4.2. 集成技术开发指南

Beetl默认提供了WebRender用于帮助web集成开发，所有内置的集成均基于此方法。如果你认为Beetl内置的各个web框架集成功能不够，你可以继承此类，或者参考此类源码重新写，其代码如下

package org.beetl.ext.web;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.util.Enumeration;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.beetl.core.GroupTemplate;
import org.beetl.core.Template;
import org.beetl.core.exception.BeetlException;
/**
 *  通常web渲染的类，将request变量赋值给模板，同时赋值的还有session,request,ctxPath
 *  其他框架可以继承此类做更多的定制
 * @author joelli
 *
 */
public class WebRender{
        GroupTemplate gt = null;
        public WebRender(GroupTemplate gt){
                this.gt = gt;
        }
        /**
         * @param key 模板资源id
         * @param request
         * @param response
         * @param args 其他参数，将会传给modifyTemplate方法
         */
        public void render(String key, HttpServletRequest request, HttpServletResponse response, Object... args){
                Writer writer = null;
                OutputStream os = null;
                try{
                        //response.setContentType(contentType);
                        Template template = gt.getTemplate(key);
                        Enumeration<String> attrs = request.getAttributeNames();
                        while (attrs.hasMoreElements()){
                                String attrName = attrs.nextElement();
                                template.binding(attrName, request.getAttribute(attrName));
                        }
                        WebVariable webVariable = new WebVariable();
                        webVariable.setRequest(request);
                        webVariable.setResponse(response);
                        webVariable.setSession(request.getSession());
                        template.binding("session", new SessionWrapper(webVariable.getSession()));
                        template.binding("servlet", webVariable);
                        template.binding("request", request);
                        template.binding("ctxPath", request.getContextPath());
                        modifyTemplate(template, key, request, response, args);
                        String strWebAppExt = gt.getConf().getWebAppExt();
                        if(strWebAppExt!=null){
                                WebRenderExt renderExt = this.getWebRenderExt(strWebAppExt);
                                renderExt.modify(template, gt, request, response);
                        }
                        if (gt.getConf().isDirectByteOutput()){
                                os = response.getOutputStream();
                                template.renderTo(os);
                        }else{
                                writer = response.getWriter();
                                template.renderTo(writer);
                        }
                } catch (IOException e){
                        handleClientError(e);
                } catch (BeetlException e){
                        handleBeetlException(e);
                } finally{
                        try{
                                if (writer != null)
                                        writer.flush();
                                if (os != null)
                                        os.flush();
                        } catch (IOException e){
                                handleClientError(e);
                        }
                }
        }
        /**
         * 可以添加更多的绑定
         * @param template 模板
         * @param key 模板的资源id
         * @param request
         * @param response
         * @param args  调用render的时候传的参数
         */
        protected void modifyTemplate(Template template, String key, HttpServletRequest request,
                HttpServletResponse response, Object... args){
        }
        /**处理客户端抛出的IO异常
         * @param ex
         */
        protected void handleClientError(IOException ex){
                //do nothing
        }
        /**处理客户端抛出的IO异常
         * @param ex
         */
        protected void handleBeetlException(BeetlException ex){
                throw ex;
        }
}