我的查询返回一个空列表，而不是一个条目

Question

我想从表中得到我的用户：

我通过表单保存此值（所以卡宴配置似乎也不错）。

的UserInfoFactory类：

public class UserInfoFactory extends _UserInfo implements Serializable { 
    private static final long serialVersionUID = 1L; 

    public static ObjectContext getContext() { 
     @SuppressWarnings("deprecation") 
     ServerRuntime runtime = new ServerRuntime("cayenne-myapplication.xml"); 
     return runtime.newContext(); 
    } 

    @SuppressWarnings("unchecked") 
    public static List<UserInfoFactory> getUsersInfo() { 

     SQLTemplate select = new SQLTemplate(UserInfoFactory.class, 
       "SELECT * FROM mam.userinfo"); 

     return getContext().performQuery(select); 
    } 
} 

我_UserInfo类是：

package com.example.myapplication.model; 

import org.apache.cayenne.CayenneDataObject; 

/** 
* Class _UserInfo was generated by Cayenne. 
* It is probably a good idea to avoid changing this class manually, 
* since it may be overwritten next time code is regenerated. 
* If you need to make any customizations, please use subclass. 
*/ 
public abstract class _UserInfo extends CayenneDataObject { 

    public static final String ADDRESS_PROPERTY = "address"; 
    public static final String EMAIL_PROPERTY = "email"; 
    public static final String FIRSTNAME_PROPERTY = "firstname"; 
    public static final String LASTNAME_PROPERTY = "lastname"; 
    public static final String PHONENUMBER_PROPERTY = "phonenumber"; 
    public static final String USERPASSWORD_PROPERTY = "userpassword"; 
    public static final String USERPRIVILEGES_PROPERTY = "userprivileges"; 

    public static final String USERID_PK_COLUMN = "USERID"; 

    public void setAddress(String address) { 
     writeProperty(ADDRESS_PROPERTY, address); 
    } 
    public String getAddress() { 
     return (String)readProperty(ADDRESS_PROPERTY); 
    } 

    public void setEmail(String email) { 
     writeProperty(EMAIL_PROPERTY, email); 
    } 
    public String getEmail() { 
     return (String)readProperty(EMAIL_PROPERTY); 
    } 

    public void setFirstname(String firstname) { 
     writeProperty(FIRSTNAME_PROPERTY, firstname); 
    } 
    public String getFirstname() { 
     return (String)readProperty(FIRSTNAME_PROPERTY); 
    } 

    public void setLastname(String lastname) { 
     writeProperty(LASTNAME_PROPERTY, lastname); 
    } 
    public String getLastname() { 
     return (String)readProperty(LASTNAME_PROPERTY); 
    } 

    public void setPhonenumber(Integer phonenumber) { 
     writeProperty(PHONENUMBER_PROPERTY, phonenumber); 
    } 
    public Integer getPhonenumber() { 
     return (Integer)readProperty(PHONENUMBER_PROPERTY); 
    } 

    public void setUserpassword(String userpassword) { 
     writeProperty(USERPASSWORD_PROPERTY, userpassword); 
    } 
    public String getUserpassword() { 
     return (String)readProperty(USERPASSWORD_PROPERTY); 
    } 

    public void setUserprivileges(Short userprivileges) { 
     writeProperty(USERPRIVILEGES_PROPERTY, userprivileges); 
    } 
    public Short getUserprivileges() { 
     return (Short)readProperty(USERPRIVILEGES_PROPERTY); 
    } 

} 

我打电话这样的方法：

List<UserInfoFactory> users = UserInfoFactory.getUsersInfo(); 

但用户列表返回NULL 。

这不应该是null，而是一个值（测试用户）。

我做错了什么？

谢谢，

Answer 1

原因卡宴返回null代替一个目的是，PK场或者在结果集中未发现，或者其值NULL。 在你的情况下，我认为卡宴无法找到结果中的PK，因为它似乎被定义为userid id DB，在Cayenne代码中，我看到它是USERID。

请让我给你一些关于你的代码的一般建议。 为每个请求创建ServerRuntime并不是真正有效的解决方案，您应该将其保留为应用程序单例，有关详细信息，请参阅this question。此外，ObjectSelect（或SelectQuery，如果您使用旧版Cayenne）是一种更好（更灵活）的选择对象的方式。

您可以使用它像这样：

List<UserInfoFactory> result = ObjectSelect.query(UserInfoFactory.class) 
            .select(context);