实现一个客户端的DataSet-----ClientDataSet.htc

2024-07-21 02:16:59

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<public:component lightweight="true">
    <public:property name="name" value="dataset" />
    <public:property name="namespace" value="http://tempuri.org" />
    <public:property name="xmldata" />
    <public:property name="xmlschema" />

    <public:method name="readxml" />
    <public:method name="readxmlschema" />
    <public:method name="gettable" />
    <public:method name="acceptchanges" />
    <public:method name="rejectchanges" />
    <public:method name="getchanges" />

    <public:event name="ondatachanged" id="datachanged" />
</public:component>

<script>

//////////////////////////////////////////////////////////
// 实现一个客户端的dataset
//////////////////////////////////////////////////////////

function datarow(dt, onode)
{
    this.datatable        = dt;
    this.xmlnode        = onode;
    this.getvalue        = datarow_getvalue;
    this.setvalue        = datarow_setvalue;
    this.delete        = datarow_delete;
}

function datarow_getvalue(vindex)
{
    var onode;
    switch (typeof(vindex))
    {
        case "string":
            onode = this.xmlnode.selectsinglenode(vindex);
            break;
        default:
            throw "you must index into a datarow using the string name.";
    }

    if (onode != null)
    {
        return onode.text;
    }

    return null;
}

function datarow_setvalue(vindex, vvalue)
{
    var onode;
    var oschemanode;

    switch (typeof(vindex))
    {
        case "string":
            onode = this.xmlnode.selectsinglenode(vindex);
            oschemanode = this.datatable.schemanode.selectsinglenode('xsd:complextype/xsd:sequence/xsd:element[@name="' + vindex + '"]');
            if (oschemanode == null)
                throw "invaid column index: " + vindex;
            break;
        default:
            //onode = this.xmlnode.childnodes[vindex];
            throw "invaid column index: " + vindex;
    }

    var minoccurs = oschemanode.getattribute("minoccurs");

    // minoccurs默认为1
    if (minoccurs == null)
        minoccurs = 1;
    else
        minoccurs = new number(minoccurs);

    // 如果该列允许空值或请求值为空就去掉节点
    if (vvalue == null && minoccurs == 0) {
        if (onode != null)
            onode.parentnode.removechild(onode);
        return;
    }

    // 如果以前没有设置值则添加值
    if (onode == null) {
        var colname = oschemanode.getattribute("name");
        onode = this.xmlnode.ownerdocument.createelement(colname);
        onode.text = vvalue;
        this.xmlnode.appendchild(onode);
        return;
    }

    // 如果该列已存在值则只有在值不同时才更改
    var curvalue = onode.text;
    if (curvalue != vvalue.tostring())
    {
        if (this.xmlnode.getattribute("diffgr:haschanges") != "inserted") {
            // 备份原始值
            var odiffgrambefore = this.datatable.dataset.xmldata.documentelement.selectsinglenode("diffgr:before");
            if (odiffgrambefore == null) {
                odiffgrambefore = this.xmlnode.ownerdocument.createnode(1, "diffgr:before", "urn:schemas-microsoft-com:xml-diffgram-v1");
                this.xmlnode.ownerdocument.documentelement.appendchild(odiffgrambefore);
            }

            var path = this.datatable.tablename + "[@diffgr:id='" + this.xmlnode.getattribute("diffgr:id") + "']";
            var ooriginalrow = odiffgrambefore.selectsinglenode(path);
            if (ooriginalrow == null) {
                // 拷贝原始行
                odiffgrambefore.appendchild(this.xmlnode.clonenode(true));
            }

            this.xmlnode.setattribute("diffgr:haschanges", "modified");
        }

        onode.text = new string(vvalue);
    }
}

function datarow_delete()
{
    var odiffgrambefore = this.datatable.dataset.xmldata.documentelement.selectsinglenode("diffgr:before");
    if (odiffgrambefore == null) {
        odiffgrambefore = this.xmlnode.ownerdocument.createnode(1, "diffgr:before", "urn:schemas-microsoft-com:xml-diffgram-v1");
        this.xmlnode.ownerdocument.documentelement.appendchild(odiffgrambefore);
    }

    var obeforenode = odiffgrambefore.selectsinglenode(this.xmlnode.nodename + "[@diffgr:id='" + this.xmlnode.getattribute("diffgr:id") + "']");
    if (obeforenode == null) {
        //this.xmlnode.setattribute("xmlns", this.datatable.dataset.namespace);
        odiffgrambefore.appendchild(this.xmlnode);
        this.xmlnode.setattribute("xmlns", this.datatable.dataset.namespace);
    }
    else {
        this.xmlnode.parentnode.removechild(this.xmlnode);
    }

    this.xmlnode = null;
}

function datatable(ds, name, onodes)
{
    this.xmlnodes        = onodes;
    this.dataset        = ds;
    this.tablename        = name;
    this.getrowcount    = datatable_getrowcount;
    this.getrow            = datatable_getrow;
    this.addrow            = datatable_addrow;
    this.findrow        = datatable_findrow;
    this.schemanode        = ds.xmlschema.selectsinglenode('//xsd:element[@name="' + name + '"]');


    if (this.schemanode == null) {
        throw name + " table not found in dataset schema.";
    }
}

function datatable_getrowcount()
{
    return this.xmlnodes.length;
}

function datatable_getrow(i)
{
    return new datarow(this, this.xmlnodes[i]);
}

function datatable_addrow()
{
    var orow = this.dataset.xmldata.createelement(this.tablename);
    orow.setattribute("diffgr:id", createid());
    //orow.setattribute("msdata:roworder", this.getrowcount());
    orow.setattribute("diffgr:haschanges", "inserted");

