entity(Integer id, Object value) { this.id = id; this.value = value; }
       public Entity(Integer id, String name) { this.id = id; this.name = name; }
       public Entity(String name) { this.name = name; }
    
       public Integer getId() { return id; }
       public Object getValue() { return value; }        
       public String getName() { return name; }
    
       public void setId(Integer id) { this.id = id; }
       public void setName(String name) { this.name = name; }
       public void setValue(Object value) { this.value = value; }
    }

### 5.2 例2 ###

读取集合多个元素的某个属性

List<Entity> entities = new ArrayList<Entity>();
 entities.add(new Entity("wenshao"));
 entities.add(new Entity("ljw2083"));
 
 List<String> names = (List<String>)JSONPath.eval(entities, "$.name"); // 返回enties的所有名称
 Assert.assertSame(entities.get(0).getName(), names.get(0));
 Assert.assertSame(entities.get(1).getName(), names.get(1));

### 5.3 例3 ###

返回集合中多个元素

List<Entity> entities = new ArrayList<Entity>();
 entities.add(new Entity("wenshao"));
 entities.add(new Entity("ljw2083"));
 entities.add(new Entity("Yako"));
 
 List<Entity> result = (List<Entity>)JSONPath.eval(entities, "[1,2]"); // 返回下标为1和2的元素
 Assert.assertEquals(2, result.size());
 Assert.assertSame(entities.get(1), result.get(0));
 Assert.assertSame(entities.get(2), result.get(1));

### 5.4 例4 ###

按范围返回集合的子集

List<Entity> entities = new ArrayList<Entity>();
 entities.add(new Entity("wenshao"));
 entities.add(new Entity("ljw2083"));
 entities.add(new Entity("Yako"));
 
 List<Entity> result = (List<Entity>)JSONPath.eval(entities, "[0:2]"); // 返回下标从0到2的元素
 Assert.assertEquals(3, result.size());
 Assert.assertSame(entities.get(0), result.get(0));
 Assert.assertSame(entities.get(1), result.get(1));
 Assert.assertSame(entities.get(2), result.get(1));

### 5.5 例5 ###

通过条件过滤，返回集合的子集

List<Entity> entities = new ArrayList<Entity>();
 entities.add(new Entity(1001, "ljw2083"));
 entities.add(new Entity(1002, "wenshao"));
 entities.add(new Entity(1003, "yakolee"));
 entities.add(new Entity(1004, null));
 
 List<Object> result = (List<Object>) JSONPath.eval(entities, "[id in (1001)]");
 Assert.assertEquals(1, result.size());
 Assert.assertSame(entities.get(0), result.get(0));

### 5.6 例6 ###

根据属性值过滤条件判断是否返回对象，修改对象，数组属性添加元素

Entity entity = new Entity(1001, "ljw2083");
    Assert.assertSame(entity , JSONPath.eval(entity, "[id = 1001]"));
    Assert.assertNull(JSONPath.eval(entity, "[id = 1002]"));
    
    JSONPath.set(entity, "id", 123456); //将id字段修改为123456
    Assert.assertEquals(123456, entity.getId().intValue());
    
    JSONPath.set(entity, "value", new int[0]); //将value字段赋值为长度为0的数组
    JSONPath.arrayAdd(entity, "value", 1, 2, 3); //将value字段的数组添加元素1,2,3

### 5.7 例7 ###

Map root = Collections.singletonMap("company", //
 Collections.singletonMap("departs", //
 Arrays.asList( //
 Collections.singletonMap("id",
 1001), //
 Collections.singletonMap("id",
 1002), //
 Collections.singletonMap("id", 1003) //
 ) //
 ));
 
 List<Object> ids = (List<Object>) JSONPath.eval(root, "$..id");
 assertEquals(3, ids.size());
 assertEquals(1001, ids.get(0));
 assertEquals(1002, ids.get(1));
 assertEquals(1003, ids.get(2));

## 具体用例测试请看下面: ##

/** * @author itguang * @create 2017-12-10 10:03 **/
 
 @RunWith(SpringRunner.class)
 @SpringBootTest
 @Slf4j
 public class JSONpathControllerTest { 
 
 
 @Test
 public void test() {
 
 User user = new User("itguang", "123456", "123@qq.com");
 String username = (String) JSONPath.eval(user, "$.username");
 
 log.info("$.username = {}", username);
 
 Entity entity = new Entity(123, user);
 User user1 = (User) JSONPath.eval(entity, "$.value");
 log.info("user={}", user1.toString());
 
 
 }
 
 
 @Test
 public void test2() {
 
 User user = new User("itguang", "123456", "123@qq.com");
 Entity entity = new Entity(123, user);
 
 //判断entity中是否有 data
 boolean contains = JSONPath.contains(entity, "$.data");
 Assert.assertTrue(contains);
 
 //判断 entity.data.username 属性值是否为 itguang
 boolean containsValue = JSONPath.containsValue(entity, "$.data.username", "itguang");
 Assert.assertTrue(containsValue);
 
 Assert.assertEquals(2, JSONPath.size(entity, "$"));
 
