Jackson Study Notes

Jackson won praise for his excellent analytical performance, and today he has a look at some of Jackson's simple uses.
Jackson has to download before use, there are a total of three jar packages, to get the perfect Jackson experience, these three jar packages are indispensable. Java–>json

1. Output a class as a JSON string:

    Outputs a class as a JSON string
    @Test public
    void Test1 () {
        Objectmapper mapper = new Objectmapper ();
        User user = new user ();
        User.setmoney (1000);
        User.setusername ("John");
        User.setpassword ("123");
        try {
            System.out.println (mapper.writevalueasstring (user));
        } catch (IOException e) {
            E.printstacktrace ();
        }
    

User.java

Import java.io.Serializable;

public class User implements serializable{

    private String username;
    private String password;

    Fields that have been added to the transient property are not stored as
    private int money;



    public int Getmoney () {return money
        ;
    }
    public void Setmoney (int $) {
        This.money = money;
    }
    Public user () {
    } public
    User (string Username, string password, int-money) {
        this.username = username;
  this.password = password;
        This.money = money;
    }
    Public String GetUserName () {return
        username;
    }
    public void Setusername (String username) {
        this.username = username;
    }
    Public String GetPassword () {return
        password;
    }
    public void SetPassword (String password) {
        this.password = password;
    }

Output:

2. Output a slightly more complex class in the form of a JSON string:

Book.java

public class Book {private int id;
    private String name;
    private int price;
    Private String author;
    Private Detail Detail;

    private attribute attribute;
    Public Attributes GetAttribute () {return attribute;
    public void SetAttribute (attribute) {this.attribute = attribute;
    Public Detail Getdetail () {return Detail;
    public void Setdetail (Detail Detail) {this.detail = Detail;
    public int getId () {return id;
    The public void setId (int id) {this.id = ID;
    Public String GetName () {return name;
    public void SetName (String name) {this.name = name;
    public int GetPrice () {return price;
    public void Setprice (int price) {this.price = Price;
    Public String Getauthor () {return author;
    } public void Setauthor (String author) {this.author = author;
 }
}

Detail.java

public class Detail {

    private String presstime;
    Private String Storytime;
    Public String Getpresstime () {return
        presstime;
    }
    public void Setpresstime (String presstime) {
        this.presstime = presstime;
    }
    Public String Getstorytime () {return
        storytime;
    }
    public void Setstorytime (String storytime) {
        this.storytime = storytime;
    }
}

Attribute.java

public class Attribute {

    private String category;
    Private String edition;
    Public String GetCategory () {return
        category;
    }
    public void Setcategory (String category) {
        this.category = category;
    }
    Public String getedition () {return
        edition;
    }
    public void Setedition (String edition) {
        this.edition = edition;
    }

}

The output is:

{"id": 1, "name": "The Chinese Kingdoms", "Price": "Author": "Luo Guan Zhong", "detail": {"presstime": "2001-01-01", "Storytime": "196-05-06"}, " Attribute ": {" category ":" Novel "," edition ":" 9 "}}

3. Output a list collection as a JSON string:

    @Test public
    void Test2 () {
        Objectmapper mapper = new Objectmapper ();
        list<user> list = new arraylist<user> ();
        User U = New User ("John", "123", 1000);
        List.add (u);
        u = new User ("Dick", "456",);
        List.add (u);
        u = new User ("Harry", "789", 3000);
        List.add (u);
        u = new User ("Zhao Liu", "555", 4000);
        List.add (u);
        try {
            System.out.println (mapper.writevalueasstring (list);
        } catch (Jsonprocessingexception e) {
            // TODO auto-generated Catch block
            e.printstacktrace ();
        }
    

Output results:

[{"username": "John", "Password": "123", "Money": 1000},{"username": "Dick", "Password": "456", "Money": 2000},{"username": " Harry "," Password ":" 789 "," Money ": 3000},{" username ":" Zhao Liu "," Password ":" 555 "," Money ": 4000}]

4. Output a map as a JSON string:

    @Test public
    void Test3 () {
        Objectmapper mapper = new Objectmapper ();
        map<string, string> map = new hashmap<string, string> ();
        Map.put ("username", "John");
        Map.put ("Password", "123456");
        try {
            System.out.println (mapper.writevalueasstring (map));
        } catch (Jsonprocessingexception e) {
            E.printstacktrace ();
        }
    

