FastJson的常用操作

轉載：https://www.cnblogs.com/Ming8006/p/6944954.html

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常用操作包括以下內容：

1. 對象與（JsonObject或JsonArray）與String的互換
2. String轉換為（JsonObject或JsonArray）如何保持順序
3. Eval的使用
4. 值為null的（JsonObject或JsonArray）轉換為String時如何保存

代碼：

package Demo.Sample1;import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONPath;
import com.alibaba.fastjson.parser.Feature;
import com.alibaba.fastjson.serializer.SerializerFeature;public class Sample {public static void main(String[] args) {Group group = GenerateGroup();String ss="{\"id\":1.1,\"name\":\"admin\",\"users\":[{\"id\":2.2,\"name\":\"guest\"},{\"id\":3.3,\"name\":\"root\"}]}";        Group groupWithNull=GenerateGroupWithNull();BasicObjectToStringCompare();JsonObjectToStringCompare(ss);NJsonObjectToStringCompare(group);JsonStringSequence(group, ss);        JsonEval(ss,"$.users");DealWithNullToStringString(groupWithNull);        }public static void BasicObjectToStringCompare(){System.out.println("---------- 基元類型 toString() toJSONString() 比較: ----------");System.out.println("ZifuChuan");System.out.println(JSON.toJSONString("ZifuChuan"));System.out.println(true);System.out.println(JSON.toJSONString(true));System.out.println(1.1);System.out.println(JSON.toJSONString(1.1));}public static String NJsonObjectToStringCompare(Group group) {String jsonString = JSON.toJSONString(group);System.out.println("---------- 非JsonObject toString() toJSONString() 比較: ----------");System.out.println(group.toString());System.out.println(JSON.toJSONString(group));return jsonString;}public static String JsonObjectToStringCompare(String ss) {Object o=JSON.parse(ss,Feature.OrderedField);System.out.println("---------- JsonObject toString() toJSONString() 比較: ----------");System.out.println(o.toString());System.out.println(JSON.toJSONString(o));return ss;}public static void JsonStringSequence(Group group, String jsonString) {System.out.println("---------- 是否有序: ----------");Object o=JSON.parse(jsonString);System.out.println(o.toString());;Object o1=JSON.parse(jsonString,Feature.OrderedField);System.out.println(o1.toString());Object o2 = JSON.toJSON(group);System.out.println(o2.toString());}public static void JsonEval(String ss,String jsonPath) {System.out.println("---------- Json Eval: ----------");        Object o3=JSONPath.eval(JSON.parse(ss,Feature.OrderedField),jsonPath);System.out.println(o3.toString());}public static void DealWithNullToStringString(Group groupWithNull) {System.out.println("---------- JsonObject with null emlement: ----------");System.out.println(JSON.toJSONString(groupWithNull));System.out.println(JSON.toJSONString(groupWithNull,SerializerFeature.WriteMapNullValue));}private static Group GenerateGroup() {Group group = new Group();group.setId(1.1);group.setName("admin");User guestUser = new User();guestUser.setId(2.2);guestUser.setName("guest");User rootUser = new User();rootUser.setId(3.3);rootUser.setName("root");group.addUser(guestUser);group.addUser(rootUser);return group;}private static Group GenerateGroupWithNull() {Group group = new Group();group.setId(1.1);group.setName("");User guestUser1 = new User();guestUser1.setId(null);guestUser1.setName("guest");User guestUser2 = new User();guestUser2.setId(3.3);User guestUser3 = new User();        group.addUser(guestUser1);group.addUser(guestUser2);group.addUser(guestUser3);return group;}
}

　　結果：

---------- 基元類型 toString() toJSONString() 比較: ----------
ZifuChuan
"ZifuChuan"
true
true
1.1
1.1
---------- JsonObject toString() toJSONString() 比較: ----------
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
---------- 非JsonObject toString() toJSONString() 比較: ----------
Demo.Sample1.Group@23ab930d
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
---------- 是否有序: ----------
{"name":"admin","id":1.1,"users":[{"name":"guest","id":2.2},{"name":"root","id":3.3}]}
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
{"name":"admin","id":1.1,"users":[{"name":"guest","id":2.2},{"name":"root","id":3.3}]}
---------- Json Eval: ----------
[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]
---------- JsonObject with null emlement: ----------
{"id":1.1,"name":"","users":[{"name":"guest"},{"id":3.3},{}]}
{"id":1.1,"name":"","users":[{"id":null,"name":"guest"},{"id":3.3,"name":null},{"id":null,"name":null}]}

參考：

[1]?Introducing JSON

http://www.json.org/

[2]?FastJson 教程

?https://www.w3cschool.cn/fastjson/%20