ajax、Struts、spring的无缝结合

   采用Struts+JDBC（自定义采用适配器模式封装了HashMap动态VO实现的持久层）。   

   数据交互过程，我们考虑采用xml来组织数据结构，更新/保存:前台封装需要的xml，通过ajax提交---〉action解析xml ---〉改造原有的持久层实现xml持久化；
    查询时：持久层根据实际需要返回xml，document对象，---〉action 处理 --〉前台自己封装js库来解析xml，并刷新部分页面。

    ajax:已经有很多方法实现跨浏览器的方式，这里只介绍最简单的方式，同步模式下提交xmlStr给action（*.do）。

/**
 * 将数据同步传递给后台请求url
 *  @return 返回xmlhttp 响应的信息
 *  @param-url = '/web/module/xxx.do?p1=YY&p2=RR';
 *  @param-xmlStr：xml格式的字符串 <data><xpath><![CDATA[数据信息]]></xpath></data>
 * @author zhipingch
 * @date 2005-03-17
 */
function sendData(urlStr, xmlStr) {
    var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    xmlhttp.open("POST", urlStr, false);
    xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    if (xmlStr) {
        xmlhttp.send(xmlStr);
    } else {
        xmlhttp.send();
    }
    return xmlhttp.responseXml;
}

    struts中我们扩展了Action，实现了xmlStr转化成document对象（dom4j），并且完善了转发方式。如
[quote]
1.DispatchAction
     以一个Controller响应一组动作绝对是Controller界的真理，Struts的DispatchAction同样可以做到这点。

[list]
<action path="/admin/user" name="userForm" scope="request" parameter="method" validate="false">
    <forward name="list" path="/admin/userList.jsp"/>
</action>
[/list]
    其中parameter="method" 设置了用来指定响应方法名的url参数名为method，即/admin/user.do?method=list 将调用UserAction的public ActionForward list(....) 函数。  

    public ActionForward unspecified(....) 函数可以指定不带method方法时的默认方法。[/quote]
    但是这样需要在url后多传递参数[size=18][color=red]method=list [/color][/size]；并且action节点配置中的[color=red]parameter="method" [/color]
也没有被充分利用，反而觉得是累赘！

    因此我们直接在BaseDispatchAction中增加xml字符串解析，并充分利用action节点配置中的[color=red]parameter="targetMethod" [/color]，使得转发的时候，action能够直接转发到子类的相应方法中，减少了url参数传递，增强了配置信息可读性，方便团队开发。
    同样以上述为例，扩展后的配置方式如下：
[quote]
<action path="/admin/user" scope="request" [color=red]parameter="list"[/color] validate="false">
    <forward name="list" path="/admin/userList.jsp"/>
</action> 
 [/quote]
    其中[color=red]parameter="list"[/color] 设置了用来指定响应url=/admin/user.do的方法名,它将调用UserAction的public ActionForward list(....) 函数。
     BaseDispatchDocumentAction 的代码如下，它做了三件重要的事情：
     1、采用dom4j直接解析xml字符串，并返回document，如果没有提交xml数据，或者采用form形式提交的话，返回null；
     2、采用模版方法处理系统异常，减少了子类中无尽的try{...}catch(){...};其中异常处理部分另作描述（你可以暂时去掉异常处理，实现xml提交和解析，如果你有兴趣，我们可以进一步交流）；
     3、提供了Spring配置Bean的直接调用，虽然她没有注入那么优雅，但是实现了ajax、struts、spring的结合。
BaseDispatchDocumentAction 的源码如下：

package com.ufida.haisheng.struts;

import java.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.sql.Timestamp;
import java.util.Date;
import java.util.HashMap;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.beanutils.ConvertUtils;
import org.apache.commons.beanutils.converters.BigDecimalConverter;
import org.apache.commons.beanutils.converters.ClassConverter;
import org.apache.commons.beanutils.converters.IntegerConverter;
import org.apache.commons.beanutils.converters.LongConverter;
import org.apache.log4j.Logger;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.util.MessageResources;
import org.dom4j.Document;
import org.dom4j.io.SAXReader;
import org.hibernate.HibernateException;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.dao.DataAccessException;
import org.springframework.web.context.support.WebApplicationContextUtils;

