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This article mainly introduces "how to use JSONObject.toJSONString () to include or exclude specified attributes" related knowledge, editor through the actual case to show you the operation process, the method of operation is simple and fast, practical, I hope that this "how to use JSONObject.toJSONString () to include or exclude specified attributes" article can help you solve the problem.

JSONObject.toJSONString contains or excludes specified attributes

Converts an entity object to a Json string JSON.toJSONString ()

The SerializeFilter class provided by FastJson can specify the properties to be included in the transformation, or the properties to be excluded during the transformation.

JSONObject.toJSONString () ignores attributes whose value is null by default.

Use the following methods provided by JSONObject to convert entity objects into Json strings: (the toJSONString source code provided by JSONObject has not been read yet)

Public static final String toJSONString (Object object, SerializerFeature... Features) {SerializeWriter out = new SerializeWriter (); try {JSONSerializer serializer = new JSONSerializer (out); for (com.alibaba.fastjson.serializer.SerializerFeature feature: features) {serializer.config (feature, true);} serializer.write (object); return out.toString ();} finally {out.close () }} demo program import com.alibaba.fastjson.JSONObject;import com.alibaba.fastjson.serializer.SerializerFeature;import com.alibaba.fastjson.support.spring.PropertyPreFilters;/** * uses FastJson to convert entity objects into Json string test classes * / public class FastJsonApplication {public static void main (String [] args) {User user = new User (); user.setId (1L); user.setUsername ("Zhang San") User.setPassword (""); user.setMobile (null); user.setCountry ("China"); user.setCity ("Wuhan"); String jsonUser = null / * specify exclusion attribute filter and include attribute filter * specify exclusion attribute filter: which attributes are excluded when converted to JSON strings * specify which attributes filters are included when converted to JSON strings * / String [] excludeProperties = {"country", "city"} String [] includeProperties = {"id", "username", "mobile"}; PropertyPreFilters filters = new PropertyPreFilters (); PropertyPreFilters.MySimplePropertyPreFilter excludefilter = filters.addFilter (); excludefilter.addExcludes (excludeProperties); PropertyPreFilters.MySimplePropertyPreFilter includefilter = filters.addFilter (); includefilter.addIncludes (includeProperties) / * case 1: ignore the attribute with the value of null by default * / jsonUser = JSONObject.toJSONString (user, SerializerFeature.PrettyFormat); System.out.println ("case 1:\ n" + jsonUser); / * case 2: include the attribute with the value of null * / jsonUser = JSONObject.toJSONString (user, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue) System.out.println ("case 2:\ n" + jsonUser); / * case 3: ignore the attribute with the value of null by default, but exclude the attributes country and city * / jsonUser = JSONObject.toJSONString (user, excludefilter, SerializerFeature.PrettyFormat); System.out.println ("case 3:\ n" + jsonUser) / * case 4: contains attributes with the value of null, but excludes the attributes country and city * / jsonUser = JSONObject.toJSONString (user, excludefilter, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue); System.out.println ("case 4:\ n" + jsonUser) / * case 5: the attribute with the value of null is ignored by default, but contains three attributes: id, username and mobile * / jsonUser = JSONObject.toJSONString (user, includefilter, SerializerFeature.PrettyFormat); System.out.println ("case 5:\ n" + jsonUser) / * case 6: contains attributes with the value of null, but contains three attributes: id, username and mobile * / jsonUser = JSONObject.toJSONString (user, includefilter, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue); System.out.println ("case 6:\ n" + jsonUser);} / * * user entity class * / public static class User {private Long id Private String username; private String password; private String mobile; private String country; private String city; / / the set and get methods of the corresponding properties are omitted here.

Running result:

The results show that:

Case one and case two illustrate public static String toJSONString (Object object, SerializeFilter filter, SerializerFeature... Features) when converting an entity object to a JSON string, the default is to ignore the attribute whose value is null, and shows how to make the converted JSON string contain the attribute with the value null.

Cases 3 and 4 show how to use SerializeFilter to exclude specified attributes so that these attributes are not included in the converted JSON string.

Cases 5 and 6 show how to use SerializeFilter to include specified attributes so that only these attributes are included in the converted JSON string.

The pit encountered by JSONObject toJSONString introduces the pom file com.alibaba fastjson 1.2.73 test uses JSONObject to output map of type int

Non-json format

Import java.util.HashMap;import java.util.Map;import com.alibaba.fastjson.JSONObject;public class JsonTest {public static void main (String [] args) {Map map = new HashMap (); map.put (1, "aaasa"); map.put (2, "bbbbb"); map.put (3, "ccccc"); map.put (4, "ddddd") Map.put (5, "eeeee"); System.out.println (JSONObject.toJSONString (map));}}

Output result

That's all for "how to include or exclude specified attributes with JSONObject.toJSONString ()". Thank you for reading. If you want to know more about the industry, you can follow the industry information channel. The editor will update different knowledge points for you every day.

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