FAQ(English Version)

1. how to get fastjson?

you can download fastjson:

• maven central repo: http://central.maven.org/maven2/com/alibaba/fastjson/
• Sourceforge.net: https://sourceforge.net/projects/fastjson/files/
• maven the newest version of fastjson will be published to central maven repo, you can add the dependency.

<dependency>
     <groupId>com.alibaba</groupId>
     <artifactId>fastjson</artifactId>
     <version>1.2.12</version>
</dependency>

for android

<dependency>
     <groupId>com.alibaba</groupId>
     <artifactId>fastjson</artifactId>
     <version>1.1.52.android</version>
</dependency>

2. fastjson main API？

the entrance Class of fastjson is com.alibaba.fastjson.JSON，the main API are JSON.toJSONString and parseObject。

package com.alibaba.fastjson;
public abstract class JSON {
      public static final String toJSONString(Object object);
      public static final <T> T parseObject(String text, Class<T> clazz, Feature... features);
}

serialize：

String jsonString = JSON.toJSONString(obj);

deserialize：

VO vo = JSON.parseObject("...", VO.class);

vector deserialize：

import com.alibaba.fastjson.TypeReference;

List<VO> list = JSON.parseObject("...", new TypeReference<List<VO>>() {});

3. where can i find examples using fastjson

fastjson examples：https://github.com/alibaba/fastjson/wiki/Samples-DataBind

4. how about the performance of fastjson？

Until now, fastjson is the fastest json lib for Java, faster than the self-announced fastest jackson. The link is the third-party test result: https://github.com/eishay/jvm-serializers/wiki/Staging-Results

When doing yourself testing, disable circular reference detect.

JSON.toJSONString(obj, SerializerFeature.DisableCircularReferenceDetect)
VO vo = JSON.parseObject("...", VO.class, Feature.DisableCircularReferenceDetect)

Here is the comment about fastjon of the author of jackson cowtowncoder: https://groups.google.com/forum/#!topic/java-serialization-benchmarking/8eS1KOquAhw

5. fastjson v.s. gson?

fastjson is 6 times faster than gson, here is the testing result: https://github.com/eishay/jvm-serializers/wiki/Staging-Results 。gson的g可能是“龟”拼音的缩写，龟速的json库。

6. can fastjson be used in android?

fastjson has specific version for android, whose unusually function is removed. the size of jar is smaller. git branch address: https://github.com/alibaba/fastjson/tree/android

7. fastjson serialize is same with json-lib, who need to setting java ben serialize?

no, the only need is that the class is a java bean specification satisfied class.

8. how to do with date with fastjson?

so easy, for example:

JSON.toJSONStringWithDateFormat(date, "yyyy-MM-dd HH:mm:ss.SSS")

with ISO-8601 date format

JSON.toJSONString(obj, SerializerFeature.UseISO8601DateFormat);

global setting of date format

JSON.DEFFAULT_DATE_FORMAT = "yyyy-MM-dd";
JSON.toJSONString(obj, SerializerFeature.WriteDateUseDateFormat);

auto recognize date format as below when deserialize:

• ISO-8601 format
• yyyy-MM-dd
• yyyy-MM-dd HH:mm:ss
• yyyy-MM-dd HH:mm:ss.SSS
• miliseconds
• miliseconds string
• .NET JSON format
• new Date(198293238)

9. how to customize the serialize？

use SimplePrePropertyFilter to filter the property，more info here：https://github.com/alibaba/fastjson/wiki/%E4%BD%BF%E7%94%A8SimplePropertyPreFilter%E8%BF%87%E6%BB%A4%E5%B1%9E%E6%80%A7

here is the detailed introduction about customizing serialize： https://github.com/alibaba/fastjson/wiki/%E5%AE%9A%E5%88%B6%E5%BA%8F%E5%88%97%E5%8C%96

10. when the object has some refrence property, what if not supported by the browser?

use SerializerFeature.DisableCircularReferenceDetect to close the refrence check and generate:

String  jsonString = JSON.toJSONString(obj, SerializerFeature.DisableCircularReferenceDetect);

11. IE 6 not support JSON with Chinese character，how to deal with it？

fastjson has BrowserCompatible configuration，after opened，all Chinese will be serialized to the format with \uXXXX.

String  jsonString = JSON.toJSONString(obj, SerializerFeature.BrowserCompatible);

12. fastjson how to deal with extreme super object and JSON String.

fastjson offers Stream API: https://github.com/alibaba/fastjson/wiki/Stream-api

13. @JSONField customize the serialize

fastjson offers Annotation to customize the serialize and deserialize: https://github.com/alibaba/fastjson/wiki/JSONField