import com.ufida.haisheng.constants.Globals;
import com.ufida.haisheng.converter.DateConverter;
import com.ufida.haisheng.converter.TimestampConverter;
import com.ufida.haisheng.exp.ExceptionDTO;
import com.ufida.haisheng.exp.ExceptionDisplayDTO;
import com.ufida.haisheng.exp.exceptionhandler.ExceptionHandlerFactory;
import com.ufida.haisheng.exp.exceptionhandler.ExceptionUtil;
import com.ufida.haisheng.exp.exceptionhandler.IExceptionHandler;
import com.ufida.haisheng.exp.exceptions.BaseAppException;
import com.ufida.haisheng.exp.exceptions.MappingConfigException;
import com.ufida.haisheng.exp.exceptions.NoSuchBeanConfigException;

/**
 * 系统的Ajax转发基类。增加模版处理异常信息。
 * 
 * @author 陈志平 chenzp
 * @desc BaseDispatchDocumentAction.java
 * 
 * @说明: web 应用基础平台
 * @date 2005-03-02 11:18:01 AM
 * @版权所有: All Right Reserved 2006-2008
 */
public abstract class BaseDispatchDocumentAction extends Action {

    protected Class clazz = this.getClass();

    protected static Logger log = Logger.getLogger(BaseDispatchDocumentAction.class);

    /**
     * 异常信息
     */
    protected static ThreadLocal<ExceptionDisplayDTO> expDisplayDetails = new ThreadLocal<ExceptionDisplayDTO>();
    
    private static final Long defaultLong = null;

    private static ApplicationContext ctx = null;
    /**
     * 注册转换的工具类 使得From中的string --
     * Model中的对应的类型(Date,BigDecimal,Timestamp,Double...)
     */
    static {
        ConvertUtils.register(new ClassConverter(), Double.class);
        ConvertUtils.register(new DateConverter(), Date.class);
        ConvertUtils.register(new DateConverter(), String.class);
        ConvertUtils.register(new LongConverter(defaultLong), Long.class);
        ConvertUtils.register(new IntegerConverter(defaultLong), Integer.class);
        ConvertUtils.register(new TimestampConverter(), Timestamp.class);
        ConvertUtils.register(new BigDecimalConverter(defaultLong), BigDecimal.class);
    }

    /**
     * The message resources for this package.
     */
    protected static MessageResources messages = MessageResources.getMessageResources("org.apache.struts.actions.LocalStrings");

    /**
     * The set of Method objects we have introspected for this class, keyed by
     * method name. This collection is populated as different methods are
     * called, so that introspection needs to occur only once per method name.
     */
    protected HashMap<String, Method> methods = new HashMap<String, Method>();

    /**
     * The set of argument type classes for the reflected method call. These are
     * the same for all calls, so calculate them only once.
     */
    protected Class[] types = { ActionMapping.class, ActionForm.class, Document.class, HttpServletRequest.class,
            HttpServletResponse.class };

    /**
     * Process the specified HTTP request, and create the corresponding HTTP
     * response (or forward to another web component that will create it).
     * Return an <code>ActionForward</code> instance describing where and how
     * control should be forwarded, or <code>null</code> if the response has
     * already been completed.
     * 
     * @param mapping
     *            The ActionMapping used to select this instance
     * @param form
     *            The optional ActionForm bean for this request (if any)
     * @param request
     *            The HTTP request we are processing
     * @param response
     *            The HTTP response we are creating
     * 
     * @exception Exception
     *                if an exception occurs
     */
    public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request,
            HttpServletResponse response) throws Exception {
        response.setContentType("text/html; charset=UTF-8");
        ExceptionDisplayDTO expDTO = null;
        try {
            Document doc = createDocumentFromRequest(request);
            /*
             * 这里直接调用mapping的parameter配置
             */
            String actionMethod = mapping.getParameter();
            /*
             * 校验配置的方法是否正确、有效
             */
            isValidMethod(actionMethod);

