The requested list key 'map' could not be resolved as a collection/array/map/enumeration/iterator type. Example: people or peopl

最新推荐文章于 2021-04-08 10:19:32 发布

原创最新推荐文章于 2021-04-08 10:19:32 发布 · 2.3w 阅读

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文章标签：

#list #string #integer #user #action #dao

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本文介绍了一个关于Struts2框架中使用select标签时出现的错误及其解决方法。问题出现在试图显示用户列表时，由于未正确设置返回的用户列表而导致。通过在Action类中设置属性userlist的值，成功解决了这个问题。

昨天学习 struts2组件，当使用select标签时报错

1.页面代码

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<body>
  <div id="glo" style="width: 200px">
   <h3>
    select2
   </h3>
   <s:form action="../select2.action">

    <s:select list="userlist" listKey="id" listValue="firstname"></s:select>
   </s:form>
  </div>

</body>

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2.pojo 类

private Integer id;
private String firstname;
private String lastname;
private String password;
private String description;

public User(){}
public User(Integer id,String lastname){
  this.id=id;
  this.lastname=lastname;
}
public String getDescription() {
  return description;
}
public void setDescription(String description) {
  this.description = description;
}
public String getPassword() {
  return password;
}
public void setPassword(String password) {
  this.password = password;
}
private int age;
public Integer getId() {
  return id;
}
public void setId(Integer id) {
  this.id = id;
}
public String getFirstname() {
  return firstname;
}
public void setFirstname(String firstname) {
  this.firstname = firstname;
}
public String getLastname() {
  return lastname;
}
public void setLastname(String lastname) {
  this.lastname = lastname;
}
public int getAge() {
  return age;
}
public void setAge(int age) {
  this.age = age;
}

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3.action 类 java代码

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/***
*
*
* 组件学习
* @return
*/
private User user;
private UserService service;
private String userType;
private String username;
private List<User> userlist;
private final static Logger log=Logger.getLogger(Component.class);

public List<User> getUserlist() {
return userlist;
}

public void setUserlist(List<User> userlist) {
this.userlist = userlist;
}

public static Logger getLog() {
return log;
}

public User getUser() {
return user;
}

public void setUser(User user) {
this.user = user;
}

//select
public String select2(){

  List<User> userlist=new ArrayList<User>();
  //从dao查出所有用户
  userlist=service.findAll();
  log.info("userlist's value:"+userlist);

  return "back";
}

--------------------------------------------------------------------------------------------------------------------------------------------------

4.struts2.xml

  <action name="select2" class="select2Action" method="select2">
  <result name="back">/components/select2.jsp</result>
  </action>

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页面报错

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tag 'select', field 'list': The requested list key 'userlist' could not be resolved as a collection/array/map/enumeration/iterator type. Example: people or people.{name} - [unknown location]
at org.apache.struts2.components.Component.fieldError(Component.java:231)
at org.apache.struts2.components.Component.findValue(Component.java:293)
at org.apache.struts2.components.ListUIBean.evaluateExtraParams(ListUIBean.java:79)
at org.apache.struts2.components.Select.evaluateExtraParams(Select.java:99)
at org.apache.struts2.components.UIBean.evaluateParams(UIBean.java:780)
at org.apache.struts2.components.UIBean.end(UIBean.java:481)
at org.apache.struts2.views.jsp.ComponentTagSupport.doEndTag(ComponentTagSupport.java:43)
at org.apache.jsp.components.select2_jsp._jspx_meth_s_005fselect_005f0(select2_jsp.java:155)
at org.apache.jsp.components.select2_jsp._jspx_meth_s_005fform_005f0(select2_jsp.java:120)
at org.apache.jsp.components.select2_jsp._jspService(select2_jsp.java:79)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

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解决方法：分析原因，可能是list中值为空，userlist=service.findAll();此行代码没有setUserList（），导致属性userlist再页面上值为空，如下修改action类

//select
public String select2(){

  List<User> userlist=new ArrayList<User>();
  //从dao查出所有用户
  userlist=service.findAll();
  log.info("userlist's value:"+userlist);
  //设置属性值
  this.setUserlist(userlist);
  return "back";
}

问题解决。。。。。。。。。。。。。。。。。。。

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