搜索提示 Suggest

    仿照 Goolge Suggest,主要用到的技术是ajax。定时的发送请求道数据库比对。
    
     基本原理分析，当用户输入关键字，便向服务器发送请求，服务器根据用户输入的关键字，在数据库中搜索相关的关键字信息，并返回给客户端。
    
     代码分析：java 根据输入关键字返回相应结果
   

 package book.suggest;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Vector;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SearchSuggest extends HttpServlet {
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, java.io.IOException {

		String search = request.getParameter("search");//获得请求中cate的值
		System.out.println("哈哈  现在进的去了");
		//定义查询数据库的SQL语句
		String sql = "select title from suggest where title like '"+search+"%' order by title";

		Connection conn = null;//声明Connection对象
		Statement stmt = null;//声明Statement对象
		ResultSet rs = null;//声明ResultSet对象
		Vector vData = new Vector();
		//response.setContentType("text/xml");//设置返回数据类型为xml格式
		java.io.PrintWriter out = response.getWriter();

		try {
			// 加载数据库驱动类
			Class.forName("com.mysql.jdbc.Driver");
			// 访问数据库的地址
			String url = "jdbc:mysql://localhost/treeview";
			//创建Connection对象
			conn = DriverManager.getConnection(url, "root", "12345678");
			// 创建Statement对象
			stmt = conn.createStatement();
			// 执行SQL语句，返回记录集
			rs = stmt.executeQuery(sql);
			//定义AblumEO实体对象
			while (rs.next())
			{
				vData.add(rs.getString("TITLE"));
			}
			StringBuffer buf = new StringBuffer();
			for (int i=0;i<vData.size();i++)
			{
				String keyword = (String)vData.get(i);
				buf.append(keyword+"\n");
			}
			out.print(buf.toString());
			System.out.println(buf.toString());
//			out.print(parasToXML(vData));//调用parasToXML()方法
		} catch (Exception e) {

			e.printStackTrace();

		} finally {//最后关必记录集，Connection对象
			try {
				// this will close any associated ResultSets
				if (stmt != null)
					stmt.close();
				if (conn != null)
					conn.close();
			} catch (SQLException sqle) {
			}
		}
	
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, java.io.IOException {

		doPost(request, response);
	}
/*
	public String parasToXML(Vector v) {// 该方法将数据转化成XML格式输出
		StringBuffer buf = new StringBuffer();
		buf.append("<?xml version=\"1.0\" encoding=\"utf-8\"?>");
		buf.append("<pictures>");
		for (int i = 0; i < v.size(); i++) {
			AlbumEO album = (AlbumEO) v.get(i);
			buf.append("<item>");
			buf.append("<name>" + album.getAlbumName() + "</name>");
			buf.append("<url>" + album.getAlbumURL() + "</url>");
			buf.append("<description>" + album.getAlbumDescription()
					+ "</description>");
			buf.append("</item>");
		}
		buf.append("</pictures>");
		return buf.toString();
	}
*/
}

       
    ajax发送请求和处理返回信息

//Gets the browser specific XmlHttpRequest Object
function getXmlHttpRequestObject() {
	if (window.XMLHttpRequest) {
		return new XMLHttpRequest();
	} else if(window.ActiveXObject) {
		return new ActiveXObject("Microsoft.XMLHTTP");
	} else {
		alert("Your Browser Sucks!\nIt's about time to upgrade don't you think?");
	}
}
function createAjaxObj(){
  var httprequest=false
  if (window.XMLHttpRequest)
  { // if Mozilla, Safari etc
    httprequest=new XMLHttpRequest()
    if (httprequest.overrideMimeType)
      httprequest.overrideMimeType('text/xml')
   }
   else if (window.ActiveXObject)
   { // if IE
     try {
       httprequest=new ActiveXObject("Msxml2.XMLHTTP");
     }
     catch (e){
       try{
          httprequest=new ActiveXObject("Microsoft.XMLHTTP");
       }
       catch (e){}
     }
   }
   return httprequest
}
//Our XmlHttpRequest object to get the auto suggest
var searchReq = createAjaxObj();

//Called from keyup on the search textbox.
//Starts the AJAX request.
function searchSuggest() {
	if (searchReq.readyState == 4 || searchReq.readyState == 0) {
		var str = escape(document.getElementById('txtSearch').value);
		searchReq.open("GET", 'search?search=' + str, true);
		searchReq.onreadystatechange = handleSearchSuggest; 
		searchReq.send(null);
	}		
}

//Called when the AJAX response is returned.
function handleSearchSuggest() {
	if (searchReq.readyState == 4) {
		var ss = document.getElementById('search_suggest')
		ss.innerHTML = '';
		var str = searchReq.responseText.split("\n");
		for(i=0; i < str.length - 1; i++) {
			//Build our element string.  This is cleaner using the DOM, but
			//IE doesn't support dynamically added attributes.
			var suggest = '<div onmouseover="javascript:suggestOver(this);" ';
			suggest += 'onmouseout="javascript:suggestOut(this);" ';
			suggest += 'onclick="javascript:setSearch(this.innerHTML);" ';
			suggest += 'class="suggest_link">' + str[i] + '</div>';
			ss.innerHTML += suggest;
		}
	}
}

//Mouse over function
function suggestOver(div_value) {
	div_value.className = 'suggest_link_over';
}
//Mouse out function
function suggestOut(div_value) {
	div_value.className = 'suggest_link';
}
//Click function
function setSearch(value) {
	document.getElementById('txtSearch').value = value;
	document.getElementById('search_suggest').innerHTML = '';
}
    

当输入框出发Onkeyup事件就发送请求

              <html>
	<head>
		<style type="text/css" media="screen">
			body {
				font: 11px arial;
			}
			.suggest_link {
				background-color: #FFFFFF;
				padding: 2px 6px 2px 6px;
			}
			.suggest_link_over {
				background-color: #E8F2FE;
				padding: 2px 6px 2px 6px;
			}
			#search_suggest {
				position: absolute; 
				background-color: #FFFFFF; 
				text-align: left; 
				border: 1px solid #000000;			
			}		
		</style>
		<script language="JavaScript" type="text/javascript" src="ajax_search.js"></script>
	</head>
	<body>
		<h3>Simple AJAX Search Suggest</h3>
		<div style="width: 500px;">
			<form id="frmSearch" action="">
				<input type="text" id="txtSearch" name="txtSearch" alt="Search Criteria" onkeyup="searchSuggest();" autocomplete="off" />
				<input type="submit" id="cmdSearch" name="cmdSearch" value="Search" alt="Run Search" /><br />
				<div id="search_suggest">
				</div>
			</form>
		</div>
	</body>
</html>

       xml配置文件：配置请求url
       <?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <servlet>
    <servlet-name>search</servlet-name>
    <servlet-class>book.suggest.SearchSuggest</servlet-class>
   </servlet>

   <servlet-mapping>
     <servlet-name>search</servlet-name>
     <url-pattern>/search</url-pattern>
   </servlet-mapping>
</web-app>