    // add the column elements with their default values to the new empty row
    var columns = this.schemanode.selectnodes("xsd:complextype/xsd:sequence/xsd:element");
    for (var i=0; i<columns.length; i++)
    {
        var col = columns[i];
        var minoccurs = col.getattribute("minoccurs");
        var defaultvalue = col.getattribute("default");

        if (minoccurs == null)
            minoccurs = 1;
        else
            minoccurs = new number(minoccurs);

        if (minoccurs > 0 || defaultvalue != null) {
            var colname = col.getattribute("name");

            var ocol = this.dataset.xmldata.createelement(colname);
            if (defaultvalue != null)
                ocol.text = new string(defaultvalue);

            orow.appendchild(ocol);
        }
    }

    var odataset = this.dataset.xmldata.documentelement.selectsinglenode(this.dataset.name);
    odataset.appendchild(orow);

    this.xmlnodes = odataset.selectnodes(this.tablename);

    return new datarow(this, orow);
}

function datatable_findrow(xpr)
{
    var odataset = this.dataset.xmldata.selectnodes(this.dataset.name);
    if (odataset) {
        var orow = odataset.selectsinglenode(this.tablename + "[" + expr + "]");
        if (orow) {
            return new datarow(this, orow);
        }
    }

    return null;
}

//////////////////////////////////////////////////////////
// private variables
//////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////
// private methods
//////////////////////////////////////////////////////////

function createid()
{
    return element.document.createelement("div").uniqueid;
}

//////////////////////////////////////////////////////////
// public methods
//////////////////////////////////////////////////////////

function gettable(vindex)
{
    var onodes;
    var tablename = "";
    switch (typeof(vindex))
    {
        case "string":
            // 返回行
            tablename = vindex;
            onodes = xmldata.documentelement.selectnodes(name + "/" + tablename);
            break;
        case "number":
            throw "index by position not supported.";
            break;
    }

    if (onodes != null)
    {
        return new datatable(this, tablename, onodes);
    }

    return null;
}

function acceptchanges()
{
    // 删除节点
    var beforenode = this.xmldata.documentelement.selectsinglenode("diffgr:before");

    if (beforenode) {
        this.xmldata.documentelement.removechild(beforenode);
    }

    // 改变diffgr:haschanges属性
    var haschangesattributes = xmldata.selectnodes("//@diffgr:haschanges");
    while (haschangesattributes.peeknode() != null) {
        haschangesattributes.removenext();
    }
}

function rejectchanges()
{
    // 删除数据
    var datasetnode = this.xmldata.documentelement.selectsinglenode(this.name);
    var beforenodes = this.xmldata.documentelement.selectnodes("diffgr:before/*");
    while (beforenodes.peeknode() != null) {
        var beforenode = beforenodes.nextnode();
        var path = beforenode.nodename + "[@diffgr:id='" + beforenode.getattribute("diffgr:id") + "']";
        var changedrow = datasetnode.selectsinglenode(path);

        if (changedrow != null)
            datasetnode.replacechild(beforenode, changedrow)
        else
            datasetnode.appendchild(beforenode);

    }

    // 删除节点
    var beforenode = this.xmldata.documentelement.selectsinglenode("diffgr:before");
    this.xmldata.documentelement.removechild(beforenode);
}

function getchanges()
{
    var ds = new activexobject("microsoft.xmldom");
    ds.async = false;
    ds.loadxml('<dataset/>');

    var schemanode = xmlschema.documentelement.clonenode(true);
    var diffnode = ds.createnode(1, "diffgr:diffgram", "urn:schemas-microsoft-com:xml-diffgram-v1");
    diffnode.setattribute("xmlns:msdata", "urn:schemas-microsoft-com:xml-msdata");

    var datanode = ds.createelement(name);
    datanode.setattribute("xmlns", this.namespace);
    var changednodes = xmldata.documentelement.selectnodes(name + '/*[@diffgr:haschanges]');
    while (changednodes.peeknode() != null) {
        var changednode = changednodes.nextnode();
        datanode.appendchild(changednode.clonenode(true));
    }
    diffnode.appendchild(datanode);

    var beforenode = xmldata.documentelement.selectsinglenode("diffgr:before");
    if (beforenode) {
        diffnode.appendchild(beforenode.clonenode(true));
    }

    // 合并schema和数据
    ds.documentelement.appendchild(schemanode);
    ds.documentelement.appendchild(diffnode);

    return ds.documentelement;
}

function readxml(doc)
{
    readxmlschema(doc);

    var odiffgram = doc.selectsinglenode("diffgr:diffgram");
    if (odiffgram != null) {
        xmldata    = new activexobject("microsoft.xmldom");
        xmldata.documentelement    = odiffgram;
    }
}

function readxmlschema(doc)
{
    xmldata = null;

    // 得到schema
    var oschema = doc.selectsinglenode("xsd:schema");
    if (oschema != null)
    {
        xmlschema            = new activexobject("microsoft.xmldom");
        xmlschema.documentelement    = oschema;
        name                = oschema.selectsinglenode('xsd:element[@msdata:isdataset="true"]').getattribute("name")
        namespace            = oschema.getattribute("targetnamespace");
    }
}
</script>

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