Load from json in list of elements

I need to load this king json file into some object in Java.

[
    {
       开发者_开发问答 "id": 1,
        "name": "FA1_M",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 1,
        "index_ring": 1,
        "order": 0
    },
    {
        "id": 2,
        "name": "A1_1_LED",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 1,
        "index_ring": 2,
        "order": 1
    },
    {
        "id": 3,
        "name": "FA1_A",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 2,
        "index_ring": 3,
        "order": 2
    },
    {
        "id": 4,
        "name": "A1_2_LED",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 2,
        "index_ring": 4,
        "order": 3
    },
    {
        "id": 5,
        "name": "FA1_BMA",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 3,
        "index_ring": 5,
        "order": 4
    },
    {
        "id": 6,
        "name": "A1_3_LED",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 3,
        "index_ring": 6,
        "order": 5
    },
    {
        "id": 7,
        "name": "Reserve_IN_4",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 4,
        "index_ring": 7,
        "order": 6
    },
    {
        "id": 8,
        "name": "A1_4_LED",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 4,
        "index_ring": 8,
        "order": 7
    },
    {
        "id": 9,
        "name": "Reserve_IN_5",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 5,
        "index_ring": 9,
        "order": 8
    },
    {
        "id": 10,
        "name": "A1_5_LED",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 5,
        "index_ring": 10,
        "order": 9
    },
    {
        "id": 11,
        "name": "Reserve_IN_6",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 6,
        "index_ring": 11,
        "order": 10
    },
    {
        "id": 12,
        "name": "Reserve_OUT_6",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 6,
        "index_ring": 12,
        "order": 11
    },
    {
        "id": 13,
        "name": "Reserve_IN_7",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 7,
        "index_ring": 13,
        "order": 12
    },
    {
        "id": 14,
        "name": "KK1_ENB",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 7,
        "index_ring": 14,
        "order": 13
    },
    {
        "id": 15,
        "name": "FA2_BMA",
        "ring_number": 1,
        "type": 3,
        "unit_index": 1,
        "device_type": 3,
        "address": 8,
        "index_ring": 15,
        "order": 14
    },
    {
        "id": 16,
        "name": "KK2_ENB",
        "ring_number": 1,
        "type": 4,
        "unit_index": 1,
        "device_type": 3,
        "address": 8,
        "index_ring": 16,
        "order": 15
    },
    {
        "id": 17,
        "name": "Smoke1_1",
        "ring_number": 1,
        "type": 2,
        "unit_index": 2,
        "device_type": 2,
        "address": 1,
        "index_ring": 17,
        "order": 16
    },
    {
        "id": 18,
        "name": "Smoke1_2",
        "ring_number": 1,
        "type": 2,
        "unit_index": 3,
        "device_type": 12,
        "address": 1,
        "index_ring": 18,
        "order": 17
    },
    {
        "id": 19,
        "name": "Smoke1_3",
        "ring_number": 1,
        "type": 2,
        "unit_index": 4,
        "device_type": 2,
        "address": 1,
        "index_ring": 19,
        "order": 18
    },
    {
        "id": 20,
        "name": "Smoke1_4",
        "ring_number": 1,
        "type": 2,
        "unit_index": 5,
        "device_type": 2,
        "address": 1,
        "index_ring": 20,
        "order": 19
    },
    {
        "id": 21,
        "name": "Fire1_1",
        "ring_number": 1,
        "type": 1,
        "unit_index": 6,
        "device_type": 4,
        "address": 1,
        "index_ring": 21,
        "order": 20
    },
    {
        "id": 22,
        "name": "Fire1_2",
        "ring_number": 1,
        "type": 1,
        "unit_index": 6,
        "device_type": 4,
        "address": 2,
        "index_ring": 22,
        "order": 21
    },
    {
        "id": 23,
        "name": "Fire1_3",
        "ring_number": 1,
        "type": 1,
        "unit_index": 7,
        "device_type": 1,
        "address": 1,
        "index_ring": 23,
        "order": 22
    },
    {
        "id": 24,
        "name": "Motorless1",
        "ring_number": 1,
        "type": 5,
        "unit_index": 8,
        "device_type": 13,
        "address": 1,
        "index_ring": 24,
        "order": 23
    },
    {
        "id": 25,
        "name": "Fire1_4",
        "ring_number": 1,
        "type": 1,
        "unit_index": 9,
        "device_type": 14,
        "address": 1,
        "index_ring": 25,
        "order": 24
    },
    {
        "id": 26,
        "name": "Fire1_5",
        "ring_number": 1,
        "type": 1,
        "unit_index": 9,
        "device_type": 14,
        "address": 2,
        "index_ring": 26,
        "order": 25
    }
]

