jsf配置问题 Error performing conversion of value ' of type class java.lang.String to type class

managed-bean:UserBean

/**
 *
 */
package com.joary.jsf;

/**
 * @author Administrator
 *
 */
public class UserBean {
    private java.lang.String name;
    private Friend friend;

    public UserBean() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Friend getFriend() {
        return friend;
    }

    public void setFriend(Friend friend) {
        this.friend = friend;
    }

    public String add(){
        return "success";
    }
}

//对应的配置文件

 <managed-bean>
  <managed-bean-name>userBean</managed-bean-name>
  <managed-bean-class>com.joary.jsf.UserBean</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
  <managed-property>
   <property-name>name</property-name>
   <property-class>java.lang.String</property-class>
   <value/>

 

<property-name>friend</property-name>
   <property-class>com.joary.jsf.Friend</property-class>
   <null-value/>

  </managed-property>

  </managed-property>
 </managed-bean>

（此为正确的配置文件）

 <managed-bean>
  <managed-bean-name>userBean</managed-bean-name>
  <managed-bean-class>com.joary.jsf.UserBean</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
  <managed-property>
   <property-name>name</property-name>
   <property-class>java.lang.String</property-class>
   <value/>

<property-name>friend</property-name>
   <property-class>com.joary.jsf.Friend</property-class>
   <value/>

  </managed-property>
 </managed-bean>

（此为错误的配置文件）

问题应该是：如是类型是JSF不能自己从String为型中转换过来的话，vlaue值就必须得设置成null-value才行。