2006年7月8日

Struts 中的 html:options(摘抄)

html:options是Struts中比较复杂的一个tage lib,用法灵活,但是Sturts提供的源码exercise taglib中没有提出常用jsp+ActionForm这样形式的最直接的总结,现从中总结如下,分两种情况:数组和Collection。
  
  需求,要达到:
  <select name="beanCollectionSelect" multiple="multiple" size="10">
  <option value="value 0">Label 0</option>
  <option value="value 1" selected="selected">Label 1</option>
  <option value="value 2">Label 2</option>
  <option value="value 3" selected="selected">Label 3</option>
  <option value="value 4">Label 4</option>
  <option value="value 5" selected="selected">Label 5</option>
  <option value="value 6">Label 6</option>
  <option value="value 7">Label 7</option>
  <option value="value 8">Label 8</option>
  <option value="value 9">Label 9</option></select>
  
  要实现上述效果,需要两步:
  第一:设置ActionForm,
  也分两小步:第一小步必须在ActionForm中,有一句
  private Collection beanCollection;
  public Collection getBeanCollection();
  
  Collection beanCollection要确保是一个实现,如ArrayList,如果不是则会报No collection found的错误,Struts的最大不方便就是一旦出问题,定位很难,不知道什么地方使用错误,或忘记设置什么了。
  
  因为前面需求中option的value值和label值不一样,那么在beanCollection中保存的就是一个value和label组成的对象,名为LabelvalueBean,在LabelvalueBean中有两个属性value和label,
  
  在程序某个地方要为beanCollection赋值,如:
  
  Vector entries = new Vector(10); 
  entries.add(new LabelvalueBean("Label 0", "value 0"));     
  entries.add(new LabelvalueBean("Label 1", "value 1"));     
  entries.add(new LabelvalueBean("Label 2", "value 2"));     
  entries.add(new LabelvalueBean("Label 3", "value 3"));     
  entries.add(new LabelvalueBean("Label 4", "value 4"));      
  entries.add(new LabelvalueBean("Label 5", "value 5"));     
   entries.add(new LabelvalueBean("Label 6", "value 6"));      
  entries.add(new LabelvalueBean("Label 7", "value 7"));      
  entries.add(new LabelvalueBean("Label 8", "value 8"));      
  entries.add(new LabelvalueBean("Label 9", "value 9"));
  
  然后执行setBeanCollection(entries);
  这样ActionForm中的beanCollection算有值了。
  第二小步,需要设置Selected,selected有两种,单选和多选:
  在ActionForm中必须有:
  
  private String singleSelect = "Single 5"; 
  public String getSingleSelect()
   {
     return (this.singleSelect);
    } 
  public void setSingleSelect(String singleSelect)
   {
     this.singleSelect = singleSelect;
    }
  
  或多选,多选必须是数组:
  
  private String[] beanCollectionSelect = { "value 1", "value 3",
                         "value 5" }; 
  public String[] getBeanCollectionSelect() {
    return (this.beanCollectionSelect);  }
    public void setBeanCollectionSelect(String beanCollectionSelect[])
   {
      this.beanCollectionSelect = beanCollectionSelect;
    }
  
  第二:在Jsp中写入tang lib语句如下:
  
  <html:select property="beanCollectionSelect" size="10" multiple="true">
      <html:optionsCollection name="testbean" property="beanCollection"/>  
   </html:select>
  
  其中testbean是ActionForm的名称。
  
  以上是html:options的Collection解决方案,如果option值很少,简单地可以实现为数组,两步:
  第一:在ActionForm中,
  
  private String values[] =
     { "Magazine", "Journal", "News Paper","Other" }; 
  private String labels[] =
     { "L-Magazine", "L-Journal", "L-News Paper","L-Other"};
    private String selected = "Magazine";  
  public String getSelected()
  {
     return selected;
    }  
  public void setSelected(String selected)
  {
     this.selected = selected;
    } 
  public String[] getvalues()
  {
     return values;
    }  
  public void setvalues(String[] values)
  {   this.values = values;
    } 
  public String[] getLabels()
  {
     return values;
    }  
  public void setLabels(String[] labels)
  {
     this.labels = labels;
    }
  
  第二步在jsp中:
  
  <html:select property="selected" >     
  <html:options name="testbean" property="values" labelProperty="label"/>   </html:select>
  
  Struts标签库的使用还是需要小心,不必完全使用Struts的标签库,个人感觉Struts这种替代Html语句的标签库有一种牵强附会,给使用者掌握带来难度,使用者除熟悉html外,还必须理解Struts的对应标签库用法,而且这种调试出错,问题也无法准确定位,总是抽象地告诉你,no bean 或no form
posted @ 2006-07-09 00:58 Redish 阅读(810) | 评论 (1)编辑 收藏

中文转码Filter

在Struts中经常会碰到中文转码的问题,最简单的办法就是直接写一个ServletFilter
代码如下:
ChineseFilter.class


import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ChineseFilter extends HttpServlet implements Filter {

 private FilterConfig filterConfig;
     //Handle the passed-in FilterConfig
     public void init(FilterConfig filterConfig) throws ServletException {
         this.filterConfig = filterConfig;
     }
     //Process the request/response pair
     public void doFilter(ServletRequest request, ServletResponse response,
                          FilterChain filterChain) {
         try {
          
          String encoding=filterConfig.getInitParameter("encoding");//从WEB.xml配置文件中取出参数,这样我们可以通过配置修改编码格式.                  
             request.setCharacterEncoding(encoding);//设置请求的编码格式
             filterChain.doFilter(request, response);
         } catch (ServletException sx) {
             filterConfig.getServletContext().log(sx.getMessage());
         } catch (IOException iox) {
             filterConfig.getServletContext().log(iox.getMessage());
         }
     }

     //Clean up resources
     public void destroy() {
     }

  protected void doGet(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
   // TODO Auto-generated method stub
   super.doGet(arg0, arg1);  
  }

  protected void doPost(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
   // TODO Auto-generated method stub
   super.doPost(arg0, arg1);   
  } 
}

写完过滤器剩下的就是配置Web.xml了

 <filter>
  <filter-name>ChineseFilter</filter-name>
  <filter-class>com.blog.filter.ChineseFilter</filter-class>
<init-param>
    <param-name>encoding</param-name>
    <param-value>GBK</param-value> 配置编码格式,可以配置成你想要的编码(GBK,bg-2312)

</init-param>
  </filter>
   <filter-mapping>
    <filter-name>ChineseFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

好了,简单的Filter就完成了.当然也有现成的包,比如你用Struts+Spring的话,那Spring中就有现成的转码过滤器,我们只要在WEB.xml中配置一下就OK了.

<filter>
<filter-name>encodingFilter</filter-name>
 <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
 <init-param>
 <param-name>encoding</param-name>
. <param-value>GBK</param-value>
 </init-param>
 </filter>
<filter-mapping>
 <filter-name>encodingFilter</filter-name>
 <url-pattern>/*</url-pattern>
 </filter-mapping>

posted @ 2006-07-08 15:21 Redish 阅读(821) | 评论 (0)编辑 收藏