在delphi中使用msxml进行模式验证 [英] schema validation with msxml in delphi

问题描述

我试图根据模式的引用来验证XML文件。 （使用Delphi和MSXML2_TLB。）代码的相关部分如下所示：

I'm trying to validate an XML file against the schema's it references. (Using Delphi and MSXML2_TLB.) The (relevant part of the) code looks something like this:

procedure TfrmMain.ValidateXMLFile;
var
    xml: IXMLDOMDocument2;
    err: IXMLDOMParseError;
    schemas: IXMLDOMSchemaCollection;
begin
    xml := ComsDOMDocument.Create;
    if xml.load('Data/file.xml') then
    begin
        schemas := xml.namespaces;
        if schemas.length > 0 then
        begin
            xml.schemas := schemas;
            err := xml.validate;
        end;
    end;
end;

这样做的结果是加载缓存（schemas.length> 0），但是下一个赋值引发了一个例外：只能使用XMLSchemaCache-schemacollections。

This has the result that cache is loaded (schemas.length > 0), but then the next assignment raises an exception: "only XMLSchemaCache-schemacollections can be used."

我应该怎么做？

谢谢，Miel。

推荐答案

我想出了一种似乎有效的方法。我首先加载模式，然后将它们添加到schemacollection。接下来我加载xml文件并将schemacollection分配给其schemas属性。解决方案现在看起来像这样：

I've come up with an approach that seems to work. I first load the schema's explicitly, then add themn to the schemacollection. Next I load the xml-file and assign the schemacollection to its schemas property. The solution now looks like this:

uses MSXML2_TLB  
That is:  
// Type Lib: C:\Windows\system32\msxml4.dll  
// LIBID: {F5078F18-C551-11D3-89B9-0000F81FE221}

function TfrmMain.ValidXML(
    const xmlFile: String; 
    out err: IXMLDOMParseError): Boolean;
var
    xml, xsd: IXMLDOMDocument2;
    cache: IXMLDOMSchemaCollection;
begin
    xsd := CoDOMDocument40.Create;
    xsd.Async := False;
    xsd.load('http://the.uri.com/schemalocation/schema.xsd');

    cache := CoXMLSchemaCache40.Create;
    cache.add('http://the.uri.com/schemalocation', xsd);

    xml := CoDOMDocument40.Create;
    xml.async := False;
    xml.schemas := cache;

    Result := xml.load(xmlFile);
    if not Result then
      err := xml.parseError
    else
      err := nil;
end;

使用XMLSchemaCache40或更高版本很重要。早期版本不符合W3C XML Schema标准，但仅针对XDR Schema（MicroSoft规范）进行验证。

It is important to use XMLSchemaCache40 or later. Earlier versions don't follow the W3C XML Schema standard, but only validate against XDR Schema, a MicroSoft specification.

此解决方案的缺点是我需要加载模式明确。在我看来，应该可以自动检索它们。

The disadvantage of this solution is that I need to load the schema's explicitly. It seems to me that it should be possible to retrieve them automatically.

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