FastJson的常用操作

2017-06-05

常用操作包括以下内容：

1. 对象与（JsonObject或JsonArray）与String的互换
2. String转换为（JsonObject或JsonArray）如何保持顺序
3. Eval的使用
4. 值为null的（JsonObject或JsonArray）转换为String时如何保存

代码：

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("---------- 基元类型 toString() toJSONString() 比较: ----------");

        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() 比较: ----------");

        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() 比较: ----------");

        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;

    }

}

结果：

---------- 基元类型 toString() toJSONString() 比较: ----------

ZifuChuan

"ZifuChuan"

true

true

1.1

1.1

---------- JsonObject toString() toJSONString() 比较: ----------

{"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() 比较: ----------

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}]}

参考：

[1] Introducing JSON

[2] FastJson 教程