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
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>