Tài liệu XML by Example- P7 doc

var name = form.name.value, dollars = form.dollarsamount.value, euros = form.eurosamount.value, productList = form.productlist; // creates the various objects required var dollarsPrice = new Price(dollars,”usd”), eurosPrice = new Price(euros,”eur”), prices = new Array(dollarsPrice,eurosPrice), product = new Product(name,prices); // arrays are zero-based so products.length points // to one past the latest product // JavaScript automatically allocates memory var pos = products.length; products[pos] = product; var option = new Option(name,pos); productList.options[productList.length] = option; } function deleteProduct(form) { var productList = form.productlist, pos = productList.selectedIndex; if(pos != -1) { var product = productList.options[pos].value; productList.options[pos] = null; products[product] = null; } } function exportProduct(form) { 285 Creating Documents Without DOM continues 11 2429 CH09 11/12/99 1:02 PM Page 285 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. form.output.value = makeXML(); } function send() { var http = new ActiveXObject(“Microsoft.XMLHTTP”); http.open(“POST”,”http://catwoman.pineapplesoft.com/Dump”,false); http.setRequestHeader(“Content-type”,”application/xml”); http.send(“value=” + makeXML()); document.open(); document.write(http.responseText); } function makeXML() { var xmlCode = “”; var i; for(i = 0;i < products.length;i++) if(products[i] != null) xmlCode += products[i].toXML(); return element(“products”,””,xmlCode); } function resetAll(form,document) { priceList = null; form.output.value = “”; } function element(name,attributes,content) { var result = “<” + name; if(attributes != “”) result += “ “ + attributes; result += “>”; 286 Chapter 9: Writing XML Listing 9.6: continued 11 2429 CH09 11/12/99 1:02 PM Page 286 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. result += content; result += “</” + name + “>\r”; return result; } function escapeXML(string) { var result = “”, i, c; for(i = 0;i < string.length;i++) { c = string.charAt(i); if(c == ‘<’) result += “&lt;”; else if(c == ‘&’) result += “&amp;”; else result += c; } return result; } // declares two JavaScript objects // product object function Product(name,prices) { this.name = name; this.prices = prices; this.toXML = product_toXML; } function product_toXML() { var result = element(“name”,””,escapeXML(this.name)), 287 Creating Documents Without DOM continues 11 2429 CH09 11/12/99 1:02 PM Page 287 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. i; for(i = 0;i < this.prices.length;i++) result += this.prices[i].toXML(); return element(“product”,””,result); } // price object function Price(amount,currency) { this.amount = amount; this.currency = currency; this.toXML = price_toXML; } function price_toXML() { return element(“price”, “currency=\”” + this.currency + “\””, escapeXML(this.amount)); } Because this application does not use DOM, it works with browsers that have no XML support (obviously, they need to support JavaScript), such as Netscape 4. Figure 9.3 shows the result in Netscape. A Non-DOM Data Structure This application is radically different from the other applications intro- duced in this chapter. Internally, the application does not use XML, but uses its own data structure instead. In other words, it does not create Element objects; it creates Product and Price JavaScript objects. In JavaScript, an object constructor is simply a function that sets the object properties. A method is a property that is assigned a function. 288 Chapter 9: Writing XML Listing 9.6: continued OUTPUT 11 2429 CH09 11/12/99 1:02 PM Page 288 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Figure 9.3: The result in Netscape In this example, the constructor for Product declares two properties ( name and prices ) and one method ( toXML ). function Product(name,prices) { this.name = name; this.prices = prices; this.toXML = product_toXML; } These objects are created with the new operator like built-in JavaScript objects: var product = new Product(name,prices); JavaScript objects are used like built-in objects: xmlCode += products[i].toXML(); Writing XML The Product and Price objects are XML-aware because they know how to save (serialize) themselves as XML objects through the toXML() function. The makeXML() function is trivial: It iterates over the list of products calling the toXML() function. It wraps the result in a products element: function makeXML() { var xmlCode = “”; 289 Creating Documents Without DOM EXAMPLE 11 2429 CH09 11/12/99 1:02 PM Page 289 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. var i; for(i = 0;i < products.length;i++) if(products[i] != null) xmlCode += products[i].toXML(); return element(“products”,””,xmlCode); } Notice that this approach is recursive. Product implements its toXML() method partly by serializing the list of Price and wrapping it in a product element. function product_toXML() { var result = element(“name”,””,escapeXML(this.name)), i; for(i = 0;i < this.prices.length;i++) result += this.prices[i].toXML(); return element(“product”,””,result); } function price_toXML() { return element(“price”, “currency=\”” + this.currency + “\””, escapeXML(this.amount)); } XML is a convenient format because elements can nest in a way that is very similar to how objects are referenced by other objects. Hiding the Syntax This application needs to know very little about the XML syntax. Its knowl- edge is completely encapsulated in two functions— element() and escapeXML() . 