struts2或webwork嵌套集合类型转换

给出例子代码

   public class TestAction{
   
        private List users;

      //////  getter setter

   }
  ....
  public class User{

      private  String username;

    ////getter setter
  }

在以上代码中，假设users集合装的是User类实例，则在于TestAction同包下建立一个TestAction-conversion.properties文件：

  Element_users = com.xxxx.User(早期用Collection_)

页面上输入用户名如下脚本

  <input name="users[0].username"/>

假设User用户有属于多个组group，那User变为

 public class User{

      private  String username;
      private  List groups;

    ////getter setter
  }

groups中存放的是com.yyy.Group类实例

   public class Group{

     private String gname;
   
    ////getter setter
 }

在于User同包下，建立User-conversion.properties:
Element_groups= com.yyy.Group
页面上输入组名如下

    <input name=users[0][0].gname  />

struts2或webwork给我们提供了以上支持，若是想明确集合中的对象，就在变量所属的类的同包下建立对应的***-conversion.properties,在文件中指定Element_xxx即可

假设有需求是集合中的元素也是集合，那struts2或webwork是不支持的，为了解决这个问题，首先重写XworkListPropertyAccessor

public class XWorkListPropertyAccessor extends ListPropertyAccessor
{

    public XWorkListPropertyAccessor()
    {
        _sAcc = new XWorkCollectionPropertyAccessor();
    }

    public Object getProperty(Map context, Object target, Object name)
        throws OgnlException
    {
        if(OgnlContextState.isGettingByKeyProperty(context) || name.equals("makeNew"))
            return _sAcc.getProperty(context, target, name);
        if(name instanceof String)
            return super.getProperty(context, target, name);
        OgnlContextState.updateCurrentPropertyPath(context, name);
        Class lastClass = (Class)context.get("last.bean.accessed");
        String lastProperty = (String)context.get("last.property.accessed");
        if((name instanceof Number) && OgnlContextState.isCreatingNullObjects(context) && XWorkConverter.getInstance().getObjectTypeDeterminer().shouldCreateIfNew(lastClass, lastProperty, target, null, true))
        {
            List list = (List)target;
            int index = ((Number)name).intValue();
            int listSize = list.size();
            if(lastClass == null || lastProperty == null)
                return super.getProperty(context, target, name);
            Class beanClass = XWorkConverter.getInstance().getObjectTypeDeterminer().getElementClass(lastClass, lastProperty, name);
            if(listSize <= index)
            {
                Object result = null;
                for(int i = listSize; i < index; i++)
                    list.add(null);

                try
                {
                    list.add(index, result = ObjectFactory.getObjectFactory().buildBean(beanClass, context));
                }
                catch(Exception exc)
                {
                    throw new XworkException(exc);
                }
                return result;
            }
            if(list.get(index) == null)
            {
                Object result = null;
                try
                {
                    list.set(index, result = ObjectFactory.getObjectFactory().buildBean(beanClass, context));
                }
                catch(Exception exc)
                {
                    throw new XworkException(exc);
                }
                return result;
            }
        }
        return super.getProperty(context, target, name);
    }
   //////////setProperty
    private XWorkCollectionPropertyAccessor _sAcc;
}

注意在getProperty返回result时，判断result是否List类型

public class MoreXWorkListPropertyAccessor extends XWorkListPropertyAccessor
{
    public Object getProperty(Map context, Object target, Object name)
        throws OgnlException
    {
        if(OgnlContextState.isGettingByKeyProperty(context) || name.equals("makeNew"))
            return _sAcc.getProperty(context, target, name);
        if(name instanceof String)
            return super.getProperty(context, target, name);
        OgnlContextState.updateCurrentPropertyPath(context, name);
        Class lastClass = (Class)context.get("last.bean.accessed");
        String lastProperty = (String)context.get("last.property.accessed");
        if((name instanceof Number) && OgnlContextState.isCreatingNullObjects(context) && XWorkConverter.getInstance().getObjectTypeDeterminer().shouldCreateIfNew(lastClass, lastProperty, target, null, true))
        {
            List list = (List)target;
            int index = ((Number)name).intValue();
            int listSize = list.size();
            if(lastClass == null || lastProperty == null)
                return super.getProperty(context, target, name);
            Class beanClass = XWorkConverter.getInstance().getObjectTypeDeterminer().getElementClass(lastClass, lastProperty, name);
            if(listSize <= index)
            {
                Object result = null;
                for(int i = listSize; i < index; i++)
                    list.add(null);

                try
                {
                    list.add(index, result = ObjectFactory.getObjectFactory().buildBean(beanClass, context));
                }
                catch(Exception exc)
                {
                    throw new XworkException(exc);
                }
                if(result instanceof List){
                  OgnlContextState.setLastBeanPropertyAccessed(context,lastProperty+"_i");
                  }
                return result;
            }
            if(list.get(index) == null)
            {
                Object result = null;
                try
                {
                    list.set(index, result = ObjectFactory.getObjectFactory().buildBean(beanClass, context));
                }
                catch(Exception exc)
                {
                    throw new XworkException(exc);
                }
    if(result instanceof List){
                  OgnlContextState.setLastBeanPropertyAccessed(context,lastProperty+"_i");
                  }

                return result;
            }
        }
        return super.getProperty(context, target, name);

   // 单例
   instance = new MoreXWorkListPropertyAccessor();
  private MoreXWorkListPropertyAccessor{}
   public MoreXWorkListPropertyAccessor getInstance(){return instance;}
    }  

编写拦截器，设置MoreXWorkListPropertyAccessor;拦截器一定要配置在static-params之前

  public class MoreDimensesSupportInterceptor extends AroundInterceptor{

    public void before(ActionInvocation invocation)throws Exception{
      OgnlRuntime.setPropertyAccessor(List.class,MoreXWorkListPropertyAccessor.getInstance());
 }
}

现在只需在TestAction.properties中指定
Element_users=java.util.ArrayList //二维集合配置
Element_users_i=com.xxx.User //二维集合配置

Element_users=java.util.ArrayList //三维集合配置
Element_users_i=java.util.ArrayList //三维集合配置
Element_users_i_i=com.xxx.User //三维集合配置