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
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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[], "$")); } public static class Entity { private Integer id; private String name; private Object value; public Entity() {} public Entity(Integer id, Object value) { this.id = id; this.value = value; } public Entity(Integer id, String name) { this.id = id; this.name = name; } public Entity(String name) { this.name = name; } public Integer getId() { return id; } public Object getValue() { return value; } public String getName() { return name; } public void setId(Integer id) { this.id = id; } public void setName(String name) { this.name = name; } public void setValue(Object value) { this.value = value; } } 5.2 例2
读取集合多个元素的某个属性
List entities = new ArrayList (); entities.add(new Entity("wenshao")); entities.add(new Entity("ljw2083")); List names = (List )JSONPath.eval(entities, "$.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 entities = new ArrayList (); entities.add(new Entity("wenshao")); entities.add(new Entity("ljw2083")); entities.add(new Entity("Yako")); List result = (List )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 entities = new ArrayList (); entities.add(new Entity("wenshao")); entities.add(new Entity("ljw2083")); entities.add(new Entity("Yako")); List result = (List )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 entities = new ArrayList (); 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 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 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 entities = new ArrayList (); 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 names = (List ) 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 result = (List ) 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 result2 = (List ) JSONPath.eval(entities, "[0:2]"); log.info("返回下标从0到2的元素={}", result2); } @Test public void test4() { List entities = new ArrayList (); 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 result = (List ) JSONPath.eval(entities, "[id in (1001)]"); log.info("通过条件过滤，返回集合的子集={}