Composite Component，java.util.List类型的属性始终为null

Question

问题在于，我始终将null作为listofthings的值，但我将5作为test的值，这是正确的。

另外，我尝试初始化Bean构造函数中的事物列表而不是init()方法。仍然没有任何变化。

以下是我的复合材料组件的代码：

mycomponent.xhtml

<ui:component  
  xmlns="http://www.w3.org/1999/xhtml" 
  xmlns:f="http://java.sun.com/jsf/core" 
  xmlns:h="http://java.sun.com/jsf/html"
  xmlns:ui="http://java.sun.com/jsf/facelets" 
  xmlns:p="http://primefaces.org/ui" 
  xmlns:composite="http://java.sun.com/jsf/composite"
>

    <composite:interface componentType="myNewComponent">
      <composite:attribute name="listofthings" required="true" type="java.util.List"/>
      <composite:attribute name="test" type="java.lang.Integer"/>
    </composite:interface>

    <composite:implementation>
      <h:outputStylesheet library="custom" name="mycomponent/resources/mycomp.css" />
      <ui:include src="mycomponent/componentImpl.xhtml" />
      <h:outputScript library="custom" name="mycomponent/resources/mycomp.js" />
    </composite:implementation>

</ui:component>

MyNewComponent.java

package com.abc.components;

import java.io.IOException; 
import java.util.ArrayList; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map;

import javax.faces.component.FacesComponent; 
import javax.faces.component.UINamingContainer; 
import javax.faces.context.FacesContext;

@FacesComponent("myNewComponent") 
public class MyNewComponent extends UINamingContainer {    

  private List<Things> listOfThings;               

  @SuppressWarnings("unchecked")   
  @Override   
  public void encodeBegin(FacesContext context) throws IOException {
    Map<String, Object> attrs = getAttributes();

    Object obj = attrs.get("listofthings");

    //I get obj as null and attrs.get("test") correctly gives 5

    if (attrs.get("listofthings") instanceof List<?>) {
      listOfThings = (List<Things>) attrs.get("listofthings");
    } else {
      listOfThings = new ArrayList<>();
    }

    super.encodeBegin(context);   
  } 
}

用法xhtml：

 <my:mycomponent listofthings="#{bean.things}" test="5"></my:mycomponent>

用法bean：

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import javax.annotation.PostConstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

@ManagedBean
@ViewScoped
public class Bean implements Serializable {
  private static final long serialVersionUID = 1L;

  private List<Thing> things;    

  @PostConstruct
  public void init() {
    things = new ArrayList<>();
    things.add(new Thing("Name", "type"));
    things.add(new Thing("Name", "type"));
    things.add(new Thing("Name", "type"));        

  }
}

不确定我在这里缺少什么，非常感谢任何帮助。