一、 Snack3 和 JSONPath 介绍
Snack3 是一个支持JSONPath的JSON框架。JSONPath是一个很强大的功能，也可以在 Java 框架中当作对象查询语言（OQL）来使用。
<dependency> <groupId>org.noear</groupId> <artifactId>snack3</artifactId> <version>3.1.5.10</version> </dependency>
Snack3 借签了 Javascript 所有变量由 var 申明，及 Xml dom 一切都是 Node 的设计。其下一切数据都以ONode表示，ONode也即 One node 之意，代表任何类型，也可以转换为任何类型。
- 强调文档树的操控和构建能力
- 做为中间媒体，方便不同格式互转
- 高性能Json path查询（兼容性和性能很赞）
- 支持序列化、反序列化
二、接口
public class ONode{
//...
/**
* Json path select
*
* @param jpath json path express
* @param useStandard use standard mode(default: false)
* @param cacheJpath cache json path parsing results
*/ public ONode select(String jpath, boolean useStandard, boolean cacheJpath) {
return JsonPath.eval(this, jpath, useStandard, cacheJpath);
}
public ONode select(String jpath, boolean useStandard) {
return select(jpath, useStandard, true);
}
public ONode select(String jpath) {
return select(jpath, false);
}
//...
}
默认使用缓存JSONPath解析对象，可提供几倍性能效果。
三、支持语法
- 字符串使用单引号，例：[‘name’]
- 过滤操作用空隔号隔开，例：[?(@.type == 1)]
像这两种写法的语义是差不多：
$.store.book[0].title //建议使用这种
$['store']['book'][0]['title']
四、语法示例说明
五、接口使用示例
示例1:
读取对象的属性
Entity entity = new Entity(123, new Object());
ONode n = ONode.load(entity);
assert n.select("$.id").getInt() == 123;
assert n.select("$.*").count() == 2;
public static class Entity {
public int id;
public String name;
public Object value;
public Entity(int id, Object value) { this.id = id; this.value = value; }
public Entity(String name) { this.name = name; }
}
示例2
读取集合多个元素的某个属性
List<Entity> entities = new ArrayList<Entity>();
entities.add(new Entity("wenshao"));
entities.add(new Entity("ljw2083"));
ONode n = ONode.load(entities);
List<String> names = n.select("$.name").toObject(List.class);
assert names.size() == 2;
示例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"));
ONode n = ONode.load(entities);
List<Entity> result = n.select("$[1,2]").toObject((new ArrayList<Entity>() {}).getClass());
assert result.size() == 2;
示例4
按范围返回集合的子集
List<Entity> entities = new ArrayList<Entity>();
entities.add(new Entity("wenshao"));
entities.add(new Entity("ljw2083"));
entities.add(new Entity("Yako"));
ONode n = ONode.load(entities);
List<Entity> result = n.select("$[0:2]").toObject((new ArrayList<Entity>(){}).getClass());
assert result.size() == 2;
示例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));
ONode n = ONode.load(entities);
ONode rst = n.select("$[?($.id in [1001,1002])]");
assert rst.count() == 2;
示例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");
ONode n = ONode.load(entity);
assert n.select("$[?(id == 1001)]").isObject();
assert n.select("$[?(id == 1002)]").isNull();
n.select("$").set("id",123456);
assert n.get("id").getInt() == 123456;
n.get("value").add(1).add(2).add(3);
assert n.get("value").count() == 3;
示例7
Map root = Collections.singletonMap("company",
Collections.singletonMap("departs",
Arrays.asList(
Collections.singletonMap("id",
1001),
Collections.singletonMap("id",
1002),
Collections.singletonMap("id", 1003)
)
));
ONode n = ONode.load(root);
List<Object> ids = n.select("$..id").toObject(List.class);
assertEquals(3l, ids.size());
assertEquals(1001l, ids.get(0));
assertEquals(1002l, ids.get(1));
assertEquals(1003l, ids.get(2));
具体用例测试请看下面:
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" +
"}";
ONode o = ONode.load(jsonStr);
//得到所有的书
ONode books = o.select("$.store.book");
System.out.println("books=::" + books);
//得到所有的书名
ONode titles = o.select("$.store.book.title");
System.out.println("titles=::" + titles);
//第一本书title
ONode title = o.select("$.store.book[0].title");
System.out.println("title=::" + title);
//price大于10元的book
ONode list = o.select("$.store.book[?(price > 10)]");
System.out.println("price大于10元的book=::" + list);
//price大于10元的title
ONode list2 = o.select("$.store.book[?(price > 10)].title");
System.out.println("price大于10元的title=::" + list2);
//category(类别)为科幻的book
ONode list3 = o.select("$.store.book[?(category == '科幻')]");
System.out.println("category(类别)为科幻的book=::" + list3);
//bicycle的所有属性值
ONode values = o.select("$.store.bicycle.*");
System.out.println("bicycle的所有属性值=::" + values);
//bicycle的color和price属性值
ONode read = o.select("$.store.bicycle['color','price']");
System.out.println("bicycle的color和price属性值=::" + read);
打印结果
books=::[{"author":"刘慈欣","price":8.95,"category":"科幻","title":"三体"},{"author":"itguang","price":12.99,"category":"编程语言","title":"go语言实战"}]
titles=::["三体","go语言实战"]
title=::"三体"
price大于10元的book=::[{"author":"itguang","price":12.99,"category":"编程语言","title":"go语言实战"}]
price大于10元的title=::["go语言实战"]
category(类别)为科幻的book=::[{"author":"刘慈欣","price":8.95,"category":"科幻","title":"三体"}]
bicycle的所有属性值=::["red",19.95]
bicycle的color和price属性值=::["red",19.95] 