The results are:

5. What if you want to export the map in the list collection in JSON string format. Same as the previous list.

    @Test public
    void Test4 () {
        Objectmapper mapper = new Objectmapper ();
        list<map<string, string>> list = new arraylist<map<string,string>> ();
        map<string, string> map = new hashmap<string, string> ();
        Map.put ("username", "John");
        Map.put ("Password", "123456");
        List.add (map);
        Map = new hashmap<string, string> ();
        Map.put ("username", "Dick");
        Map.put ("Password", "888888");
        List.add (map);
        try {
            System.out.println (mapper.writevalueasstring (list);
        } catch (Jsonprocessingexception e) {
            E.printstacktrace ();
        }
    

6. In a look at a map there are other classes in the Book.java,book.java:

    @Test public
    void Test1 () {
        Objectmapper mapper = new Objectmapper ();
        Detail Detail = new Detail ();
        Detail.setpresstime ("2001-01-01");
        Detail.setstorytime ("196-05-06");
        Attribute attr = new attribute ();
        Attr.setcategory ("novel");
        Attr.setedition ("9");
        Book book = new book ();
        Book.setattribute (attr);
        Book.setauthor ("Luo Guan Zhong");
        Book.setdetail (detail);
        Book.setid (1);
        Book.setname ("The Kingdoms");
        Book.setprice (a);
        map<string, object> map = new hashmap<string, object> ();
        Map.put ("namespace", "books");
        Map.put ("book", book);
        try {
            System.out.println (mapper.writevalueasstring (map));
        } catch (IOException e) {
            E.printstacktrace ();
        }
    

Output results:

{"book": {"id": 1, "name": "The Chinese Kingdoms", "Price": "Author": "Luo Guan Zhong", "detail": {"presstime": "2001-01-01", "Storytime": " 196-05-06 "}," attribute ": {" category ":" Novel "," edition ":" 9 "}}," namespace ":" Books "}

Json–>java

1.json string converted to JavaBean:

    @Test public
    void Test5 () {
        String str = "{\ id\": 1,\ "name\": \ "the Chinese kingdoms \", \ "price\": 20,\ "author\": \ "Luo Guan," "," Detail\ ": {\" presstime\ ": \" 2001-01-01\ ", \" storytime\ ": \" 196-05-06\ "},\" attribute\ ": {\" category\ ": \" novel \ ", \" edition\ ": \" 9\ "}}";
        Objectmapper mapper = new Objectmapper ();
        try {book Book
            = Mapper.readvalue (str, book.class);
            System.out.println (Book.getauthor () + "," +book.getattribute (). GetCategory ());
        catch (IOException e) {
            e.printstacktrace ();
        }
    }

2.json string to List

    Json-->list
    @Test public
    void Test6 () {
        String str = "[{\ username\": \ "john \", \ "password\": \ "123\", \ " Money\ ": 1000},{\" username\ ": \" Dick \ ", \" password\ ": \" 456\ ", \" money\ ": 2000},{\" username\ ": \" Harry "," password\ ": \" 789\ ", \" money\ ": 3000},{\" username\ ": \" Zhao Liu ", \" password\ ": \" 555\ ", \" money\ ": 4000}]";
        Objectmapper mapper = new Objectmapper ();
        try {
            list<user> US = mapper.readvalue (str, new typereference<arraylist<user>> () {});
            for (User user:us) {
                System.out.println (user.getusername () + ", +user.getmoney ());
            }
        catch ( IOException e) {
            e.printstacktrace ();
        }
    }

The 3.json string is converted to map:

    Json-->map
    @Test public
    void Test7 () {
        String str = "{\ password\": \ "888888\", \ "username\": \ "Dick \"} " ;
        Objectmapper mapper = new Objectmapper ();
        try {
            map<string, string> Map = Mapper.readvalue (str, new typereference<map<string, string>> () {} );
            For (String Key:map.keySet ()) {
                System.out.println (key+ ", +map.get (key));
            }
        catch (IOException e) { C11/>e.printstacktrace ();
        }
    

Alas, carefully pondering, this Jackson really good simple, had always thought it was difficult, think of the text of the primary school "Pony River", it seems to be more practice.