Multiple layers of nested JSON data

Most of the time we see JSON data nested in multiple layers, like this:

{"name":"Orange Mulberry",  "Sex":"male",  " Age": -,"Grade":{"Gname":"three years and eight classes",         "Gdesc":"third day grade eight class"         }  }

To get the JSON data of the above type, it is the following steps:

1. Database queries

Sql:select S.name,s.sex,s.age,g.gname,g.gdesc

From Student S,grade g

where s.gid = G.gid; (You can also choose to use the internal connection method to write)

So we can find the information we want, and obviously the query result is a object[] collection.

2. New JavaBean

In fact, the development tool will automatically generate Java entity class student based on the relationship between multiple tables in the database.

However, most of the time a partial field query, if the query results are transferred directly to the existing JavaBean,

The non-queried property appears as 0, [] so I think it's necessary to create a new JavaBean class based on the query field.

For the above query, create the following two JavaBean:

// ostudent class member variables Private String name; Private String sex; Private String age; Private Ograde grade; // Ograde class member variables Private String Gname; Private String Gdesc;

3. Conversion of query Results

List<object[]> Listdb =query.list (); List<Ostudent> listout =NewArrayList (); for(object[]Object: Listdb) {String name= (String)Object[0]; String Sex= (String)Object[1]; String Age= (String)Object[2]; String Gname= (String)Object[3]; String Gdesc= (String)Object[4]; Ograde GRA=NewOgrade (GNAME,GDESC); Ostudent Stu=Newostudent (Name,sex,age,gra); Listout.add (stu);}

The query result is then transformed into a collection of N ostudent objects.

4. Response data

Because it is a collection of Ostudent objects, we can use the following statement to convert it to a JSON string

Jsonarray array == array.tostring (); Response.getwriter (). print (JSONSTR);

This responds to the query results in the form of multiple layers of nested JSON data.

5. Front-end invocation

After the front-end Ajax request succeeds, the data is obtained, which we can write in the callback function of the request success:

var json = $.parsejson (data); $.each (JSON, function (index, item) {           var name = json[in Dex].name;            var age = json[index].age;         var gname = json[index].grade.gname;     });

Isn't it simple?

6. Background calls

Here refer to a comment on the internet is written in full, modified, and then recorded

 Public Staticstring Getjson (string path, string parameter, string method) {Try{URL URL=NewURL (path); PrintWriter out=NULL;            String Line; StringBuilder SB=NewStringBuilder (); //opening and linking between URLsHttpURLConnection conn =(HttpURLConnection) url.openconnection (); //Request MethodConn.setrequestmethod (method); // //to set common request propertiesConn.setrequestproperty ("Accept","*/*"); Conn.setrequestproperty ("Connection","keep-alive"); Conn.setrequestproperty ("user-agent",                    "mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"); //Sets whether to output to httpurlconnection, sets whether to read from HttpURLConnection, and also sends a POST request to set these two//The most common HTTP requests are just get and post,get requests to get static pages, or you can put parameters behind URL strings and pass them on to the servlet.//The difference between post and get is that the post parameter is not placed inside the URL string, but is placed inside the body of the HTTP request. Conn.setdooutput (true); Conn.setdoinput (true); //gets the output stream corresponding to the URLConnection object             out=NewPrintWriter (Conn.getoutputstream ()); //send request parameters i.e. data             out. Print (parameter); //Buffered Data             out. Flush (); //gets the input stream corresponding to the URLConnection objectInputStream is=Conn.getinputstream (); //constructs a character stream cacheBufferedReader br =NewBufferedReader (NewInputStreamReader ( is));  while(line = Br.readline ())! =NULL) {sb.append (line); }            //Close the stream             is. Close (); //disconnect, preferably written on, disconnect is cut off when the underlying TCP socket link is idle.            It is not cut off if it is being used by another thread. //fixed multi-threaded words, if not disconnect, the link will increase, until the message is not sent out. Write the disconnect after the normal some. Conn.disconnect (); String Str=sb.tostring (); returnstr; } Catch(Exception e) {e.printstacktrace (); return "Something went wrong."; }    }

Call the method, get the JSON string, and the next step is to convert the JSON string into a Java object.

        String jsonstr = getjson (path, param, method);        System.  out . println (JSONSTR);         = Jsonarray.fromobject (jsonstr);         = Jsonarray. Get (0);         = Jsonobject.fromobject (o);         = (Student) Jsonobject.tobean (Jsonobject, Student.  Class);        System. out. println (Stu.getgrade ());

Because a lot of the records are usually queried, the JSON string is the form of a collection of multiple objects (arrays),

So first the JSON string---> into a JSON array---> Get array items (objects)---> Convert to JSON object---> Convert to the corresponding JavaBean object.

Then how to get the value of the member variable is not much verbose.

Multiple layers of nested JSON data