I have class Element which describe one element

public class element {
    protected int id;
    protected int type;
    protected String state;
    protected int status;
    protected int device_type;
    private Map<String, Integer>mask;


    public int getId(){return this.id;}
    public void setId(int id){this.id=id;}
    public int getType(){return this.type;}
    public void setType(int type){this.type=type;}
    public String getState(){return this.state;}
    public void setState(String state){this.state=state;}
    public int getStatus(){return this.status;}
    public void setStatus(int status){this.status=status;}
    public int getDeviceType(){return this.device_type;}
    public void setDeviceType(int device_type){this.device_type=device_type;}
    public Map<String,Integer> getMask(){return this.mask;}
    public void setMask(Map<String,Integer> mask){this.mask=mask;}

    //index start by 1, not 0
    public boolean getBit(int index){
        return ((this.status>>(index-1)) & 0x1)==1;
    }

    public ElementView generateView(){
        return null;
    }

}

How to load json in list of elements ? I looked on stackoverflow questoion with GSON, but there need to have some name this array in json and I don't have that. Can anybody help ?

You need to specify your element types/classes. for instance, you have array json bellow [{"id":"01","name":"Joe"},{"id":"02","name":"Doe"}]

You must to create student class

public class Student {
    private String id;
    private  String name;

    public Student() {

    }

    public Student(String id, String name) {
        super();
        this.id = id;
        this.name = name;
    }

    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + "]";
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((id == null) ? 0 : id.hashCode());
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Student other = (Student) obj;
        if (id == null) {
            if (other.id != null)
                return false;
        } else if (!id.equals(other.id))
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }

}

After that you need to specify collection type, and access fromJson method

Type collectionType = new TypeToken<List<Student>>(){}.getType();
List<Student> students = gson.fromJson(json, collectionType);

entire test code as follows

public class When_serialize_list_object {
    private List<Student> _students;
    private Gson gson = new Gson();

    @Before
    public void setUp() {
        _students = new ArrayList<Student>();

        Student student1 = new Student("01", "Joe");
        Student student2 = new Student("02", "Doe");

        _students.add(student1);
        _students.add(student2);
    }

    @Test
    public void should_able_to_deserialize() {      
        String json = gson.toJson(_students);

        System.out.println(json);
        Type collectionType = new TypeToken<List<Student>>(){}.getType();
        List<Student> students = gson.fromJson(json, collectionType);

        Assert.assertEquals(students, _students);
        System.out.println(students);
    }

}

Using JSON-Simple library, for instance

  Object obj=JSONValue.parse(jsonString);
  JSONArray array=(JSONArray)obj;
  JSONObject element0=(JSONObject)array.get(0);

  Element el = new Element();
  el.setId( element0.get("id") );
  ...

Take a look at Jackson. It is more effecient than GSON at parcing JSON. I ussually great my object first and send it to a Json String using Jackson so I know what my Json String needs to look like. Here is an example:

User user = new User();
        user.setFirstName("Kmb");
        ....
        UserStatus userStatus = new UserStatus();
        userStatus.setKey("1");
        userStatus.setKey("active");
        user.setUserStatus(userStatus);

        String strUser="";
        try {
            strUser =mapper.writeValueAsString(user);
        } catch (JsonGenerationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JsonMappingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
       System.out.println(strUser);

Once you see how the string should be formatted adjust your input to match the format Jackson would like. Then pass the string into the mapper along with your class.

try {
        String str; //your string here
           User user2 = mapper.readValue(str, User.class);
           System.out.println(user2.getFirstName());
           System.out.println(user2.getServiceType().getValue());

        } catch (JsonParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JsonMappingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

If you want an array of your elements you may need to create a simple class that wraps a list of elements and run that through Jackson.

  <dependencies>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>1.7.5</version>
        <type>jar</type>
        <scope>compile</scope>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.8.2</version>
        <type>jar</type>
        <scope>compile</scope>
    </dependency>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-core-asl</artifactId>
        <version>1.7.5</version>
        <type>jar</type>
        <scope>compile</scope>
    </dependency>
  </dependencies>