In my previous blog [XML Data Binding in Delphi 2007 (1)], I have described there were issues when using XML Data Binding facility in Delphi 2007.
We are going to solve name space issue in this blog.
Let’s have a look at the schemas we are going to map.
Book.xsd:
1: <?xml version="1.0" encoding="utf-8"?>
2: <xs:schema targetNamespace="http://www.bochenlin.com/book"
3: elementFormDefault="qualified"
4: xmlns="http://tempuri.org/XMLSchema.xsd"
5: xmlns:mstns="http://tempuri.org/XMLSchema.xsd"
6: xmlns:xs="http://www.w3.org/2001/XMLSchema"
7: xmlns:a="http://www.bochenlin.com/author"
8: >
9: <xs:import namespace ="http://www.bochenlin.com/author"
10: schemaLocation ="author.xsd"></xs:import>
11: <xs:element name="book">
12: <xs:complexType>
13: <xs:sequence>
14: <xs:element name ="title" type="xs:string" ></xs:element>
15: <xs:element name ="subject" type ="xs:string"></xs:element>
16: <xs:element ref ="a:author" ></xs:element>
17: </xs:sequence>
18: </xs:complexType>
19: </xs:element>
20: </xs:schema>
21:
Author.xsd:
1: <?xml version="1.0" encoding="utf-8"?>
2: <xs:schema targetNamespace="http://www.bochenlin.com/author"
3: elementFormDefault="qualified"
4: xmlns="http://tempuri.org/XMLSchema.xsd"
5: xmlns:mstns="http://tempuri.org/XMLSchema.xsd"
6: xmlns:xs="http://www.w3.org/2001/XMLSchema"
7: >
8: <xs:element name ="author">
9: <xs:complexType>
10: <xs:sequence >
11: <xs:element name ="title" type ="xs:string"></xs:element>
12: <xs:element name ="firstName" type ="xs:string"></xs:element>
13: <xs:element name ="lastName" type ="xs:string"></xs:element>
14: </xs:sequence>
15: </xs:complexType>
16: </xs:element>
17: </xs:schema>
18:
By using the XML Data Binding Wizard in XE, we can get following code:
1: unit book;
2:
3: interface
4:
5: uses xmldom, XMLDoc, XMLIntf;
6:
7: type
8:
9: { Forward Decls }
10:
11: IXMLBook = interface;
12:
13: { IXMLBook }
14:
15: IXMLBook = interface(IXMLNode)
16: ['{C013C828-0F4C-4537-ACD3-B7C550D3B813}']
17: { Property Accessors }
18: function Get_Title: WideString;
19: function Get_Subject: WideString;
20: function Get_Author: WideString;
21: procedure Set_Title(Value: WideString);
22: procedure Set_Subject(Value: WideString);
23: procedure Set_Author(Value: WideString);
24: { Methods & Properties }
25: property Title: WideString read Get_Title write Set_Title;
26: property Subject: WideString read Get_Subject write Set_Subject;
27: property Author: WideString read Get_Author write Set_Author;
28: end;
29:
30: { Forward Decls }
31:
32: TXMLBook = class;
33:
34: { TXMLBook }
35:
36: TXMLBook = class(TXMLNode, IXMLBook)
37: protected
38: { IXMLBook }
39: function Get_Title: WideString;
40: function Get_Subject: WideString;
41: function Get_Author: WideString;
42: procedure Set_Title(Value: WideString);
43: procedure Set_Subject(Value: WideString);
44: procedure Set_Author(Value: WideString);
45: end;
46:
47: { Global Functions }
48:
49: function Getbook(Doc: IXMLDocument): IXMLBook;
50: function Loadbook(const FileName: string): IXMLBook;
51: function Newbook: IXMLBook;
52:
53: const
54: TargetNamespace = 'http://www.bochenlin.com/book';
55:
56: implementation
57:
58: { Global Functions }
59:
60: function Getbook(Doc: IXMLDocument): IXMLBook;
61: begin
62: Result := Doc.GetDocBinding('book', TXMLBook, TargetNamespace) as IXMLBook;
63: end;
64:
65: function Loadbook(const FileName: string): IXMLBook;
66: begin
67: Result := LoadXMLDocument(FileName).GetDocBinding('book', TXMLBook, TargetNamespace) as IXMLBook;
68: end;
69:
70: function Newbook: IXMLBook;
71: begin
72: Result := NewXMLDocument.GetDocBinding('book', TXMLBook, TargetNamespace) as IXMLBook;
73: end;
74:
75: { TXMLBook }
76:
77: function TXMLBook.Get_Title: WideString;
78: begin
79: Result := ChildNodes['title'].Text;
80: end;
81:
82: procedure TXMLBook.Set_Title(Value: WideString);
83: begin
84: ChildNodes['title'].NodeValue := Value;
85: end;
86:
87: function TXMLBook.Get_Subject: WideString;
88: begin
89: Result := ChildNodes['subject'].Text;
90: end;
91:
92: procedure TXMLBook.Set_Subject(Value: WideString);
93: begin
94: ChildNodes['subject'].NodeValue := Value;
95: end;
96:
97: function TXMLBook.Get_Author: WideString;
98: begin
99: Result := ChildNodes['a:author'].Text;
100: end;
101:
102: procedure TXMLBook.Set_Author(Value: WideString);
103: begin
104: ChildNodes['a:author'].NodeValue := Value;
105: end;
106:
107: end.
