Jackson Use (iii)----use annotations

Jackson has provided us with a series of annotations in practical application, which improves the flexibility of development, and describes some of the most common annotations

Reference: http://blog.csdn.net/sdyy321/article/details/40298081

1. @JsonIgnoreProperties

This annotation is a class annotation that ignores some properties in a Java bean when JSON is serialized. Both serialization and deserialization are affected.

2. @JsonIgnore

Word annotations are used in properties or methods, as well as @jsonigonreproperties. Returns NULL when deserializing, how the field is marked with Jsonignore

3. @JsonFormat

In the properties and methods, it is convenient to format the conversion, such as converting the date to the pattern we want @jsonformat (pattern = "Yyyy-mm-dd hh-mm-ss")

4. @JsonSerialize

Used for attributes and getter () methods, which embed our custom code when serializing, such as when serializing a igedouble, after which 2 decimal places are restricted

5. @JsonDeserialize

This annotation is used on properties or setter methods to embed our custom code when deserializing

Code:

Entity class:

public class Student {
	private int id;
	private String name;
	private String password;
	@JsonSerialize (Using=mydateserializer.class)  //Serialization Converter
	@JsonDeserialize (Using=mydatedeserializer.class)  //Deserialization converter
	private date date;
	
	Public Student () {
		System.out.println ("Initialize Student object");
	}
Setter,getter omitted
}

Serialization Converter:

/**
 * Date Serialization Converter
 * @author root * * */Public
class Mydateserializer extends Jsonserializer<date >{

	@Override public
	void Serialize (date date, Jsongenerator Jgen, Serializerprovider provider)
			throws IOException, jsonprocessingexception {
		SimpleDateFormat sdf = new SimpleDateFormat ("Yyyy-mm-dd  HH:mm:ss");
		String str = sdf.format (date);
		Jgen.writestring (str);
	}
	
}

Date Deserialization converter:

/**
 * Date deserialization converter
 * @author root * * */Public
class Mydatedeserializer extends jsondeserializer< date>{

	@Override Public
	Date Deserialize (jsonparser parser, Deserializationcontext context)
			throws IOException, jsonprocessingexception {
		System.out.println ("deserialization");
		String datestr = parser.getvalueasstring ();
		SimpleDateFormat SDF = new SimpleDateFormat ("Yyyy-mm-dd  HH:mm:ss");
		Date date = null;
		try {
			date = Sdf.parse (DATESTR),
		} catch (ParseException e) {
			//TODO auto-generated catch block
			e.pr Intstacktrace ();
		}
		return date;
	}
}

6. @JsonUnwrapped

When a member property in an entity class is an object of a class, the wrapper is ignored: (really bad explanation, see the example to understand)

User class:

public class User {
	private String name;
	private String password;
	@JsonIgnore
	private list<string> STRs;
	@JsonUnwrapped
	Private person p;
       Setter,getter omitted
}

Person class:

public class Person {  
    private String pName;  
    private int age;  
    Private Boolean sex; 
    @JsonFormat (pattern = "Yyyy-mm-dd hh-mm-ss")
    private Date birthday;  
    Private String word;  
    private double salary;  
Setter,getter omitted
  }

@Test public
	void testjsonunwrapped () throws ioexception{
		user U = New User ("Guofeipeng", "123");
		list<string> ls = new arraylist<string> ();
		Ls.add ("123");
		Ls.add ("234");
		Ls.add ("345");
		U.setstrs (LS);
		person person = new Person ("nomouse", +, True, new Date (), "Programmer",
				2500.0);
		U.SETP (person);
		Objectmapper mapper = new Objectmapper ();
		String json = mapper.writevalueasstring (u);  Java 2 JSON
		SYSTEM.OUT.PRINTLN (JSON);
		
		User user = Mapper.readvalue (JSON, User.class);//json 2 java
		System.out.println (user);
	

Note: The person attribute in the 1.User class is not @jsonunwarpped, and the converted JSON is: {"name": "Guofeipeng", "Password": "123", "P": {"age": +, "sex": true, " Birthday ":" 2014-12-22 07-15-29 "," word ":" Programmer "," pname ":" Nomouse "," Salary ":" 2500.00 "}}

2. Add the @jsonunwarpped annotation, then remove the P key (wrapper), the converted JSON is:

{"Name": "Guofeipeng", "Password": "123", "age": +, "sex": true, "Birthday": "2014-12-22 07-16-38", "word": "Programmer", "PName" : "Nomouse", "Salary": "2500.00"}

7. @JsonProperty

Acting on a field or method, used to serialize/deserialize a property, to avoid missing attributes, and to provide renaming of property names, such as in many scenarios where the properties of a Java object are written according to the specifications of the hump, but the actual display is similar to C-style or c++/microsolft Style

	@JsonProperty (value= "Stu_name")
	private String name;

/**
 * Date deserialization converter
 * @author root * * */Public
class Mydatedeserializer extends jsondeserializer< date>{

	@Override Public
	Date Deserialize (jsonparser parser, Deserializationcontext context)
			throws IOException, jsonprocessingexception {
		System.out.println ("deserialization");
		String datestr = parser.getvalueasstring ();
		SimpleDateFormat SDF = new SimpleDateFormat ("Yyyy-mm-dd  HH:mm:ss");
		Date date = null;
		try {
			date = Sdf.parse (DATESTR),
		} catch (ParseException e) {
			//TODO auto-generated catch block
			e.pr Intstacktrace ();
		}
		return date;
	}
}