Use of JSON Superobject in Delphi: Data sets and JSON objects are transferred to each other

In Delphi, datasets are the most common way of accessing data. Therefore, we must establish the relationship between JSON and Tdataset, and realize the communication and transformation between the data. It is important to note that this is only the normal conversion between Tdataset and JSON, since CDs contains delta packets, whose data formats are far more complex than ordinary tdataset.

The dataset field information is a complete dictionary information. Therefore, we must also establish the dictionary information in JSON in order to create the field information of the dataset. We set its JSON information as follows:

cols:[field List information], such as:

"Cols": [{"Jsontype": "Integer", "Fieldindex": 0, "FieldType": "Integer", "FieldSize": 0, "FieldName": "ID", "Required": false},{"Jsontype": "string", "Fieldindex": 1, "FieldType": "string", "FieldSize": +, "FieldName": "Title", "Required" : false},{"Jsontype": "Variant", "Fieldindex": 2, "FieldType": "Blob", "FieldSize": 0, "FieldName": "Picture", "Required" : false}]

The data information is the node of the database, and it is also an array nesting record information:

"Data": [Recordset information]

Say less nonsense, directly on the code: Unit Udbjson;

Interface

Uses

Sysutils,classes,variants,db,dbclient,superobject;

Type

Ttablejson = Class

Private

Const CSTFIELDTYPE = ' FieldType ';

Const CSTFIELDNAME = ' FieldName ';

Const CSTFIELDSIZE = ' FieldSize ';

Const CSTJSONTYPE = ' Jsontype ';

Const cstrequired = ' Required ';

Const CSTFIELDINDEX = ' Fieldindex ';

Const cstcols= ' Cols ';

Const cstdata= ' Data ';

Public

class function Jsonfromdataset (Dataset:tdataset): string;

class function Createfieldbyjson (fields:tfielddefs; Colsjson:isuperobject): Boolean;

class function Importdatafromjson (dataset:tdataset;datajson:isuperobject): Integer;

class function Cdsfromjson (Cds:tclientdataset; Json:isuperobject): Boolean;

class function GetValue (Json:isuperobject;const name:string): Variant;

class function Createjsonvalue (Json:isuperobject;const name:string;const value:variant): Boolean;

class function Createjsonvaluebyfield (Json:isuperobject; Field:tfield): Boolean;

class function Getvalue2field (Field:tfield; Jsonvalue:isuperobject): Variant;

End

Implementation

Uses TYPINFO,ENCDDECD;

{Ttablejson}

class function Ttablejson.cdsfromjson (Cds:tclientdataset;

Json:isuperobject): Boolean;

Var

Colsjson:isuperobject;

Begin

Result: = False;

If Json = Nil Then

Exit;

Cds. Close;

Cds. Data: = Null;

Create a field

Colsjson: = Json.o[cstcols];

Createfieldbyjson (CDS. Fielddefs,colsjson);

If CDS. Fielddefs.count >0 Then

Cds. CreateDataSet;

Importdatafromjson (Cds,json.o[cstdata]);

Result: = True;

End

class function Ttablejson.createfieldbyjson (fields:tfielddefs;

Colsjson:isuperobject): Boolean;

Var

Subjson:isuperobject;

Ft:tfieldtype;

Begin

Result: = False;

Fields.DataSet.Close;

Fields.clear;

For Subjson in Colsjson do

Begin

FT: = Tfieldtype (GetEnumValue (TypeInfo (Tfieldtype), ' ft ' +subjson.s[cstfieldtype]);

If ft= ftautoinc then//increment field cannot be entered and must be changed

FT: = Ftinteger;

Fields.Add (subjson.s[cstfieldname],ft,subjson.i[cstfieldsize],subjson.b[cstrequired]);

End

Result: = True;

End

class function Ttablejson.createjsonvalue (Json:isuperobject;

Const name:string; Const value:variant): Boolean;

Begin

Result: = False;

Json.o[name]: = SO (Value);

Result: = True;

End

class function Ttablejson.createjsonvaluebyfield (Json:isuperobject;

Field:tfield): Boolean;

Begin

Result: = False;

If Field is Tdatetimefield then

Json.o[field.fieldname]: = SO (field.asdatetime)

else if Field is Tblobfield then

Json.s[field.fieldname]: = encodestring (field.asstring)

Else

Json.o[field.fieldname]: = SO (Field.value);

Result: = True;

End

class function Ttablejson.getvalue (

Json:isuperobject;const name:string): Variant;

Begin

Case Json.datatype of

Stnull:result: = Null;

Stboolean:result: = Json.b[name];

Stdouble:result: = Json.d[name];

Stcurrency:result: = Json.c[name];

Stint:result: = Json.i[name];

Ststring:result: = Json.s[name];

End

End

class function Ttablejson.getvalue2field (Field:tfield; Jsonvalue:isuperobject): Variant;

