3.2 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;
  }
}