1. element() is in charge of the tagging. Again, the core XML syntax function is simple and it shows in this function. function element(name,attributes,content) { var result = “<” + name; 290 Chapter 9: Writing XML EXAMPLE 11 2429 CH09 11/12/99 1:02 PM Page 290 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. if(attributes != “”) result += “ “ + attributes; result += “>”; result += content; result += “</” + name + “>\r”; return result; } 2. escapeXML() ensures that the angle bracket and ampersand characters are escaped. These characters are not allowed in the text of an ele- ment. function escapeXML(string) { var result = “”, i, c; for(i = 0;i < string.length;i++) { c = string.charAt(i); if(c == ‘<’) result += “&lt;”; else if(c == ‘&’) result += “&amp;”; else result += c; } return result; } Creating Documents from Non-XML Data Structures For most applications, it is easy to write an XML generator. Indeed, the core XML syntax (essentially composed of tags) is not complex. Furthermore, XML elements nest in a way that is very convenient for object-oriented applications. Typically, creating documents from non-XML data structures is more effi- cient than the DOM-based approach because the application doesn’t have to duplicate its data structure. Figure 9.4 compares the two approaches. 291 Creating Documents from Non-XML Data Structures EXAMPLE 11 2429 CH09 11/12/99 1:02 PM Page 291 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. TIP So, when do you use DOM and when do you write your own generator? I find that DOM is ideal for modifying existing documents. In most other cases, I prefer my own generator. 292 Chapter 9: Writing XML Figure 9.4: Comparing DOM with an ad hoc generator Doing Something with the XML Documents Now that you can create XML documents, you probably want to do some- thing more involved than display the XML code in an HTML form. In most cases, the application can either save the document to a file or send it to a server. ✔ This section looks briefly at your options to save the document or send it to the server. We will revisit this topic in Chapter 12, “Putting It All Together: An e-Commerce Example,” (page 381). Sending the Document to the Server There are two options to send the document to the server. You can place the XML document in an HTML form and have it sent along with the form, you can use a JavaBean or an ActiveX control to post the XML document to the Web server. 1. Sending the XML document in a form is the most portable approach. Because you already create the XML document in a form, this is easy to do. The FORM tag needs an ACTION attribute and the INPUT field must be changed from BUTTON to SUBMIT . You might also want to change the TEXTAREA in a HIDDEN field so XML does not appear onscreen: 11 2429 CH09 11/12/99 1:02 PM Page 292 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Listing 9.8: HTML Form to Send the Document <FORM NAME=”controls” ACTION=”/Dump” METHOD=”POST”> Product name: <INPUT TYPE=”TEXT” NAME=”name”> Price (Dollars): <INPUT TYPE=”TEXT” NAME=”dollarsamount” SIZE=”7”> Price (Euros): <INPUT TYPE=”TEXT” NAME=”eurosamount” SIZE=”7”><BR> <SELECT NAME=”productlist” SIZE=”5” WIDTH=”250”> </SELECT><BR> <INPUT TYPE=”BUTTON” VALUE=”Add” ONCLICK=”addProduct(controls)”> <INPUT TYPE=”BUTTON” VALUE=”Delete” ONCLICK=”deleteProduct(controls)”> <INPUT TYPE=”SUBMIT” VALUE=”Send in XML” ONCLICK=”exportProduct(controls)”> <INPUT TYPE=”BUTTON” VALUE=”Clear” ONCLICK=”output.value=’’”><BR> <!-- there must be one character in the text area --> <INPUT TYPE=”HIDDEN” NAME=”output” VALUE=””> </FORM> The Web server will receive the XML document in a parameter called “out- put.” You would have to write a servlet or a CGI script to retrieve the docu- ment on the Web server. The beauty of this approach is that the document is returned in a form so the servlet simply accesses form parameters to retrieve the XML document. ✔ The section “Viewer and Editor” in Chapter 12 (page 444) shows such a servlet. CAUTION This example uses the Dump service that comes standard with Jetty, the Web server. Dump replies with a document that contains whatever it originally received. It is conve- nient for testing. If you don’t use Jetty, you will need to write your own servlet to accept the XML docu- ment. ✔ The section “Servlet Engine” in Appendix A explains how to install Jetty (page 460). Alternatively, you can post the data directly to the Web server, without going through a form. This method has the added benefit of not changing the current page. However, you have to go through an ActiveX object 293 Doing Something with the XML Documents 11 2429 CH09 11/12/99 1:02 PM Page 293 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. (Internet Explorer), a plug-in (all browsers), or a JavaBean (all browsers, all platforms). 