使用AJAX完成用户名是否存在异步校验

参考原文：http://www.cnblogs.com/guoxianda/p/5670647.html

1.jsp代码

1.1 事件触发：鼠标移开（onblur）"姓名"输入框时

1.2 编写ajax:向Action中提交，传递username参数

<script>
    function checkUsername(){
        //获得文本框的值
        
        var username=document.getElementById("username").value;
        //判断是否输入用户名
        if(username.length !=0){
            //1.创建异步交互对象
            var xhr=createXmlHttp();
            //2.设置监听
            xhr.onreadystatechange=function(){
                if(xhr.readyState==4){
                    if(xhr.status==200){

		//填充action输出的内容
                        document.getElementById("span1").innerHTML=xhr.responseText;
                    }
                }
            }
            //3.打开连接，发送到action，传递username
            xhr.open("GET","${pageContext.request.contextPath}/user_findByName.action?time="+new Date().getTime()+"&username="+username,true);
            //4.发送
            xhr.send(null);
        }else{
            document.getElementById("span1").innerHTML="";
        }
    }
    
    function createXmlHttp(){
        var xmlHttp;
        try{//Firefox,opera,Safari
            xmlHttp=new XMLHttpRequest();
        }
        catch(e){
            try{//Internet explorer
                xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
            }
            catch(e){
                try{
                    xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
                }
                catch(e){}
            }
        }
        return xmlHttp;
    }
}

<!-- 事件触发 -->
<!-- <input type="text" id="username" name="username" class="text" maxlength="20" οnblur="checkUsername(this);"/> -->
<input type="text" id="username" name="username" class="text" maxlength="20" οnblur="checkUsername();"/>
<span id="span1"></span>

2.java方法类Action代码

接收username:模型驱动接收

public class UserAction extends ActionSupport implements ModelDriven<User>{
    //模型驱动要使用的对象
    private User user=new User();
    public User getModel() {
        return user;
    }
    //注入UserService
    private UserService userService;
    
    public void setUserService(UserService userService) {
        this.userService = userService;
    }/*
     * ajax进行异步校验用户名的执行方法 
     */
    public String findByName() throws IOException{
        //调用Service进行查询
        User existUser=userService.findByUsername(user.getUsername());
        //获得response对象，向页面输出：
        HttpServletResponse response=ServletActionContext.getResponse();
        response.setContentType("text/html;charset=UTF-8");
        //判断
        if(existUser != null){
            //查询到该用户：用户名已经存在
            response.getWriter().println("<font color='red'>用户名已经存在</font>");
        }
        else{
            //没查到该用户：用户名可以使用
            response.getWriter().println("<font color='green'>用户名可以使用</font>");
        }
        return NONE;
    }
}

3.java实体类代码

3.1编写User类

/*
 * 用户模块的实体类
 */
public class User {
    private Integer uid;
    private String username;
    private String password;public Integer getUid() {
        return uid;
    }
    public void setUid(Integer uid) {
        this.uid = uid;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

3.2 编写hibernate映射

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 
    
<hibernate-mapping>
    <class name="cn.itcast.shop.user.vo.User" table="user">
        <id name="uid">
            <generator class="native"/>
        </id>
        <property name="username"/>
        <property name="password"/>
        <property name="name"/>
    </class>
</hibernate-mapping>

3.3 Dao层代码

*
 * 用户模块持久层的代码
 */
public class UserDao extends HibernateDaoSupport {
    
    //按名次查询是否有该用户
    public User findByUsername(String username){
        String hql="from User where username=?";
        List<User> list=this.getHibernateTemplate().find(hql,username);
        if(list !=null && list.size()>0){
            return list.get(0);
        }
        return null;
    }
}

3.4 service层代码

/*
 * 用户模块业务层的代码
 */
@Transactional
public class UserService {
    //注入UserDao
    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
    
    //按用户名查询用户的方法
    public User findByUsername(String username){
        return userDao.findByUsername(username);
    }

}

3.5 在spring中配置实体类、映射和注入

<!-- 配置Hibernate的映射文件 -->
    <property name="mappingResources">
        <list>
            <value>cn/itcast/shop/user/vo/User.hbm.xml</value>
        </list>
    </property>
    </bean>    
    
    <!-- 事务管理: -->
    <!-- 事务管理器 -->
    <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory"/>  
    </bean>
    
    <!-- 开启注解事务 -->
    <tx:annotation-driven transaction-manager="transactionManager"/>
         
    <!-- 首页访问的action -->
    <bean id="indexAction" class="cn.itcast.shop.index.action.IndexAction" scope="prototype">
    </bean>
    
    <!-- 用户模块的action -->
    <bean id="userAction" class="cn.itcast.shop.user.action.UserAction" scope="prototype">
        <!-- 注入service -->
        <property name="userService" ref="userService"/>
    </bean>
    
    <!-- Service配置 -->
    <bean id="userService" class="cn.itcast.shop.user.service.UserService">
        <property name="userDao" ref="userDao"/>
    </bean>
    
    <!-- Dao配置 -->
    <bean id="userDao" class="cn.itcast.shop.user.dao.UserDao">
        <property name="sessionFactory" ref="sessionFactory"/>
    </bean>