 
 }
 
 
 @Test
 public void test3() {
 
 List<Entity> entities = new ArrayList<Entity>();
 entities.add(new Entity("逻辑"));
 entities.add(new Entity("叶文杰"));
 entities.add(new Entity("程心"));
 
 //返回集合中多个元素
 List<String> names = (List<String>) JSONPath.eval(entities, "$.name");
 log.info("返回集合中多个元素names={}", names);
 
 
 //返回下标 0 和 2 的元素
 List<Entity> result = (List<Entity>) JSONPath.eval(entities, "[0,2]");
 log.info("返回下标 0 和 2 的元素={}", result);
 
 // 返回下标从0到2的元素
 List<Entity> result2 = (List<Entity>) JSONPath.eval(entities, "[0:2]");
 
 log.info("返回下标从0到2的元素={}", result2);
 
 
 }
 
 
 @Test
 public void test4() {
 
 List<Entity> entities = new ArrayList<Entity>();
 entities.add(new Entity(1001, "逻辑"));
 entities.add(new Entity(1002, "程心"));
 entities.add(new Entity(1003, "叶文杰"));
 entities.add(new Entity(1004, null));
 
 //通过条件过滤，返回集合的子集
 
 List<Entity> result = (List<Entity>) JSONPath.eval(entities, "[id in (1001)]");
 log.info("通过条件过滤，返回集合的子集={}", result);
 
 
 }
 
 /** * 使用JSONPrase 解析JSON字符串或者Object对象 * * read(String json, String path)//直接使用json字符串匹配 * * eval(Object rootObject, String path) //直接使用 对象匹配 * * * {"store":{"bicycle":{"color":"red","price":19.95},"book":[{"author":"Nigel Rees","price":8.95,"category":"reference","title":"Sayings of the Century"},{"author":"Evelyn Waugh","price":12.99,"isbn":"0-553-21311-3","category":"fiction","title":"Sword of Honour"}]}} */
 @Test
 public void test5() {
 
 
 String jsonStr = "{\n" +
 " \"store\": {\n" +
 " \"bicycle\": {\n" +
 " \"color\": \"red\",\n" +
 " \"price\": 19.95\n" +
 " },\n" +
 " \"book\": [\n" +
 " {\n" +
 " \"author\": \"刘慈欣\",\n" +
 " \"price\": 8.95,\n" +
 " \"category\": \"科幻\",\n" +
 " \"title\": \"三体\"\n" +
 " },\n" +
 " {\n" +
 " \"author\": \"itguang\",\n" +
 " \"price\": 12.99,\n" +
 " \"category\": \"编程语言\",\n" +
 " \"title\": \"go语言实战\"\n" +
 " }\n" +
 " ]\n" +
 " }\n" +
 "}";
 
 JSONObject jsonObject = JSON.parseObject(jsonStr);
 
 log.info(jsonObject.toString());
 
 //得到所有的书
 List<Book> books = (List<Book>) JSONPath.eval(jsonObject, "$.store.book");
 log.info("books={}", books);
 
 //得到所有的书名
 List<String> titles = (List<String>) JSONPath.eval(jsonObject, "$.store.book.title");
 log.info("titles={}", titles);
 
 //第一本书title
 String title = (String) JSONPath.read(jsonStr, "$.store.book[0].title");
 log.info("title={}", title);
 
 //price大于10元的book
 List<Book> list = (List<Book>) JSONPath.read(jsonStr, "$.store.book[price > 10]");
 log.info("price大于10元的book={}",list);
 
 //price大于10元的title
 List<String> list2 =(List<String>) JSONPath.read(jsonStr, "$.store.book[price > 10].title");
 log.info("price大于10元的title={}",list2);
 
 //category(类别)为科幻的book
 List<Book> list3 = (List<Book>) JSONPath.read(jsonStr,"$.store.book[category = '科幻']");
 log.info("category(类别)为科幻的book={}",list3);
 
 
 //bicycle的所有属性值
 
 Collection<String> values = (Collection<String>) JSONPath.eval(jsonObject, "$.store.bicycle.*");
 
 log.info("bicycle的所有属性值={}",values);
 
 
 //bicycle的color和price属性值
 List<String> read =(List<String>) JSONPath.read(jsonStr, "$.store.bicycle['color','price']");
 
 log.info("bicycle的color和price属性值={}",read);
 
 
 }
 
 
 }

> 源码地址: [https://github.com/itguang/gitbook-smile/blob/master/springboot-fastjson/fastjson%E4%B9%8BJSONPath%E4%BD%BF%E7%94%A8.md][https_github.com_itguang_gitbook-smile_blob_master_springboot-fastjson_fastjson_E4_B9_8BJSONPath_E4_BD_BF_E7_94_A8.md]

[https_github.com_alibaba_fastjson_wiki_JSONPath]: https://github.com/alibaba/fastjson/wiki/JSONPath
[https_github.com_itguang_gitbook-smile_blob_master_springboot-fastjson_fastjson_E4_B9_8BJSONPath_E4_BD_BF_E7_94_A8.md]: https://github.com/itguang/gitbook-smile/blob/master/springboot-fastjson/fastjson%E4%B9%8BJSONPath%E4%BD%BF%E7%94%A8.md

fastJson 之 JSONPath使用

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