Begin

If Jsonvalue.datatype = Stnull Then

Result: = Null

else if Field is Tdatetimefield then

Result: = Javatodelphidatetime (Jsonvalue.asinteger)

else if (field is Tintegerfield) or (field was Tlargeintfield) then

Result: = Jsonvalue.asinteger

else if Field is Tnumericfield then

Result: = jsonvalue.asdouble

else if Field is Tbooleanfield then

Result: = Jsonvalue.asboolean

else if Field is Tstringfield then

Result: = jsonvalue.asstring

else if Field is Tblobfield then

Result: = decodestring (jsonvalue.asstring)

End

class function Ttablejson.importdatafromjson (Dataset:tdataset;

Datajson:isuperobject): Integer;

Var

Subjson:isuperobject;

I:integer;

Iter:tsuperobjectiter;

Begin

If not dataset.active then

Dataset.open;

Dataset.disablecontrols;

Try

For Subjson in Datajson do

Begin

Dataset.append;

If Objectfindfirst (Subjson,iter) Then

Begin

Repeat

If Dataset.findfield (ITER). Ite.Current.Name) <>nil Then

Dataset.findfield (ITER). Ite.Current.Name). Value: =

Getvalue2field (

Dataset.findfield (ITER). Ite.Current.Name),

Iter. Ite.Current.Value);

Until not Objectfindnext (ITER);

End

Dataset.post;

End

Finally

Dataset.enablecontrols;

End

End

class function Ttablejson.jsonfromdataset (Dataset:tdataset): string;

Procedure Getfieldtypeinfo (Field:tfield;var fieldtyp,jsontyp:string);

Begin

Fieldtyp: = Getenumname (TypeInfo (Tfieldtype), Ord (Field.datatype));

Delete (fieldtyp,1,2);

If Field is Tstringfield then

Jsontyp: = ' string '

else if Field is Tdatetimefield then

Jsontyp: = ' integer '

else if (field is Tintegerfield) or (field was Tlargeintfield) then

Jsontyp: = ' integer '

else if Field is Tcurrencyfield then

Jsontyp: = ' Currency '

else if Field is Tnumericfield then

Jsontyp: = ' Double '

else if Field is Tbooleanfield then

Jsontyp: = ' Boolean '

Else

Jsontyp: = ' variant ';

End

Var

Sj,aj,sj2:isuperobject;

I:integer;

fieldtyp,jsontyp:string;

List:tstringlist;

Begin

SJ: = SO ();

Create columns

AJ: = SA ([]);

List: = tstringlist.create;

Try

list.sorted: = True;

For I: = 0 to Dataset.fieldcount-1 do

Begin

SJ2: = SO ();

Getfieldtypeinfo (Dataset.fields[i],fieldtyp,jsontyp);

Sj2. S[cstfieldname]: = Dataset.fields[i]. FieldName;

Sj2. S[cstfieldtype]: = Fieldtyp;

Sj2. S[cstjsontype]: = Jsontyp;

Sj2. I[cstfieldsize]: = Dataset.fields[i]. Size;

Sj2. B[cstrequired]: = Dataset.fields[i]. Required;

Sj2. I[cstfieldindex]: = Dataset.fields[i]. Index;

Aj. Asarray.add (SJ2);

List.add (Dataset.fields[i]. fieldname+ ' = ' +jsontyp);

End

Sj. o[' Cols ']: = AJ;

To create data for a dataset

Dataset.disablecontrols;

Dataset.first;

AJ: = SA ([]);

While not dataset.eof do

Begin

SJ2: = SO ();

For I: = 0 to Dataset.fieldcount-1 do

Begin

Sj2. S[inttostr (Dataset.fields[i]. Index)]: = Vartostrdef (Dataset.fields[i]. Value, ');

If Varisnull (Dataset.fields[i]. Value) Then

Sj2. O[dataset.fields[i]. FieldName]: = SO (Null)

Else

Begin

Createjsonvaluebyfield (Sj2,dataset.fields[i]);

End

End

Aj. Asarray.add (SJ2);

Dataset.next;

End

Sj. o[' Data ': = AJ;

Result: = SJ. asstring;

Finally

List.free;

Dataset.enablecontrols;

End

End

End.

Invocation Example:

DataSet to JSON object or JSON text

Var

Json:ttablejson;

s:string;

Begin

S: = json. Jsonfromdataset (ADODATASET1);

Read the string s in Tstringstream, save it as text, and look at its format.

End

JSON object or text, loading to the dataset

Var

Json:isuperobject;

Begin

JSON: = Tsuperobject.parsefile (' json.txt ', False);

Ttablejson.cdsfromjson (Cdsjson,json);

End

http://blog.csdn.net/diligentcatrich/article/details/6916288

Use of JSON Superobject in Delphi: Data sets and JSON objects are transferred to each other