JSON path

https://github.com/itguang/gitbook-smile/blob/master/springboot-fastjson/fastjson%E4%B9%8BJSONPath%E4%BD%BF%E7%94%A8.md

1. JSONPath介绍

官网地址: 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

JSONPATH	描述
$	根对象，例如$.name
[num]	数组访问，其中num是数字，可以是负数。例如$[0].leader.departments[-1].name
[num0,num1,num2...]	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$[0,3,-2,5]
[start:end]	数组范围访问，其中start和end是开始小表和结束下标，可以是负数，返回数组中的多个元素。例如$[0:5]
[start:end :step]	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$[0:5:2]
[?(key)]	对象属性非空过滤，例如$.departs[?(name)]
[key > 123]	数值类型对象属性比较过滤，例如$.departs[id >= 123]，比较操作符支持=,!=,>,>=,<,<=
[key = '123']	字符串类型对象属性比较过滤，例如$.departs[name = '123']，比较操作符支持=,!=,>,>=,<,<=
[key like 'aa%']	字符串类型like过滤， 例如$.departs[name like 'sz*']，通配符只支持%  支持not like
[key rlike 'regexpr']	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
[key in ('v0', 'v1')]	IN过滤, 支持字符串和数值类型  例如:  $.departs[name in ('wenshao','Yako')]  $.departs[id not in (101,102)]
[key between 234 and 456]	BETWEEN过滤, 支持数值类型，支持not between  例如:  $.departs[id between 101 and 201] $.departs[id not between 101 and 201]
length() 或者 size()	数组长度。例如$.values.size()  支持类型java.util.Map和java.util.Collection和数组
.	属性访问，例如$.name
..	deepScan属性访问，例如$..name
*	对象的所有属性，例如$.leader.*
['key']	属性访问。例如$['name']
['key0','key1']	多个属性访问。例如$['id','name']

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

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

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
     * <p>
     * read(String json, String path)//直接使用json字符串匹配
     * <p>
     * eval(Object rootObject, String path) //直接使用 对象匹配
     * <p>
     * <p>
     * {"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);

    }

}