ajax如何向action发送数据的

首先定义一个javascript函数，用来验证注册时用户名是否已经存在

function validateName(){	
	    //validateName值得是structs.xml中的名字是validateName那个action，在spring配置文件中注入
		var url = 'validateName!execute';
		var json = document.getElementById("name").value;//获取用户名
        var jsonName = {name:json}//创建json对象
		var name = JSON.stringify(jsonName); //将json对象转换成json格式的字符串    
        $.post(url, {json: name}, function(json){
        	$("#tip").text(json.msg); }, "json");
		
}

看看具体的ValidateAction实现

package org.arthur.lr.system.action;



import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.ServletActionContext;
import org.arthur.lr.system.dao.UserManager;
import org.json.JSONObject;

import com.googlecode.jsonplugin.annotations.JSON;
import com.opensymphony.xwork2.ActionSupport;

public class ValidateAction extends ActionSupport {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	//这个属性已经在spring配置文件中注入，千万不要在这里写UserManger mgr = new UserMangerImpl();
	private UserManager mgr;
	private String json;
	@JSON
	public String getJson() {
		return json;
	}

	public void setJson(String json) {
		this.json = json;
	}


	public UserManager getMgr() {
		return mgr;
	}

	public void setMgr(UserManager mgr) {
		this.mgr = mgr;
		System.out.println("启动tomcat时初始化");
	}

	@Override
	public String execute() throws Exception {
		JSONObject jsonObj = new JSONObject(json);    //将JSON格式的字符串构造成JSON对象
        String name = jsonObj.getString("name"); //获取JSON对象中的name属性的值
		
        if (mgr.validateName(name)) {
		  json =  "{msg:'you can use this name to regist'}";
			System.out.println("有户名有效");
		} else {
			 json =  "{msg:'the name is already exits'}";
			System.out.println("用户名已经存在");
		}

		this.sendMsg(json);//发送数据到客户端，供回调函数调用
		return SUCCESS;
	}
	
	public void sendMsg(String msg) throws IOException{
		System.out.println("发送json");
		HttpServletResponse res = ServletActionContext.getResponse();
		PrintWriter out = res.getWriter();
                   //out.println(msg);这样写也行
		out.write(msg);
		if(null != out){
			 out.close();//如果不关闭的话，ajax的回调函数不会调用
		}
       
	}

}