248 lines
12 KiB
Markdown
248 lines
12 KiB
Markdown
# FASTJSON2 JSONPath支持介绍
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在FASTJSON2中，JSONPath是一等公民，支持通过JSONPath在不完整解析JSON Document的情况下，根据JSONPath读取内容；也支持用JSONPath对JavaBean求值，可以在Java框架中当做对象查询语言（OQL）来使用。
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## 语法兼容标准
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支持[SQL 2016](https://en.wikipedia.org/wiki/SQL:2016)的JSON Path的语法 [ISO/IEC 19075-6](https://www.iso.org/standard/78937.html)
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## 1. 支持语法
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| JSONPATH | 描述 |
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|----------------------------------|-----------------------------------------------------------------------------------------------------------------------------|
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| $ | 根对象，例如$.name |
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| [num] | 数组访问，其中num是数字，可以是负数。例如$[0].leader.departments[-1].name |
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| [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$[0,3,-2,5] |
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| [start:end] | 数组范围访问，其中start和end是开始小表和结束下标，可以是负数，返回数组中的多个元素。例如$[0:5] |
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| [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$[0:5:2] |
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| [?(@.key)] | 对象属性非空过滤，例如$.departs[?(@.name)] |
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| [?(@.key > 123)] | 数值类型对象属性比较过滤，例如$.departs[id >= 123]，比较操作符支持=,!=,>,>=,<,<= |
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| [?(@.key = '123')] | 字符串类型对象属性比较过滤，例如$.departs[?(@..name = '123')]，比较操作符支持=,!=,>,>=,<,<= |
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| [?(@.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 |
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| [?(@.key rlike 'regexpr')] | 字符串类型正则匹配过滤， | 例如departs[name rlike 'aa(.)*']，正则语法为jdk的正则语法，支持not rlike |
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| [?(@.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)] |
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| [?(@.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)] <br/> $.departs[?(@.id not between 101 and 201)] |
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| length() 或者 size() | 数组长度。例如$.values.size() 支持类型java.util.Map和java.util.Collection和数组 |
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| keySet() | 获取Map的keySet或者对象的非空属性名称。例如$.val.keySet() 支持类型：Map和普通对象. 不支持：Collection和数组（返回null） |
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| . | 属性访问，例如$.name |
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| .. | deepScan属性访问，例如$..name |
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| * | 对象的所有属性，例如$.leader.* |
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| ['key'] | 属性访问。例如$['name'] |
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| ['key0','key1'] | 多个属性访问。例如$['id','name'] |
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以下两种写法的语义是相同的：
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```java
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$.store.book[0].title
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```
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和
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```java
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$['store']['book'][0]['title']
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```
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### 1.1 函数
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| Function | 返回类型 | Description |
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|---------------|----------|------------------|
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| type | string | 返回对象的类型 |
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| length/size | integer | 返回集合或者字符串的长度 |
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| first | Any | 集合中第一个元素 |
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| last | Any | 集合中最后一个元素 |
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| keys / keySet | sequence | 返回Map类型的KeySet |
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| values | sequence | Map类型的Values |
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| entries | sequence | Map类型的EntrySet |
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| trim | string | 对字符串做trim后返回 |
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| double | double | 将目标类型转换为double类型 |
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| ceil | number | 对数值类型做ceil处理返回 |
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| abs | number | 返回对数值类型的绝对值 |
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| lower | string | 将字符串转换小写 |
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| upper | string | 将字符串转换成大写 |
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| index(x) | int | 其中参数x支持数值和字符串 |
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### 1.2 聚合函数
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| Function | 返回类型 | Description |
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|----------|--------|---------------|
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| min | | |
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| max | | |
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| first | | 返回集合中的第一个元素 |
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| last | | 返回集合中的最后一个个元素 |
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| avg | double | |
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### 1.3 Filter Operators
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| Operator | Description |
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|-----------------|--------------|
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| = | 相等 |
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| != or <> | 不等 |
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| > | 大于 |
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| >= | 大于等于 |
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| < | 小于 |
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| <= | 小于等于 |
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| ~= | |
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| like | 类似SQL中LIKE语法 |
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| not like | |
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| rlike | |
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| not rlike | |
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| in | |
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| not in | |
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| between | |
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| not between | |
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| starts_with | |
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| not starts_with | |
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| ends_with | |
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| not ends_with | |
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| contains | |
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| not contains | |
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## 2. 语法举例
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| JSONPath | 语义 |
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| ---------- | ----------------- |
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| $ | 根对象 |
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| $[-1] | 最后元素 |
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| $[:-2] | 第1个至倒数第2个 |
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| $[1:] | 第2个之后所有元素 |
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| $[1,2,3] | 集合中1,2,3个元素 |
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# 3. API 示例
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### 3.1 例1
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```java
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public void test_entity() throws Exception {
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Entity entity = new Entity(123, new Object());
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assertSame(entity.getValue(), JSONPath.eval(entity, "$.value"));
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assertTrue(JSONPath.contains(entity, "$.value"));
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assertTrue(JSONPath.containsValue(entity, "$.id", 123));
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assertTrue(JSONPath.containsValue(entity, "$.value", entity.getValue()));
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assertEquals(2, JSONPath.size(entity, "$"));
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assertEquals(0, JSONPath.size(new Object[], "$"));
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}
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public static class Entity {
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private Integer id;
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private String name;
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private Object value;
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public Entity() {}
