需求
通过ajax异步刷新页面验证用户输入的账号密码是否在数据库中存在。
技术栈
jsp+servlet+oracle
具体代码
jsp部分：
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<%@ page language="java" contenttype="text/html; charset=utf-8"
pageencoding="utf-8"%>
<!doctype html public "-//w3c//dtd html 4.01 transitional//en" "http://www.w3.org/tr/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>insert title here</title>
</head>
<script>
function createxmlhttprequest() {
try {
xmlhttp = new xmlhttprequest();//除了ie之外的其他浏览器使用ajax
} catch (tryms) {
try {
xmlhttp = new activexobject("msxml2.xmlhttp");//ie浏览器适配
} catch (otherms) {
try {
xmlhttp = new activexobject("microsoft.xmlhttp");//ie浏览器适配
} catch (failed) {
xmlhttp = null;
}
}
}
return xmlhttp;
}
//提交请求
var xmlhttp;
function checkuserexists() {
var u = document.getelementbyid("uname");
var username = u.value;
if (username == "") {
alert("请输入用户名");
u.focus();
return false;
}
//访问字符串
var url = "loginservlet";
//创建核心xmlhttprequest组件
xmlhttp = createxmlhttprequest();
//设置回调函数
xmlhttp.onreadystatechange = proessrequest;
//初始化核心组件
xmlhttp.open("post", url, true);
//设置请求头
xmlhttp.setrequestheader("content-type","application/x-www-form-urlencoded;");
//发送请求
xmlhttp.send("uname="+username);
}
//回调函数
function proessrequest() {
if (xmlhttp.status==200 && xmlhttp.readystate == 4) {
var b = xmlhttp.responsetext;//得到服务端的输出结果
if (b=="true") {
document.getelementbyid("alert").innerhtml = "<font color='red'>用户名已经存在！</font>";
}else {
document.getelementbyid("alert").innerhtml = "<font color='blue'>用户名可以使用！</font>";
}
}
}
</script>
<body>
请输入用户名：
<input id="uname" name="uname" type="text" onblur="checkuserexists()" /><div id="alert" style="display:inline"></div>
</body>
</html>
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这里没有用dao层，直接用servlet和service层进行验证。
下面是service下jdbc查询的代码：
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import java.sql.connection;
import java.sql.resultset;
import java.sql.sqlexception;
import java.sql.statement;
import com.stx.service.user;
import com.stx.service.connectionmanager;
public class ajaxservice {
public boolean searchuser (string uname) {
//jdbc查询用户名是否存在
boolean isfalse = false;
connection connection = null;
statement stmt = null;
resultset rs = null;
connection = connectionmanager.getconnection();
try {
stmt = connection.createstatement();
string sql = "select * from user_b where uname='"+uname+"'";//sql语句
rs = stmt.executequery(sql);
isfalse=rs.next();
} catch (sqlexception e) {
e.printstacktrace();
} finally {
connectionmanager.closeresultset(rs);
connectionmanager.closestatement(stmt);
connectionmanager.closeconnection(connection);
}
return isfalse;
}
}
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jdbc连接代码：
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import java.sql.connection;
import java.sql.drivermanager;
import java.sql.resultset;
import java.sql.sqlexception;
import java.sql.statement;
public class connectionmanager {
private final static string driver_class = "oracle.jdbc.oracledriver";
private final static string url = "jdbc:oracle:thin:@localhost:1521:orcl";
private final static string dbname = "ibook";
private final static string password = "qwer";
public static connection getconnection() {
connection connection = null;
try {
class.forname(driver_class);
connection = drivermanager.getconnection(url, dbname, password);
} catch (classnotfoundexception e) {
e.printstacktrace();
} catch (sqlexception e) {
e.printstacktrace();
}
return connection;
}
public static void closeresultset(resultset rs) {
try {
if (rs != null)
rs.close();
} catch (sqlexception e) {
e.printstacktrace();
}
}
public static void closeconnection(connection connection) {
try {
if (connection != null && !connection.isclosed())
connection.close();
} catch (sqlexception e) {
e.printstacktrace();
}
}
public static void closestatement(statement stmt) {
try {
if (stmt != null)
stmt.close();
} catch (sqlexception e) {
e.printstacktrace();
}
}
}
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关于user类：
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public class user {
private string uname;
public user() {
super();
}
public user(string uname) {
super();
this.uname = uname;
}
public string getuname() {
return uname;
}
public void setuname(string uname) {
this.uname = uname;
}
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关于控制层servlet：
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import java.io.ioexception;
import java.io.printwriter;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import com.stx.service.ajaxservice;
/**
* servlet implementation class loginservlet
*/
public class loginservlet extends httpservlet {
private static final long serialversionuid = 1l;
private ajaxservice ajaxservice = new ajaxservice();
/**
* @see httpservlet#httpservlet()
*/
public loginservlet() {
super();
// todo auto-generated constructor stub
}
/**
* @see httpservlet#doget(httpservletrequest request, httpservletresponse response)
*/
protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
request.setcharacterencoding("utf-8");
string uname = request.getparameter("uname");//获取到输入的用户名
boolean isuname = ajaxservice.searchuser(uname);//调用service中的查询方法
response.setcharacterencoding("utf-8");//设置字符编码
printwriter out = response.getwriter();
out.print(isuname);
out.flush();
out.close();//关闭资源
}
/**
* @see httpservlet#dopost(httpservletrequest request, httpservletresponse response)
*/
protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
// todo auto-generated method stub
doget(request, response);
}
}
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以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：https://segmentfault.com/a/1190000015150083