            return dispatchMethod(mapping, form, doc, request, response, actionMethod);
        } catch (BaseAppException ex) {
            expDTO = handlerException(request, response, ex);
        } catch (Exception ex) {
            ExceptionUtil.logException(this.getClass(), ex);
            renderText(response,"[Error :对不起,系统出现错误了,请向管理员报告以下异常信息./n" + ex.getMessage() + "]");
            request.setAttribute(Globals.ERRORMSG, "对不起,系统出现错误了,请向管理员报告以下异常信息./n" + ex.getMessage());
            expDTO = handlerException(request,response, ex);
        } finally {
            expDisplayDetails.set(null);
        }
        return null == expDTO ? null : (expDTO.getActionForwardName() == null ? null : mapping.findForward(expDTO.getActionForwardName()));
    }

    /**
     * 直接输出纯字符串
     */
    public void renderText(HttpServletResponse response, String text) {
        PrintWriter out = null;
        try {
            out = response.getWriter();
            response.setContentType("text/plain;charset=UTF-8");
            out.write(text);
        } catch (IOException e) {
            log.error(e);
        } finally {
            if (out != null) {
                out.flush();
                out.close();
                out = null;
            }
        }
    }
    
    /**
     * 直接输出纯HTML
     */
    public void renderHtml(HttpServletResponse response, String text) {
        PrintWriter out = null;
        try {
            out = response.getWriter();
            response.setContentType("text/html;charset=UTF-8");
            out.write(text);
        } catch (IOException e) {
            log.error(e);
        } finally {
            if (out != null) {
                out.flush();
                out.close();
                out = null;
            }
        }
    }

    /**
     * 直接输出纯XML
     */
    public void renderXML(HttpServletResponse response, String text) {
        PrintWriter out = null;
        try {
            out = response.getWriter();
            response.setContentType("text/xml;charset=UTF-8");
            out.write(text);
        } catch (IOException e) {
            log.error(e);
        } finally {
            if (out != null) {
                out.flush();
                out.close();
                out = null;
            }
        }
    }

    /**
     * 异常处理
     * @param request
     * @param out
     * @param ex
     * @return ExceptionDisplayDTO异常描述对象
     */
    private ExceptionDisplayDTO handlerException(HttpServletRequest request,HttpServletResponse response, Exception ex) {
        ExceptionDisplayDTO expDTO = (ExceptionDisplayDTO) expDisplayDetails.get();
        if (null == expDTO) {            
            expDTO = new ExceptionDisplayDTO(null,this.getClass().getName());
        }
        IExceptionHandler expHandler = ExceptionHandlerFactory.getInstance().create();
        ExceptionDTO exDto = expHandler.handleException(expDTO.getContext(), ex);
        request.setAttribute("ExceptionDTO", exDto);
        renderText(response,"[Error:" + (exDto == null ? "ExceptionDTO is null,请检查expinfo.xml配置文件." : exDto.getMessageCode())
                + "]");
        return expDTO;
    }

    private void isValidMethod(String actionMethod) throws MappingConfigException {
        if (actionMethod == null || "execute".equals(actionMethod) || "perform".equals(actionMethod)) {
            log.error("[BaseDispatchAction->error] parameter = " + actionMethod);
            expDisplayDetails.set(new ExceptionDisplayDTO(null, "MappingConfigException"));
            throw new MappingConfigException("对不起,配置的方法名不能为 " + actionMethod);
        }
    }

  /**
     * 解析xml流
     * @param request
     * @return Document对象
     */
    protected static Document createDocumentFromRequest(HttpServletRequest request) throws Exception {
        try {
            request.setCharacterEncoding("UTF-8");
            Document document = null;
            SAXReader reader = new SAXReader();
            document = reader.read(request.getInputStream());
            return document;
        } catch (Exception ex) {
            log.warn("TIPS：没有提交获取XML格式数据流! ");
            return null;
        }
    }

    /**
     * Dispatch to the specified method.
     * 
     * @since Struts 1.1
     */
    protected ActionForward dispatchMethod(ActionMapping mapping, ActionForm form, Document doc,HttpServletRequest request, HttpServletResponse response, String name) throws Exception {
        Method method = null;
        try {
            method = getMethod(name);
        } catch (NoSuchMethodException e) {
            String message = messages.getMessage("dispatch.method", mapping.getPath(), name);
            log.error(message, e);
            expDisplayDetails.set(new ExceptionDisplayDTO(null, "MappingConfigException"));
            throw new MappingConfigException(message, e);
        }