2. Internet Explorer 5.0 ships with XMLHTTP, an ActiveX control that can send XML documents from JavaScript. Listing 9.9 shows how to use XMLHTTP. Listing 9.9: Posting the Result on a Web Site function send() { var http = new ActiveXObject(“Microsoft.XMLHTTP”); http.open(“POST”,”http://catwoman.pineapplesoft.com/Dump”,false); http.setRequestHeader(“Content-type”,”application/xml”); http.send(makeXML()); document.open(); document.write(http.responseText); } The ActiveX object has the following methods: • open(protocol,url,asynchronous) connects to a url . Set the protocol to POST . Set asynchronous to false to send synchronously. • setRequestHeader(keyword,value) adds a new keyword in the header of the document; you must use this function to set the content-type. • send(data) posts the data to the server. You need to change the “Send in XML” button in Listing 9.9 to call this function: <INPUT TYPE=”SUBMIT” VALUE=”Send in XML” ONCLICK=”send()”> Again, you need a servlet or CGI script on the server to receive the XML document. The URL http://catwoman.pineapplesoft.com/Dump points the Dump ser- vice on my machine. You will need to change this URL to your Web server. Listing 9.10 is a typical response from the server. TIP Jetty’s Dump returns an HTML document that contains the POST parameters. Choose “View Source” in your browser options to see the XML document. Listing 9.10: XML Document Returned by the Server <products><product><name>XML Editor</name> <price currency=”usd”>499.00</price> <price currency=”eur”>475.00</price> 294 Chapter 9: Writing XML EXAMPLE OUTPUT 11 2429 CH09 11/12/99 1:02 PM Page 294 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. [...]... exportProduct(form ,xml, xslt) { var selected = form.format.selectedIndex, format = form.format.options[selected].value; if(format == “default”) form.output.value = makeXML(); else { var xmlDoc = makeXML(); xml. async = false; // passes an XML string to the parser xml. loadXML(xmlDoc); form.output.value = xml. transformNode(xslt.XMLDocument); } } function send() { var http = new ActiveXObject(“Microsoft.XMLHTTP”);... Chapter 9: Writing XML else { var xmlDoc = makeXML(); xml. async = false; // passes an XML string to the parser xml. loadXML(xmlDoc); form.output.value = xml. transformNode(xslt.XMLDocument); } } Unfortunately, the DOM standard does not specify how to apply an XSLT style sheet to a document Again, you can use a browser-specific extension For Internet Explorer, the XSL processor is called by the transformNode()... document here // xmldoc.save(Server.MapPath(“request .xml )); %> Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark 11 2429 CH09 11/12/99 1:02 PM Page 296 296 Chapter 9: Writing XML NOTE To create an XML parser from ASP you cannot use an XML island Instead create the , XML parser directly as an ActiveXObject as in var xmldoc = new ActiveXObject(“Microsoft.XMLDOM”); This is... http.setRequestHeader(“Content-type”,”application /xml ); http.send(“value=” + makeXML()); document.open(); document.write(http.responseText); } function makeXML() { var xmlCode = “”; var i; for(i = 0;i < products.length;i++) if(products[i] != null) Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark continues 11 2429 CH09 11/12/99 1:02 PM Page 300 300 Chapter 9: Writing XML Listing 9.13: continued xmlCode += products[i].toXML();... this.prices = prices; this.toXML = product_toXML; } function product_toXML() { var result = element(“name”,””,escapeXML(this.name)), i; for(i = 0;i < this.prices.length;i++) result += this.prices[i].toXML(); return element(“product”,””,result); } // price object function Price(amount,currency) { this.amount = amount; this.currency = currency; this.toXML = price_toXML; } function price_toXML() { return element(“price”,... the document Microsoft parser supports the save() function However, as I have just explained, this extension does not work on the browser It is therefore only useful when writing CGI scripts or ASP pages The example in Listing 9.11 shows how to save a file from JavaScript in an ASP server Listing 9.11: Saving the XML Document Listing 10.10: WriteIT Style Sheet < ?xml version=”1.0”?> < /xml> Which Structure for the Document? If your application supports several DTDs, you may wonder which one to use as the default DTD Experience shows that it pays to be dumb when designing . var xmlDoc = makeXML(); xml. async = false; // passes an XML string to the parser xml. loadXML(xmlDoc); form.output.value = xml. transformNode(xslt.XMLDocument);. the XML Document <% var xmldoc = new ActiveXObject(“Microsoft.XMLDOM”); // creates the XML document here // . xmldoc.save(Server.MapPath(“request .xml ));