In above Delphi code, there are two problems. First it does not generate correct code for element “author”. In line 27, type of property is WideString instead of a class type. Secondly, the generated Delphi code only specify the target name space http://www.bochenlin.com/book , no other name space http://www.bochenlin.com/author is specified anywhere else, in stead, it uses fixed tag name “a:author” to map the element “author” in the name space http://www.bochenlin.com/author. Even “author” is a simple type, this is only fine for XML instance which uses “a” as the prefix for name space http://www.bochenlin.com/author. If the final application will only deal with the XML coming from one source, it probably will be OK. It definitely has problem if the XML instances are coming from different sources in which they might have choose different prefixes for the same name space. Besides, the XML instance generated by using above code will be invalid as it will be missing the name space http://www.bochenlin.com/author for the element “author”. To solve these problems, schema “author” needs to have a small tweak.
Tweaked Author.xsd
1: <?xml version="1.0" encoding="utf-8"?>
2: <xs:schema targetNamespace="http://www.bochenlin.com/author"
3: elementFormDefault="qualified"
4: xmlns="http://tempuri.org/XMLSchema.xsd"
5: xmlns:mstns="http://tempuri.org/XMLSchema.xsd"
6: xmlns:xs="http://www.w3.org/2001/XMLSchema"
7: xmlns:a="http://www.bochenlin.com/author"
8: >
9: <xs:element name ="author">
10: <xs:complexType>
11: <xs:sequence >
12: <xs:element name ="title" type ="xs:string"></xs:element>
13: <xs:element name ="firstName" type ="xs:string"></xs:element>
14: <xs:element name ="lastName" type ="xs:string"></xs:element>
15: </xs:sequence>
16: </xs:complexType>
17: </xs:element>
18: </xs:schema>
19:
Line 7 in above tweaked Author.xsd is added for Delphi to generated correct type for element “author”, updated unit book is provided below:
1: unit book;
2:
3: interface
4:
5: uses xmldom, XMLDoc, XMLIntf;
6:
7: type
8:
9: { Forward Decls }
10:
11: IXMLBook = interface;
12: IXMLAuthor_a = interface;
13:
14: { IXMLBook }
15:
16: IXMLBook = interface(IXMLNode)
17: ['{C873AF71-B66F-4FC1-8273-93F023EFAFBB}']
18: { Property Accessors }
19: function Get_Title: WideString;
20: function Get_Subject: WideString;
21: function Get_Author: IXMLAuthor_a;
22: procedure Set_Title(Value: WideString);
23: procedure Set_Subject(Value: WideString);
24: { Methods & Properties }
25: property Title: WideString read Get_Title write Set_Title;
26: property Subject: WideString read Get_Subject write Set_Subject;
27: property Author: IXMLAuthor_a read Get_Author;
28: end;
29:
30: { IXMLAuthor_a }
31:
32: IXMLAuthor_a = interface(IXMLNode)
33: ['{23B0F904-2759-4810-9DDA-4E79248128E8}']
34: { Property Accessors }
35: function Get_Title: WideString;
36: function Get_FirstName: WideString;
37: function Get_LastName: WideString;
38: procedure Set_Title(Value: WideString);
39: procedure Set_FirstName(Value: WideString);
40: procedure Set_LastName(Value: WideString);
41: { Methods & Properties }
42: property Title: WideString read Get_Title write Set_Title;
43: property FirstName: WideString read Get_FirstName write Set_FirstName;
44: property LastName: WideString read Get_LastName write Set_LastName;
45: end;
46:
47: { Forward Decls }
48:
49: TXMLBook = class;
50: TXMLAuthor_a = class;
51:
52: { TXMLBook }
53:
54: TXMLBook = class(TXMLNode, IXMLBook)
55: protected
56: { IXMLBook }
57: function Get_Title: WideString;
58: function Get_Subject: WideString;
59: function Get_Author: IXMLAuthor_a;
60: procedure Set_Title(Value: WideString);
61: procedure Set_Subject(Value: WideString);
62: public
63: procedure AfterConstruction; override;
64: end;
65:
66: { TXMLAuthor_a }
67:
68: TXMLAuthor_a = class(TXMLNode, IXMLAuthor_a)
69: protected
70: { IXMLAuthor_a }
71: function Get_Title: WideString;
72: function Get_FirstName: WideString;
73: function Get_LastName: WideString;
74: procedure Set_Title(Value: WideString);
75: procedure Set_FirstName(Value: WideString);
76: procedure Set_LastName(Value: WideString);
77: end;
78:
79: { Global Functions }
80:
81: function Getbook(Doc: IXMLDocument): IXMLBook;
82: function Loadbook(const FileName: string): IXMLBook;
83: function Newbook: IXMLBook;
84:
85: const
86: TargetNamespace = 'http://www.bochenlin.com/book';
87:
88: implementation
89:
90: { Global Functions }
91:
92: function Getbook(Doc: IXMLDocument): IXMLBook;
93: begin
94: Result := Doc.GetDocBinding('book', TXMLBook, TargetNamespace) as IXMLBook;
95: end;
96:
97: function Loadbook(const FileName: string): IXMLBook;
98: begin
99: Result := LoadXMLDocument(FileName).GetDocBinding('book', TXMLBook, TargetNamespace) as IXMLBook;
100: end;
101:
102: function Newbook: IXMLBook;
103: begin
104: Result := NewXMLDocument.GetDocBinding('book', TXMLBook, TargetNamespace) as IXMLBook;
105: end;
106:
107: { TXMLBook }
108:
109: procedure TXMLBook.AfterConstruction;
110: begin
111: RegisterChildNode('author', TXMLAuthor_a);
112: inherited;
113: end;
114:
115: function TXMLBook.Get_Title: WideString;
116: begin
117: Result := ChildNodes['title'].Text;
118: end;
119:
120: procedure TXMLBook.Set_Title(Value: WideString);
121: begin
122: ChildNodes['title'].NodeValue := Value;
123: end;
124:
125: function TXMLBook.Get_Subject: WideString;
126: begin
127: Result := ChildNodes['subject'].Text;
128: end;
129:
130: procedure TXMLBook.Set_Subject(Value: WideString);
131: begin
132: ChildNodes['subject'].NodeValue := Value;
133: end;
134:
135: function TXMLBook.Get_Author: IXMLAuthor_a;
136: begin
137: Result := ChildNodes['author'] as IXMLAuthor_a;
138: end;
139:
140: { TXMLAuthor_a }
141:
142: function TXMLAuthor_a.Get_Title: WideString;
143: begin
144: Result := ChildNodes['title'].Text;
145: end;
146:
147: procedure TXMLAuthor_a.Set_Title(Value: WideString);
148: begin
149: ChildNodes['title'].NodeValue := Value;
150: end;
151:
152: function TXMLAuthor_a.Get_FirstName: WideString;
153: begin
154: Result := ChildNodes['firstName'].Text;
155: end;
156:
157: procedure TXMLAuthor_a.Set_FirstName(Value: WideString);
158: begin
159: ChildNodes['firstName'].NodeValue := Value;
160: end;
161:
162: function TXMLAuthor_a.Get_LastName: WideString;
163: begin
164: Result := ChildNodes['lastName'].Text;
165: end;
166:
167: procedure TXMLAuthor_a.Set_LastName(Value: WideString);
168: begin
169: ChildNodes['lastName'].NodeValue := Value;
170: end;
171:
172: end.
Although above code has generated “author” as a class instead of a WideString, it has not put in its name space http://www.bochenlin.com/author at all. It can be solved by modify line 111 in above code:
111: RegisterChildNode(‘author’, TXMLAuthor_a, ‘http://www.bochenlin.com/author’);
Yes, it is simple, but it is not perfect yet. If the schemas are as simple as these two in this blog and you are pretty sure they won’t going to be changed, congratulations, you have done the job. But if the number of involved schemas is large and they are likely to change in the near future, it means you are going to regenerate the code again and again so that you are going to loose the modifications and have to redo manually. Don’t know if you have noticed that it does not only loose the changes you have put in but also the GUIDs of the interfaces are changed every time the code is regenerated. So the maintenance of the code becomes very trivial and difficult. I have a better solution in terms of maintaining these auto-generated code. I will introduce Class Helpers to solved this problem in my next blog.
