Fastjson Simple to use

Fastjson is a high-performance, fully functional, standard JSON library written in the Java language that supports http://json.org . More do not say, Baidu a lot.

Here, simply summarize the methods you have used and tested.

If you use MAVEN, add the following dependencies to the Pom.xml file.

<dependency>     <groupId>com.alibaba</groupId>     <artifactid>fastjson</ artifactid>     <version>1.2.15</version> </dependency>

　　

Serialization of

Serialization refers to a string that turns the JavaBean object into a JSON format.

Com.alibaba.fastjson.JSON provides a number of methods (polymorphic) for serialization.

1. Basic serialization

String Objjson = Json.tojsonstring (Object object);

　　

Pass in an object and turn the object into a JSON string.

Example 1: Turning a map into JSON

map<string, object> map = new hashmap<string, object> (); Map.put ("Key1", "one"); Map.put ("Key2", "both");          String Mapjson = json.tojsonstring (map);

　　

Output Result:

{"Key1": "One", "Key2": "One"}

　　

Example 2: Turn list<map> into JSON.

list<map<string, object>> list = new arraylist<map<string, object>> ();          map<string, object> map1 = new hashmap<string, object> (); Map1.put ("Key1", "one"); Map1.put ("Key2", "both");          map<string, object> map2 = new hashmap<string, object> (); Map2.put ("Key1", "three"); Map2.put ("Key2", "four");         List.add (MAP1); List.add (MAP2);      String Listjson = json.tojsonstring (list);

　　

Output Result:

[{"Key1": "One", "Key2": "Both"},{"Key3": "Three", "Key4": "Four"}]

　　

Example 3: Custom JavaBean user turns JSON.

User user = new user (); User.setusername ("John Doe"); User.setage ();          String Userjson = json.tojsonstring (user);

　　

Output Result:

{"Age": $, "userName": "John Doe"}

　　

You can output a formatted JSON string.

String Objjson = Json.tojsonstring (Object object, Boolean Prettyformat);

　　

Passes in an object and a Boolean type (whether formatted), and turns the object into a formatted JSON string.

Example 4: Take example 2 code for example.

String Listjson = json.tojsonstring (list, true);

　　

The output is:

[      {          "Key1": "One",          "Key2": "One"      },      {        "Key3": "Three",          "Key4": "Four"    }]

　　

Fastjson provides a number of feature support.

　　

A mutable variable that passes in an object and Serializerfeature type. Serializerfeature is an enumeration.

Com.alibaba.fastjson.serializer.SerializerFeature

You can use these features according to your own situation.

Briefly say a few common features:

1. Date formatting:

Fastjson can be formatted directly on a date type and, by default, Fastjson will convert date to long.

Example 5:fastjson turns java.util.Date into a long.

String Datejson = json.tojsonstring (New Date ());         System.out.println (Datejson);

　　

Output Result:

1401370199040

　　

Example 6: Formatting dates with the Serializerfeature attribute.

String Datejson = json.tojsonstring (New Date (), serializerfeature.writedateusedateformat);         System.out.println (Datejson);

　　

Output Result:

"2014-05-29 21:36:24"

　　

You can also specify the output date format.

Example 7: Specify the output date format.

String Datejson = Json.tojsonstringwithdateformat (New Date (), "Yyyy-mm-dd HH:mm:ss. SSS ");          System.out.println (Datejson);

　　

Output Result:

"2014-05-29 21:47:00.154"

　　

2. Use single quotation marks.

Example 8: Take example 2 for example.

String Listjson = json.tojsonstring (list, serializerfeature.usesinglequotes);

　　

Output Result:

[{' Key1 ': ' One ', ' key2 ': ' Both '},{' Key3 ': ' Three ', ' Key4 ': ' Four '}]

　　

3.JSON format.

Example 9:

String Listjson = json.tojsonstring (list, serializerfeature.prettyformat);

　　

Output: Consistent with example 4 results.

4. Output a null field.

By default Fastjson does not enter a field with a value of NULL, you can use Serializerfeature.writemapnullvalue to make it output.

Example 10:

map<string, object> map = new hashmap<string,object> ();          String B = null; Integer i = 1;          Map.put ("A", b); Map.put ("B", I);          String Listjson = json.tojsonstring (map, Serializerfeature.writemapnullvalue);

　　

Output Result:

{"A": null, "B": 1}

　　

5. Serialization is the write type information.

Example 11:

User user = new user ();          User.setage (18); User.setusername ("John Doe");          String Listjson = json.tojsonstring (user, serializerfeature.writeclassname);

　　

Output Result:

{"@type": "User", "Age": "UserName": "John Doe"}

　　

Because serialization has type information, it enables type recognition to be automated when deserializing.

Example 12: Deserialization of Example 11.

User User1 = (user) json.parse (listjson);          System.out.println (User1.getage ());

　　

Output Result:

18

　　

If user serialization is not joined to type information (serializerfeature.writeclassname), an error (Java.lang.ClassCastException) will be followed by example 12.

deserialization

Deserialization is the conversion of a JSON-formatted string into a Java bean object.

Com.alibaba.fastjson.JSON provides a number of methods (polymorphic) for deserialization

Give a few examples.

Specifies the class information to deserialize.

Example 13: Deserialization of Example 3.

User user1 = Json.parseobject (Userjson, User.class); System.out.println (User1.getusername ());

　　

Output Result:

John doe

　　

Sets the deserialization of the collection.

Example 14: Deserialization of Example 2.

List<map> List1 = Json.parsearray (Listjson, map.class);           For (map<string, object> map:list1) {     System.out.println (map.get ("Key1"));     System.out.println (Map.get ("Key2"));          }

　　

Output Result:

One, three four

　　

The deserialization of generics (using TypeReference to pass in type information).

Example 15: Deserialization of Example 1.

map<string, object> map1 = Json.parseobject (Mapjson, New typereference<map<string, Object>> () {}); System.out.println (Map1.get ("Key1")); System.out.println (Map1.get ("Key2"));

　　

Output Result:

Onetwo

　　

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Jsonobject,jsonarray is the two subclass of JSON.

Jsonobject equivalent to map<string, Object>

Jsonarray equivalent to list<object>.

An example of a simple method:

Example 16: Convert Map to Jsonobject, then add element, output.

map<string, object> map = new hashmap<string, object> ();  Map.put ("Key1", "one");  Map.put ("Key2", "both");                               Jsonobject j = new Jsonobject (map);                       J.put ("Key3", "three");              System.out.println (J.get ("Key1")); System.out.println (J.get ("Key2")); System.out.println (J.get ("Key3"));

　　

Output Result:

One and three

　　

Example 17: Turn the list object into Jsonarray and output.

list<map<string, object>> list = new arraylist<map<string, object>> ();            map<string, object> map = new hashmap<string, object> ();  Map.put ("Key1", "one"); Map.put ("Key2", "both");            map<string, object> map2 = new hashmap<string, object> ();  Map2.put ("Key1", "three");  Map2.put ("Key2", "four");          List.add (map); List.add (MAP2);          Jsonarray j = Jsonarray.parsearray (json.tojsonstring (list));           for (int i=0; i<j.size (); i++) {     System.out.println (J.get (i));

　　

Output Result:

{"Key1": "One", "Key2": "One"} {"Key1": "Three", "Key2": "Four"}

　　

Fastjson Simple to use