        ActionForward forward = null;
        try {
            Object args[] = { mapping, form, doc, request, response };
            log.debug("[execute-begin] -> " + mapping.getPath() + "->[" + clazz.getName() + "->" + name + "]");
            forward = (ActionForward) method.invoke(this, args);
            log.debug(" [execute-end] -> " + (null == forward ? "use ajax send to html/htm" : forward.getPath()));
        } catch (ClassCastException e) {
            String message = messages.getMessage("dispatch.return", mapping.getPath(), name);
            log.error(message, e);
            throw new BaseAppException(message, e);

        } catch (IllegalAccessException e) {
            String message = messages.getMessage("dispatch.error", mapping.getPath(), name);
            log.error(message, e);
            throw new BaseAppException(message, e);

        } catch (InvocationTargetException e) {
            Throwable t = e.getTargetException();
            String message = messages.getMessage("dispatch.error", mapping.getPath(), name);
            throw new BaseAppException(message, t);
        }

        return (forward);
    }

    /**
     * Introspect the current class to identify a method of the specified name
     * that accepts the same parameter types as the <code>execute</code>
     * method does.
     * 
     * @param name
     *            Name of the method to be introspected
     * 
     * @exception NoSuchMethodException
     *                if no such method can be found
     */
    protected Method getMethod(String name) throws NoSuchMethodException {
        synchronized (methods) {
            Method method = (Method) methods.get(name);
            if (method == null) {
                method = clazz.getMethod(name, types);
                methods.put(name, method);
            }
            return (method);
        }
    }

  /**
   * 返回spring bean对象
   * @param name Spring Bean的名称
   * @exception BaseAppException
   */
    protected Object getSpringBean(String name) throws BaseAppException {
        if (ctx == null) {
            ctx = WebApplicationContextUtils.getWebApplicationContext(this.getServlet().getServletContext());
        }
        Object bean = null;
        try {
            bean = ctx.getBean(name);
        } catch (BeansException ex) {
            throw new NoSuchBeanConfigException("对不起,您没有配置名为:" + name + "的bean。请检查配置文件!", ex.getRootCause());
        }
        if (null == bean) {
            throw new NoSuchBeanConfigException("对不起,您没有配置名为:" + name + "的bean。请检查配置文件!");
        }
        return bean;
    }
}

开发人员只需要继承它就可以了，我们写个简单的示例action，如下：

/**
 * 带Ajax提交xml数据的action类模版
 * 
 * @author 陈志平 chenzp
 * 
 * @说明: web 应用基础平台
 * @date Aug 1, 2006 10:52:13 AM
 * @版权所有: All Right Reserved 2006-2008
 */
public class UserAction extends BaseDispatchDocumentAction {
         /**
          * 这里 actionForm 和 doc 参数必有一个为空，请聪明的你分析一下
          * @param mapping --转发的映射对象
          [color=blue]* @param actionForm --仍然支持表单提交，此时doc == null
          * @param doc document对象，解析xml后的文档对象[/color]
          * @param request --请求
          * @param response --响应
          */
    public ActionForward list(ActionMapping mapping, ActionForm actionForm, [color=red]Document doc[/color],HttpServletRequest request, HttpServletResponse response) throws BaseAppException {
        /**
         * 转发的名称 userAction.search: 系统上下文 用于异常处理
         */
        expDisplayDetails.set(new ExceptionDisplayDTO(null, "userAction.search"));
        /**
         * 处理业务逻辑部分：
         * 
         * 获取各种类型的参数 RequestUtil.getStrParameter(request,"ParameterName");
         * 
         * 调用父类的 getSpringBean("serviceID")方法获取spring的配置bean
         * 
         */
        UserManager userManager = (LogManager) getSpringBean("userManager");
        //返回xml对象到前台
        renderXML(response, userManager.findUsersByDoc(doc))；        
                     return null;
    }