【正文】 主要內容包括 C的基本語法、面向對象編程、 Windows 應用程序設計、數據庫編程、網絡編程、 Wed 應用程序及 Wed 服務、異常處理機制以及程序的部署和打包等 ? [9]楊德宏，李玲 客戶關系管理成功案例 北京：機械工業(yè)出版社， 書共例舉了 5 個行業(yè)，如金融業(yè)、制造業(yè)、 IT 業(yè)、郵政及通 信業(yè)和零售業(yè)共 20 多個案例。適當地使用 JavaScript，再加上基本的 DOM 管理， Ajax 可以提供高度的交互性，而這在此前的 Web 上是做不到的。有一些純粹基于客戶，還有一些需要在服務器上工作。 4. 服務器可以做你想做的事情，包括訪問數據庫，甚至訪問另一個系統(tǒng)。 1. 一個客戶端事件觸發(fā)一個 Ajax 事件。 string getResponseHeader(string header)： 這個方法與getAllResponseHeaders()是對應的，不過它有一個參數表示你希望得到的指定首部值，并且把這個值作為串返回。傳入這個方法的內容會作為請求體的一部分發(fā)送。默認值為 true，表示請求本質上是異步的。 url參數可以是相對 URL 或絕對 URL。 如果 調用失?。ǚ祷?null）， JavaScript 就會轉到 else 語句分支，確定瀏覽器是否把 XMLHttpRequest 實現為一個本地 JavaScript 對象。由于 XMLHttpRequest 不是一個 W3C 標準，所以可以采用多種方法使用 JavaScript 來創(chuàng)建 XMLHttpRequest 的實例。需要重點說明的是，XMLHttpRequest 并不是一個 W3C 標準，不過許多功能已經涵蓋在一個新提案中： DOM Level 3 加載和保存規(guī)約（ DOM Level 3 Load and Save Specification）。 we’ll talk about these methods in greater detail in a moment. Table 21. Standard XMLHttpRequest Operations Method Description abort() The current request. getAllResponseHeaders() Returns all the response headers for the HTTP request as key/value pairs. getResponseHeader(header) Returns the string value of the specified header. open(method, url) Sets the stage for a call to the server. The method argument can be either GET, POST, or PUT. The url argument can be relative or absolute. This method includes three optional arguments. send(content) Sends the request to the server. setRequestHeader(header, value) Sets the specified header to the supplied value. open() must be called before attempting to set any headers. Let’s take a closer look at these methods. void open(string method, string url, boolean asynch, string username, string password): This method sets up your call to the server. This method is meant to be the scriptonly method of initializing a request. It has two required arguments and three optional arguments. You are required to supply the specific method you are invoking (GET, POST, or PUT) and the URL of the resource you are calling. You may optionally pass a Boolean indicating whether this call is meant to be asynchronous— the default is true, which means the request is asynchronous in nature. If you pass a false, processing waits until the response returns from the server. Since making calls asynchronously is one of the main benefits of using Ajax, setting this parameter to false somewhat defeats the purpose of using the XMLHttpRequest object. That said, you may find it useful in certain circumstances such as validating user input before allowing the page to be persisted. The last two parameters are selfexplanatory, allowing you to include a specific username and password. void send(content): This method actually makes the request to the server. If the request was declared as asynchronous, this method returns immediately, otherwise it waits until the response is received. The optional argument can be an instance of a DOM object, an input stream, or a string. The content passed to this method is sent as part of the request body. void setRequestHeader(string header, string value): This method sets a value for a given header value in the HTTP request. It takes a string representing the header to set and a string representing the value to place in the header. Note that it must be called after a call to open(). Of all these methods, the two you will use the most are open() and send(). The XMLHttpRequest object has a number of properties that prove themselves quite useful while designing Ajax i