JsonPath | FastJson的JSONPath使用_fastjson jsonpath

一. 简介

JSONPath - 用于JSON的XPath

用来解析多层嵌套的json数据;JsonPath 是一种信息抽取类库，是从JSON文档中抽取指定信息的工具.

 JsonPath有许多编程语言，如Javascript、Python、PHP、Java等

JsonPath提供的json解析非常强大，它提供了类似正则表达式的语法，基本上可以满足所有你想要获得的json内容。

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

JsonPath表达式始终引用JSON结构，其方式与XPath表达式与XML文档结合使用的方式相同。$无论是对象还是数组，JsonPath中的“根成员对象”始终被称为。

JsonPath表达式可以使用点表示法

$.store.book[0].title

或括号表示法

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

 二、API

使用的时候建议缓存JSONPath对象，这样能够提高求值的性能。

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);
}

三、支持语法

以下两种写法的语义是相同的：

$.store.book[0].title

和

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

四、语法示例

五、API示例

5.1 基础例子

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 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 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 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 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 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 具体用例测试

 
@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);
 
 
    }
 
 
}

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