Fastjson JSONPath

1. JSONPath介紹

fastjson 1.2.0之后的版本支持JSONPath。這是一個(gè)很強(qiáng)大的功能，可以在java框架中當(dāng)作對象查詢語言（OQL）來使用。

2. API

package com.alibaba.fastjson;

public class JSONPath {          
     //  求值，靜態(tài)方法
     public static Object eval(Object rootObject, String path);

     // 計(jì)算Size，Map非空元素個(gè)數(shù)，對象非空元素個(gè)數(shù)，Collection的Size，數(shù)組的長度。其他無法求值返回-1
     public static int size(Object rootObject, String path);

     // 是否包含，path中是否存在對象
     public static boolean contains(Object rootObject, String path) { }

     // 是否包含，path中是否存在指定值，如果是集合或者數(shù)組，在集合中查找value是否存在
     public static boolean containsValue(Object rootObject, String path, Object value) { }

     // 修改制定路徑的值，如果修改成功，返回true，否則返回false
     public static boolean set(Object rootObject, String path, Object value) {}

     // 在數(shù)組或者集合中添加元素
     public static boolean array_add(Object rootObject, String path, Object... values);
}

建議緩存JSONPath對象，這樣能夠提高求值的性能。

3. 支持語法

以下兩種寫法的語義是相同的：

$.store.book[0].title

和

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

4. 語法示例

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

讀取集合多個(gè)元素的某個(gè)屬性

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的所有名稱
Assert.assertSame(entities.get(0).getName(), names.get(0));
Assert.assertSame(entities.get(1).getName(), names.get(1));

5.3 例3

返回集合中多個(gè)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]"); // 返回下標(biāo)為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

按范圍返回集合的子集

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]"); // 返回下標(biāo)從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

通過條件過濾，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

根據(jù)屬性值過濾條件判斷是否返回對象，修改對象，數(shù)組屬性添加元素

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); //將id字段修改為123456
Assert.assertEquals(123456, entity.getId().intValue());

JSONPath.set(entity, "value", new int[0]); //將value字段賦值為長度為0的數(shù)組
JSONPath.arrayAdd(entity, "value", 1, 2, 3); //將value字段的數(shù)組添加元素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));