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public Entity(Integer id, Object value) { this.id = id; this.value = value; }
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public Entity(Integer id, String name) { this.id = id; this.name = name; }
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public Entity(String name) { this.name = name; }
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public Integer getId() { return id; }
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public Object getValue() { return value; }
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public String getName() { return name; }
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public void setId(Integer id) { this.id = id; }
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public void setName(String name) { this.name = name; }
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public void setValue(Object value) { this.value = value; }
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}
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```
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### 3.2 例2
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读取集合多个元素的某个属性
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```java
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List<Entity> entities = new ArrayList<Entity>();
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entities.add(new Entity("wenshao"));
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entities.add(new Entity("ljw2083"));
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List<String> names = (List<String>)JSONPath.eval(entities, "$.name"); // 返回enties的所有名称
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assertSame(entities.get(0).getName(), names.get(0));
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assertSame(entities.get(1).getName(), names.get(1));
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```
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### 3.3 例3
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返回集合中多个元素
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```java
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List<Entity> entities = new ArrayList<Entity>();
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entities.add(new Entity("wenshao"));
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entities.add(new Entity("ljw2083"));
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entities.add(new Entity("Yako"));
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List<Entity> result = (List<Entity>)JSONPath.eval(entities, "[1,2]"); // 返回下标为1和2的元素
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assertEquals(2, result.size());
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assertSame(entities.get(1), result.get(0));
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assertSame(entities.get(2), result.get(1));
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```
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### 3.4 例4
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按范围返回集合的子集
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```java
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List<Entity> entities = new ArrayList<Entity>();
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entities.add(new Entity("wenshao"));
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entities.add(new Entity("ljw2083"));
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entities.add(new Entity("Yako"));
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List<Entity> result = (List<Entity>)JSONPath.eval(entities, "[0:2]"); // 返回下标从0到2的元素
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assertEquals(3, result.size());
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assertSame(entities.get(0), result.get(0));
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assertSame(entities.get(1), result.get(1));
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assertSame(entities.get(2), result.get(1));
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```
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### 3.5 例5
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通过条件过滤，返回集合的子集
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```java
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List<Entity> entities = new ArrayList<Entity>();
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entities.add(new Entity(1001, "ljw2083"));
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entities.add(new Entity(1002, "wenshao"));
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entities.add(new Entity(1003, "yakolee"));
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entities.add(new Entity(1004, null));
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List<Object> result = (List<Object>) JSONPath.eval(entities, "[?(@.id in (1001))]");
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assertEquals(1, result.size());
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assertSame(entities.get(0), result.get(0));
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```
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### 3.6 例6
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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
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```java
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Entity entity = new Entity(1001, "ljw2083");
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assertSame(entity , JSONPath.eval(entity, "[?(@.id = 1001)]"));
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assertNull(JSONPath.eval(entity, "[id = 1002]"));
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JSONPath.set(entity, "id", 123456); //将id字段修改为123456
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assertEquals(123456, entity.getId().intValue());
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JSONPath.set(entity, "value", new int[0]); //将value字段赋值为长度为0的数组
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JSONPath.arrayAdd(entity, "value", 1, 2, 3); //将value字段的数组添加元素1,2,3
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```
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### 3.7 例7
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```java
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Map root = Collections.singletonMap("company",
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Collections.singletonMap("departs",
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Arrays.asList(
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Collections.singletonMap("id", 1001),
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Collections.singletonMap("id", 1002),
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Collections.singletonMap("id", 1003)
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)
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));
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List<Object> ids = (List<Object>) JSONPath.eval(root, "$..id");
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assertEquals(3, ids.size());
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assertEquals(1001, ids.get(0));
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assertEquals(1002, ids.get(1));
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assertEquals(1003, ids.get(2));
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```
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### 3.8 例8 keySet
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使用keySet抽取对象的属性名，null值属性的名字并不包含在keySet结果中，使用时需要注意，详细可参考示例。
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```java
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Entity e = new Entity();
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e.setId(null);
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e.setName("hello");
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Map<String, Entity> map = Collections.singletonMap("e", e);
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Collection<String> result;
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// id is null, excluded by keySet
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result = (Collection<String>)JSONPath.eval(map, "$.e.keySet()");
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assertEquals(1, result.size());
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assertTrue(result.contains("name"));
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e.setId(1L);
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result = (Collection<String>)JSONPath.eval(map, "$.e.keySet()");
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assertEquals(2, result.size());
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.assertTrue(result.contains("id")); // included
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assertTrue(result.contains("name"));
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// Same result
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assertEquals(result, JSONPath.keySet(map, "$.e"));
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assertEquals(result, new JSONPath("$.e").keySet(map));
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```
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